Commit a282ac7a91

Jonathan Marler <johnnymarler@gmail.com>
2020-06-09 06:34:50
Support Reader for InStream
1 parent 4302f27
lib/std/fs/file.zig
@@ -642,8 +642,14 @@ pub const File = struct {
         }
     }
 
-    pub const InStream = io.InStream(File, ReadError, read);
+    pub const Reader = io.Reader(File, ReadError, read);
+    /// Deprecated: use `Reader`
+    pub const InStream = Reader;
 
+    pub fn reader(file: File) io.Reader(File, ReadError, read) {
+        return .{ .context = file };
+    }
+    /// Deprecated: use `reader`
     pub fn inStream(file: File) io.InStream(File, ReadError, read) {
         return .{ .context = file };
     }
lib/std/io/bit_in_stream.zig
@@ -1,243 +1,5 @@
-const std = @import("../std.zig");
-const builtin = std.builtin;
-const io = std.io;
-const assert = std.debug.assert;
-const testing = std.testing;
-const trait = std.meta.trait;
-const meta = std.meta;
-const math = std.math;
+/// Deprecated: use `std.io.bit_reader.BitReader`
+pub const BitInStream = @import("./bit_reader.zig").BitReader;
 
-/// Creates a stream which allows for reading bit fields from another stream
-pub fn BitInStream(endian: builtin.Endian, comptime InStreamType: type) type {
-    return struct {
-        in_stream: InStreamType,
-        bit_buffer: u7,
-        bit_count: u3,
-
-        pub const Error = InStreamType.Error;
-        pub const InStream = io.InStream(*Self, Error, read);
-
-        const Self = @This();
-        const u8_bit_count = comptime meta.bitCount(u8);
-        const u7_bit_count = comptime meta.bitCount(u7);
-        const u4_bit_count = comptime meta.bitCount(u4);
-
-        pub fn init(in_stream: InStreamType) Self {
-            return Self{
-                .in_stream = in_stream,
-                .bit_buffer = 0,
-                .bit_count = 0,
-            };
-        }
-
-        /// Reads `bits` bits from the stream and returns a specified unsigned int type
-        ///  containing them in the least significant end, returning an error if the
-        ///  specified number of bits could not be read.
-        pub fn readBitsNoEof(self: *Self, comptime U: type, bits: usize) !U {
-            var n: usize = undefined;
-            const result = try self.readBits(U, bits, &n);
-            if (n < bits) return error.EndOfStream;
-            return result;
-        }
-
-        /// Reads `bits` bits from the stream and returns a specified unsigned int type
-        ///  containing them in the least significant end. The number of bits successfully
-        ///  read is placed in `out_bits`, as reaching the end of the stream is not an error.
-        pub fn readBits(self: *Self, comptime U: type, bits: usize, out_bits: *usize) Error!U {
-            comptime assert(trait.isUnsignedInt(U));
-
-            //by extending the buffer to a minimum of u8 we can cover a number of edge cases
-            // related to shifting and casting.
-            const u_bit_count = comptime meta.bitCount(U);
-            const buf_bit_count = bc: {
-                assert(u_bit_count >= bits);
-                break :bc if (u_bit_count <= u8_bit_count) u8_bit_count else u_bit_count;
-            };
-            const Buf = std.meta.Int(false, buf_bit_count);
-            const BufShift = math.Log2Int(Buf);
-
-            out_bits.* = @as(usize, 0);
-            if (U == u0 or bits == 0) return 0;
-            var out_buffer = @as(Buf, 0);
-
-            if (self.bit_count > 0) {
-                const n = if (self.bit_count >= bits) @intCast(u3, bits) else self.bit_count;
-                const shift = u7_bit_count - n;
-                switch (endian) {
-                    .Big => {
-                        out_buffer = @as(Buf, self.bit_buffer >> shift);
-                        if (n >= u7_bit_count)
-                            self.bit_buffer = 0
-                        else
-                            self.bit_buffer <<= n;
-                    },
-                    .Little => {
-                        const value = (self.bit_buffer << shift) >> shift;
-                        out_buffer = @as(Buf, value);
-                        if (n >= u7_bit_count)
-                            self.bit_buffer = 0
-                        else
-                            self.bit_buffer >>= n;
-                    },
-                }
-                self.bit_count -= n;
-                out_bits.* = n;
-            }
-            //at this point we know bit_buffer is empty
-
-            //copy bytes until we have enough bits, then leave the rest in bit_buffer
-            while (out_bits.* < bits) {
-                const n = bits - out_bits.*;
-                const next_byte = self.in_stream.readByte() catch |err| {
-                    if (err == error.EndOfStream) {
-                        return @intCast(U, out_buffer);
-                    }
-                    //@BUG: See #1810. Not sure if the bug is that I have to do this for some
-                    // streams, or that I don't for streams with emtpy errorsets.
-                    return @errSetCast(Error, err);
-                };
-
-                switch (endian) {
-                    .Big => {
-                        if (n >= u8_bit_count) {
-                            out_buffer <<= @intCast(u3, u8_bit_count - 1);
-                            out_buffer <<= 1;
-                            out_buffer |= @as(Buf, next_byte);
-                            out_bits.* += u8_bit_count;
-                            continue;
-                        }
-
-                        const shift = @intCast(u3, u8_bit_count - n);
-                        out_buffer <<= @intCast(BufShift, n);
-                        out_buffer |= @as(Buf, next_byte >> shift);
-                        out_bits.* += n;
-                        self.bit_buffer = @truncate(u7, next_byte << @intCast(u3, n - 1));
-                        self.bit_count = shift;
-                    },
-                    .Little => {
-                        if (n >= u8_bit_count) {
-                            out_buffer |= @as(Buf, next_byte) << @intCast(BufShift, out_bits.*);
-                            out_bits.* += u8_bit_count;
-                            continue;
-                        }
-
-                        const shift = @intCast(u3, u8_bit_count - n);
-                        const value = (next_byte << shift) >> shift;
-                        out_buffer |= @as(Buf, value) << @intCast(BufShift, out_bits.*);
-                        out_bits.* += n;
-                        self.bit_buffer = @truncate(u7, next_byte >> @intCast(u3, n));
-                        self.bit_count = shift;
-                    },
-                }
-            }
-
-            return @intCast(U, out_buffer);
-        }
-
-        pub fn alignToByte(self: *Self) void {
-            self.bit_buffer = 0;
-            self.bit_count = 0;
-        }
-
-        pub fn read(self: *Self, buffer: []u8) Error!usize {
-            var out_bits: usize = undefined;
-            var out_bits_total = @as(usize, 0);
-            //@NOTE: I'm not sure this is a good idea, maybe alignToByte should be forced
-            if (self.bit_count > 0) {
-                for (buffer) |*b, i| {
-                    b.* = try self.readBits(u8, u8_bit_count, &out_bits);
-                    out_bits_total += out_bits;
-                }
-                const incomplete_byte = @boolToInt(out_bits_total % u8_bit_count > 0);
-                return (out_bits_total / u8_bit_count) + incomplete_byte;
-            }
-
-            return self.in_stream.read(buffer);
-        }
-
-        pub fn inStream(self: *Self) InStream {
-            return .{ .context = self };
-        }
-    };
-}
-
-pub fn bitInStream(
-    comptime endian: builtin.Endian,
-    underlying_stream: var,
-) BitInStream(endian, @TypeOf(underlying_stream)) {
-    return BitInStream(endian, @TypeOf(underlying_stream)).init(underlying_stream);
-}
-
-test "api coverage" {
-    const mem_be = [_]u8{ 0b11001101, 0b00001011 };
-    const mem_le = [_]u8{ 0b00011101, 0b10010101 };
-
-    var mem_in_be = io.fixedBufferStream(&mem_be);
-    var bit_stream_be = bitInStream(.Big, mem_in_be.inStream());
-
-    var out_bits: usize = undefined;
-
-    const expect = testing.expect;
-    const expectError = testing.expectError;
-
-    expect(1 == try bit_stream_be.readBits(u2, 1, &out_bits));
-    expect(out_bits == 1);
-    expect(2 == try bit_stream_be.readBits(u5, 2, &out_bits));
-    expect(out_bits == 2);
-    expect(3 == try bit_stream_be.readBits(u128, 3, &out_bits));
-    expect(out_bits == 3);
-    expect(4 == try bit_stream_be.readBits(u8, 4, &out_bits));
-    expect(out_bits == 4);
-    expect(5 == try bit_stream_be.readBits(u9, 5, &out_bits));
-    expect(out_bits == 5);
-    expect(1 == try bit_stream_be.readBits(u1, 1, &out_bits));
-    expect(out_bits == 1);
-
-    mem_in_be.pos = 0;
-    bit_stream_be.bit_count = 0;
-    expect(0b110011010000101 == try bit_stream_be.readBits(u15, 15, &out_bits));
-    expect(out_bits == 15);
-
-    mem_in_be.pos = 0;
-    bit_stream_be.bit_count = 0;
-    expect(0b1100110100001011 == try bit_stream_be.readBits(u16, 16, &out_bits));
-    expect(out_bits == 16);
-
-    _ = try bit_stream_be.readBits(u0, 0, &out_bits);
-
-    expect(0 == try bit_stream_be.readBits(u1, 1, &out_bits));
-    expect(out_bits == 0);
-    expectError(error.EndOfStream, bit_stream_be.readBitsNoEof(u1, 1));
-
-    var mem_in_le = io.fixedBufferStream(&mem_le);
-    var bit_stream_le = bitInStream(.Little, mem_in_le.inStream());
-
-    expect(1 == try bit_stream_le.readBits(u2, 1, &out_bits));
-    expect(out_bits == 1);
-    expect(2 == try bit_stream_le.readBits(u5, 2, &out_bits));
-    expect(out_bits == 2);
-    expect(3 == try bit_stream_le.readBits(u128, 3, &out_bits));
-    expect(out_bits == 3);
-    expect(4 == try bit_stream_le.readBits(u8, 4, &out_bits));
-    expect(out_bits == 4);
-    expect(5 == try bit_stream_le.readBits(u9, 5, &out_bits));
-    expect(out_bits == 5);
-    expect(1 == try bit_stream_le.readBits(u1, 1, &out_bits));
-    expect(out_bits == 1);
-
-    mem_in_le.pos = 0;
-    bit_stream_le.bit_count = 0;
-    expect(0b001010100011101 == try bit_stream_le.readBits(u15, 15, &out_bits));
-    expect(out_bits == 15);
-
-    mem_in_le.pos = 0;
-    bit_stream_le.bit_count = 0;
-    expect(0b1001010100011101 == try bit_stream_le.readBits(u16, 16, &out_bits));
-    expect(out_bits == 16);
-
-    _ = try bit_stream_le.readBits(u0, 0, &out_bits);
-
-    expect(0 == try bit_stream_le.readBits(u1, 1, &out_bits));
-    expect(out_bits == 0);
-    expectError(error.EndOfStream, bit_stream_le.readBitsNoEof(u1, 1));
-}
+/// Deprecated: use `std.io.bit_reader.bitReader`
+pub const bitInStream = @import("./bit_reader.zig").bitReader;
lib/std/io/bit_reader.zig
@@ -0,0 +1,250 @@
+const std = @import("../std.zig");
+const builtin = std.builtin;
+const io = std.io;
+const assert = std.debug.assert;
+const testing = std.testing;
+const trait = std.meta.trait;
+const meta = std.meta;
+const math = std.math;
+
+/// Creates a stream which allows for reading bit fields from another stream
+pub fn BitReader(endian: builtin.Endian, comptime ReaderType: type) type {
+    return struct {
+        forward_reader: ReaderType,
+        bit_buffer: u7,
+        bit_count: u3,
+
+        pub const Error = ReaderType.Error;
+        pub const Reader = io.Reader(*Self, Error, read);
+        /// Deprecated: use `Reader`
+        pub const InStream = io.InStream(*Self, Error, read);
+
+        const Self = @This();
+        const u8_bit_count = comptime meta.bitCount(u8);
+        const u7_bit_count = comptime meta.bitCount(u7);
+        const u4_bit_count = comptime meta.bitCount(u4);
+
+        pub fn init(forward_reader: ReaderType) Self {
+            return Self{
+                .forward_reader = forward_reader,
+                .bit_buffer = 0,
+                .bit_count = 0,
+            };
+        }
+
+        /// Reads `bits` bits from the stream and returns a specified unsigned int type
+        ///  containing them in the least significant end, returning an error if the
+        ///  specified number of bits could not be read.
+        pub fn readBitsNoEof(self: *Self, comptime U: type, bits: usize) !U {
+            var n: usize = undefined;
+            const result = try self.readBits(U, bits, &n);
+            if (n < bits) return error.EndOfStream;
+            return result;
+        }
+
+        /// Reads `bits` bits from the stream and returns a specified unsigned int type
+        ///  containing them in the least significant end. The number of bits successfully
+        ///  read is placed in `out_bits`, as reaching the end of the stream is not an error.
+        pub fn readBits(self: *Self, comptime U: type, bits: usize, out_bits: *usize) Error!U {
+            comptime assert(trait.isUnsignedInt(U));
+
+            //by extending the buffer to a minimum of u8 we can cover a number of edge cases
+            // related to shifting and casting.
+            const u_bit_count = comptime meta.bitCount(U);
+            const buf_bit_count = bc: {
+                assert(u_bit_count >= bits);
+                break :bc if (u_bit_count <= u8_bit_count) u8_bit_count else u_bit_count;
+            };
+            const Buf = std.meta.Int(false, buf_bit_count);
+            const BufShift = math.Log2Int(Buf);
+
+            out_bits.* = @as(usize, 0);
+            if (U == u0 or bits == 0) return 0;
+            var out_buffer = @as(Buf, 0);
+
+            if (self.bit_count > 0) {
+                const n = if (self.bit_count >= bits) @intCast(u3, bits) else self.bit_count;
+                const shift = u7_bit_count - n;
+                switch (endian) {
+                    .Big => {
+                        out_buffer = @as(Buf, self.bit_buffer >> shift);
+                        if (n >= u7_bit_count)
+                            self.bit_buffer = 0
+                        else
+                            self.bit_buffer <<= n;
+                    },
+                    .Little => {
+                        const value = (self.bit_buffer << shift) >> shift;
+                        out_buffer = @as(Buf, value);
+                        if (n >= u7_bit_count)
+                            self.bit_buffer = 0
+                        else
+                            self.bit_buffer >>= n;
+                    },
+                }
+                self.bit_count -= n;
+                out_bits.* = n;
+            }
+            //at this point we know bit_buffer is empty
+
+            //copy bytes until we have enough bits, then leave the rest in bit_buffer
+            while (out_bits.* < bits) {
+                const n = bits - out_bits.*;
+                const next_byte = self.forward_reader.readByte() catch |err| {
+                    if (err == error.EndOfStream) {
+                        return @intCast(U, out_buffer);
+                    }
+                    //@BUG: See #1810. Not sure if the bug is that I have to do this for some
+                    // streams, or that I don't for streams with emtpy errorsets.
+                    return @errSetCast(Error, err);
+                };
+
+                switch (endian) {
+                    .Big => {
+                        if (n >= u8_bit_count) {
+                            out_buffer <<= @intCast(u3, u8_bit_count - 1);
+                            out_buffer <<= 1;
+                            out_buffer |= @as(Buf, next_byte);
+                            out_bits.* += u8_bit_count;
+                            continue;
+                        }
+
+                        const shift = @intCast(u3, u8_bit_count - n);
+                        out_buffer <<= @intCast(BufShift, n);
+                        out_buffer |= @as(Buf, next_byte >> shift);
+                        out_bits.* += n;
+                        self.bit_buffer = @truncate(u7, next_byte << @intCast(u3, n - 1));
+                        self.bit_count = shift;
+                    },
+                    .Little => {
+                        if (n >= u8_bit_count) {
+                            out_buffer |= @as(Buf, next_byte) << @intCast(BufShift, out_bits.*);
+                            out_bits.* += u8_bit_count;
+                            continue;
+                        }
+
+                        const shift = @intCast(u3, u8_bit_count - n);
+                        const value = (next_byte << shift) >> shift;
+                        out_buffer |= @as(Buf, value) << @intCast(BufShift, out_bits.*);
+                        out_bits.* += n;
+                        self.bit_buffer = @truncate(u7, next_byte >> @intCast(u3, n));
+                        self.bit_count = shift;
+                    },
+                }
+            }
+
+            return @intCast(U, out_buffer);
+        }
+
+        pub fn alignToByte(self: *Self) void {
+            self.bit_buffer = 0;
+            self.bit_count = 0;
+        }
+
+        pub fn read(self: *Self, buffer: []u8) Error!usize {
+            var out_bits: usize = undefined;
+            var out_bits_total = @as(usize, 0);
+            //@NOTE: I'm not sure this is a good idea, maybe alignToByte should be forced
+            if (self.bit_count > 0) {
+                for (buffer) |*b, i| {
+                    b.* = try self.readBits(u8, u8_bit_count, &out_bits);
+                    out_bits_total += out_bits;
+                }
+                const incomplete_byte = @boolToInt(out_bits_total % u8_bit_count > 0);
+                return (out_bits_total / u8_bit_count) + incomplete_byte;
+            }
+
+            return self.forward_reader.read(buffer);
+        }
+
+        pub fn reader(self: *Self) Reader {
+            return .{ .context = self };
+        }
+
+        /// Deprecated: use `reader`
+        pub fn inStream(self: *Self) InStream {
+            return .{ .context = self };
+        }
+    };
+}
+
+pub fn bitReader(
+    comptime endian: builtin.Endian,
+    underlying_stream: var,
+) BitReader(endian, @TypeOf(underlying_stream)) {
+    return BitReader(endian, @TypeOf(underlying_stream)).init(underlying_stream);
+}
+
+test "api coverage" {
+    const mem_be = [_]u8{ 0b11001101, 0b00001011 };
+    const mem_le = [_]u8{ 0b00011101, 0b10010101 };
+
+    var mem_in_be = io.fixedBufferStream(&mem_be);
+    var bit_stream_be = bitReader(.Big, mem_in_be.reader());
+
+    var out_bits: usize = undefined;
+
+    const expect = testing.expect;
+    const expectError = testing.expectError;
+
+    expect(1 == try bit_stream_be.readBits(u2, 1, &out_bits));
+    expect(out_bits == 1);
+    expect(2 == try bit_stream_be.readBits(u5, 2, &out_bits));
+    expect(out_bits == 2);
+    expect(3 == try bit_stream_be.readBits(u128, 3, &out_bits));
+    expect(out_bits == 3);
+    expect(4 == try bit_stream_be.readBits(u8, 4, &out_bits));
+    expect(out_bits == 4);
+    expect(5 == try bit_stream_be.readBits(u9, 5, &out_bits));
+    expect(out_bits == 5);
+    expect(1 == try bit_stream_be.readBits(u1, 1, &out_bits));
+    expect(out_bits == 1);
+
+    mem_in_be.pos = 0;
+    bit_stream_be.bit_count = 0;
+    expect(0b110011010000101 == try bit_stream_be.readBits(u15, 15, &out_bits));
+    expect(out_bits == 15);
+
+    mem_in_be.pos = 0;
+    bit_stream_be.bit_count = 0;
+    expect(0b1100110100001011 == try bit_stream_be.readBits(u16, 16, &out_bits));
+    expect(out_bits == 16);
+
+    _ = try bit_stream_be.readBits(u0, 0, &out_bits);
+
+    expect(0 == try bit_stream_be.readBits(u1, 1, &out_bits));
+    expect(out_bits == 0);
+    expectError(error.EndOfStream, bit_stream_be.readBitsNoEof(u1, 1));
+
+    var mem_in_le = io.fixedBufferStream(&mem_le);
+    var bit_stream_le = bitReader(.Little, mem_in_le.reader());
+
+    expect(1 == try bit_stream_le.readBits(u2, 1, &out_bits));
+    expect(out_bits == 1);
+    expect(2 == try bit_stream_le.readBits(u5, 2, &out_bits));
+    expect(out_bits == 2);
+    expect(3 == try bit_stream_le.readBits(u128, 3, &out_bits));
+    expect(out_bits == 3);
+    expect(4 == try bit_stream_le.readBits(u8, 4, &out_bits));
+    expect(out_bits == 4);
+    expect(5 == try bit_stream_le.readBits(u9, 5, &out_bits));
+    expect(out_bits == 5);
+    expect(1 == try bit_stream_le.readBits(u1, 1, &out_bits));
+    expect(out_bits == 1);
+
+    mem_in_le.pos = 0;
+    bit_stream_le.bit_count = 0;
+    expect(0b001010100011101 == try bit_stream_le.readBits(u15, 15, &out_bits));
+    expect(out_bits == 15);
+
+    mem_in_le.pos = 0;
+    bit_stream_le.bit_count = 0;
+    expect(0b1001010100011101 == try bit_stream_le.readBits(u16, 16, &out_bits));
+    expect(out_bits == 16);
+
+    _ = try bit_stream_le.readBits(u0, 0, &out_bits);
+
+    expect(0 == try bit_stream_le.readBits(u1, 1, &out_bits));
+    expect(out_bits == 0);
+    expectError(error.EndOfStream, bit_stream_le.readBitsNoEof(u1, 1));
+}
lib/std/io/buffered_in_stream.zig
@@ -1,86 +1,5 @@
-const std = @import("../std.zig");
-const io = std.io;
-const assert = std.debug.assert;
-const testing = std.testing;
+/// Deprecated: use `std.io.buffered_reader.BufferedReader`
+pub const BufferedInStream = @import("./buffered_reader.zig").BufferedReader;
 
-pub fn BufferedInStream(comptime buffer_size: usize, comptime InStreamType: type) type {
-    return struct {
-        unbuffered_in_stream: InStreamType,
-        fifo: FifoType = FifoType.init(),
-
-        pub const Error = InStreamType.Error;
-        pub const InStream = io.InStream(*Self, Error, read);
-
-        const Self = @This();
-        const FifoType = std.fifo.LinearFifo(u8, std.fifo.LinearFifoBufferType{ .Static = buffer_size });
-
-        pub fn read(self: *Self, dest: []u8) Error!usize {
-            var dest_index: usize = 0;
-            while (dest_index < dest.len) {
-                const written = self.fifo.read(dest[dest_index..]);
-                if (written == 0) {
-                    // fifo empty, fill it
-                    const writable = self.fifo.writableSlice(0);
-                    assert(writable.len > 0);
-                    const n = try self.unbuffered_in_stream.read(writable);
-                    if (n == 0) {
-                        // reading from the unbuffered stream returned nothing
-                        // so we have nothing left to read.
-                        return dest_index;
-                    }
-                    self.fifo.update(n);
-                }
-                dest_index += written;
-            }
-            return dest.len;
-        }
-
-        pub fn inStream(self: *Self) InStream {
-            return .{ .context = self };
-        }
-    };
-}
-
-pub fn bufferedInStream(underlying_stream: var) BufferedInStream(4096, @TypeOf(underlying_stream)) {
-    return .{ .unbuffered_in_stream = underlying_stream };
-}
-
-test "io.BufferedInStream" {
-    const OneByteReadInStream = struct {
-        str: []const u8,
-        curr: usize,
-
-        const Error = error{NoError};
-        const Self = @This();
-        const InStream = io.InStream(*Self, Error, read);
-
-        fn init(str: []const u8) Self {
-            return Self{
-                .str = str,
-                .curr = 0,
-            };
-        }
-
-        fn read(self: *Self, dest: []u8) Error!usize {
-            if (self.str.len <= self.curr or dest.len == 0)
-                return 0;
-
-            dest[0] = self.str[self.curr];
-            self.curr += 1;
-            return 1;
-        }
-
-        fn inStream(self: *Self) InStream {
-            return .{ .context = self };
-        }
-    };
-
-    const str = "This is a test";
-    var one_byte_stream = OneByteReadInStream.init(str);
-    var buf_in_stream = bufferedInStream(one_byte_stream.inStream());
-    const stream = buf_in_stream.inStream();
-
-    const res = try stream.readAllAlloc(testing.allocator, str.len + 1);
-    defer testing.allocator.free(res);
-    testing.expectEqualSlices(u8, str, res);
-}
+/// Deprecated: use `std.io.buffered_reader.bufferedReader`
+pub const bufferedInStream = @import("./buffered_reader.zig").bufferedReader;
lib/std/io/buffered_reader.zig
@@ -0,0 +1,93 @@
+const std = @import("../std.zig");
+const io = std.io;
+const assert = std.debug.assert;
+const testing = std.testing;
+
+pub fn BufferedReader(comptime buffer_size: usize, comptime ReaderType: type) type {
+    return struct {
+        unbuffered_reader: ReaderType,
+        fifo: FifoType = FifoType.init(),
+
+        pub const Error = ReaderType.Error;
+        pub const Reader = io.Reader(*Self, Error, read);
+        /// Deprecated: use `Reader`
+        pub const InStream = Reader;
+
+        const Self = @This();
+        const FifoType = std.fifo.LinearFifo(u8, std.fifo.LinearFifoBufferType{ .Static = buffer_size });
+
+        pub fn read(self: *Self, dest: []u8) Error!usize {
+            var dest_index: usize = 0;
+            while (dest_index < dest.len) {
+                const written = self.fifo.read(dest[dest_index..]);
+                if (written == 0) {
+                    // fifo empty, fill it
+                    const writable = self.fifo.writableSlice(0);
+                    assert(writable.len > 0);
+                    const n = try self.unbuffered_reader.read(writable);
+                    if (n == 0) {
+                        // reading from the unbuffered stream returned nothing
+                        // so we have nothing left to read.
+                        return dest_index;
+                    }
+                    self.fifo.update(n);
+                }
+                dest_index += written;
+            }
+            return dest.len;
+        }
+
+        pub fn reader(self: *Self) Reader {
+            return .{ .context = self };
+        }
+
+        /// Deprecated: use `reader`
+        pub fn inStream(self: *Self) InStream {
+            return .{ .context = self };
+        }
+    };
+}
+
+pub fn bufferedReader(underlying_stream: var) BufferedReader(4096, @TypeOf(underlying_stream)) {
+    return .{ .unbuffered_reader = underlying_stream };
+}
+
+test "io.BufferedReader" {
+    const OneByteReadReader = struct {
+        str: []const u8,
+        curr: usize,
+
+        const Error = error{NoError};
+        const Self = @This();
+        const Reader = io.Reader(*Self, Error, read);
+
+        fn init(str: []const u8) Self {
+            return Self{
+                .str = str,
+                .curr = 0,
+            };
+        }
+
+        fn read(self: *Self, dest: []u8) Error!usize {
+            if (self.str.len <= self.curr or dest.len == 0)
+                return 0;
+
+            dest[0] = self.str[self.curr];
+            self.curr += 1;
+            return 1;
+        }
+
+        fn reader(self: *Self) Reader {
+            return .{ .context = self };
+        }
+    };
+
+    const str = "This is a test";
+    var one_byte_stream = OneByteReadReader.init(str);
+    var buf_reader = bufferedReader(one_byte_stream.reader());
+    const stream = buf_reader.reader();
+
+    const res = try stream.readAllAlloc(testing.allocator, str.len + 1);
+    defer testing.allocator.free(res);
+    testing.expectEqualSlices(u8, str, res);
+}
lib/std/io/fixed_buffer_stream.zig
@@ -4,8 +4,8 @@ const testing = std.testing;
 const mem = std.mem;
 const assert = std.debug.assert;
 
-/// This turns a byte buffer into an `io.OutStream`, `io.InStream`, or `io.SeekableStream`.
-/// If the supplied byte buffer is const, then `io.OutStream` is not available.
+/// This turns a byte buffer into an `io.Writer`, `io.Reader`, or `io.SeekableStream`.
+/// If the supplied byte buffer is const, then `io.Writer` is not available.
 pub fn FixedBufferStream(comptime Buffer: type) type {
     return struct {
         /// `Buffer` is either a `[]u8` or `[]const u8`.
@@ -17,6 +17,8 @@ pub fn FixedBufferStream(comptime Buffer: type) type {
         pub const SeekError = error{};
         pub const GetSeekPosError = error{};
 
+        pub const Reader = io.Reader(*Self, ReadError, read);
+        /// Deprecated: use `Reader`
         pub const InStream = io.InStream(*Self, ReadError, read);
         pub const Writer = io.Writer(*Self, WriteError, write);
         /// Deprecated: use `Writer`
@@ -34,6 +36,11 @@ pub fn FixedBufferStream(comptime Buffer: type) type {
 
         const Self = @This();
 
+        pub fn reader(self: *Self) Reader {
+            return .{ .context = self };
+        }
+
+        /// Deprecated: use `inStream`
         pub fn inStream(self: *Self) InStream {
             return .{ .context = self };
         }
@@ -165,14 +172,14 @@ test "FixedBufferStream input" {
 
     var dest: [4]u8 = undefined;
 
-    var read = try fbs.inStream().read(dest[0..4]);
+    var read = try fbs.reader().read(dest[0..4]);
     testing.expect(read == 4);
     testing.expect(mem.eql(u8, dest[0..4], bytes[0..4]));
 
-    read = try fbs.inStream().read(dest[0..4]);
+    read = try fbs.reader().read(dest[0..4]);
     testing.expect(read == 3);
     testing.expect(mem.eql(u8, dest[0..3], bytes[4..7]));
 
-    read = try fbs.inStream().read(dest[0..4]);
+    read = try fbs.reader().read(dest[0..4]);
     testing.expect(read == 0);
 }
lib/std/io/in_stream.zig
@@ -1,296 +1,2 @@
-const std = @import("../std.zig");
-const builtin = std.builtin;
-const math = std.math;
-const assert = std.debug.assert;
-const mem = std.mem;
-const testing = std.testing;
-
-pub fn InStream(
-    comptime Context: type,
-    comptime ReadError: type,
-    /// Returns the number of bytes read. It may be less than buffer.len.
-    /// If the number of bytes read is 0, it means end of stream.
-    /// End of stream is not an error condition.
-    comptime readFn: fn (context: Context, buffer: []u8) ReadError!usize,
-) type {
-    return struct {
-        pub const Error = ReadError;
-
-        context: Context,
-
-        const Self = @This();
-
-        /// Returns the number of bytes read. It may be less than buffer.len.
-        /// If the number of bytes read is 0, it means end of stream.
-        /// End of stream is not an error condition.
-        pub fn read(self: Self, buffer: []u8) Error!usize {
-            return readFn(self.context, buffer);
-        }
-
-        /// Returns the number of bytes read. If the number read is smaller than `buffer.len`, it
-        /// means the stream reached the end. Reaching the end of a stream is not an error
-        /// condition.
-        pub fn readAll(self: Self, buffer: []u8) Error!usize {
-            var index: usize = 0;
-            while (index != buffer.len) {
-                const amt = try self.read(buffer[index..]);
-                if (amt == 0) return index;
-                index += amt;
-            }
-            return index;
-        }
-
-        /// Returns the number of bytes read. If the number read would be smaller than buf.len,
-        /// error.EndOfStream is returned instead.
-        pub fn readNoEof(self: Self, buf: []u8) !void {
-            const amt_read = try self.readAll(buf);
-            if (amt_read < buf.len) return error.EndOfStream;
-        }
-
-        pub const readAllBuffer = @compileError("deprecated; use readAllArrayList()");
-
-        /// Appends to the `std.ArrayList` contents by reading from the stream until end of stream is found.
-        /// If the number of bytes appended would exceed `max_append_size`, `error.StreamTooLong` is returned
-        /// and the `std.ArrayList` has exactly `max_append_size` bytes appended.
-        pub fn readAllArrayList(self: Self, array_list: *std.ArrayList(u8), max_append_size: usize) !void {
-            try array_list.ensureCapacity(math.min(max_append_size, 4096));
-            const original_len = array_list.items.len;
-            var start_index: usize = original_len;
-            while (true) {
-                array_list.expandToCapacity();
-                const dest_slice = array_list.span()[start_index..];
-                const bytes_read = try self.readAll(dest_slice);
-                start_index += bytes_read;
-
-                if (start_index - original_len > max_append_size) {
-                    array_list.shrink(original_len + max_append_size);
-                    return error.StreamTooLong;
-                }
-
-                if (bytes_read != dest_slice.len) {
-                    array_list.shrink(start_index);
-                    return;
-                }
-
-                // This will trigger ArrayList to expand superlinearly at whatever its growth rate is.
-                try array_list.ensureCapacity(start_index + 1);
-            }
-        }
-
-        /// Allocates enough memory to hold all the contents of the stream. If the allocated
-        /// memory would be greater than `max_size`, returns `error.StreamTooLong`.
-        /// Caller owns returned memory.
-        /// If this function returns an error, the contents from the stream read so far are lost.
-        pub fn readAllAlloc(self: Self, allocator: *mem.Allocator, max_size: usize) ![]u8 {
-            var array_list = std.ArrayList(u8).init(allocator);
-            defer array_list.deinit();
-            try self.readAllArrayList(&array_list, max_size);
-            return array_list.toOwnedSlice();
-        }
-
-        /// Replaces the `std.ArrayList` contents by reading from the stream until `delimiter` is found.
-        /// Does not include the delimiter in the result.
-        /// If the `std.ArrayList` length would exceed `max_size`, `error.StreamTooLong` is returned and the
-        /// `std.ArrayList` is populated with `max_size` bytes from the stream.
-        pub fn readUntilDelimiterArrayList(
-            self: Self,
-            array_list: *std.ArrayList(u8),
-            delimiter: u8,
-            max_size: usize,
-        ) !void {
-            array_list.shrink(0);
-            while (true) {
-                var byte: u8 = try self.readByte();
-
-                if (byte == delimiter) {
-                    return;
-                }
-
-                if (array_list.items.len == max_size) {
-                    return error.StreamTooLong;
-                }
-
-                try array_list.append(byte);
-            }
-        }
-
-        /// Allocates enough memory to read until `delimiter`. If the allocated
-        /// memory would be greater than `max_size`, returns `error.StreamTooLong`.
-        /// Caller owns returned memory.
-        /// If this function returns an error, the contents from the stream read so far are lost.
-        pub fn readUntilDelimiterAlloc(
-            self: Self,
-            allocator: *mem.Allocator,
-            delimiter: u8,
-            max_size: usize,
-        ) ![]u8 {
-            var array_list = std.ArrayList(u8).init(allocator);
-            defer array_list.deinit();
-            try self.readUntilDelimiterArrayList(&array_list, delimiter, max_size);
-            return array_list.toOwnedSlice();
-        }
-
-        /// Reads from the stream until specified byte is found. If the buffer is not
-        /// large enough to hold the entire contents, `error.StreamTooLong` is returned.
-        /// If end-of-stream is found, returns the rest of the stream. If this
-        /// function is called again after that, returns null.
-        /// Returns a slice of the stream data, with ptr equal to `buf.ptr`. The
-        /// delimiter byte is not included in the returned slice.
-        pub fn readUntilDelimiterOrEof(self: Self, buf: []u8, delimiter: u8) !?[]u8 {
-            var index: usize = 0;
-            while (true) {
-                const byte = self.readByte() catch |err| switch (err) {
-                    error.EndOfStream => {
-                        if (index == 0) {
-                            return null;
-                        } else {
-                            return buf[0..index];
-                        }
-                    },
-                    else => |e| return e,
-                };
-
-                if (byte == delimiter) return buf[0..index];
-                if (index >= buf.len) return error.StreamTooLong;
-
-                buf[index] = byte;
-                index += 1;
-            }
-        }
-
-        /// Reads from the stream until specified byte is found, discarding all data,
-        /// including the delimiter.
-        /// If end-of-stream is found, this function succeeds.
-        pub fn skipUntilDelimiterOrEof(self: Self, delimiter: u8) !void {
-            while (true) {
-                const byte = self.readByte() catch |err| switch (err) {
-                    error.EndOfStream => return,
-                    else => |e| return e,
-                };
-                if (byte == delimiter) return;
-            }
-        }
-
-        /// Reads 1 byte from the stream or returns `error.EndOfStream`.
-        pub fn readByte(self: Self) !u8 {
-            var result: [1]u8 = undefined;
-            const amt_read = try self.read(result[0..]);
-            if (amt_read < 1) return error.EndOfStream;
-            return result[0];
-        }
-
-        /// Same as `readByte` except the returned byte is signed.
-        pub fn readByteSigned(self: Self) !i8 {
-            return @bitCast(i8, try self.readByte());
-        }
-
-        /// Reads exactly `num_bytes` bytes and returns as an array.
-        /// `num_bytes` must be comptime-known
-        pub fn readBytesNoEof(self: Self, comptime num_bytes: usize) ![num_bytes]u8 {
-            var bytes: [num_bytes]u8 = undefined;
-            try self.readNoEof(&bytes);
-            return bytes;
-        }
-
-        /// Reads a native-endian integer
-        pub fn readIntNative(self: Self, comptime T: type) !T {
-            const bytes = try self.readBytesNoEof((T.bit_count + 7) / 8);
-            return mem.readIntNative(T, &bytes);
-        }
-
-        /// Reads a foreign-endian integer
-        pub fn readIntForeign(self: Self, comptime T: type) !T {
-            const bytes = try self.readBytesNoEof((T.bit_count + 7) / 8);
-            return mem.readIntForeign(T, &bytes);
-        }
-
-        pub fn readIntLittle(self: Self, comptime T: type) !T {
-            const bytes = try self.readBytesNoEof((T.bit_count + 7) / 8);
-            return mem.readIntLittle(T, &bytes);
-        }
-
-        pub fn readIntBig(self: Self, comptime T: type) !T {
-            const bytes = try self.readBytesNoEof((T.bit_count + 7) / 8);
-            return mem.readIntBig(T, &bytes);
-        }
-
-        pub fn readInt(self: Self, comptime T: type, endian: builtin.Endian) !T {
-            const bytes = try self.readBytesNoEof((T.bit_count + 7) / 8);
-            return mem.readInt(T, &bytes, endian);
-        }
-
-        pub fn readVarInt(self: Self, comptime ReturnType: type, endian: builtin.Endian, size: usize) !ReturnType {
-            assert(size <= @sizeOf(ReturnType));
-            var bytes_buf: [@sizeOf(ReturnType)]u8 = undefined;
-            const bytes = bytes_buf[0..size];
-            try self.readNoEof(bytes);
-            return mem.readVarInt(ReturnType, bytes, endian);
-        }
-
-        pub fn skipBytes(self: Self, num_bytes: u64) !void {
-            var i: u64 = 0;
-            while (i < num_bytes) : (i += 1) {
-                _ = try self.readByte();
-            }
-        }
-
-        /// Reads `slice.len` bytes from the stream and returns if they are the same as the passed slice
-        pub fn isBytes(self: Self, slice: []const u8) !bool {
-            var i: usize = 0;
-            var matches = true;
-            while (i < slice.len) : (i += 1) {
-                if (slice[i] != try self.readByte()) {
-                    matches = false;
-                }
-            }
-            return matches;
-        }
-
-        pub fn readStruct(self: Self, comptime T: type) !T {
-            // Only extern and packed structs have defined in-memory layout.
-            comptime assert(@typeInfo(T).Struct.layout != builtin.TypeInfo.ContainerLayout.Auto);
-            var res: [1]T = undefined;
-            try self.readNoEof(mem.sliceAsBytes(res[0..]));
-            return res[0];
-        }
-
-        /// Reads an integer with the same size as the given enum's tag type. If the integer matches
-        /// an enum tag, casts the integer to the enum tag and returns it. Otherwise, returns an error.
-        /// TODO optimization taking advantage of most fields being in order
-        pub fn readEnum(self: Self, comptime Enum: type, endian: builtin.Endian) !Enum {
-            const E = error{
-                /// An integer was read, but it did not match any of the tags in the supplied enum.
-                InvalidValue,
-            };
-            const type_info = @typeInfo(Enum).Enum;
-            const tag = try self.readInt(type_info.tag_type, endian);
-
-            inline for (std.meta.fields(Enum)) |field| {
-                if (tag == field.value) {
-                    return @field(Enum, field.name);
-                }
-            }
-
-            return E.InvalidValue;
-        }
-    };
-}
-
-test "InStream" {
-    var buf = "a\x02".*;
-    const in_stream = std.io.fixedBufferStream(&buf).inStream();
-    testing.expect((try in_stream.readByte()) == 'a');
-    testing.expect((try in_stream.readEnum(enum(u8) {
-        a = 0,
-        b = 99,
-        c = 2,
-        d = 3,
-    }, undefined)) == .c);
-    testing.expectError(error.EndOfStream, in_stream.readByte());
-}
-
-test "InStream.isBytes" {
-    const in_stream = std.io.fixedBufferStream("foobar").inStream();
-    testing.expectEqual(true, try in_stream.isBytes("foo"));
-    testing.expectEqual(false, try in_stream.isBytes("qux"));
-}
+/// Deprecated: use `std.io.reader.Reader`
+pub const InStream = @import("./reader.zig").Reader;
lib/std/io/peek_stream.zig
@@ -5,24 +5,26 @@ const testing = std.testing;
 
 /// Creates a stream which supports 'un-reading' data, so that it can be read again.
 /// This makes look-ahead style parsing much easier.
-/// TODO merge this with `std.io.BufferedInStream`: https://github.com/ziglang/zig/issues/4501
+/// TODO merge this with `std.io.BufferedReader`: https://github.com/ziglang/zig/issues/4501
 pub fn PeekStream(
     comptime buffer_type: std.fifo.LinearFifoBufferType,
-    comptime InStreamType: type,
+    comptime ReaderType: type,
 ) type {
     return struct {
-        unbuffered_in_stream: InStreamType,
+        unbuffered_in_stream: ReaderType,
         fifo: FifoType,
 
-        pub const Error = InStreamType.Error;
-        pub const InStream = io.InStream(*Self, Error, read);
+        pub const Error = ReaderType.Error;
+        pub const Reader = io.Reader(*Self, Error, read);
+        /// Deprecated: use `Reader`
+        pub const InStream = Reader;
 
         const Self = @This();
         const FifoType = std.fifo.LinearFifo(u8, buffer_type);
 
         pub usingnamespace switch (buffer_type) {
             .Static => struct {
-                pub fn init(base: InStreamType) Self {
+                pub fn init(base: ReaderType) Self {
                     return .{
                         .unbuffered_in_stream = base,
                         .fifo = FifoType.init(),
@@ -30,7 +32,7 @@ pub fn PeekStream(
                 }
             },
             .Slice => struct {
-                pub fn init(base: InStreamType, buf: []u8) Self {
+                pub fn init(base: ReaderType, buf: []u8) Self {
                     return .{
                         .unbuffered_in_stream = base,
                         .fifo = FifoType.init(buf),
@@ -38,7 +40,7 @@ pub fn PeekStream(
                 }
             },
             .Dynamic => struct {
-                pub fn init(base: InStreamType, allocator: *mem.Allocator) Self {
+                pub fn init(base: ReaderType, allocator: *mem.Allocator) Self {
                     return .{
                         .unbuffered_in_stream = base,
                         .fifo = FifoType.init(allocator),
@@ -65,6 +67,11 @@ pub fn PeekStream(
             return dest_index;
         }
 
+        pub fn reader(self: *Self) Reader {
+            return .{ .context = self };
+        }
+
+        /// Deprecated: use `reader`
         pub fn inStream(self: *Self) InStream {
             return .{ .context = self };
         }
@@ -81,31 +88,31 @@ pub fn peekStream(
 test "PeekStream" {
     const bytes = [_]u8{ 1, 2, 3, 4, 5, 6, 7, 8 };
     var fbs = io.fixedBufferStream(&bytes);
-    var ps = peekStream(2, fbs.inStream());
+    var ps = peekStream(2, fbs.reader());
 
     var dest: [4]u8 = undefined;
 
     try ps.putBackByte(9);
     try ps.putBackByte(10);
 
-    var read = try ps.inStream().read(dest[0..4]);
+    var read = try ps.reader().read(dest[0..4]);
     testing.expect(read == 4);
     testing.expect(dest[0] == 10);
     testing.expect(dest[1] == 9);
     testing.expect(mem.eql(u8, dest[2..4], bytes[0..2]));
 
-    read = try ps.inStream().read(dest[0..4]);
+    read = try ps.reader().read(dest[0..4]);
     testing.expect(read == 4);
     testing.expect(mem.eql(u8, dest[0..4], bytes[2..6]));
 
-    read = try ps.inStream().read(dest[0..4]);
+    read = try ps.reader().read(dest[0..4]);
     testing.expect(read == 2);
     testing.expect(mem.eql(u8, dest[0..2], bytes[6..8]));
 
     try ps.putBackByte(11);
     try ps.putBackByte(12);
 
-    read = try ps.inStream().read(dest[0..4]);
+    read = try ps.reader().read(dest[0..4]);
     testing.expect(read == 2);
     testing.expect(dest[0] == 12);
     testing.expect(dest[1] == 11);
lib/std/io/reader.zig
@@ -0,0 +1,296 @@
+const std = @import("../std.zig");
+const builtin = std.builtin;
+const math = std.math;
+const assert = std.debug.assert;
+const mem = std.mem;
+const testing = std.testing;
+
+pub fn Reader(
+    comptime Context: type,
+    comptime ReadError: type,
+    /// Returns the number of bytes read. It may be less than buffer.len.
+    /// If the number of bytes read is 0, it means end of stream.
+    /// End of stream is not an error condition.
+    comptime readFn: fn (context: Context, buffer: []u8) ReadError!usize,
+) type {
+    return struct {
+        pub const Error = ReadError;
+
+        context: Context,
+
+        const Self = @This();
+
+        /// Returns the number of bytes read. It may be less than buffer.len.
+        /// If the number of bytes read is 0, it means end of stream.
+        /// End of stream is not an error condition.
+        pub fn read(self: Self, buffer: []u8) Error!usize {
+            return readFn(self.context, buffer);
+        }
+
+        /// Returns the number of bytes read. If the number read is smaller than `buffer.len`, it
+        /// means the stream reached the end. Reaching the end of a stream is not an error
+        /// condition.
+        pub fn readAll(self: Self, buffer: []u8) Error!usize {
+            var index: usize = 0;
+            while (index != buffer.len) {
+                const amt = try self.read(buffer[index..]);
+                if (amt == 0) return index;
+                index += amt;
+            }
+            return index;
+        }
+
+        /// Returns the number of bytes read. If the number read would be smaller than buf.len,
+        /// error.EndOfStream is returned instead.
+        pub fn readNoEof(self: Self, buf: []u8) !void {
+            const amt_read = try self.readAll(buf);
+            if (amt_read < buf.len) return error.EndOfStream;
+        }
+
+        pub const readAllBuffer = @compileError("deprecated; use readAllArrayList()");
+
+        /// Appends to the `std.ArrayList` contents by reading from the stream until end of stream is found.
+        /// If the number of bytes appended would exceed `max_append_size`, `error.StreamTooLong` is returned
+        /// and the `std.ArrayList` has exactly `max_append_size` bytes appended.
+        pub fn readAllArrayList(self: Self, array_list: *std.ArrayList(u8), max_append_size: usize) !void {
+            try array_list.ensureCapacity(math.min(max_append_size, 4096));
+            const original_len = array_list.items.len;
+            var start_index: usize = original_len;
+            while (true) {
+                array_list.expandToCapacity();
+                const dest_slice = array_list.span()[start_index..];
+                const bytes_read = try self.readAll(dest_slice);
+                start_index += bytes_read;
+
+                if (start_index - original_len > max_append_size) {
+                    array_list.shrink(original_len + max_append_size);
+                    return error.StreamTooLong;
+                }
+
+                if (bytes_read != dest_slice.len) {
+                    array_list.shrink(start_index);
+                    return;
+                }
+
+                // This will trigger ArrayList to expand superlinearly at whatever its growth rate is.
+                try array_list.ensureCapacity(start_index + 1);
+            }
+        }
+
+        /// Allocates enough memory to hold all the contents of the stream. If the allocated
+        /// memory would be greater than `max_size`, returns `error.StreamTooLong`.
+        /// Caller owns returned memory.
+        /// If this function returns an error, the contents from the stream read so far are lost.
+        pub fn readAllAlloc(self: Self, allocator: *mem.Allocator, max_size: usize) ![]u8 {
+            var array_list = std.ArrayList(u8).init(allocator);
+            defer array_list.deinit();
+            try self.readAllArrayList(&array_list, max_size);
+            return array_list.toOwnedSlice();
+        }
+
+        /// Replaces the `std.ArrayList` contents by reading from the stream until `delimiter` is found.
+        /// Does not include the delimiter in the result.
+        /// If the `std.ArrayList` length would exceed `max_size`, `error.StreamTooLong` is returned and the
+        /// `std.ArrayList` is populated with `max_size` bytes from the stream.
+        pub fn readUntilDelimiterArrayList(
+            self: Self,
+            array_list: *std.ArrayList(u8),
+            delimiter: u8,
+            max_size: usize,
+        ) !void {
+            array_list.shrink(0);
+            while (true) {
+                var byte: u8 = try self.readByte();
+
+                if (byte == delimiter) {
+                    return;
+                }
+
+                if (array_list.items.len == max_size) {
+                    return error.StreamTooLong;
+                }
+
+                try array_list.append(byte);
+            }
+        }
+
+        /// Allocates enough memory to read until `delimiter`. If the allocated
+        /// memory would be greater than `max_size`, returns `error.StreamTooLong`.
+        /// Caller owns returned memory.
+        /// If this function returns an error, the contents from the stream read so far are lost.
+        pub fn readUntilDelimiterAlloc(
+            self: Self,
+            allocator: *mem.Allocator,
+            delimiter: u8,
+            max_size: usize,
+        ) ![]u8 {
+            var array_list = std.ArrayList(u8).init(allocator);
+            defer array_list.deinit();
+            try self.readUntilDelimiterArrayList(&array_list, delimiter, max_size);
+            return array_list.toOwnedSlice();
+        }
+
+        /// Reads from the stream until specified byte is found. If the buffer is not
+        /// large enough to hold the entire contents, `error.StreamTooLong` is returned.
+        /// If end-of-stream is found, returns the rest of the stream. If this
+        /// function is called again after that, returns null.
+        /// Returns a slice of the stream data, with ptr equal to `buf.ptr`. The
+        /// delimiter byte is not included in the returned slice.
+        pub fn readUntilDelimiterOrEof(self: Self, buf: []u8, delimiter: u8) !?[]u8 {
+            var index: usize = 0;
+            while (true) {
+                const byte = self.readByte() catch |err| switch (err) {
+                    error.EndOfStream => {
+                        if (index == 0) {
+                            return null;
+                        } else {
+                            return buf[0..index];
+                        }
+                    },
+                    else => |e| return e,
+                };
+
+                if (byte == delimiter) return buf[0..index];
+                if (index >= buf.len) return error.StreamTooLong;
+
+                buf[index] = byte;
+                index += 1;
+            }
+        }
+
+        /// Reads from the stream until specified byte is found, discarding all data,
+        /// including the delimiter.
+        /// If end-of-stream is found, this function succeeds.
+        pub fn skipUntilDelimiterOrEof(self: Self, delimiter: u8) !void {
+            while (true) {
+                const byte = self.readByte() catch |err| switch (err) {
+                    error.EndOfStream => return,
+                    else => |e| return e,
+                };
+                if (byte == delimiter) return;
+            }
+        }
+
+        /// Reads 1 byte from the stream or returns `error.EndOfStream`.
+        pub fn readByte(self: Self) !u8 {
+            var result: [1]u8 = undefined;
+            const amt_read = try self.read(result[0..]);
+            if (amt_read < 1) return error.EndOfStream;
+            return result[0];
+        }
+
+        /// Same as `readByte` except the returned byte is signed.
+        pub fn readByteSigned(self: Self) !i8 {
+            return @bitCast(i8, try self.readByte());
+        }
+
+        /// Reads exactly `num_bytes` bytes and returns as an array.
+        /// `num_bytes` must be comptime-known
+        pub fn readBytesNoEof(self: Self, comptime num_bytes: usize) ![num_bytes]u8 {
+            var bytes: [num_bytes]u8 = undefined;
+            try self.readNoEof(&bytes);
+            return bytes;
+        }
+
+        /// Reads a native-endian integer
+        pub fn readIntNative(self: Self, comptime T: type) !T {
+            const bytes = try self.readBytesNoEof((T.bit_count + 7) / 8);
+            return mem.readIntNative(T, &bytes);
+        }
+
+        /// Reads a foreign-endian integer
+        pub fn readIntForeign(self: Self, comptime T: type) !T {
+            const bytes = try self.readBytesNoEof((T.bit_count + 7) / 8);
+            return mem.readIntForeign(T, &bytes);
+        }
+
+        pub fn readIntLittle(self: Self, comptime T: type) !T {
+            const bytes = try self.readBytesNoEof((T.bit_count + 7) / 8);
+            return mem.readIntLittle(T, &bytes);
+        }
+
+        pub fn readIntBig(self: Self, comptime T: type) !T {
+            const bytes = try self.readBytesNoEof((T.bit_count + 7) / 8);
+            return mem.readIntBig(T, &bytes);
+        }
+
+        pub fn readInt(self: Self, comptime T: type, endian: builtin.Endian) !T {
+            const bytes = try self.readBytesNoEof((T.bit_count + 7) / 8);
+            return mem.readInt(T, &bytes, endian);
+        }
+
+        pub fn readVarInt(self: Self, comptime ReturnType: type, endian: builtin.Endian, size: usize) !ReturnType {
+            assert(size <= @sizeOf(ReturnType));
+            var bytes_buf: [@sizeOf(ReturnType)]u8 = undefined;
+            const bytes = bytes_buf[0..size];
+            try self.readNoEof(bytes);
+            return mem.readVarInt(ReturnType, bytes, endian);
+        }
+
+        pub fn skipBytes(self: Self, num_bytes: u64) !void {
+            var i: u64 = 0;
+            while (i < num_bytes) : (i += 1) {
+                _ = try self.readByte();
+            }
+        }
+
+        /// Reads `slice.len` bytes from the stream and returns if they are the same as the passed slice
+        pub fn isBytes(self: Self, slice: []const u8) !bool {
+            var i: usize = 0;
+            var matches = true;
+            while (i < slice.len) : (i += 1) {
+                if (slice[i] != try self.readByte()) {
+                    matches = false;
+                }
+            }
+            return matches;
+        }
+
+        pub fn readStruct(self: Self, comptime T: type) !T {
+            // Only extern and packed structs have defined in-memory layout.
+            comptime assert(@typeInfo(T).Struct.layout != builtin.TypeInfo.ContainerLayout.Auto);
+            var res: [1]T = undefined;
+            try self.readNoEof(mem.sliceAsBytes(res[0..]));
+            return res[0];
+        }
+
+        /// Reads an integer with the same size as the given enum's tag type. If the integer matches
+        /// an enum tag, casts the integer to the enum tag and returns it. Otherwise, returns an error.
+        /// TODO optimization taking advantage of most fields being in order
+        pub fn readEnum(self: Self, comptime Enum: type, endian: builtin.Endian) !Enum {
+            const E = error{
+                /// An integer was read, but it did not match any of the tags in the supplied enum.
+                InvalidValue,
+            };
+            const type_info = @typeInfo(Enum).Enum;
+            const tag = try self.readInt(type_info.tag_type, endian);
+
+            inline for (std.meta.fields(Enum)) |field| {
+                if (tag == field.value) {
+                    return @field(Enum, field.name);
+                }
+            }
+
+            return E.InvalidValue;
+        }
+    };
+}
+
+test "Reader" {
+    var buf = "a\x02".*;
+    const reader = std.io.fixedBufferStream(&buf).reader();
+    testing.expect((try reader.readByte()) == 'a');
+    testing.expect((try reader.readEnum(enum(u8) {
+        a = 0,
+        b = 99,
+        c = 2,
+        d = 3,
+    }, undefined)) == .c);
+    testing.expectError(error.EndOfStream, reader.readByte());
+}
+
+test "Reader.isBytes" {
+    const reader = std.io.fixedBufferStream("foobar").reader();
+    testing.expectEqual(true, try reader.isBytes("foo"));
+    testing.expectEqual(false, try reader.isBytes("qux"));
+}
lib/std/io/seekable_stream.zig
@@ -1,5 +1,4 @@
 const std = @import("../std.zig");
-const InStream = std.io.InStream;
 
 pub fn SeekableStream(
     comptime Context: type,
lib/std/io/serialization.zig
@@ -24,16 +24,16 @@ pub const Packing = enum {
 ///  which will be called when the deserializer is used to deserialize
 ///  that type. It will pass a pointer to the type instance to deserialize
 ///  into and a pointer to the deserializer struct.
-pub fn Deserializer(comptime endian: builtin.Endian, comptime packing: Packing, comptime InStreamType: type) type {
+pub fn Deserializer(comptime endian: builtin.Endian, comptime packing: Packing, comptime ReaderType: type) type {
     return struct {
-        in_stream: if (packing == .Bit) io.BitInStream(endian, InStreamType) else InStreamType,
+        in_stream: if (packing == .Bit) io.BitReader(endian, ReaderType) else ReaderType,
 
         const Self = @This();
 
-        pub fn init(in_stream: InStreamType) Self {
+        pub fn init(in_stream: ReaderType) Self {
             return Self{
                 .in_stream = switch (packing) {
-                    .Bit => io.bitInStream(endian, in_stream),
+                    .Bit => io.bitReader(endian, in_stream),
                     .Byte => in_stream,
                 },
             };
@@ -45,7 +45,7 @@ pub fn Deserializer(comptime endian: builtin.Endian, comptime packing: Packing,
         }
 
         //@BUG: inferred error issue. See: #1386
-        fn deserializeInt(self: *Self, comptime T: type) (InStreamType.Error || error{EndOfStream})!T {
+        fn deserializeInt(self: *Self, comptime T: type) (ReaderType.Error || error{EndOfStream})!T {
             comptime assert(trait.is(.Int)(T) or trait.is(.Float)(T));
 
             const u8_bit_count = 8;
@@ -368,7 +368,7 @@ fn testIntSerializerDeserializer(comptime endian: builtin.Endian, comptime packi
     var _serializer = serializer(endian, packing, out.outStream());
 
     var in = io.fixedBufferStream(&data_mem);
-    var _deserializer = deserializer(endian, packing, in.inStream());
+    var _deserializer = deserializer(endian, packing, in.reader());
 
     comptime var i = 0;
     inline while (i <= max_test_bitsize) : (i += 1) {
@@ -425,7 +425,7 @@ fn testIntSerializerDeserializerInfNaN(
     var _serializer = serializer(endian, packing, out.outStream());
 
     var in = io.fixedBufferStream(&data_mem);
-    var _deserializer = deserializer(endian, packing, in.inStream());
+    var _deserializer = deserializer(endian, packing, in.reader());
 
     //@TODO: isInf/isNan not currently implemented for f128.
     try _serializer.serialize(std.math.nan(f16));
@@ -554,7 +554,7 @@ fn testSerializerDeserializer(comptime endian: builtin.Endian, comptime packing:
     var _serializer = serializer(endian, packing, out.outStream());
 
     var in = io.fixedBufferStream(&data_mem);
-    var _deserializer = deserializer(endian, packing, in.inStream());
+    var _deserializer = deserializer(endian, packing, in.reader());
 
     try _serializer.serialize(my_inst);
 
@@ -589,7 +589,7 @@ fn testBadData(comptime endian: builtin.Endian, comptime packing: io.Packing) !v
     var _serializer = serializer(endian, packing, out.outStream());
 
     var in = io.fixedBufferStream(&data_mem);
-    var _deserializer = deserializer(endian, packing, in.inStream());
+    var _deserializer = deserializer(endian, packing, in.reader());
 
     try _serializer.serialize(@as(u14, 3));
     testing.expectError(error.InvalidEnumTag, _deserializer.deserialize(A));
lib/std/io/stream_source.zig
@@ -2,7 +2,7 @@ const std = @import("../std.zig");
 const io = std.io;
 const testing = std.testing;
 
-/// Provides `io.InStream`, `io.OutStream`, and `io.SeekableStream` for in-memory buffers as
+/// Provides `io.Reader`, `io.Writer`, and `io.SeekableStream` for in-memory buffers as
 /// well as files.
 /// For memory sources, if the supplied byte buffer is const, then `io.OutStream` is not available.
 /// The error set of the stream functions is the error set of the corresponding file functions.
@@ -16,8 +16,12 @@ pub const StreamSource = union(enum) {
     pub const SeekError = std.fs.File.SeekError;
     pub const GetSeekPosError = std.fs.File.GetPosError;
 
-    pub const InStream = io.InStream(*StreamSource, ReadError, read);
-    pub const OutStream = io.OutStream(*StreamSource, WriteError, write);
+    pub const Reader = io.Reader(*StreamSource, ReadError, read);
+    /// Deprecated: use `Reader`
+    pub const InStream = Reader;
+    pub const Writer = io.Writer(*StreamSource, WriteError, write);
+    /// Deprecated: use `Writer`
+    pub const OutStream = Writer;
     pub const SeekableStream = io.SeekableStream(
         *StreamSource,
         SeekError,
@@ -76,10 +80,20 @@ pub const StreamSource = union(enum) {
         }
     }
 
+    pub fn reader(self: *StreamSource) Reader {
+        return .{ .context = self };
+    }
+
+    /// Deprecated: use `reader`
     pub fn inStream(self: *StreamSource) InStream {
         return .{ .context = self };
     }
 
+    pub fn writer(self: *StreamSource) Writer {
+        return .{ .context = self };
+    }
+
+    /// Deprecated: use `writer`
     pub fn outStream(self: *StreamSource) OutStream {
         return .{ .context = self };
     }
lib/std/io/test.zig
@@ -50,8 +50,8 @@ test "write a file, read it, then delete it" {
         const expected_file_size: u64 = "begin".len + data.len + "end".len;
         expectEqual(expected_file_size, file_size);
 
-        var buf_stream = io.bufferedInStream(file.inStream());
-        const st = buf_stream.inStream();
+        var buf_stream = io.bufferedReader(file.reader());
+        const st = buf_stream.reader();
         const contents = try st.readAllAlloc(std.testing.allocator, 2 * 1024);
         defer std.testing.allocator.free(contents);
 
@@ -85,7 +85,7 @@ test "BitStreams with File Stream" {
         var file = try tmp.dir.openFile(tmp_file_name, .{});
         defer file.close();
 
-        var bit_stream = io.bitInStream(builtin.endian, file.inStream());
+        var bit_stream = io.bitReader(builtin.endian, file.reader());
 
         var out_bits: usize = undefined;
 
lib/std/elf.zig
@@ -5,7 +5,6 @@ const os = std.os;
 const math = std.math;
 const mem = std.mem;
 const debug = std.debug;
-const InStream = std.stream.InStream;
 const File = std.fs.File;
 
 pub const AT_NULL = 0;
lib/std/fifo.zig
@@ -216,11 +216,15 @@ pub fn LinearFifo(
         }
 
         /// Same as `read` except it returns an error union
-        /// The purpose of this function existing is to match `std.io.InStream` API.
+        /// The purpose of this function existing is to match `std.io.Reader` API.
         fn readFn(self: *Self, dest: []u8) error{}!usize {
             return self.read(dest);
         }
 
+        pub fn reader(self: *Self) std.io.Reader(*Self, error{}, readFn) {
+            return .{ .context = self };
+        }
+        /// Deprecated: `use reader`
         pub fn inStream(self: *Self) std.io.InStream(*Self, error{}, readFn) {
             return .{ .context = self };
         }
@@ -431,10 +435,10 @@ test "LinearFifo(u8, .Dynamic)" {
     {
         try fifo.outStream().writeAll("This is a test");
         var result: [30]u8 = undefined;
-        testing.expectEqualSlices(u8, "This", (try fifo.inStream().readUntilDelimiterOrEof(&result, ' ')).?);
-        testing.expectEqualSlices(u8, "is", (try fifo.inStream().readUntilDelimiterOrEof(&result, ' ')).?);
-        testing.expectEqualSlices(u8, "a", (try fifo.inStream().readUntilDelimiterOrEof(&result, ' ')).?);
-        testing.expectEqualSlices(u8, "test", (try fifo.inStream().readUntilDelimiterOrEof(&result, ' ')).?);
+        testing.expectEqualSlices(u8, "This", (try fifo.reader().readUntilDelimiterOrEof(&result, ' ')).?);
+        testing.expectEqualSlices(u8, "is", (try fifo.reader().readUntilDelimiterOrEof(&result, ' ')).?);
+        testing.expectEqualSlices(u8, "a", (try fifo.reader().readUntilDelimiterOrEof(&result, ' ')).?);
+        testing.expectEqualSlices(u8, "test", (try fifo.reader().readUntilDelimiterOrEof(&result, ' ')).?);
     }
 }
 
lib/std/io.zig
@@ -101,7 +101,9 @@ pub fn getStdIn() File {
     };
 }
 
-pub const InStream = @import("io/in_stream.zig").InStream;
+pub const Reader = @import("io/reader.zig").Reader;
+/// Deprecated: use `Reader`
+pub const InStream = Reader;
 pub const Writer = @import("io/writer.zig").Writer;
 /// Deprecated: use `Writer`
 pub const OutStream = Writer;
@@ -114,8 +116,12 @@ pub const BufferedOutStream = BufferedWriter;
 /// Deprecated: use `bufferedWriter`
 pub const bufferedOutStream = bufferedWriter;
 
-pub const BufferedInStream = @import("io/buffered_in_stream.zig").BufferedInStream;
-pub const bufferedInStream = @import("io/buffered_in_stream.zig").bufferedInStream;
+pub const BufferedReader = @import("io/buffered_reader.zig").BufferedReader;
+pub const bufferedReader = @import("io/buffered_reader.zig").bufferedReader;
+/// Deprecated: use `BufferedReader`
+pub const BufferedInStream = BufferedReader;
+/// Deprecated: use `bufferedReader`
+pub const bufferedInStream = bufferedReader;
 
 pub const PeekStream = @import("io/peek_stream.zig").PeekStream;
 pub const peekStream = @import("io/peek_stream.zig").peekStream;
@@ -144,8 +150,12 @@ pub const MultiOutStream = MultiWriter;
 /// Deprecated: use `multiWriter`
 pub const multiOutStream = multiWriter;
 
-pub const BitInStream = @import("io/bit_in_stream.zig").BitInStream;
-pub const bitInStream = @import("io/bit_in_stream.zig").bitInStream;
+pub const BitReader = @import("io/bit_reader.zig").BitReader;
+pub const bitReader = @import("io/bit_reader.zig").bitReader;
+/// Deprecated: use `BitReader`
+pub const BitInStream = BitReader;
+/// Deprecated: use `bitReader`
+pub const bitInStream = bitReader;
 
 pub const BitWriter = @import("io/bit_writer.zig").BitWriter;
 pub const bitWriter = @import("io/bit_writer.zig").bitWriter;
@@ -184,15 +194,15 @@ test "null_writer" {
 }
 
 test "" {
-    _ = @import("io/bit_in_stream.zig");
+    _ = @import("io/bit_reader.zig");
     _ = @import("io/bit_writer.zig");
     _ = @import("io/buffered_atomic_file.zig");
-    _ = @import("io/buffered_in_stream.zig");
+    _ = @import("io/buffered_reader.zig");
     _ = @import("io/buffered_writer.zig");
     _ = @import("io/c_writer.zig");
     _ = @import("io/counting_writer.zig");
     _ = @import("io/fixed_buffer_stream.zig");
-    _ = @import("io/in_stream.zig");
+    _ = @import("io/reader.zig");
     _ = @import("io/writer.zig");
     _ = @import("io/peek_stream.zig");
     _ = @import("io/seekable_stream.zig");
lib/std/pdb.zig
@@ -495,7 +495,7 @@ const Msf = struct {
     streams: []MsfStream,
 
     fn openFile(self: *Msf, allocator: *mem.Allocator, file: File) !void {
-        const in = file.inStream();
+        const in = file.reader();
 
         const superblock = try in.readStruct(SuperBlock);
 
@@ -528,7 +528,7 @@ const Msf = struct {
         );
 
         const begin = self.directory.pos;
-        const stream_count = try self.directory.inStream().readIntLittle(u32);
+        const stream_count = try self.directory.reader().readIntLittle(u32);
         const stream_sizes = try allocator.alloc(u32, stream_count);
         defer allocator.free(stream_sizes);
 
@@ -537,7 +537,7 @@ const Msf = struct {
         // and must be taken into account when resolving stream indices.
         const Nil = 0xFFFFFFFF;
         for (stream_sizes) |*s, i| {
-            const size = try self.directory.inStream().readIntLittle(u32);
+            const size = try self.directory.reader().readIntLittle(u32);
             s.* = if (size == Nil) 0 else blockCountFromSize(size, superblock.BlockSize);
         }
 
@@ -552,7 +552,7 @@ const Msf = struct {
                 var blocks = try allocator.alloc(u32, size);
                 var j: u32 = 0;
                 while (j < size) : (j += 1) {
-                    const block_id = try self.directory.inStream().readIntLittle(u32);
+                    const block_id = try self.directory.reader().readIntLittle(u32);
                     const n = (block_id % superblock.BlockSize);
                     // 0 is for SuperBlock, 1 and 2 for FPMs.
                     if (block_id == 0 or n == 1 or n == 2 or block_id * superblock.BlockSize > try file.getEndPos())
@@ -647,7 +647,7 @@ const MsfStream = struct {
     pub fn readNullTermString(self: *MsfStream, allocator: *mem.Allocator) ![]u8 {
         var list = ArrayList(u8).init(allocator);
         while (true) {
-            const byte = try self.inStream().readByte();
+            const byte = try self.reader().readByte();
             if (byte == 0) {
                 return list.span();
             }
@@ -661,7 +661,7 @@ const MsfStream = struct {
         var offset = self.pos % self.block_size;
 
         try self.in_file.seekTo(block * self.block_size + offset);
-        const in = self.in_file.inStream();
+        const in = self.in_file.reader();
 
         var size: usize = 0;
         var rem_buffer = buffer;
@@ -708,6 +708,10 @@ const MsfStream = struct {
         return block * self.block_size + offset;
     }
 
+    pub fn reader(self: *MsfStream) std.io.Reader(*MsfStream, Error, read) {
+        return .{ .context = self };
+    }
+    /// Deprecated: use `reader`
     pub fn inStream(self: *MsfStream) std.io.InStream(*MsfStream, Error, read) {
         return .{ .context = self };
     }
lib/std/process.zig
@@ -615,8 +615,8 @@ pub fn getUserInfo(name: []const u8) !UserInfo {
 /// TODO this reads /etc/passwd. But sometimes the user/id mapping is in something else
 /// like NIS, AD, etc. See `man nss` or look at an strace for `id myuser`.
 pub fn posixGetUserInfo(name: []const u8) !UserInfo {
-    var in_stream = try io.InStream.open("/etc/passwd", null);
-    defer in_stream.close();
+    var reader = try io.Reader.open("/etc/passwd", null);
+    defer reader.close();
 
     const State = enum {
         Start,
@@ -633,7 +633,7 @@ pub fn posixGetUserInfo(name: []const u8) !UserInfo {
     var gid: u32 = 0;
 
     while (true) {
-        const amt_read = try in_stream.read(buf[0..]);
+        const amt_read = try reader.read(buf[0..]);
         for (buf[0..amt_read]) |byte| {
             switch (state) {
                 .Start => switch (byte) {