Commit 1657bead46
lib/std/fifo.zig
@@ -0,0 +1,318 @@
+// FIFO of fixed size items
+// Usually used for e.g. byte buffers
+
+const std = @import("std");
+const math = std.math;
+const mem = std.mem;
+const Allocator = mem.Allocator;
+const debug = std.debug;
+const assert = debug.assert;
+const testing = std.testing;
+
+pub fn FixedSizeFifo(comptime T: type) type {
+ return struct {
+ allocator: *Allocator,
+ buf: []u8,
+ head: usize,
+ count: usize,
+
+ const Self = @This();
+
+ pub fn init(allocator: *Allocator) Self {
+ return Self{
+ .allocator = allocator,
+ .buf = [_]T{},
+ .head = 0,
+ .count = 0,
+ };
+ }
+
+ pub fn deinit(self: *Self) void {
+ self.allocator.free(self.buf);
+ self.* = undefined;
+ }
+
+ pub fn realign(self: *Self) void {
+ if (self.buf.len - self.head >= self.count) {
+ // this copy overlaps
+ mem.copy(T, self.buf[0..self.count], self.buf[self.head..][0..self.count]);
+ self.head = 0;
+ } else {
+ var tmp: [mem.page_size / 2 / @sizeOf(T)]T = undefined;
+
+ while (self.head != 0) {
+ const n = math.min(self.head, tmp.len);
+ const m = self.buf.len - n;
+ mem.copy(T, tmp[0..n], self.buf[0..n]);
+ // this middle copy overlaps; the others here don't
+ mem.copy(T, self.buf[0..m], self.buf[n..][0..m]);
+ mem.copy(T, self.buf[m..], tmp[0..n]);
+ self.head -= n;
+ }
+ }
+ { // set unused area to undefined
+ const unused = @sliceToBytes(self.buf[self.count..]);
+ @memset(unused.ptr, undefined, unused.len);
+ }
+ }
+
+ /// Reduce allocated capacity to `size`.
+ pub fn shrink(self: *Self, size: usize) void {
+ assert(size >= self.count);
+ self.realign();
+ self.buf = self.allocator.realloc(self.buf, size) catch |e| switch (e) {
+ error.OutOfMemory => return, // no problem, capacity is still correct then.
+ };
+ }
+
+ /// Ensure that the buffer can fit at least `size` items
+ pub fn ensureCapacity(self: *Self, size: usize) error{OutOfMemory}!void {
+ if (self.buf.len >= size) return;
+ self.realign();
+ const new_size = math.ceilPowerOfTwo(usize, size) catch return error.OutOfMemory;
+ self.buf = try self.allocator.realloc(self.buf, new_size);
+ }
+
+ /// Makes sure at least `size` items are unused
+ pub fn ensureUnusedCapacity(self: *Self, size: usize) error{OutOfMemory}!void {
+ if (self.writableLength() >= size) return;
+
+ return try self.ensureCapacity(math.add(usize, self.count, size) catch return error.OutOfMemory);
+ }
+
+ /// Returns number of items currently in fifo
+ pub fn readableLength(self: Self) usize {
+ return self.count;
+ }
+
+ /// Returns a writable slice from the 'read' end of the fifo
+ fn readableSliceMut(self: Self, offset: usize) []T {
+ if (offset > self.count) return [_]T{};
+
+ const start = self.head + offset;
+ if (start >= self.buf.len) {
+ return self.buf[start - self.buf.len ..][0 .. self.count - offset];
+ } else {
+ const end: usize = self.head + self.count;
+ if (end >= self.buf.len) {
+ return self.buf[start..self.buf.len];
+ } else {
+ return self.buf[start..end];
+ }
+ }
+ }
+
+ /// Returns a readable slice from `offset`
+ pub fn readableSlice(self: Self, offset: usize) []const T {
+ return self.readableSliceMut(offset);
+ }
+
+ const autoalign = false;
+
+ /// Discard first `count` bytes of readable data
+ pub fn discard(self: *Self, count: usize) void {
+ assert(count <= self.count);
+ { // set old range to undefined. Note: may be wrapped around
+ const slice = self.readableSliceMut(0);
+ if (slice.len >= count) {
+ const unused = @sliceToBytes(slice[0..count]);
+ @memset(unused.ptr, undefined, unused.len);
+ } else {
+ const unused = @sliceToBytes(slice[0..]);
+ @memset(unused.ptr, undefined, unused.len);
+ const unused2 = @sliceToBytes(self.readableSliceMut(slice.len)[0 .. count - slice.len]);
+ @memset(unused2.ptr, undefined, unused2.len);
+ }
+ }
+ self.head = (self.head + count) % self.buf.len;
+ self.count -= count;
+ if (autoalign and self.count == 0)
+ self.head = 0;
+ }
+
+ /// Read the next item from the fifo
+ pub fn readItem(self: *Self) !T {
+ if (self.count == 0) return error.EndOfStream;
+
+ const c = self.buf[self.head];
+ self.discard(1);
+ return c;
+ }
+
+ /// Read data from the fifo into `dst`, returns slice of bytes copied (subslice of `dst`)
+ pub fn read(self: *Self, dst: []T) []T {
+ var dst_left = dst;
+
+ while (dst_left.len > 0) {
+ const slice = self.readableSlice(0);
+ if (slice.len == 0) break;
+ const n = math.min(slice.len, dst_left.len);
+ mem.copy(T, dst_left, slice[0..n]);
+ self.discard(n);
+ dst_left = dst_left[n..];
+ }
+
+ return dst[0 .. dst.len - dst_left.len];
+ }
+
+ /// Returns number of bytes available in fifo
+ pub fn writableLength(self: Self) usize {
+ return self.buf.len - self.count;
+ }
+
+ /// Returns the first section of writable buffer
+ /// Note that this may be of length 0
+ pub fn writableSlice(self: Self, offset: usize) []T {
+ if (offset > self.buf.len) return [_]T{};
+
+ const tail = self.head + offset + self.count;
+ if (tail < self.buf.len) {
+ return self.buf[tail..];
+ } else {
+ return self.buf[tail - self.buf.len ..][0 .. self.writableLength() - offset];
+ }
+ }
+
+ /// Returns a writable buffer of at least `size` bytes, allocating memory as needed.
+ /// Use `fifo.update` once you've written data to it.
+ pub fn writeableWithSize(self: *Self, size: usize) ![]T {
+ try self.ensureUnusedCapacity(size);
+
+ // try to avoid realigning buffer
+ var slice = self.writableSlice(0);
+ if (slice.len < size) {
+ self.realign();
+ slice = self.writableSlice(0);
+ }
+ return slice;
+ }
+
+ /// Update the tail location of the buffer (usually follows use of writable/writeableWithSize)
+ pub fn update(self: *Self, count: usize) void {
+ assert(self.count + count <= self.buf.len);
+ self.count += count;
+ }
+
+ /// Appends the data in `src` to the fifo. You must
+ pub fn writeAssumeCapacity(self: *Self, src: []const T) void {
+ assert(self.writableLength() >= src.len);
+
+ var src_left = src;
+ while (src_left.len > 0) {
+ const writable_slice = self.writableSlice(0);
+ assert(writable_slice.len != 0);
+ const n = math.min(writable_slice.len, src_left.len);
+ mem.copy(T, writable_slice, src_left[0..n]);
+ self.update(n);
+ src_left = src_left[n..];
+ }
+ }
+
+ /// Appends the data in `src` to the fifo.
+ /// Allocates more memory as necessary
+ pub fn write(self: *Self, src: []const T) !void {
+ try self.ensureUnusedCapacity(src.len);
+
+ return self.writeAssumeCapacity(src);
+ }
+
+ pub fn print(self: *Self, comptime format: []const u8, args: ...) !void {
+ return std.fmt.format(self, error{OutOfMemory}, Self.write, format, args);
+ }
+
+ /// Make `count` bytes available before the current read location
+ fn rewind(self: *Self, size: usize) void {
+ assert(self.writableLength() >= size);
+
+ self.head = (self.head + (self.buf.len - size)) % self.buf.len;
+ self.count += size;
+ }
+
+ /// Place data back into the read stream
+ pub fn unget(self: *Self, src: []const T) !void {
+ try self.ensureUnusedCapacity(src.len);
+
+ self.rewind(src.len);
+
+ const slice = self.readableSliceMut(0);
+ mem.copy(T, slice, src[0..slice.len]);
+ const slice2 = self.readableSliceMut(slice.len);
+ mem.copy(T, slice2, src[slice.len..]);
+ }
+
+ /// Peek at the item at `offset`
+ pub fn peekItem(self: Self, offset: usize) error{EndOfStream}!T {
+ if (offset >= self.count)
+ return error.EndOfStream;
+
+ return self.buf[(self.head + offset) % self.buf.len];
+ }
+ };
+}
+
+const ByteFifo = FixedSizeFifo(u8);
+
+test "ByteFifo" {
+ var fifo = ByteFifo.init(debug.global_allocator);
+ defer fifo.deinit();
+
+ try fifo.write("HELLO");
+ testing.expectEqual(usize(5), fifo.readableLength());
+ testing.expectEqualSlices(u8, "HELLO", fifo.readableSlice(0));
+
+ {
+ var i: usize = 0;
+ while (i < 5) : (i += 1) {
+ try fifo.write([_]u8{try fifo.peekItem(i)});
+ }
+ testing.expectEqual(usize(10), fifo.readableLength());
+ testing.expectEqualSlices(u8, "HELLOHELLO", fifo.readableSlice(0));
+ }
+
+ {
+ testing.expectEqual(u8('H'), try fifo.readItem());
+ testing.expectEqual(u8('E'), try fifo.readItem());
+ testing.expectEqual(u8('L'), try fifo.readItem());
+ testing.expectEqual(u8('L'), try fifo.readItem());
+ testing.expectEqual(u8('O'), try fifo.readItem());
+ }
+ testing.expectEqual(usize(5), fifo.readableLength());
+
+ { // Writes that wrap around
+ testing.expectEqual(usize(11), fifo.writableLength());
+ testing.expectEqual(usize(6), fifo.writableSlice(0).len);
+ fifo.writeAssumeCapacity("6<chars<11");
+ testing.expectEqualSlices(u8, "HELLO6<char", fifo.readableSlice(0));
+ testing.expectEqualSlices(u8, "s<11", fifo.readableSlice(11));
+ fifo.discard(11);
+ testing.expectEqualSlices(u8, "s<11", fifo.readableSlice(0));
+ fifo.discard(4);
+ testing.expectEqual(usize(0), fifo.readableLength());
+ }
+
+ {
+ const buf = try fifo.writeableWithSize(12);
+ testing.expectEqual(usize(12), buf.len);
+ var i: u8 = 0;
+ while (i < 10) : (i += 1) {
+ buf[i] = i + 'a';
+ }
+ fifo.update(10);
+ testing.expectEqualSlices(u8, "abcdefghij", fifo.readableSlice(0));
+ }
+
+ {
+ try fifo.unget("prependedstring");
+ var result: [30]u8 = undefined;
+ testing.expectEqualSlices(u8, "prependedstringabcdefghij", fifo.read(&result));
+ }
+
+ fifo.shrink(0);
+
+ {
+ try fifo.print("{}, {}!", "Hello", "World");
+ var result: [30]u8 = undefined;
+ testing.expectEqualSlices(u8, "Hello, World!", fifo.read(&result));
+ testing.expectEqual(usize(0), fifo.readableLength());
+ }
+}
lib/std/std.zig
@@ -37,6 +37,7 @@ pub const debug = @import("debug.zig");
pub const dwarf = @import("dwarf.zig");
pub const elf = @import("elf.zig");
pub const event = @import("event.zig");
+pub const fifo = @import("fifo.zig");
pub const fmt = @import("fmt.zig");
pub const fs = @import("fs.zig");
pub const hash = @import("hash.zig");