Commit 125221cce9

Andrew Kelley <andrew@ziglang.org>
2023-04-28 00:16:01
std: update to use `@memcpy` directly
1 parent 73d3fb9
lib/std/compress/deflate/compressor.zig
@@ -10,7 +10,6 @@ const Allocator = std.mem.Allocator;
 const deflate_const = @import("deflate_const.zig");
 const fast = @import("deflate_fast.zig");
 const hm_bw = @import("huffman_bit_writer.zig");
-const mu = @import("mem_utils.zig");
 const token = @import("token.zig");
 
 pub const Compression = enum(i5) {
@@ -296,7 +295,7 @@ pub fn Compressor(comptime WriterType: anytype) type {
         fn fillDeflate(self: *Self, b: []const u8) u32 {
             if (self.index >= 2 * window_size - (min_match_length + max_match_length)) {
                 // shift the window by window_size
-                mem.copy(u8, self.window, self.window[window_size .. 2 * window_size]);
+                mem.copyForwards(u8, self.window, self.window[window_size .. 2 * window_size]);
                 self.index -= window_size;
                 self.window_end -= window_size;
                 if (self.block_start >= window_size) {
@@ -328,7 +327,7 @@ pub fn Compressor(comptime WriterType: anytype) type {
                     }
                 }
             }
-            var n = mu.copy(self.window[self.window_end..], b);
+            const n = std.compress.deflate.copy(self.window[self.window_end..], b);
             self.window_end += n;
             return @intCast(u32, n);
         }
@@ -369,7 +368,7 @@ pub fn Compressor(comptime WriterType: anytype) type {
                 b = b[b.len - window_size ..];
             }
             // Add all to window.
-            mem.copy(u8, self.window, b);
+            @memcpy(self.window[0..b.len], b);
             var n = b.len;
 
             // Calculate 256 hashes at the time (more L1 cache hits)
@@ -706,7 +705,7 @@ pub fn Compressor(comptime WriterType: anytype) type {
         }
 
         fn fillStore(self: *Self, b: []const u8) u32 {
-            var n = mu.copy(self.window[self.window_end..], b);
+            const n = std.compress.deflate.copy(self.window[self.window_end..], b);
             self.window_end += n;
             return @intCast(u32, n);
         }
@@ -1091,8 +1090,8 @@ test "bulkHash4" {
         // double the test data
         var out = try testing.allocator.alloc(u8, x.out.len * 2);
         defer testing.allocator.free(out);
-        mem.copy(u8, out[0..x.out.len], x.out);
-        mem.copy(u8, out[x.out.len..], x.out);
+        @memcpy(out[0..x.out.len], x.out);
+        @memcpy(out[x.out.len..], x.out);
 
         var j: usize = 4;
         while (j < out.len) : (j += 1) {
lib/std/compress/deflate/decompressor.zig
@@ -9,7 +9,6 @@ const ArrayList = std.ArrayList;
 const bu = @import("bits_utils.zig");
 const ddec = @import("dict_decoder.zig");
 const deflate_const = @import("deflate_const.zig");
-const mu = @import("mem_utils.zig");
 
 const max_match_offset = deflate_const.max_match_offset;
 const end_block_marker = deflate_const.end_block_marker;
@@ -451,7 +450,7 @@ pub fn Decompressor(comptime ReaderType: type) type {
         pub fn read(self: *Self, output: []u8) Error!usize {
             while (true) {
                 if (self.to_read.len > 0) {
-                    var n = mu.copy(output, self.to_read);
+                    const n = std.compress.deflate.copy(output, self.to_read);
                     self.to_read = self.to_read[n..];
                     if (self.to_read.len == 0 and
                         self.err != null)
lib/std/compress/deflate/deflate_fast.zig
@@ -237,7 +237,7 @@ pub const DeflateFast = struct {
         }
         self.cur += @intCast(i32, src.len);
         self.prev_len = @intCast(u32, src.len);
-        mem.copy(u8, self.prev[0..self.prev_len], src);
+        @memcpy(self.prev[0..self.prev_len], src);
         return;
     }
 
lib/std/compress/deflate/deflate_fast_test.zig
@@ -123,13 +123,13 @@ test "best speed max match offset" {
                 var src = try testing.allocator.alloc(u8, src_len);
                 defer testing.allocator.free(src);
 
-                mem.copy(u8, src, abc);
+                @memcpy(src[0..abc.len], abc);
                 if (!do_match_before) {
-                    var src_offset: usize = @intCast(usize, offset - @as(i32, xyz.len));
-                    mem.copy(u8, src[src_offset..], xyz);
+                    const src_offset: usize = @intCast(usize, offset - @as(i32, xyz.len));
+                    @memcpy(src[src_offset..][0..xyz.len], xyz);
                 }
-                var src_offset: usize = @intCast(usize, offset);
-                mem.copy(u8, src[src_offset..], abc);
+                const src_offset: usize = @intCast(usize, offset);
+                @memcpy(src[src_offset..][0..abc.len], abc);
 
                 var compressed = ArrayList(u8).init(testing.allocator);
                 defer compressed.deinit();
lib/std/compress/deflate/dict_decoder.zig
@@ -47,7 +47,8 @@ pub const DictDecoder = struct {
         self.wr_pos = 0;
 
         if (dict != null) {
-            mem.copy(u8, self.hist, dict.?[dict.?.len -| self.hist.len..]);
+            const src = dict.?[dict.?.len -| self.hist.len..];
+            @memcpy(self.hist[0..src.len], src);
             self.wr_pos = @intCast(u32, dict.?.len);
         }
 
@@ -103,12 +104,15 @@ pub const DictDecoder = struct {
         self.wr_pos += 1;
     }
 
+    /// TODO: eliminate this function because the callsites should care about whether
+    /// or not their arguments alias and then they should directly call `@memcpy` or
+    /// `mem.copyForwards`.
     fn copy(dst: []u8, src: []const u8) u32 {
         if (src.len > dst.len) {
-            mem.copy(u8, dst, src[0..dst.len]);
+            mem.copyForwards(u8, dst, src[0..dst.len]);
             return @intCast(u32, dst.len);
         }
-        mem.copy(u8, dst, src);
+        mem.copyForwards(u8, dst[0..src.len], src);
         return @intCast(u32, src.len);
     }
 
lib/std/compress/deflate/huffman_code.zig
@@ -202,7 +202,7 @@ pub const HuffmanEncoder = struct {
                     // more values in the level below
                     l.last_freq = l.next_pair_freq;
                     // Take leaf counts from the lower level, except counts[level] remains the same.
-                    mem.copy(u32, leaf_counts[level][0..level], leaf_counts[level - 1][0..level]);
+                    @memcpy(leaf_counts[level][0..level], leaf_counts[level - 1][0..level]);
                     levels[l.level - 1].needed = 2;
                 }
 
lib/std/compress/deflate/mem_utils.zig
@@ -1,15 +0,0 @@
-const std = @import("std");
-const math = std.math;
-const mem = std.mem;
-
-// Copies elements from a source `src` slice into a destination `dst` slice.
-// The copy never returns an error but might not be complete if the destination is too small.
-// Returns the number of elements copied, which will be the minimum of `src.len` and `dst.len`.
-pub fn copy(dst: []u8, src: []const u8) usize {
-    if (dst.len <= src.len) {
-        mem.copy(u8, dst[0..], src[0..dst.len]);
-    } else {
-        mem.copy(u8, dst[0..src.len], src[0..]);
-    }
-    return math.min(dst.len, src.len);
-}
lib/std/compress/xz/block.zig
@@ -59,9 +59,9 @@ pub fn Decoder(comptime ReaderType: type) type {
             while (true) {
                 if (self.to_read.items.len > 0) {
                     const input = self.to_read.items;
-                    const n = std.math.min(input.len, output.len);
-                    std.mem.copy(u8, output[0..n], input[0..n]);
-                    std.mem.copy(u8, input, input[n..]);
+                    const n = @min(input.len, output.len);
+                    @memcpy(output[0..n], input[0..n]);
+                    std.mem.copyForwards(u8, input, input[n..]);
                     self.to_read.shrinkRetainingCapacity(input.len - n);
                     if (self.to_read.items.len == 0 and self.err != null) {
                         if (self.err.? == DecodeError.EndOfStreamWithNoError) {
lib/std/compress/deflate.zig
@@ -12,6 +12,20 @@ pub const Decompressor = inflate.Decompressor;
 pub const compressor = deflate.compressor;
 pub const decompressor = inflate.decompressor;
 
+/// Copies elements from a source `src` slice into a destination `dst` slice.
+/// The copy never returns an error but might not be complete if the destination is too small.
+/// Returns the number of elements copied, which will be the minimum of `src.len` and `dst.len`.
+/// TODO: remove this smelly function
+pub fn copy(dst: []u8, src: []const u8) usize {
+    if (dst.len <= src.len) {
+        @memcpy(dst, src[0..dst.len]);
+        return dst.len;
+    } else {
+        @memcpy(dst[0..src.len], src);
+        return src.len;
+    }
+}
+
 test {
     _ = @import("deflate/token.zig");
     _ = @import("deflate/bits_utils.zig");
lib/std/crypto/argon2.zig
@@ -149,7 +149,7 @@ fn blake2bLong(out: []u8, in: []const u8) void {
         h.update(&outlen_bytes);
         h.update(in);
         h.final(&out_buf);
-        mem.copy(u8, out, out_buf[0..out.len]);
+        @memcpy(out, out_buf[0..out.len]);
         return;
     }
 
@@ -158,19 +158,19 @@ fn blake2bLong(out: []u8, in: []const u8) void {
     h.update(in);
     h.final(&out_buf);
     var out_slice = out;
-    mem.copy(u8, out_slice, out_buf[0 .. H.digest_length / 2]);
+    out_slice[0 .. H.digest_length / 2].* = out_buf[0 .. H.digest_length / 2].*;
     out_slice = out_slice[H.digest_length / 2 ..];
 
     var in_buf: [H.digest_length]u8 = undefined;
     while (out_slice.len > H.digest_length) {
-        mem.copy(u8, &in_buf, &out_buf);
+        in_buf = out_buf;
         H.hash(&in_buf, &out_buf, .{});
-        mem.copy(u8, out_slice, out_buf[0 .. H.digest_length / 2]);
+        out_slice[0 .. H.digest_length / 2].* = out_buf[0 .. H.digest_length / 2].*;
         out_slice = out_slice[H.digest_length / 2 ..];
     }
-    mem.copy(u8, &in_buf, &out_buf);
+    in_buf = out_buf;
     H.hash(&in_buf, &out_buf, .{ .expected_out_bits = out_slice.len * 8 });
-    mem.copy(u8, out_slice, out_buf[0..out_slice.len]);
+    @memcpy(out_slice, out_buf[0..out_slice.len]);
 }
 
 fn initBlocks(
lib/std/crypto/kyber_d00.zig
@@ -323,9 +323,9 @@ fn Kyber(comptime p: Params) type {
                 s += InnerSk.bytes_length;
                 ret.pk = InnerPk.fromBytes(buf[s .. s + InnerPk.bytes_length]);
                 s += InnerPk.bytes_length;
-                mem.copy(u8, &ret.hpk, buf[s .. s + h_length]);
+                ret.hpk = buf[s..][0..h_length].*;
                 s += h_length;
-                mem.copy(u8, &ret.z, buf[s .. s + shared_length]);
+                ret.z = buf[s..][0..shared_length].*;
                 return ret;
             }
         };
@@ -345,7 +345,7 @@ fn Kyber(comptime p: Params) type {
                     break :sk random_seed;
                 };
                 var ret: KeyPair = undefined;
-                mem.copy(u8, &ret.secret_key.z, seed[inner_seed_length..seed_length]);
+                ret.secret_key.z = seed[inner_seed_length..seed_length].*;
 
                 // Generate inner key
                 innerKeyFromSeed(
@@ -356,7 +356,7 @@ fn Kyber(comptime p: Params) type {
                 ret.secret_key.pk = ret.public_key.pk;
 
                 // Copy over z from seed.
-                mem.copy(u8, &ret.secret_key.z, seed[inner_seed_length..seed_length]);
+                ret.secret_key.z = seed[inner_seed_length..seed_length].*;
 
                 // Compute H(pk)
                 var h = sha3.Sha3_256.init(.{});
@@ -418,7 +418,7 @@ fn Kyber(comptime p: Params) type {
             fn fromBytes(buf: *const [bytes_length]u8) InnerPk {
                 var ret: InnerPk = undefined;
                 ret.th = V.fromBytes(buf[0..V.bytes_length]).normalize();
-                mem.copy(u8, &ret.rho, buf[V.bytes_length..bytes_length]);
+                ret.rho = buf[V.bytes_length..bytes_length].*;
                 ret.aT = M.uniform(ret.rho, true);
                 return ret;
             }
@@ -459,7 +459,7 @@ fn Kyber(comptime p: Params) type {
             var h = sha3.Sha3_512.init(.{});
             h.update(&seed);
             h.final(&expanded_seed);
-            mem.copy(u8, &pk.rho, expanded_seed[0..32]);
+            pk.rho = expanded_seed[0..32].*;
             const sigma = expanded_seed[32..64];
             pk.aT = M.uniform(pk.rho, false); // Expand ρ to A; we'll transpose later on
 
@@ -1381,7 +1381,7 @@ fn Vec(comptime K: u8) type {
             const cs = comptime Poly.compressedSize(d);
             var ret: [compressedSize(d)]u8 = undefined;
             inline for (0..K) |i| {
-                mem.copy(u8, ret[i * cs .. (i + 1) * cs], &v.ps[i].compress(d));
+                ret[i * cs .. (i + 1) * cs].* = v.ps[i].compress(d);
             }
             return ret;
         }
@@ -1399,11 +1399,7 @@ fn Vec(comptime K: u8) type {
         fn toBytes(v: Self) [bytes_length]u8 {
             var ret: [bytes_length]u8 = undefined;
             inline for (0..K) |i| {
-                mem.copy(
-                    u8,
-                    ret[i * Poly.bytes_length .. (i + 1) * Poly.bytes_length],
-                    &v.ps[i].toBytes(),
-                );
+                ret[i * Poly.bytes_length .. (i + 1) * Poly.bytes_length].* = v.ps[i].toBytes();
             }
             return ret;
         }
@@ -1742,15 +1738,15 @@ const NistDRBG = struct {
             g.incV();
             var block: [16]u8 = undefined;
             ctx.encrypt(&block, &g.v);
-            mem.copy(u8, buf[i * 16 .. (i + 1) * 16], &block);
+            buf[i * 16 ..][0..16].* = block;
         }
         if (pd) |p| {
             for (&buf, p) |*b, x| {
                 b.* ^= x;
             }
         }
-        mem.copy(u8, &g.key, buf[0..32]);
-        mem.copy(u8, &g.v, buf[32..48]);
+        g.key = buf[0..32].*;
+        g.v = buf[32..48].*;
     }
 
     // randombytes.
@@ -1763,10 +1759,10 @@ const NistDRBG = struct {
             g.incV();
             ctx.encrypt(&block, &g.v);
             if (dst.len < 16) {
-                mem.copy(u8, dst, block[0..dst.len]);
+                @memcpy(dst, block[0..dst.len]);
                 break;
             }
-            mem.copy(u8, dst, &block);
+            dst[0..block.len].* = block;
             dst = dst[16..dst.len];
         }
         g.update(null);
lib/std/crypto/scrypt.zig
@@ -27,7 +27,7 @@ const max_salt_len = 64;
 const max_hash_len = 64;
 
 fn blockCopy(dst: []align(16) u32, src: []align(16) const u32, n: usize) void {
-    mem.copy(u32, dst, src[0 .. n * 16]);
+    @memcpy(dst[0 .. n * 16], src[0 .. n * 16]);
 }
 
 fn blockXor(dst: []align(16) u32, src: []align(16) const u32, n: usize) void {
@@ -242,7 +242,7 @@ const crypt_format = struct {
             pub fn fromSlice(slice: []const u8) EncodingError!Self {
                 if (slice.len > capacity) return EncodingError.NoSpaceLeft;
                 var bin_value: Self = undefined;
-                mem.copy(u8, &bin_value.buf, slice);
+                @memcpy(bin_value.buf[0..slice.len], slice);
                 bin_value.len = slice.len;
                 return bin_value;
             }
@@ -314,7 +314,7 @@ const crypt_format = struct {
 
     fn serializeTo(params: anytype, out: anytype) !void {
         var header: [14]u8 = undefined;
-        mem.copy(u8, header[0..3], prefix);
+        header[0..3].* = prefix.*;
         Codec.intEncode(header[3..4], params.ln);
         Codec.intEncode(header[4..9], params.r);
         Codec.intEncode(header[9..14], params.p);
lib/std/crypto/tls.zig
@@ -312,11 +312,11 @@ pub fn hkdfExpandLabel(
     buf[2] = @intCast(u8, tls13.len + label.len);
     buf[3..][0..tls13.len].* = tls13.*;
     var i: usize = 3 + tls13.len;
-    mem.copy(u8, buf[i..], label);
+    @memcpy(buf[i..][0..label.len], label);
     i += label.len;
     buf[i] = @intCast(u8, context.len);
     i += 1;
-    mem.copy(u8, buf[i..], context);
+    @memcpy(buf[i..][0..context.len], context);
     i += context.len;
 
     var result: [len]u8 = undefined;
lib/std/http/Client.zig
@@ -284,7 +284,7 @@ pub const BufferedConnection = struct {
             if (available > 0) {
                 const can_read = @truncate(u16, @min(available, left));
 
-                std.mem.copy(u8, buffer[out_index..], bconn.buf[bconn.start..][0..can_read]);
+                @memcpy(buffer[out_index..][0..can_read], bconn.buf[bconn.start..][0..can_read]);
                 out_index += can_read;
                 bconn.start += can_read;
 
lib/std/http/Headers.zig
@@ -38,7 +38,8 @@ pub const Field = struct {
 
     pub fn modify(entry: *Field, allocator: Allocator, new_value: []const u8) !void {
         if (entry.value.len <= new_value.len) {
-            std.mem.copy(u8, @constCast(entry.value), new_value);
+            // TODO: eliminate this use of `@constCast`.
+            @memcpy(@constCast(entry.value)[0..new_value.len], new_value);
         } else {
             allocator.free(entry.value);
 
lib/std/http/protocol.zig
@@ -654,7 +654,7 @@ const MockBufferedConnection = struct {
             if (available > 0) {
                 const can_read = @truncate(u16, @min(available, left));
 
-                std.mem.copy(u8, buffer[out_index..], bconn.buf[bconn.start..][0..can_read]);
+                @memcpy(buffer[out_index..][0..can_read], bconn.buf[bconn.start..][0..can_read]);
                 out_index += can_read;
                 bconn.start += can_read;
 
lib/std/http/Server.zig
@@ -128,7 +128,7 @@ pub const BufferedConnection = struct {
             if (available > 0) {
                 const can_read = @truncate(u16, @min(available, left));
 
-                std.mem.copy(u8, buffer[out_index..], bconn.buf[bconn.start..][0..can_read]);
+                @memcpy(buffer[out_index..][0..can_read], bconn.buf[bconn.start..][0..can_read]);
                 out_index += can_read;
                 bconn.start += can_read;
 
lib/std/os/linux/bpf.zig
@@ -1631,7 +1631,7 @@ test "map lookup, update, and delete" {
     const status = try map_get_next_key(map, &lookup_key, &next_key);
     try expectEqual(status, true);
     try expectEqual(next_key, key);
-    std.mem.copy(u8, &lookup_key, &next_key);
+    lookup_key = next_key;
     const status2 = try map_get_next_key(map, &lookup_key, &next_key);
     try expectEqual(status2, false);
 
lib/std/os/linux/io_uring.zig
@@ -1856,7 +1856,7 @@ test "write_fixed/read_fixed" {
     var raw_buffers: [2][11]u8 = undefined;
     // First buffer will be written to the file.
     @memset(&raw_buffers[0], 'z');
-    std.mem.copy(u8, &raw_buffers[0], "foobar");
+    raw_buffers[0][0.."foobar".len].* = "foobar".*;
 
     var buffers = [2]os.iovec{
         .{ .iov_base = &raw_buffers[0], .iov_len = raw_buffers[0].len },
lib/std/os/linux/tls.zig
@@ -287,7 +287,7 @@ pub fn prepareTLS(area: []u8) usize {
         .VariantII => area.ptr + tls_image.tcb_offset,
     };
     // Copy the data
-    mem.copy(u8, area[tls_image.data_offset..], tls_image.init_data);
+    @memcpy(area[tls_image.data_offset..][0..tls_image.init_data.len], tls_image.init_data);
 
     // Return the corrected value (if needed) for the tp register.
     // Overflow here is not a problem, the pointer arithmetic involving the tp
lib/std/os/uefi/protocols/device_path_protocol.zig
@@ -48,7 +48,7 @@ pub const DevicePathProtocol = extern struct {
         // DevicePathProtocol for the extra node before the end
         var buf = try allocator.alloc(u8, path_size + 2 * (path.len + 1) + @sizeOf(DevicePathProtocol));
 
-        mem.copy(u8, buf, @ptrCast([*]const u8, self)[0..path_size]);
+        @memcpy(buf[0..path_size.len], @ptrCast([*]const u8, self)[0..path_size]);
 
         // Pointer to the copy of the end node of the current chain, which is - 4 from the buffer
         // as the end node itself is 4 bytes (type: u8 + subtype: u8 + length: u16).
lib/std/os/windows.zig
@@ -754,7 +754,7 @@ pub fn CreateSymbolicLink(
         .Flags = if (dir) |_| SYMLINK_FLAG_RELATIVE else 0,
     };
 
-    std.mem.copy(u8, buffer[0..], std.mem.asBytes(&symlink_data));
+    @memcpy(buffer[0..@sizeOf(SYMLINK_DATA)], std.mem.asBytes(&symlink_data));
     @memcpy(buffer[@sizeOf(SYMLINK_DATA)..][0 .. target_path.len * 2], @ptrCast([*]const u8, target_path));
     const paths_start = @sizeOf(SYMLINK_DATA) + target_path.len * 2;
     @memcpy(buffer[paths_start..][0 .. target_path.len * 2], @ptrCast([*]const u8, target_path));
@@ -1208,8 +1208,8 @@ pub fn GetFinalPathNameByHandle(
 
                     if (out_buffer.len < drive_letter.len + file_name_u16.len) return error.NameTooLong;
 
-                    mem.copy(u16, out_buffer, drive_letter);
-                    mem.copy(u16, out_buffer[drive_letter.len..], file_name_u16);
+                    @memcpy(out_buffer[0..drive_letter.len], drive_letter);
+                    @memcpy(out_buffer[drive_letter.len..][0..file_name_u16.len], file_name_u16);
                     const total_len = drive_letter.len + file_name_u16.len;
 
                     // Validate that DOS does not contain any spurious nul bytes.
@@ -2012,7 +2012,7 @@ pub fn sliceToPrefixedFileW(s: []const u8) !PathSpace {
     }
     const prefix_u16 = [_]u16{ '\\', '?', '?', '\\' };
     const start_index = if (prefix_index > 0 or !std.fs.path.isAbsolute(s)) 0 else blk: {
-        mem.copy(u16, path_space.data[0..], prefix_u16[0..]);
+        path_space.data[0..prefix_u16.len].* = prefix_u16;
         break :blk prefix_u16.len;
     };
     path_space.len = start_index + try std.unicode.utf8ToUtf16Le(path_space.data[start_index..], s);
@@ -2025,7 +2025,7 @@ pub fn sliceToPrefixedFileW(s: []const u8) !PathSpace {
                 std.debug.assert(temp_path.len == path_space.len);
                 temp_path.data[path_space.len] = 0;
                 path_space.len = prefix_u16.len + try getFullPathNameW(&temp_path.data, path_space.data[prefix_u16.len..]);
-                mem.copy(u16, &path_space.data, &prefix_u16);
+                path_space.data[0..prefix_u16.len].* = prefix_u16;
                 std.debug.assert(path_space.data[path_space.len] == 0);
                 return path_space;
             }
@@ -2053,12 +2053,12 @@ pub fn wToPrefixedFileW(s: []const u16) !PathSpace {
 
     const start_index = if (mem.startsWith(u16, s, &[_]u16{ '\\', '?' })) 0 else blk: {
         const prefix = [_]u16{ '\\', '?', '?', '\\' };
-        mem.copy(u16, path_space.data[0..], &prefix);
+        path_space.data[0..prefix.len].* = prefix;
         break :blk prefix.len;
     };
     path_space.len = start_index + s.len;
     if (path_space.len > path_space.data.len) return error.NameTooLong;
-    mem.copy(u16, path_space.data[start_index..], s);
+    @memcpy(path_space.data[start_index..][0..s.len], s);
     // > File I/O functions in the Windows API convert "/" to "\" as part of
     // > converting the name to an NT-style name, except when using the "\\?\"
     // > prefix as detailed in the following sections.
lib/std/bit_set.zig
@@ -765,7 +765,7 @@ pub const DynamicBitSetUnmanaged = struct {
         const num_masks = numMasks(self.bit_length);
         var copy = Self{};
         try copy.resize(new_allocator, self.bit_length, false);
-        std.mem.copy(MaskInt, copy.masks[0..num_masks], self.masks[0..num_masks]);
+        @memcpy(copy.masks[0..num_masks], self.masks[0..num_masks]);
         return copy;
     }
 
lib/std/debug.zig
@@ -309,8 +309,8 @@ pub fn panicExtra(
     // error being part of the @panic stack trace (but that error should
     // only happen rarely)
     const msg = std.fmt.bufPrint(buf[0..size], format, args) catch |err| switch (err) {
-        std.fmt.BufPrintError.NoSpaceLeft => blk: {
-            std.mem.copy(u8, buf[size..], trunc_msg);
+        error.NoSpaceLeft => blk: {
+            @memcpy(buf[size..], trunc_msg);
             break :blk &buf;
         },
     };
lib/std/fs.zig
@@ -106,7 +106,7 @@ pub fn atomicSymLink(allocator: Allocator, existing_path: []const u8, new_path:
     var rand_buf: [AtomicFile.RANDOM_BYTES]u8 = undefined;
     const tmp_path = try allocator.alloc(u8, dirname.len + 1 + base64_encoder.calcSize(rand_buf.len));
     defer allocator.free(tmp_path);
-    mem.copy(u8, tmp_path[0..], dirname);
+    @memcpy(tmp_path[0..dirname.len], dirname);
     tmp_path[dirname.len] = path.sep;
     while (true) {
         crypto.random.bytes(rand_buf[0..]);
@@ -1541,9 +1541,9 @@ pub const Dir = struct {
             return error.NameTooLong;
         }
 
-        mem.copy(u8, out_buffer, out_path);
-
-        return out_buffer[0..out_path.len];
+        const result = out_buffer[0..out_path.len];
+        @memcpy(result, out_path);
+        return result;
     }
 
     /// Windows-only. Same as `Dir.realpath` except `pathname` is WTF16 encoded.
@@ -1593,9 +1593,9 @@ pub const Dir = struct {
             return error.NameTooLong;
         }
 
-        mem.copy(u8, out_buffer, out_path);
-
-        return out_buffer[0..out_path.len];
+        const result = out_buffer[0..out_path.len];
+        @memcpy(result, out_path);
+        return result;
     }
 
     /// Same as `Dir.realpath` except caller must free the returned memory.
@@ -2346,8 +2346,9 @@ pub const Dir = struct {
                             if (cleanup_dir_parent) |*d| d.close();
                             cleanup_dir_parent = iterable_dir;
                             iterable_dir = new_dir;
-                            mem.copy(u8, &dir_name_buf, entry.name);
-                            dir_name = dir_name_buf[0..entry.name.len];
+                            const result = dir_name_buf[0..entry.name.len];
+                            @memcpy(result, entry.name);
+                            dir_name = result;
                             continue :scan_dir;
                         } else {
                             if (iterable_dir.dir.deleteFile(entry.name)) {
@@ -2974,8 +2975,9 @@ pub fn selfExePath(out_buffer: []u8) SelfExePathError![]u8 {
         var real_path_buf: [MAX_PATH_BYTES]u8 = undefined;
         const real_path = try std.os.realpathZ(&symlink_path_buf, &real_path_buf);
         if (real_path.len > out_buffer.len) return error.NameTooLong;
-        std.mem.copy(u8, out_buffer, real_path);
-        return out_buffer[0..real_path.len];
+        const result = out_buffer[0..real_path.len];
+        @memcpy(result, real_path);
+        return result;
     }
     switch (builtin.os.tag) {
         .linux => return os.readlinkZ("/proc/self/exe", out_buffer),
@@ -3014,8 +3016,9 @@ pub fn selfExePath(out_buffer: []u8) SelfExePathError![]u8 {
                 const real_path = try os.realpathZ(os.argv[0], &real_path_buf);
                 if (real_path.len > out_buffer.len)
                     return error.NameTooLong;
-                mem.copy(u8, out_buffer, real_path);
-                return out_buffer[0..real_path.len];
+                const result = out_buffer[0..real_path.len];
+                @memcpy(result, real_path);
+                return result;
             } else if (argv0.len != 0) {
                 // argv[0] is not empty (and not a path): search it inside PATH
                 const PATH = std.os.getenvZ("PATH") orelse return error.FileNotFound;
@@ -3032,8 +3035,9 @@ pub fn selfExePath(out_buffer: []u8) SelfExePathError![]u8 {
                         // found a file, and hope it is the right file
                         if (real_path.len > out_buffer.len)
                             return error.NameTooLong;
-                        mem.copy(u8, out_buffer, real_path);
-                        return out_buffer[0..real_path.len];
+                        const result = out_buffer[0..real_path.len];
+                        @memcpy(result, real_path);
+                        return result;
                     } else |_| continue;
                 }
             }
lib/std/net.zig
@@ -107,7 +107,7 @@ pub const Address = extern union {
         if (path.len + 1 > sock_addr.path.len) return error.NameTooLong;
 
         @memset(&sock_addr.path, 0);
-        mem.copy(u8, &sock_addr.path, path);
+        @memcpy(sock_addr.path[0..path.len], path);
 
         return Address{ .un = sock_addr };
     }
@@ -416,7 +416,7 @@ pub const Ip6Address = extern struct {
             index += 1;
             ip_slice[index] = @truncate(u8, x);
             index += 1;
-            mem.copy(u8, result.sa.addr[16 - index ..], ip_slice[0..index]);
+            @memcpy(result.sa.addr[16 - index ..][0..index], ip_slice[0..index]);
             return result;
         }
     }
@@ -550,7 +550,7 @@ pub const Ip6Address = extern struct {
             index += 1;
             ip_slice[index] = @truncate(u8, x);
             index += 1;
-            mem.copy(u8, result.sa.addr[16 - index ..], ip_slice[0..index]);
+            @memcpy(result.sa.addr[16 - index ..][0..index], ip_slice[0..index]);
             return result;
         }
     }
@@ -662,7 +662,7 @@ fn if_nametoindex(name: []const u8) !u32 {
         var sockfd = try os.socket(os.AF.UNIX, os.SOCK.DGRAM | os.SOCK.CLOEXEC, 0);
         defer os.closeSocket(sockfd);
 
-        std.mem.copy(u8, &ifr.ifrn.name, name);
+        @memcpy(ifr.ifrn.name[0..name.len], name);
         ifr.ifrn.name[name.len] = 0;
 
         // TODO investigate if this needs to be integrated with evented I/O.
@@ -676,7 +676,7 @@ fn if_nametoindex(name: []const u8) !u32 {
             return error.NameTooLong;
 
         var if_name: [os.IFNAMESIZE:0]u8 = undefined;
-        std.mem.copy(u8, &if_name, name);
+        @memcpy(if_name[0..name.len], name);
         if_name[name.len] = 0;
         const if_slice = if_name[0..name.len :0];
         const index = os.system.if_nametoindex(if_slice);
@@ -1041,14 +1041,14 @@ fn linuxLookupName(
         var salen: os.socklen_t = undefined;
         var dalen: os.socklen_t = undefined;
         if (addr.addr.any.family == os.AF.INET6) {
-            mem.copy(u8, &da6.addr, &addr.addr.in6.sa.addr);
+            da6.addr = addr.addr.in6.sa.addr;
             da = @ptrCast(*os.sockaddr, &da6);
             dalen = @sizeOf(os.sockaddr.in6);
             sa = @ptrCast(*os.sockaddr, &sa6);
             salen = @sizeOf(os.sockaddr.in6);
         } else {
-            mem.copy(u8, &sa6.addr, "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff");
-            mem.copy(u8, &da6.addr, "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff");
+            sa6.addr[0..12].* = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff".*;
+            da6.addr[0..12].* = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff".*;
             mem.writeIntNative(u32, da6.addr[12..], addr.addr.in.sa.addr);
             da4.addr = addr.addr.in.sa.addr;
             da = @ptrCast(*os.sockaddr, &da4);
@@ -1343,7 +1343,7 @@ fn linuxLookupNameFromDnsSearch(
     // name is not a CNAME record) and serves as a buffer for passing
     // the full requested name to name_from_dns.
     try canon.resize(canon_name.len);
-    mem.copy(u8, canon.items, canon_name);
+    @memcpy(canon.items, canon_name);
     try canon.append('.');
 
     var tok_it = mem.tokenize(u8, search, " \t");
@@ -1567,7 +1567,7 @@ fn resMSendRc(
         for (0..ns.len) |i| {
             if (ns[i].any.family != os.AF.INET) continue;
             mem.writeIntNative(u32, ns[i].in6.sa.addr[12..], ns[i].in.sa.addr);
-            mem.copy(u8, ns[i].in6.sa.addr[0..12], "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff");
+            ns[i].in6.sa.addr[0..12].* = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff".*;
             ns[i].any.family = os.AF.INET6;
             ns[i].in6.sa.flowinfo = 0;
             ns[i].in6.sa.scope_id = 0;
@@ -1665,7 +1665,7 @@ fn resMSendRc(
             if (i == next) {
                 while (next < queries.len and answers[next].len != 0) : (next += 1) {}
             } else {
-                mem.copy(u8, answer_bufs[i], answer_bufs[next][0..rlen]);
+                @memcpy(answer_bufs[i][0..rlen], answer_bufs[next][0..rlen]);
             }
 
             if (next == queries.len) break :outer;
lib/std/tar.zig
@@ -55,9 +55,9 @@ pub const Header = struct {
         const p = prefix(header);
         if (p.len == 0)
             return n;
-        std.mem.copy(u8, buffer[0..p.len], p);
+        @memcpy(buffer[0..p.len], p);
         buffer[p.len] = '/';
-        std.mem.copy(u8, buffer[p.len + 1 ..], n);
+        @memcpy(buffer[p.len + 1 ..][0..n.len], n);
         return buffer[0 .. p.len + 1 + n.len];
     }
 
@@ -101,8 +101,9 @@ pub fn pipeToFileSystem(dir: std.fs.Dir, reader: anytype, options: Options) !voi
     var end: usize = 0;
     header: while (true) {
         if (buffer.len - start < 1024) {
-            std.mem.copy(u8, &buffer, buffer[start..end]);
-            end -= start;
+            const dest_end = end - start;
+            @memcpy(buffer[0..dest_end], buffer[start..end]);
+            end = dest_end;
             start = 0;
         }
         const ask_header = @min(buffer.len - end, 1024 -| (end - start));
@@ -138,8 +139,9 @@ pub fn pipeToFileSystem(dir: std.fs.Dir, reader: anytype, options: Options) !voi
                 var file_off: usize = 0;
                 while (true) {
                     if (buffer.len - start < 1024) {
-                        std.mem.copy(u8, &buffer, buffer[start..end]);
-                        end -= start;
+                        const dest_end = end - start;
+                        @memcpy(buffer[0..dest_end], buffer[start..end]);
+                        end = dest_end;
                         start = 0;
                     }
                     // Ask for the rounded up file size + 512 for the next header.