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Optimize file splatting on Windows, Darwin and Haiku #24784

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123 changes: 69 additions & 54 deletions lib/std/fs/File.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -1612,63 +1612,48 @@ pub const Writer = struct {
const w: *Writer = @alignCast(@fieldParentPtr("interface", io_w));
const handle = w.file.handle;
const buffered = io_w.buffered();
if (is_windows) switch (w.mode) {
.positional, .positional_reading => {
if (buffered.len != 0) {
const n = windows.WriteFile(handle, buffered, w.pos) catch |err| {
w.err = err;
return error.WriteFailed;
};
w.pos += n;
return io_w.consume(n);
}
for (data[0 .. data.len - 1]) |buf| {
if (buf.len == 0) continue;
const n = windows.WriteFile(handle, buf, w.pos) catch |err| {
w.err = err;
return error.WriteFailed;
};
w.pos += n;
return io_w.consume(n);
const has_pwritev = !is_windows and
!((native_os.isDarwin() or native_os == .haiku) and
(w.mode == .positional or w.mode == .positional_reading));
if (!has_pwritev) {
const pos: ?u64 = switch (w.mode) {
.positional, .positional_reading => w.pos,
.streaming, .streaming_reading => null,
.failure => return error.WriteFailed,
};
if (buffered.len != 0) {
return w.pwrite(buffered, pos);
}
for (data[0 .. data.len - 1]) |buf| {
if (buf.len == 0) continue;
return w.pwrite(buf, pos);
}
const pattern = data[data.len - 1];
if (pattern.len == 0 or splat == 0) return 0;
const splat_buffer: []const u8 = if (splat > 1) buf: {
const splat_buffer_candidate = io_w.buffer[io_w.end..];
var backup_buffer: [64]u8 = undefined;
const splat_buffer = if (splat_buffer_candidate.len >= backup_buffer.len)
splat_buffer_candidate
else
&backup_buffer;
if (pattern.len > splat_buffer.len / 2) {
break :buf pattern;
}
const pattern = data[data.len - 1];
if (pattern.len == 0 or splat == 0) return 0;
const n = windows.WriteFile(handle, pattern, w.pos) catch |err| {
w.err = err;
return error.WriteFailed;
};
w.pos += n;
return io_w.consume(n);
},
.streaming, .streaming_reading => {
if (buffered.len != 0) {
const n = windows.WriteFile(handle, buffered, null) catch |err| {
w.err = err;
return error.WriteFailed;
};
w.pos += n;
return io_w.consume(n);
if (pattern.len == 1) {
const memset_len = @min(splat_buffer.len, splat);
const buf = splat_buffer[0..memset_len];
@memset(buf, pattern[0]);
break :buf buf;
}
for (data[0 .. data.len - 1]) |buf| {
if (buf.len == 0) continue;
const n = windows.WriteFile(handle, buf, null) catch |err| {
w.err = err;
return error.WriteFailed;
};
w.pos += n;
return io_w.consume(n);
const repeat_count = @min(splat_buffer.len / pattern.len, splat);
for (0..repeat_count) |i| {
@memcpy(splat_buffer[i * pattern.len ..][0..pattern.len], pattern);
}
const pattern = data[data.len - 1];
if (pattern.len == 0 or splat == 0) return 0;
const n = windows.WriteFile(handle, pattern, null) catch |err| {
w.err = err;
return error.WriteFailed;
};
w.pos += n;
return io_w.consume(n);
},
.failure => return error.WriteFailed,
};
break :buf splat_buffer[0 .. pattern.len * repeat_count];
} else pattern;
return w.pwrite(splat_buffer, pos);
}
var iovecs: [max_buffers_len]std.posix.iovec_const = undefined;
var len: usize = 0;
if (buffered.len > 0) {
Expand Down Expand Up @@ -1757,6 +1742,36 @@ pub const Writer = struct {
}
}

fn pwrite(w: *Writer, data: []const u8, offset: ?u64) std.Io.Writer.Error!usize {
const result = if (is_windows)
windows.WriteFile(w.file.handle, data, offset)
else if (offset) |p|
posix.pwrite(w.file.handle, data, p) catch |err| switch (err) {
error.Unseekable => {
w.mode = w.mode.toStreaming();
const pos = w.pos;
if (pos != 0) {
w.pos = 0;
w.seekTo(@intCast(pos)) catch {
w.mode = .failure;
return error.WriteFailed;
};
}
return 0;
},
else => |e| e,
}
else
posix.write(w.file.handle, data);

const n = result catch |err| {
w.err = err;
return error.WriteFailed;
};
w.pos += n;
return w.interface.consume(n);
}

pub fn sendFile(
io_w: *std.Io.Writer,
file_reader: *Reader,
Expand Down