Source
pub fn drain(io_w: *std.Io.Writer, data: []const []const u8, splat: usize) std.Io.Writer.Error!usize {
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 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);
}
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 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,
};
var iovecs: [max_buffers_len]std.posix.iovec_const = undefined;
var len: usize = 0;
if (buffered.len > 0) {
iovecs[len] = .{ .base = buffered.ptr, .len = buffered.len };
len += 1;
}
for (data[0 .. data.len - 1]) |d| {
if (d.len == 0) continue;
iovecs[len] = .{ .base = d.ptr, .len = d.len };
len += 1;
if (iovecs.len - len == 0) break;
}
const pattern = data[data.len - 1];
if (iovecs.len - len != 0) switch (splat) {
0 => {},
1 => if (pattern.len != 0) {
iovecs[len] = .{ .base = pattern.ptr, .len = pattern.len };
len += 1;
},
else => switch (pattern.len) {
0 => {},
1 => {
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;
const memset_len = @min(splat_buffer.len, splat);
const buf = splat_buffer[0..memset_len];
@memset(buf, pattern[0]);
iovecs[len] = .{ .base = buf.ptr, .len = buf.len };
len += 1;
var remaining_splat = splat - buf.len;
while (remaining_splat > splat_buffer.len and iovecs.len - len != 0) {
assert(buf.len == splat_buffer.len);
iovecs[len] = .{ .base = splat_buffer.ptr, .len = splat_buffer.len };
len += 1;
remaining_splat -= splat_buffer.len;
}
if (remaining_splat > 0 and iovecs.len - len != 0) {
iovecs[len] = .{ .base = splat_buffer.ptr, .len = remaining_splat };
len += 1;
}
},
else => for (0..splat) |_| {
iovecs[len] = .{ .base = pattern.ptr, .len = pattern.len };
len += 1;
if (iovecs.len - len == 0) break;
},
},
};
if (len == 0) return 0;
switch (w.mode) {
.positional, .positional_reading => {
const n = std.posix.pwritev(handle, iovecs[0..len], w.pos) 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| {
w.err = e;
return error.WriteFailed;
},
};
w.pos += n;
return io_w.consume(n);
},
.streaming, .streaming_reading => {
const n = std.posix.writev(handle, iovecs[0..len]) catch |err| {
w.err = err;
return error.WriteFailed;
};
w.pos += n;
return io_w.consume(n);
},
.failure => return error.WriteFailed,
}
}