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std.Io.Reader: fix readSliceShort with smaller buffer than Reader

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closes #24443
This commit is contained in:
Andrew Kelley 2025-07-16 23:43:46 -07:00
parent 86699acbb9
commit 5784500572
1 changed files with 30 additions and 36 deletions
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56
lib/std/Io/Reader.zig
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@ -593,48 +593,29 @@ pub fn readSliceAll(r: *Reader, buffer: []u8) Error!void {
/// See also:
/// * `readSliceAll`
pub fn readSliceShort(r: *Reader, buffer: []u8) ShortError!usize {
const in_buffer = r.buffer[r.seek..r.end];
const copy_len = @min(buffer.len, in_buffer.len);
@memcpy(buffer[0..copy_len], in_buffer[0..copy_len]);
if (buffer.len - copy_len == 0) {
var i: usize = 0;
while (true) {
const buffer_contents = r.buffer[r.seek..r.end];
const dest = buffer[i..];
const copy_len = @min(dest.len, buffer_contents.len);
@memcpy(dest[0..copy_len], buffer_contents[0..copy_len]);
if (dest.len - copy_len == 0) {
@branchHint(.likely);
r.seek += copy_len;
return buffer.len;
}
var i: usize = copy_len;
i += copy_len;
r.end = 0;
r.seek = 0;
while (true) {
const remaining = buffer[i..];
var wrapper: Writer.VectorWrapper = .{
.it = .{
.first = remaining,
.last = r.buffer,
},
.writer = .{
.buffer = if (remaining.len >= r.buffer.len) remaining else r.buffer,
.vtable = Writer.VectorWrapper.vtable,
},
};
const n = r.vtable.stream(r, &wrapper.writer, .unlimited) catch |err| switch (err) {
error.WriteFailed => {
if (!wrapper.used) {
assert(r.seek == 0);
r.seek = remaining.len;
r.end = wrapper.writer.end;
@memcpy(remaining, r.buffer[0..remaining.len]);
}
return buffer.len;
},
const new_remaining_len = readVecInner(r, &.{}, remaining, remaining.len) catch |err| switch (err) {
error.EndOfStream => return i,
error.ReadFailed => return error.ReadFailed,
};
if (n < remaining.len) {
i += n;
continue;
if (new_remaining_len == 0) return buffer.len;
i += remaining.len - new_remaining_len;
}
r.end = n - remaining.len;
return buffer.len;
}
}
/// Fill `buffer` with the next `buffer.len` bytes from the stream, advancing
@ -1640,6 +1621,19 @@ test readSliceShort {
try testing.expectEqual(0, try r.readSliceShort(&buf));
}
test "readSliceShort with smaller buffer than Reader" {
var reader_buf: [15]u8 = undefined;
const str = "This is a test";
var one_byte_stream: testing.Reader = .init(&reader_buf, &.{
.{ .buffer = str },
});
one_byte_stream.artificial_limit = .limited(1);
var buf: [14]u8 = undefined;
try testing.expectEqual(14, try one_byte_stream.interface.readSliceShort(&buf));
try testing.expectEqualStrings(str, &buf);
}
test readVec {
var r: Reader = .fixed(std.ascii.letters);
var flat_buffer: [52]u8 = undefined;