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std.Io.Reader: rework peekDelimiterInclusive

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Now it's based on calling fillMore rather than an illegal aliased stream
into the Reader buffer.

This commit also includes a disambiguation block inspired by #25162. If
`StreamTooLong` was added to `RebaseError` then this logic could be
replaced by removing the exit condition from the while loop. That error
code would represent when `buffer` capacity is too small for an
operation, replacing the current use of asserts.
This commit is contained in:
Andrew Kelley 2025-10-08 19:14:01 -07:00
parent b9f8b6ef06
commit d83d79c032
1 changed files with 29 additions and 20 deletions
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45
lib/std/Io/Reader.zig
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@ -792,28 +792,37 @@ pub fn takeDelimiterInclusive(r: *Reader, delimiter: u8) DelimiterError![]u8 {
/// * `peekDelimiterExclusive`
/// * `takeDelimiterInclusive`
pub fn peekDelimiterInclusive(r: *Reader, delimiter: u8) DelimiterError![]u8 {
const buffer = r.buffer[0..r.end];
{
const contents = r.buffer[0..r.end];
const seek = r.seek;
if (std.mem.indexOfScalarPos(u8, buffer, seek, delimiter)) |delimiter_index| {
if (std.mem.findScalarPos(u8, contents, seek, delimiter)) |end| {
@branchHint(.likely);
return buffer[seek .. delimiter_index + 1];
}
// TODO take a parameter for max search length rather than relying on buffer capacity
try rebase(r, r.buffer.len);
while (r.buffer.len - r.end != 0) {
const existing_buffered_len = r.end - r.seek;
const end_cap = r.buffer[r.end..];
var writer: Writer = .fixed(end_cap);
const n = r.vtable.stream(r, &writer, .limited(end_cap.len)) catch |err| switch (err) {
error.WriteFailed => unreachable,
else => |e| return e,
};
r.end += n;
if (std.mem.indexOfScalarPos(u8, r.buffer[0..r.end], r.seek + existing_buffered_len, delimiter)) |delimiter_index| {
return r.buffer[r.seek .. delimiter_index + 1];
return contents[seek .. end + 1];
}
}
return error.StreamTooLong;
while (true) {
const content_len = r.end - r.seek;
if (r.buffer.len - content_len == 0) break;
try fillMore(r);
const seek = r.seek;
const contents = r.buffer[0..r.end];
if (std.mem.findScalarPos(u8, contents, seek + content_len, delimiter)) |end| {
return contents[seek .. end + 1];
}
}
// It might or might not be end of stream. There is no more buffer space
// left to disambiguate. If `StreamTooLong` was added to `RebaseError` then
// this logic could be replaced by removing the exit condition from the
// above while loop. That error code would represent when `buffer` capacity
// is too small for an operation, replacing the current use of asserts.
var failing_writer = Writer.failing;
while (r.vtable.stream(r, &failing_writer, .limited(1))) |n| {
assert(n == 0);
} else |err| switch (err) {
error.WriteFailed => return error.StreamTooLong,
error.ReadFailed => |e| return e,
error.EndOfStream => |e| return e,
}
}
/// Returns a slice of the next bytes of buffered data from the stream until