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Fix bugs in Windows readVec implementations #24915

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Merged
merged 1 commit into from
Aug 19, 2025
Merged

Fix bugs in Windows readVec implementations #24915

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24 changes: 13 additions & 11 deletions lib/std/fs/File.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -1343,14 +1343,15 @@ pub const Reader = struct {
if (is_windows) {
// Unfortunately, `ReadFileScatter` cannot be used since it
// requires page alignment.
assert(io_reader.seek == io_reader.end);
io_reader.seek = 0;
io_reader.end = 0;
if (io_reader.seek == io_reader.end) {
io_reader.seek = 0;
io_reader.end = 0;
}
const first = data[0];
if (first.len >= io_reader.buffer.len) {
if (first.len >= io_reader.buffer.len - io_reader.end) {
return readPositional(r, first);
} else {
io_reader.end += try readPositional(r, io_reader.buffer);
io_reader.end += try readPositional(r, io_reader.buffer[io_reader.end..]);
return 0;
}
}
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@castholm castholm Aug 19, 2025

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I think this entire branch (and the identical copy below) could be removed, since posix.preadv/readv is implemented as a single buffer ReadFile on Windows anyway.

Expand Down Expand Up @@ -1391,14 +1392,15 @@ pub const Reader = struct {
if (is_windows) {
// Unfortunately, `ReadFileScatter` cannot be used since it
// requires page alignment.
assert(io_reader.seek == io_reader.end);
io_reader.seek = 0;
io_reader.end = 0;
if (io_reader.seek == io_reader.end) {
io_reader.seek = 0;
io_reader.end = 0;
}
const first = data[0];
if (first.len >= io_reader.buffer.len) {
return readStreaming(r, first);
if (first.len >= io_reader.buffer.len - io_reader.end) {
return readPositional(r, first);
} else {
io_reader.end += try readStreaming(r, io_reader.buffer);
io_reader.end += try readPositional(r, io_reader.buffer[io_reader.end..]);
return 0;
}
}
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3 changes: 1 addition & 2 deletions lib/std/net.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -1992,8 +1992,7 @@ pub const Stream = struct {
};
if (n == 0) return error.EndOfStream;
if (n > data_size) {
io_r.seek = 0;
io_r.end = n - data_size;
io_r.end += n - data_size;
return data_size;
}
return n;
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