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Have encapsulation.ReadData return an error when the buffer is short.

Browse source 
https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/merge_requests/154#note_2919109

Still ignoring the io.ErrShortBuffer at the callers, which retains
current behavior.
This commit is contained in:
David Fifield 2023-11-07 05:49:48 +00:00
parent 001f691b47
commit d99f31d881
4 changed files with 24 additions and 16 deletions
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19
common/encapsulation/encapsulation.go
View file

@ -53,11 +53,12 @@ var ErrTooLong = errors.New("length prefix is too long")
// ReadData the next available data chunk, skipping over any padding chunks that
// may come first, and copies the data into p. If p is shorter than the length
// of the data chunk, only the first len(p) bytes are copied into p. The
// returned error value is nil if and only if a data chunk was present and was
// read in its entirety. The returned error is io.EOF only if r ended before the
// first byte of a length prefix. If r ended in the middle of a length prefix or
// data/padding, the returned error is io.ErrUnexpectedEOF.
// of the data chunk, only the first len(p) bytes are copied into p, and the
// error return is io.ErrShortBuffer. The returned error value is nil if and
// only if a data chunk was present and was read in its entirety. The returned
// error is io.EOF only if r ended before the first byte of a length prefix. If
// r ended in the middle of a length prefix or data/padding, the returned error
// is io.ErrUnexpectedEOF.
func ReadData(r io.Reader, p []byte) (int, error) {
for {
var b [1]byte
@ -89,9 +90,13 @@ func ReadData(r io.Reader, p []byte) (int, error) {
}
numData, err := io.ReadFull(r, p)
if err == nil && numData < n {
// Discard the rest of the data, if the caller's
// buffer was too short.
// If the caller's buffer was too short, discard
// the rest of the data and return
// io.ErrShortBuffer.
_, err = io.CopyN(ioutil.Discard, r, int64(n-numData))
if err == nil {
err = io.ErrShortBuffer
}
}
if err == io.EOF {
err = io.ErrUnexpectedEOF