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fix(Stream): compare terminator/target bytes as unsigned char #629

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fix(Stream): compare terminator/target bytes as unsigned char #629

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15 changes: 11 additions & 4 deletions cores/arduino/Stream.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -221,7 +221,10 @@ size_t Stream::readBytesUntil(char terminator, char *buffer, size_t length)
size_t index = 0;
while (index < length) {
int c = timedRead();
if (c < 0 || c == terminator) break;
// Compare against the terminator as unsigned char: on AVR char is signed,
// so a terminator byte >= 0x80 would otherwise sign-extend to a negative
// int and never match a valid read byte returned by timedRead().
if (c < 0 || c == (unsigned char)terminator) break;
*buffer++ = (char)c;
index++;
}
Expand All @@ -244,7 +247,9 @@ String Stream::readStringUntil(char terminator)
{
String ret;
int c = timedRead();
while (c >= 0 && c != terminator)
// See readBytesUntil() above: compare as unsigned char to correctly match
// terminator bytes >= 0x80 on platforms where char is signed.
while (c >= 0 && c != (unsigned char)terminator)
{
ret += (char)c;
c = timedRead();
Expand All @@ -267,7 +272,9 @@ int Stream::findMulti( struct Stream::MultiTarget *targets, int tCount) {

for (struct MultiTarget *t = targets; t < targets+tCount; ++t) {
// the simple case is if we match, deal with that first.
if (c == t->str[t->index]) {
// Compare as unsigned char: char is signed on AVR, so target bytes
// >= 0x80 would otherwise sign-extend and never match c.
if (c == (unsigned char)t->str[t->index]) {
if (++t->index == t->len)
return t - targets;
else
Expand All @@ -285,7 +292,7 @@ int Stream::findMulti( struct Stream::MultiTarget *targets, int tCount) {
do {
--t->index;
// first check if current char works against the new current index
if (c != t->str[t->index])
if (c != (unsigned char)t->str[t->index])
continue;

// if it's the only char then we're good, nothing more to check
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