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| author | Daniel Walton <dwalton76@gmail.com> | 2017-09-12 17:48:03 -0400 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2017-09-12 17:48:03 -0400 |
| commit | e775854d9c87fc3dd163559b344f50b2acf4d562 (patch) | |
| tree | 72b04b908620fcd1fd70ac849558c353c32b2be9 /lib/stream.h | |
| parent | 016bded5d504dec6af791cb468e7b316a52af05a (diff) | |
| parent | 937652c6e43fc74ba969bbace475bdf929cdc5d0 (diff) | |
Merge pull request #1133 from opensourcerouting/shift-sign
*: fix be32 reading / 24-bit left shift
Diffstat (limited to 'lib/stream.h')
| -rw-r--r-- | lib/stream.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/lib/stream.h b/lib/stream.h index 33dd64c4a3..7dcdca69f6 100644 --- a/lib/stream.h +++ b/lib/stream.h @@ -239,4 +239,22 @@ extern struct stream *stream_fifo_head(struct stream_fifo *fifo); extern void stream_fifo_clean(struct stream_fifo *fifo); extern void stream_fifo_free(struct stream_fifo *fifo); +/* This is here because "<< 24" is particularly problematic in C. + * This is because the left operand of << is integer-promoted, which means + * an uint8_t gets converted into a *signed* int. Shifting into the sign + * bit of a signed int is theoretically undefined behaviour, so - the left + * operand needs to be cast to unsigned. + * + * This is not a problem for 16- or 8-bit values (they don't reach the sign + * bit), for 64-bit values (you need to cast them anyway), and neither for + * encoding (because it's downcasted.) + */ +static inline uint8_t *ptr_get_be32(uint8_t *ptr, uint32_t *out) +{ + uint32_t tmp; + memcpy(&tmp, ptr, sizeof(tmp)); + *out = ntohl(tmp); + return ptr + 4; +} + #endif /* _ZEBRA_STREAM_H */ |