diff options
| -rw-r--r-- | sha3.c | 42 |
1 files changed, 36 insertions, 6 deletions
@@ -993,12 +993,42 @@ static inline void xof_absorb_done(sha3_xof_t * const xof, const size_t rate, co } // squeeze data without checking state (used by xof_once()) -static inline void xof_squeeze_raw(sha3_xof_t * const xof, const size_t rate, const size_t num_rounds, uint8_t * const dst, const size_t dst_len) { - for (size_t i = 0; i < dst_len; i++) { - dst[i] = xof->a.u8[xof->num_bytes++]; - if (xof->num_bytes == rate) { - permute(xof->a.u64, num_rounds); - xof->num_bytes = 0; +static inline void xof_squeeze_raw(sha3_xof_t * const xof, const size_t rate, const size_t num_rounds, uint8_t *dst, size_t dst_len) { + if (!xof->num_bytes) { + // num_bytes is zero, so we are reading from the start of the + // internal state buffer. while `dst_len` is greater than rate, + // copy `rate` sized chunks directly from the internal state buffer + // to the destination, then permute the internal state. squeeze + // rate-sized chunks to destination + while (dst_len >= rate) { + memcpy(dst, xof->a.u8, rate); // copy rate-sized chunk + permute(xof->a.u64, num_rounds); // permute state + + // update destination pointer and length + dst += rate; + dst_len -= rate; + } + + if (dst_len > 0) { + // the remaining destination length is less than `rate`, so copy a + // `dst_len`-sized chunk from the internal state to the + // destination buffer, then update the read byte count. + + // squeeze dst_len-sized block to destination + memcpy(dst, xof->a.u8, dst_len); // copy dst_len-sized chunk + xof->num_bytes = dst_len; // update read byte count + } + } else { + // fall back to squeezing one byte at a time + + // squeeze bytes to destination + for (size_t i = 0; i < dst_len; i++) { + dst[i] = xof->a.u8[xof->num_bytes++]; // squeeze byte to destination + + if (xof->num_bytes == rate) { + permute(xof->a.u64, num_rounds); // permute state + xof->num_bytes = 0; // clear read bytes count + } } } } |