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static inline void
enc_loop_generic_64_inner (const uint8_t **s, uint8_t **o)
{
uint64_t src;
// Load input:
memcpy(&src, *s, sizeof (src));
// Reorder to 64-bit big-endian, if not already in that format. The
// workset must be in big-endian, otherwise the shifted bits do not
// carry over properly among adjacent bytes:
src = BASE64_HTOBE64(src);
// Four indices for the 12-bit lookup table:
const size_t index0 = (src >> 52) & 0xFFFU;
const size_t index1 = (src >> 40) & 0xFFFU;
const size_t index2 = (src >> 28) & 0xFFFU;
const size_t index3 = (src >> 16) & 0xFFFU;
// Table lookup and store:
memcpy(*o + 0, base64_table_enc_12bit + index0, 2);
memcpy(*o + 2, base64_table_enc_12bit + index1, 2);
memcpy(*o + 4, base64_table_enc_12bit + index2, 2);
memcpy(*o + 6, base64_table_enc_12bit + index3, 2);
*s += 6;
*o += 8;
}
static inline void
enc_loop_generic_64 (const uint8_t **s, size_t *slen, uint8_t **o, size_t *olen)
{
if (*slen < 8) {
return;
}
// Process blocks of 6 bytes at a time. Because blocks are loaded 8
// bytes at a time, ensure that there will be at least 2 remaining
// bytes after the last round, so that the final read will not pass
// beyond the bounds of the input buffer:
size_t rounds = (*slen - 2) / 6;
*slen -= rounds * 6; // 6 bytes consumed per round
*olen += rounds * 8; // 8 bytes produced per round
do {
if (rounds >= 8) {
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
rounds -= 8;
continue;
}
if (rounds >= 4) {
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
rounds -= 4;
continue;
}
if (rounds >= 2) {
enc_loop_generic_64_inner(s, o);
enc_loop_generic_64_inner(s, o);
rounds -= 2;
continue;
}
enc_loop_generic_64_inner(s, o);
break;
} while (rounds > 0);
}
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