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static inline void
enc_loop_generic_32_inner (const uint8_t **s, uint8_t **o)
{
uint32_t src;
// Load input:
memcpy(&src, *s, sizeof (src));
// Reorder to 32-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_HTOBE32(src);
// Two indices for the 12-bit lookup table:
const size_t index0 = (src >> 20) & 0xFFFU;
const size_t index1 = (src >> 8) & 0xFFFU;
// Table lookup and store:
memcpy(*o + 0, base64_table_enc_12bit + index0, 2);
memcpy(*o + 2, base64_table_enc_12bit + index1, 2);
*s += 3;
*o += 4;
}
static inline void
enc_loop_generic_32 (const uint8_t **s, size_t *slen, uint8_t **o, size_t *olen)
{
if (*slen < 4) {
return;
}
// Process blocks of 3 bytes at a time. Because blocks are loaded 4
// bytes at a time, ensure that there will be at least one remaining
// byte after the last round, so that the final read will not pass
// beyond the bounds of the input buffer:
size_t rounds = (*slen - 1) / 3;
*slen -= rounds * 3; // 3 bytes consumed per round
*olen += rounds * 4; // 4 bytes produced per round
do {
if (rounds >= 8) {
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
rounds -= 8;
continue;
}
if (rounds >= 4) {
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
rounds -= 4;
continue;
}
if (rounds >= 2) {
enc_loop_generic_32_inner(s, o);
enc_loop_generic_32_inner(s, o);
rounds -= 2;
continue;
}
enc_loop_generic_32_inner(s, o);
break;
} while (rounds > 0);
}
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