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