mirror of
https://github.com/kovidgoyal/kitty
synced 2026-06-11 11:09:16 +02:00
174 lines
6.7 KiB
C
Vendored
174 lines
6.7 KiB
C
Vendored
// The input consists of six character sets in the Base64 alphabet, which we
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// need to map back to the 6-bit values they represent. There are three ranges,
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// two singles, and then there's the rest.
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//
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// # From To Add Characters
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// 1 [43] [62] +19 +
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// 2 [47] [63] +16 /
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// 3 [48..57] [52..61] +4 0..9
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// 4 [65..90] [0..25] -65 A..Z
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// 5 [97..122] [26..51] -71 a..z
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// (6) Everything else => invalid input
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//
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// We will use lookup tables for character validation and offset computation.
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// Remember that 0x2X and 0x0X are the same index for _mm_shuffle_epi8, this
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// allows to mask with 0x2F instead of 0x0F and thus save one constant
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// declaration (register and/or memory access).
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//
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// For offsets:
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// Perfect hash for lut = ((src >> 4) & 0x2F) + ((src == 0x2F) ? 0xFF : 0x00)
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// 0000 = garbage
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// 0001 = /
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// 0010 = +
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// 0011 = 0-9
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// 0100 = A-Z
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// 0101 = A-Z
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// 0110 = a-z
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// 0111 = a-z
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// 1000 >= garbage
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//
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// For validation, here's the table.
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// A character is valid if and only if the AND of the 2 lookups equals 0:
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//
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// hi \ lo 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111
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// LUT 0x15 0x11 0x11 0x11 0x11 0x11 0x11 0x11 0x11 0x11 0x13 0x1A 0x1B 0x1B 0x1B 0x1A
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//
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// 0000 0x10 char NUL SOH STX ETX EOT ENQ ACK BEL BS HT LF VT FF CR SO SI
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// andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10
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//
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// 0001 0x10 char DLE DC1 DC2 DC3 DC4 NAK SYN ETB CAN EM SUB ESC FS GS RS US
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// andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10
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//
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// 0010 0x01 char ! " # $ % & ' ( ) * + , - . /
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// andlut 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x00 0x01 0x01 0x01 0x00
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//
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// 0011 0x02 char 0 1 2 3 4 5 6 7 8 9 : ; < = > ?
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// andlut 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x02 0x02 0x02 0x02 0x02 0x02
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//
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// 0100 0x04 char @ A B C D E F G H I J K L M N O
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// andlut 0x04 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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//
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// 0101 0x08 char P Q R S T U V W X Y Z [ \ ] ^ _
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// andlut 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x08 0x08 0x08 0x08 0x08
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//
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// 0110 0x04 char ` a b c d e f g h i j k l m n o
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// andlut 0x04 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
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// 0111 0x08 char p q r s t u v w x y z { | } ~
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// andlut 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x08 0x08 0x08 0x08 0x08
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//
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// 1000 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10
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// 1001 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10
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// 1010 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10
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// 1011 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10
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// 1100 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10
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// 1101 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10
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// 1110 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10
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// 1111 0x10 andlut 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10 0x10
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static inline int
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dec_loop_ssse3_inner (const uint8_t **s, uint8_t **o, size_t *rounds)
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{
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const __m128i lut_lo = _mm_setr_epi8(
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0x15, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11,
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0x11, 0x11, 0x13, 0x1A, 0x1B, 0x1B, 0x1B, 0x1A);
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const __m128i lut_hi = _mm_setr_epi8(
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0x10, 0x10, 0x01, 0x02, 0x04, 0x08, 0x04, 0x08,
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0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10);
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const __m128i lut_roll = _mm_setr_epi8(
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0, 16, 19, 4, -65, -65, -71, -71,
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0, 0, 0, 0, 0, 0, 0, 0);
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const __m128i mask_2F = _mm_set1_epi8(0x2F);
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// Load input:
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__m128i str = _mm_loadu_si128((__m128i *) *s);
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// Table lookups:
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const __m128i hi_nibbles = _mm_and_si128(_mm_srli_epi32(str, 4), mask_2F);
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const __m128i lo_nibbles = _mm_and_si128(str, mask_2F);
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const __m128i hi = _mm_shuffle_epi8(lut_hi, hi_nibbles);
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const __m128i lo = _mm_shuffle_epi8(lut_lo, lo_nibbles);
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// Check for invalid input: if any "and" values from lo and hi are not
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// zero, fall back on bytewise code to do error checking and reporting:
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if (_mm_movemask_epi8(_mm_cmpgt_epi8(_mm_and_si128(lo, hi), _mm_setzero_si128())) != 0) {
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return 0;
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}
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const __m128i eq_2F = _mm_cmpeq_epi8(str, mask_2F);
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const __m128i roll = _mm_shuffle_epi8(lut_roll, _mm_add_epi8(eq_2F, hi_nibbles));
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// Now simply add the delta values to the input:
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str = _mm_add_epi8(str, roll);
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// Reshuffle the input to packed 12-byte output format:
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str = dec_reshuffle(str);
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// Store the output:
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_mm_storeu_si128((__m128i *) *o, str);
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*s += 16;
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*o += 12;
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*rounds -= 1;
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return 1;
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}
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static inline void
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dec_loop_ssse3 (const uint8_t **s, size_t *slen, uint8_t **o, size_t *olen)
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{
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if (*slen < 24) {
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return;
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}
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// Process blocks of 16 bytes per round. Because 4 extra zero bytes are
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// written after the output, ensure that there will be at least 8 bytes
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// of input data left to cover the gap. (6 data bytes and up to two
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// end-of-string markers.)
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size_t rounds = (*slen - 8) / 16;
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*slen -= rounds * 16; // 16 bytes consumed per round
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*olen += rounds * 12; // 12 bytes produced per round
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do {
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if (rounds >= 8) {
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if (dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds)) {
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continue;
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}
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break;
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}
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if (rounds >= 4) {
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if (dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds)) {
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continue;
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}
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break;
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}
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if (rounds >= 2) {
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if (dec_loop_ssse3_inner(s, o, &rounds) &&
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dec_loop_ssse3_inner(s, o, &rounds)) {
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continue;
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}
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break;
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}
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dec_loop_ssse3_inner(s, o, &rounds);
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break;
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} while (rounds > 0);
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// Adjust for any rounds that were skipped:
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*slen += rounds * 16;
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*olen -= rounds * 12;
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}
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