| 1 | /* |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * All rights reserved. |
| 4 | * |
| 5 | * This source code is licensed under both the BSD-style license (found in the |
| 6 | * LICENSE file in the root directory of this source tree) and the GPLv2 (found |
| 7 | * in the COPYING file in the root directory of this source tree). |
| 8 | * You may select, at your option, one of the above-listed licenses. |
| 9 | */ |
| 10 | |
| 11 | #include "seqgen.h" |
| 12 | #include "mem.h" |
| 13 | #include <string.h> |
| 14 | |
| 15 | #define MIN(a, b) ((a) < (b) ? (a) : (b)) |
| 16 | |
| 17 | static const size_t kMatchBytes = 128; |
| 18 | |
| 19 | #define SEQ_rotl32(x,r) ((x << r) | (x >> (32 - r))) |
| 20 | static BYTE SEQ_randByte(unsigned* src) |
| 21 | { |
| 22 | static const U32 prime1 = 2654435761U; |
| 23 | static const U32 prime2 = 2246822519U; |
| 24 | U32 rand32 = *src; |
| 25 | rand32 *= prime1; |
| 26 | rand32 ^= prime2; |
| 27 | rand32 = SEQ_rotl32(rand32, 13); |
| 28 | *src = rand32; |
| 29 | return (BYTE)(rand32 >> 5); |
| 30 | } |
| 31 | |
| 32 | SEQ_stream SEQ_initStream(unsigned seed) |
| 33 | { |
| 34 | SEQ_stream stream; |
| 35 | stream.state = 0; |
| 36 | XXH64_reset(&stream.xxh, 0); |
| 37 | stream.seed = seed; |
| 38 | return stream; |
| 39 | } |
| 40 | |
| 41 | /* Generates a single guard byte, then match length + 1 of a different byte, |
| 42 | * then another guard byte. |
| 43 | */ |
| 44 | static size_t SEQ_gen_matchLength(SEQ_stream* stream, unsigned value, |
| 45 | SEQ_outBuffer* out) |
| 46 | { |
| 47 | typedef enum { |
| 48 | ml_first_byte = 0, |
| 49 | ml_match_bytes, |
| 50 | ml_last_byte, |
| 51 | } ml_state; |
| 52 | BYTE* const ostart = (BYTE*)out->dst; |
| 53 | BYTE* const oend = ostart + out->size; |
| 54 | BYTE* op = ostart + out->pos; |
| 55 | |
| 56 | switch ((ml_state)stream->state) { |
| 57 | case ml_first_byte: |
| 58 | /* Generate a single byte and pick a different byte for the match */ |
| 59 | if (op >= oend) { |
| 60 | stream->bytesLeft = 1; |
| 61 | break; |
| 62 | } |
| 63 | *op = SEQ_randByte(&stream->seed) & 0xFF; |
| 64 | do { |
| 65 | stream->saved = SEQ_randByte(&stream->seed) & 0xFF; |
| 66 | } while (*op == stream->saved); |
| 67 | ++op; |
| 68 | /* State transition */ |
| 69 | stream->state = ml_match_bytes; |
| 70 | stream->bytesLeft = value + 1; |
| 71 | /* fall-through */ |
| 72 | case ml_match_bytes: { |
| 73 | /* Copy matchLength + 1 bytes to the output buffer */ |
| 74 | size_t const setLength = MIN(stream->bytesLeft, (size_t)(oend - op)); |
| 75 | if (setLength > 0) { |
| 76 | memset(op, stream->saved, setLength); |
| 77 | op += setLength; |
| 78 | stream->bytesLeft -= setLength; |
| 79 | } |
| 80 | if (stream->bytesLeft > 0) |
| 81 | break; |
| 82 | /* State transition */ |
| 83 | stream->state = ml_last_byte; |
| 84 | } |
| 85 | /* fall-through */ |
| 86 | case ml_last_byte: |
| 87 | /* Generate a single byte and pick a different byte for the match */ |
| 88 | if (op >= oend) { |
| 89 | stream->bytesLeft = 1; |
| 90 | break; |
| 91 | } |
| 92 | do { |
| 93 | *op = SEQ_randByte(&stream->seed) & 0xFF; |
| 94 | } while (*op == stream->saved); |
| 95 | ++op; |
| 96 | /* State transition */ |
| 97 | /* fall-through */ |
| 98 | default: |
| 99 | stream->state = 0; |
| 100 | stream->bytesLeft = 0; |
| 101 | break; |
| 102 | } |
| 103 | XXH64_update(&stream->xxh, ostart + out->pos, (op - ostart) - out->pos); |
| 104 | out->pos = op - ostart; |
| 105 | return stream->bytesLeft; |
| 106 | } |
| 107 | |
| 108 | /* Saves the current seed then generates kMatchBytes random bytes >= 128. |
| 109 | * Generates literal length - kMatchBytes random bytes < 128. |
| 110 | * Generates another kMatchBytes using the saved seed to generate a match. |
| 111 | * This way the match is easy to find for the compressors. |
| 112 | */ |
| 113 | static size_t SEQ_gen_litLength(SEQ_stream* stream, unsigned value, SEQ_outBuffer* out) |
| 114 | { |
| 115 | typedef enum { |
| 116 | ll_start = 0, |
| 117 | ll_run_bytes, |
| 118 | ll_literals, |
| 119 | ll_run_match, |
| 120 | } ll_state; |
| 121 | BYTE* const ostart = (BYTE*)out->dst; |
| 122 | BYTE* const oend = ostart + out->size; |
| 123 | BYTE* op = ostart + out->pos; |
| 124 | |
| 125 | switch ((ll_state)stream->state) { |
| 126 | case ll_start: |
| 127 | stream->state = ll_run_bytes; |
| 128 | stream->saved = stream->seed; |
| 129 | stream->bytesLeft = MIN(kMatchBytes, value); |
| 130 | /* fall-through */ |
| 131 | case ll_run_bytes: |
| 132 | while (stream->bytesLeft > 0 && op < oend) { |
| 133 | *op++ = SEQ_randByte(&stream->seed) | 0x80; |
| 134 | --stream->bytesLeft; |
| 135 | } |
| 136 | if (stream->bytesLeft > 0) |
| 137 | break; |
| 138 | /* State transition */ |
| 139 | stream->state = ll_literals; |
| 140 | stream->bytesLeft = value - MIN(kMatchBytes, value); |
| 141 | /* fall-through */ |
| 142 | case ll_literals: |
| 143 | while (stream->bytesLeft > 0 && op < oend) { |
| 144 | *op++ = SEQ_randByte(&stream->seed) & 0x7F; |
| 145 | --stream->bytesLeft; |
| 146 | } |
| 147 | if (stream->bytesLeft > 0) |
| 148 | break; |
| 149 | /* State transition */ |
| 150 | stream->state = ll_run_match; |
| 151 | stream->bytesLeft = MIN(kMatchBytes, value); |
| 152 | /* fall-through */ |
| 153 | case ll_run_match: { |
| 154 | while (stream->bytesLeft > 0 && op < oend) { |
| 155 | *op++ = SEQ_randByte(&stream->saved) | 0x80; |
| 156 | --stream->bytesLeft; |
| 157 | } |
| 158 | if (stream->bytesLeft > 0) |
| 159 | break; |
| 160 | } |
| 161 | /* fall-through */ |
| 162 | default: |
| 163 | stream->state = 0; |
| 164 | stream->bytesLeft = 0; |
| 165 | break; |
| 166 | } |
| 167 | XXH64_update(&stream->xxh, ostart + out->pos, (op - ostart) - out->pos); |
| 168 | out->pos = op - ostart; |
| 169 | return stream->bytesLeft; |
| 170 | } |
| 171 | |
| 172 | /* Saves the current seed then generates kMatchBytes random bytes >= 128. |
| 173 | * Generates offset - kMatchBytes of zeros to get a large offset without |
| 174 | * polluting the hash tables. |
| 175 | * Generates another kMatchBytes using the saved seed to generate a with the |
| 176 | * required offset. |
| 177 | */ |
| 178 | static size_t SEQ_gen_offset(SEQ_stream* stream, unsigned value, SEQ_outBuffer* out) |
| 179 | { |
| 180 | typedef enum { |
| 181 | of_start = 0, |
| 182 | of_run_bytes, |
| 183 | of_offset, |
| 184 | of_run_match, |
| 185 | } of_state; |
| 186 | BYTE* const ostart = (BYTE*)out->dst; |
| 187 | BYTE* const oend = ostart + out->size; |
| 188 | BYTE* op = ostart + out->pos; |
| 189 | |
| 190 | switch ((of_state)stream->state) { |
| 191 | case of_start: |
| 192 | stream->state = of_run_bytes; |
| 193 | stream->saved = stream->seed; |
| 194 | stream->bytesLeft = MIN(value, kMatchBytes); |
| 195 | /* fall-through */ |
| 196 | case of_run_bytes: { |
| 197 | while (stream->bytesLeft > 0 && op < oend) { |
| 198 | *op++ = SEQ_randByte(&stream->seed) | 0x80; |
| 199 | --stream->bytesLeft; |
| 200 | } |
| 201 | if (stream->bytesLeft > 0) |
| 202 | break; |
| 203 | /* State transition */ |
| 204 | stream->state = of_offset; |
| 205 | stream->bytesLeft = value - MIN(value, kMatchBytes); |
| 206 | } |
| 207 | /* fall-through */ |
| 208 | case of_offset: { |
| 209 | /* Copy matchLength + 1 bytes to the output buffer */ |
| 210 | size_t const setLength = MIN(stream->bytesLeft, (size_t)(oend - op)); |
| 211 | if (setLength > 0) { |
| 212 | memset(op, 0, setLength); |
| 213 | op += setLength; |
| 214 | stream->bytesLeft -= setLength; |
| 215 | } |
| 216 | if (stream->bytesLeft > 0) |
| 217 | break; |
| 218 | /* State transition */ |
| 219 | stream->state = of_run_match; |
| 220 | stream->bytesLeft = MIN(value, kMatchBytes); |
| 221 | } |
| 222 | /* fall-through */ |
| 223 | case of_run_match: { |
| 224 | while (stream->bytesLeft > 0 && op < oend) { |
| 225 | *op++ = SEQ_randByte(&stream->saved) | 0x80; |
| 226 | --stream->bytesLeft; |
| 227 | } |
| 228 | if (stream->bytesLeft > 0) |
| 229 | break; |
| 230 | } |
| 231 | /* fall-through */ |
| 232 | default: |
| 233 | stream->state = 0; |
| 234 | stream->bytesLeft = 0; |
| 235 | break; |
| 236 | } |
| 237 | XXH64_update(&stream->xxh, ostart + out->pos, (op - ostart) - out->pos); |
| 238 | out->pos = op - ostart; |
| 239 | return stream->bytesLeft; |
| 240 | } |
| 241 | |
| 242 | /* Returns the number of bytes left to generate. |
| 243 | * Must pass the same type/value until it returns 0. |
| 244 | */ |
| 245 | size_t SEQ_gen(SEQ_stream* stream, SEQ_gen_type type, unsigned value, SEQ_outBuffer* out) |
| 246 | { |
| 247 | switch (type) { |
| 248 | case SEQ_gen_ml: return SEQ_gen_matchLength(stream, value, out); |
| 249 | case SEQ_gen_ll: return SEQ_gen_litLength(stream, value, out); |
| 250 | case SEQ_gen_of: return SEQ_gen_offset(stream, value, out); |
| 251 | case SEQ_gen_max: /* fall-through */ |
| 252 | default: return 0; |
| 253 | } |
| 254 | } |
| 255 | |
| 256 | /* Returns the xxhash of the data produced so far */ |
| 257 | XXH64_hash_t SEQ_digest(SEQ_stream const* stream) |
| 258 | { |
| 259 | return XXH64_digest(&stream->xxh); |
| 260 | } |