lib/minilex.c

   1 /*
   2  * minilex.c
   3  *
   4  * High efficiency lexical state parser
   5  *
   6  * Copyright (C)2011-2014 Andy Green <andy@warmcat.com>
   7  *
   8  * Licensed under LGPL2
   9  *
  10  * Usage: gcc minilex.c -o minilex && ./minilex > lextable.h
  11  *
  12  * Run it twice to test parsing on the generated table on stderr
  13  */
  14
  15 #include <stdio.h>
  16 #include <stdlib.h>
  17 #include <string.h>
  18
  19 /* set of parsable strings -- ALL LOWER CASE */
  20
  21 const char *set[] = {
  22         "get ",
  23         "post ",
  24         "host:",
  25         "connection:",
  26         "sec-websocket-key1:",
  27         "sec-websocket-key2:",
  28         "sec-websocket-protocol:",
  29         "upgrade:",
  30         "origin:",
  31         "sec-websocket-draft:",
  32         "\x0d\x0a",
  33
  34         "sec-websocket-key:",
  35         "sec-websocket-version:",
  36         "sec-websocket-origin:",
  37
  38         "sec-websocket-extensions:",
  39
  40         "sec-websocket-accept:",
  41         "sec-websocket-nonce:",
  42         "http/1.1 ",
  43
  44         "accept:",
  45         "if-modified-since:",
  46         "accept-encoding:",
  47         "accept-language:",
  48         "pragma:",
  49         "cache-control:",
  50         "authorization:",
  51         "cookie:",
  52         "content-length:",
  53         "content-type:",
  54         "date:",
  55         "range:",
  56         "referer:",
  57         "", /* not matchable */
  58
  59 };
  60
  61 /*
  62  * b7 = 0 = 1-byte seq
  63  *          0x08 = fail
  64  *          2-byte seq
  65  *          0x00 - 0x07, then terminal as given in 2nd byte
  66             3-byte seq
  67  *          no match: go fwd 3 byte, match: jump fwd by amt in +1/+2 bytes
  68  *    = 1 = 1-byte seq
  69  *          no match: die, match go fwd 1 byte
  70  */
  71
  72 unsigned char lextable[] = {
  73         #include "lextable.h"
  74 };
  75
  76 #define PARALLEL 30
  77
  78 struct state {
  79         char c[PARALLEL];
  80         int state[PARALLEL];
  81         int count;
  82         int bytepos;
  83
  84         int real_pos;
  85 };
  86
  87 struct state state[1000];
  88 int next = 1;
  89
  90 #define FAIL_CHAR 0x08
  91
  92 int lextable_decode(int pos, char c)
  93 {
  94
  95         while (1) {
  96                 if (lextable[pos] & (1 << 7)) { /* 1-byte, fail on mismatch */
  97                         if ((lextable[pos] & 0x7f) != c)
  98                                 return -1;
  99                         /* fall thru */
 100                         pos++;
 101                         if (lextable[pos] == FAIL_CHAR)
 102                                 return -1;
 103                         return pos;
 104                 } else { /* b7 = 0, end or 3-byte */
 105                         if (lextable[pos] < FAIL_CHAR) /* terminal marker */
 106                                 return pos;
 107
 108                         if (lextable[pos] == c) /* goto */
 109                                 return pos + (lextable[pos + 1]) +
 110                                                 (lextable[pos + 2] << 8);
 111                         /* fall thru goto */
 112                         pos += 3;
 113                         /* continue */
 114                 }
 115         }
 116 }
 117
 118 int main(void)
 119 {
 120         int n = 0;
 121         int m = 0;
 122         int prev;
 123         char c;
 124         int walk;
 125         int saw;
 126         int y;
 127         int j;
 128         int pos = 0;
 129
 130         while (n < sizeof(set) / sizeof(set[0])) {
 131
 132                 m = 0;
 133                 walk = 0;
 134                 prev = 0;
 135
 136                 if (set[n][0] == '\0') {
 137                         n++;
 138                         continue;
 139                 }
 140
 141                 while (set[n][m]) {
 142
 143                         saw = 0;
 144                         for (y = 0; y < state[walk].count; y++)
 145                                 if (state[walk].c[y] == set[n][m]) {
 146                                         /* exists -- go forward */
 147                                         walk = state[walk].state[y];
 148                                         saw = 1;
 149                                         break;
 150                                 }
 151
 152                         if (saw)
 153                                 goto again;
 154
 155                         /* something we didn't see before */
 156
 157                         state[walk].c[state[walk].count] = set[n][m];
 158
 159                         state[walk].state[state[walk].count] = next;
 160                         state[walk].count++;
 161                         walk = next++;
 162 again:
 163                         m++;
 164                 }
 165
 166                 state[walk].c[0] = n++;
 167                 state[walk].state[0] = 0; /* terminal marker */
 168                 state[walk].count = 1;
 169         }
 170
 171         walk = 0;
 172         for (n = 0; n < next; n++) {
 173                 state[n].bytepos = walk;
 174                 walk += (2 * state[n].count);
 175         }
 176
 177         /* compute everyone's position first */
 178
 179         pos = 0;
 180         walk = 0;
 181         for (n = 0; n < next; n++) {
 182
 183                 state[n].real_pos = pos;
 184
 185                 for (m = 0; m < state[n].count; m++) {
 186
 187                         if (state[n].state[m] == 0)
 188                                 pos += 2; /* terminal marker */
 189                         else { /* c is a character */
 190                                 if ((state[state[n].state[m]].bytepos -
 191                                                                 walk) == 2)
 192                                         pos++;
 193                                 else {
 194                                         pos += 3;
 195                                         if (m == state[n].count - 1)
 196                                                 pos++; /* fail */
 197                                 }
 198                         }
 199                         walk += 2;
 200                 }
 201         }
 202
 203         walk = 0;
 204         pos = 0;
 205         for (n = 0; n < next; n++) {
 206                 for (m = 0; m < state[n].count; m++) {
 207
 208                         if (!m)
 209                                 fprintf(stdout, "/* pos %04x: %3d */ ",
 210                                                           state[n].real_pos, n);
 211                         else
 212                                 fprintf(stdout, "                    ");
 213
 214                         y = state[n].c[m];
 215                         saw = state[n].state[m];
 216
 217                         if (saw == 0) { // c is a terminal then
 218
 219                                 if (y > 0x7ff) {
 220                                         fprintf(stderr, "terminal too big\n");
 221                                         return 2;
 222                                 }
 223
 224                                 fprintf(stdout, "   0x%02X, 0x%02X           "
 225                                         "       "
 226                                         "/* - terminal marker %2d - */,\n",
 227                                                     y >> 8, y & 0xff, y & 0x7f);
 228                                 pos += 2;
 229                                 walk += 2;
 230                                 continue;
 231                         }
 232
 233                         /* c is a character */
 234
 235                         prev = y &0x7f;
 236                         if (prev < 32 || prev > 126)
 237                                 prev = '.';
 238
 239
 240                         if ((state[saw].bytepos - walk) == 2) {
 241                                 fprintf(stdout, "   0x%02X /* '%c' -> */,\n",
 242                                                 y | 0x80, prev);
 243                                 pos++;
 244                                 walk += 2;
 245                                 continue;
 246                         }
 247
 248                         j = state[saw].real_pos - pos;
 249
 250                         if (j > 0xffff) {
 251                                 fprintf(stderr,
 252                                   "Jump > 64K bytes ahead (%d to %d)\n",
 253                                         state[n].real_pos, state[saw].real_pos);
 254                                 return 1;
 255                         }
 256                         fprintf(stdout, "   0x%02X /* '%c' */, 0x%02X, 0x%02X  "
 257                                 "/* (to 0x%04X state %3d) */,\n",
 258                                 y, prev,
 259                                 j & 0xff, j >> 8,
 260                                 state[saw].real_pos, saw);
 261                         pos += 3;
 262
 263                         if (m == state[n].count - 1) {
 264                                 fprintf(stdout,
 265                                   "                       0x%02X, /* fail */\n",
 266                                                                 FAIL_CHAR);
 267                                 pos++; /* fail */
 268                         }
 269
 270                         walk += 2;
 271                 }
 272         }
 273
 274         fprintf(stdout, "/* total size %d bytes */\n", pos);
 275
 276         /*
 277          * Try to parse every legal input string
 278          */
 279
 280         for (n = 0; n < sizeof(set) / sizeof(set[0]); n++) {
 281                 walk = 0;
 282                 m = 0;
 283                 y = -1;
 284
 285                 if (set[n][0] == '\0')
 286                         continue;
 287
 288                 fprintf(stderr, "  trying '%s'\n", set[n]);
 289
 290                 while (set[n][m]) {
 291                         walk = lextable_decode(walk, set[n][m]);
 292                         if (walk < 0) {
 293                                 fprintf(stderr, "failed\n");
 294                                 return 3;
 295                         }
 296
 297                         if (lextable[walk] < FAIL_CHAR) {
 298                                 y = (lextable[walk] << 8) + lextable[walk + 1];
 299                                 break;
 300                         }
 301                         m++;
 302                 }
 303
 304                 if (y != n) {
 305                         fprintf(stderr, "decode failed %d\n", y);
 306                         return 4;
 307                 }
 308         }
 309
 310         fprintf(stderr, "All decode OK\n");
 311
 312         return 0;
 313 }