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         "access-control-request-headers:",
  46         "if-modified-since:",
  47         "if-none-match:"
  48         "accept-encoding:",
  49         "accept-language:",
  50         "pragma:",
  51         "cache-control:",
  52         "authorization:",
  53         "cookie:",
  54         "content-length:",
  55         "content-type:",
  56         "date:",
  57         "range:",
  58         "referer:",
  59         "", /* not matchable */
  60
  61 };
  62
  63 /*
  64  * b7 = 0 = 1-byte seq
  65  *          0x08 = fail
  66  *          2-byte seq
  67  *          0x00 - 0x07, then terminal as given in 2nd byte
  68             3-byte seq
  69  *          no match: go fwd 3 byte, match: jump fwd by amt in +1/+2 bytes
  70  *    = 1 = 1-byte seq
  71  *          no match: die, match go fwd 1 byte
  72  */
  73
  74 unsigned char lextable[] = {
  75         #include "lextable.h"
  76 };
  77
  78 #define PARALLEL 30
  79
  80 struct state {
  81         char c[PARALLEL];
  82         int state[PARALLEL];
  83         int count;
  84         int bytepos;
  85
  86         int real_pos;
  87 };
  88
  89 struct state state[1000];
  90 int next = 1;
  91
  92 #define FAIL_CHAR 0x08
  93
  94 int lextable_decode(int pos, char c)
  95 {
  96
  97         while (1) {
  98                 if (lextable[pos] & (1 << 7)) { /* 1-byte, fail on mismatch */
  99                         if ((lextable[pos] & 0x7f) != c)
 100                                 return -1;
 101                         /* fall thru */
 102                         pos++;
 103                         if (lextable[pos] == FAIL_CHAR)
 104                                 return -1;
 105                         return pos;
 106                 } else { /* b7 = 0, end or 3-byte */
 107                         if (lextable[pos] < FAIL_CHAR) /* terminal marker */
 108                                 return pos;
 109
 110                         if (lextable[pos] == c) /* goto */
 111                                 return pos + (lextable[pos + 1]) +
 112                                                 (lextable[pos + 2] << 8);
 113                         /* fall thru goto */
 114                         pos += 3;
 115                         /* continue */
 116                 }
 117         }
 118 }
 119
 120 int main(void)
 121 {
 122         int n = 0;
 123         int m = 0;
 124         int prev;
 125         char c;
 126         int walk;
 127         int saw;
 128         int y;
 129         int j;
 130         int pos = 0;
 131
 132         while (n < sizeof(set) / sizeof(set[0])) {
 133
 134                 m = 0;
 135                 walk = 0;
 136                 prev = 0;
 137
 138                 if (set[n][0] == '\0') {
 139                         n++;
 140                         continue;
 141                 }
 142
 143                 while (set[n][m]) {
 144
 145                         saw = 0;
 146                         for (y = 0; y < state[walk].count; y++)
 147                                 if (state[walk].c[y] == set[n][m]) {
 148                                         /* exists -- go forward */
 149                                         walk = state[walk].state[y];
 150                                         saw = 1;
 151                                         break;
 152                                 }
 153
 154                         if (saw)
 155                                 goto again;
 156
 157                         /* something we didn't see before */
 158
 159                         state[walk].c[state[walk].count] = set[n][m];
 160
 161                         state[walk].state[state[walk].count] = next;
 162                         state[walk].count++;
 163                         walk = next++;
 164 again:
 165                         m++;
 166                 }
 167
 168                 state[walk].c[0] = n++;
 169                 state[walk].state[0] = 0; /* terminal marker */
 170                 state[walk].count = 1;
 171         }
 172
 173         walk = 0;
 174         for (n = 0; n < next; n++) {
 175                 state[n].bytepos = walk;
 176                 walk += (2 * state[n].count);
 177         }
 178
 179         /* compute everyone's position first */
 180
 181         pos = 0;
 182         walk = 0;
 183         for (n = 0; n < next; n++) {
 184
 185                 state[n].real_pos = pos;
 186
 187                 for (m = 0; m < state[n].count; m++) {
 188
 189                         if (state[n].state[m] == 0)
 190                                 pos += 2; /* terminal marker */
 191                         else { /* c is a character */
 192                                 if ((state[state[n].state[m]].bytepos -
 193                                                                 walk) == 2)
 194                                         pos++;
 195                                 else {
 196                                         pos += 3;
 197                                         if (m == state[n].count - 1)
 198                                                 pos++; /* fail */
 199                                 }
 200                         }
 201                         walk += 2;
 202                 }
 203         }
 204
 205         walk = 0;
 206         pos = 0;
 207         for (n = 0; n < next; n++) {
 208                 for (m = 0; m < state[n].count; m++) {
 209
 210                         if (!m)
 211                                 fprintf(stdout, "/* pos %04x: %3d */ ",
 212                                                           state[n].real_pos, n);
 213                         else
 214                                 fprintf(stdout, "                    ");
 215
 216                         y = state[n].c[m];
 217                         saw = state[n].state[m];
 218
 219                         if (saw == 0) { // c is a terminal then
 220
 221                                 if (y > 0x7ff) {
 222                                         fprintf(stderr, "terminal too big\n");
 223                                         return 2;
 224                                 }
 225
 226                                 fprintf(stdout, "   0x%02X, 0x%02X           "
 227                                         "       "
 228                                         "/* - terminal marker %2d - */,\n",
 229                                                     y >> 8, y & 0xff, y & 0x7f);
 230                                 pos += 2;
 231                                 walk += 2;
 232                                 continue;
 233                         }
 234
 235                         /* c is a character */
 236
 237                         prev = y &0x7f;
 238                         if (prev < 32 || prev > 126)
 239                                 prev = '.';
 240
 241
 242                         if ((state[saw].bytepos - walk) == 2) {
 243                                 fprintf(stdout, "   0x%02X /* '%c' -> */,\n",
 244                                                 y | 0x80, prev);
 245                                 pos++;
 246                                 walk += 2;
 247                                 continue;
 248                         }
 249
 250                         j = state[saw].real_pos - pos;
 251
 252                         if (j > 0xffff) {
 253                                 fprintf(stderr,
 254                                   "Jump > 64K bytes ahead (%d to %d)\n",
 255                                         state[n].real_pos, state[saw].real_pos);
 256                                 return 1;
 257                         }
 258                         fprintf(stdout, "   0x%02X /* '%c' */, 0x%02X, 0x%02X  "
 259                                 "/* (to 0x%04X state %3d) */,\n",
 260                                 y, prev,
 261                                 j & 0xff, j >> 8,
 262                                 state[saw].real_pos, saw);
 263                         pos += 3;
 264
 265                         if (m == state[n].count - 1) {
 266                                 fprintf(stdout,
 267                                   "                       0x%02X, /* fail */\n",
 268                                                                 FAIL_CHAR);
 269                                 pos++; /* fail */
 270                         }
 271
 272                         walk += 2;
 273                 }
 274         }
 275
 276         fprintf(stdout, "/* total size %d bytes */\n", pos);
 277
 278         /*
 279          * Try to parse every legal input string
 280          */
 281
 282         for (n = 0; n < sizeof(set) / sizeof(set[0]); n++) {
 283                 walk = 0;
 284                 m = 0;
 285                 y = -1;
 286
 287                 if (set[n][0] == '\0')
 288                         continue;
 289
 290                 fprintf(stderr, "  trying '%s'\n", set[n]);
 291
 292                 while (set[n][m]) {
 293                         walk = lextable_decode(walk, set[n][m]);
 294                         if (walk < 0) {
 295                                 fprintf(stderr, "failed\n");
 296                                 return 3;
 297                         }
 298
 299                         if (lextable[walk] < FAIL_CHAR) {
 300                                 y = (lextable[walk] << 8) + lextable[walk + 1];
 301                                 break;
 302                         }
 303                         m++;
 304                 }
 305
 306                 if (y != n) {
 307                         fprintf(stderr, "decode failed %d\n", y);
 308                         return 4;
 309                 }
 310         }
 311
 312         fprintf(stderr, "All decode OK\n");
 313
 314         return 0;
 315 }