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 #include "lextable-strings.h"
  20
  21 /*
  22  * b7 = 0 = 1-byte seq
  23  *          0x08 = fail
  24  *          2-byte seq
  25  *          0x00 - 0x07, then terminal as given in 2nd byte
  26             3-byte seq
  27  *          no match: go fwd 3 byte, match: jump fwd by amt in +1/+2 bytes
  28  *    = 1 = 1-byte seq
  29  *          no match: die, match go fwd 1 byte
  30  */
  31
  32 unsigned char lextable[] = {
  33         #include "lextable.h"
  34 };
  35
  36 #define PARALLEL 30
  37
  38 struct state {
  39         char c[PARALLEL];
  40         int state[PARALLEL];
  41         int count;
  42         int bytepos;
  43
  44         int real_pos;
  45 };
  46
  47 struct state state[1000];
  48 int next = 1;
  49
  50 #define FAIL_CHAR 0x08
  51
  52 int lextable_decode(int pos, char c)
  53 {
  54         while (1) {
  55                 if (lextable[pos] & (1 << 7)) { /* 1-byte, fail on mismatch */
  56                         if ((lextable[pos] & 0x7f) != c)
  57                                 return -1;
  58                         /* fall thru */
  59                         pos++;
  60                         if (lextable[pos] == FAIL_CHAR)
  61                                 return -1;
  62                         return pos;
  63                 } else { /* b7 = 0, end or 3-byte */
  64                         if (lextable[pos] < FAIL_CHAR) /* terminal marker */
  65                                 return pos;
  66
  67                         if (lextable[pos] == c) /* goto */
  68                                 return pos + (lextable[pos + 1]) +
  69                                                 (lextable[pos + 2] << 8);
  70                         /* fall thru goto */
  71                         pos += 3;
  72                         /* continue */
  73                 }
  74         }
  75 }
  76
  77 int main(void)
  78 {
  79         int n = 0;
  80         int m = 0;
  81         int prev;
  82         char c;
  83         int walk;
  84         int saw;
  85         int y;
  86         int j;
  87         int pos = 0;
  88
  89         while (n < sizeof(set) / sizeof(set[0])) {
  90
  91                 m = 0;
  92                 walk = 0;
  93                 prev = 0;
  94
  95                 if (set[n][0] == '\0') {
  96                         n++;
  97                         continue;
  98                 }
  99
 100                 while (set[n][m]) {
 101
 102                         saw = 0;
 103                         for (y = 0; y < state[walk].count; y++)
 104                                 if (state[walk].c[y] == set[n][m]) {
 105                                         /* exists -- go forward */
 106                                         walk = state[walk].state[y];
 107                                         saw = 1;
 108                                         break;
 109                                 }
 110
 111                         if (saw)
 112                                 goto again;
 113
 114                         /* something we didn't see before */
 115
 116                         state[walk].c[state[walk].count] = set[n][m];
 117
 118                         state[walk].state[state[walk].count] = next;
 119                         state[walk].count++;
 120                         walk = next++;
 121 again:
 122                         m++;
 123                 }
 124
 125                 state[walk].c[0] = n++;
 126                 state[walk].state[0] = 0; /* terminal marker */
 127                 state[walk].count = 1;
 128         }
 129
 130         walk = 0;
 131         for (n = 0; n < next; n++) {
 132                 state[n].bytepos = walk;
 133                 walk += (2 * state[n].count);
 134         }
 135
 136         /* compute everyone's position first */
 137
 138         pos = 0;
 139         walk = 0;
 140         for (n = 0; n < next; n++) {
 141
 142                 state[n].real_pos = pos;
 143
 144                 for (m = 0; m < state[n].count; m++) {
 145
 146                         if (state[n].state[m] == 0)
 147                                 pos += 2; /* terminal marker */
 148                         else { /* c is a character */
 149                                 if ((state[state[n].state[m]].bytepos -
 150                                                                 walk) == 2)
 151                                         pos++;
 152                                 else {
 153                                         pos += 3;
 154                                         if (m == state[n].count - 1)
 155                                                 pos++; /* fail */
 156                                 }
 157                         }
 158                         walk += 2;
 159                 }
 160         }
 161
 162         walk = 0;
 163         pos = 0;
 164         for (n = 0; n < next; n++) {
 165                 for (m = 0; m < state[n].count; m++) {
 166
 167                         if (!m)
 168                                 fprintf(stdout, "/* pos %04x: %3d */ ",
 169                                                           state[n].real_pos, n);
 170                         else
 171                                 fprintf(stdout, "                    ");
 172
 173                         y = state[n].c[m];
 174                         saw = state[n].state[m];
 175
 176                         if (saw == 0) { // c is a terminal then
 177
 178                                 if (y > 0x7ff) {
 179                                         fprintf(stderr, "terminal too big\n");
 180                                         return 2;
 181                                 }
 182
 183                                 fprintf(stdout, "   0x%02X, 0x%02X           "
 184                                         "       "
 185                                         "/* - terminal marker %2d - */,\n",
 186                                                     y >> 8, y & 0xff, y & 0x7f);
 187                                 pos += 2;
 188                                 walk += 2;
 189                                 continue;
 190                         }
 191
 192                         /* c is a character */
 193
 194                         prev = y &0x7f;
 195                         if (prev < 32 || prev > 126)
 196                                 prev = '.';
 197
 198
 199                         if ((state[saw].bytepos - walk) == 2) {
 200                                 fprintf(stdout, "   0x%02X /* '%c' -> */,\n",
 201                                                 y | 0x80, prev);
 202                                 pos++;
 203                                 walk += 2;
 204                                 continue;
 205                         }
 206
 207                         j = state[saw].real_pos - pos;
 208
 209                         if (j > 0xffff) {
 210                                 fprintf(stderr,
 211                                   "Jump > 64K bytes ahead (%d to %d)\n",
 212                                         state[n].real_pos, state[saw].real_pos);
 213                                 return 1;
 214                         }
 215                         fprintf(stdout, "   0x%02X /* '%c' */, 0x%02X, 0x%02X  "
 216                                 "/* (to 0x%04X state %3d) */,\n",
 217                                 y, prev,
 218                                 j & 0xff, j >> 8,
 219                                 state[saw].real_pos, saw);
 220                         pos += 3;
 221
 222                         if (m == state[n].count - 1) {
 223                                 fprintf(stdout,
 224                                   "                       0x%02X, /* fail */\n",
 225                                                                 FAIL_CHAR);
 226                                 pos++; /* fail */
 227                         }
 228
 229                         walk += 2;
 230                 }
 231         }
 232
 233         fprintf(stdout, "/* total size %d bytes */\n", pos);
 234
 235         /*
 236          * Try to parse every legal input string
 237          */
 238
 239         for (n = 0; n < sizeof(set) / sizeof(set[0]); n++) {
 240                 walk = 0;
 241                 m = 0;
 242                 y = -1;
 243
 244                 if (set[n][0] == '\0')
 245                         continue;
 246
 247                 fprintf(stderr, "  trying '%s'\n", set[n]);
 248
 249                 while (set[n][m]) {
 250                         walk = lextable_decode(walk, set[n][m]);
 251                         if (walk < 0) {
 252                                 fprintf(stderr, "failed\n");
 253                                 return 3;
 254                         }
 255
 256                         if (lextable[walk] < FAIL_CHAR) {
 257                                 y = (lextable[walk] << 8) + lextable[walk + 1];
 258                                 break;
 259                         }
 260                         m++;
 261                 }
 262
 263                 if (y != n) {
 264                         fprintf(stderr, "decode failed %d\n", y);
 265                         return 4;
 266                 }
 267         }
 268
 269         fprintf(stderr, "All decode OK\n");
 270
 271         return 0;
 272 }