json-lexer.c

   1 /*
   2  * JSON lexer
   3  *
   4  * Copyright IBM, Corp. 2009
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qapi/qmp/qstring.h"
  15 #include "qapi/qmp/qlist.h"
  16 #include "qapi/qmp/qdict.h"
  17 #include "qapi/qmp/qint.h"
  18 #include "qemu-common.h"
  19 #include "qapi/qmp/json-lexer.h"
  20
  21 #define MAX_TOKEN_SIZE (64ULL << 20)
  22
  23 /*
  24  * \"([^\\\"]|(\\\"\\'\\\\\\/\\b\\f\\n\\r\\t\\u[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]))*\"
  25  * '([^\\']|(\\\"\\'\\\\\\/\\b\\f\\n\\r\\t\\u[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]))*'
  26  * 0|([1-9][0-9]*(.[0-9]+)?([eE]([-+])?[0-9]+))
  27  * [{}\[\],:]
  28  * [a-z]+
  29  *
  30  */
  31
  32 enum json_lexer_state {
  33     IN_ERROR = 0,
  34     IN_DQ_UCODE3,
  35     IN_DQ_UCODE2,
  36     IN_DQ_UCODE1,
  37     IN_DQ_UCODE0,
  38     IN_DQ_STRING_ESCAPE,
  39     IN_DQ_STRING,
  40     IN_SQ_UCODE3,
  41     IN_SQ_UCODE2,
  42     IN_SQ_UCODE1,
  43     IN_SQ_UCODE0,
  44     IN_SQ_STRING_ESCAPE,
  45     IN_SQ_STRING,
  46     IN_ZERO,
  47     IN_DIGITS,
  48     IN_DIGIT,
  49     IN_EXP_E,
  50     IN_MANTISSA,
  51     IN_MANTISSA_DIGITS,
  52     IN_NONZERO_NUMBER,
  53     IN_NEG_NONZERO_NUMBER,
  54     IN_KEYWORD,
  55     IN_ESCAPE,
  56     IN_ESCAPE_L,
  57     IN_ESCAPE_LL,
  58     IN_ESCAPE_I,
  59     IN_ESCAPE_I6,
  60     IN_ESCAPE_I64,
  61     IN_WHITESPACE,
  62     IN_START,
  63 };
  64
  65 #define TERMINAL(state) [0 ... 0x7F] = (state)
  66
  67 /* Return whether TERMINAL is a terminal state and the transition to it
  68    from OLD_STATE required lookahead.  This happens whenever the table
  69    below uses the TERMINAL macro.  */
  70 #define TERMINAL_NEEDED_LOOKAHEAD(old_state, terminal) \
  71             (json_lexer[(old_state)][0] == (terminal))
  72
  73 static const uint8_t json_lexer[][256] =  {
  74     /* double quote string */
  75     [IN_DQ_UCODE3] = {
  76         ['0' ... '9'] = IN_DQ_STRING,
  77         ['a' ... 'f'] = IN_DQ_STRING,
  78         ['A' ... 'F'] = IN_DQ_STRING,
  79     },
  80     [IN_DQ_UCODE2] = {
  81         ['0' ... '9'] = IN_DQ_UCODE3,
  82         ['a' ... 'f'] = IN_DQ_UCODE3,
  83         ['A' ... 'F'] = IN_DQ_UCODE3,
  84     },
  85     [IN_DQ_UCODE1] = {
  86         ['0' ... '9'] = IN_DQ_UCODE2,
  87         ['a' ... 'f'] = IN_DQ_UCODE2,
  88         ['A' ... 'F'] = IN_DQ_UCODE2,
  89     },
  90     [IN_DQ_UCODE0] = {
  91         ['0' ... '9'] = IN_DQ_UCODE1,
  92         ['a' ... 'f'] = IN_DQ_UCODE1,
  93         ['A' ... 'F'] = IN_DQ_UCODE1,
  94     },
  95     [IN_DQ_STRING_ESCAPE] = {
  96         ['b'] = IN_DQ_STRING,
  97         ['f'] =  IN_DQ_STRING,
  98         ['n'] =  IN_DQ_STRING,
  99         ['r'] =  IN_DQ_STRING,
 100         ['t'] =  IN_DQ_STRING,
 101         ['/'] = IN_DQ_STRING,
 102         ['\\'] = IN_DQ_STRING,
 103         ['\''] = IN_DQ_STRING,
 104         ['\"'] = IN_DQ_STRING,
 105         ['u'] = IN_DQ_UCODE0,
 106     },
 107     [IN_DQ_STRING] = {
 108         [1 ... 0xBF] = IN_DQ_STRING,
 109         [0xC2 ... 0xF4] = IN_DQ_STRING,
 110         ['\\'] = IN_DQ_STRING_ESCAPE,
 111         ['"'] = JSON_STRING,
 112     },
 113
 114     /* single quote string */
 115     [IN_SQ_UCODE3] = {
 116         ['0' ... '9'] = IN_SQ_STRING,
 117         ['a' ... 'f'] = IN_SQ_STRING,
 118         ['A' ... 'F'] = IN_SQ_STRING,
 119     },
 120     [IN_SQ_UCODE2] = {
 121         ['0' ... '9'] = IN_SQ_UCODE3,
 122         ['a' ... 'f'] = IN_SQ_UCODE3,
 123         ['A' ... 'F'] = IN_SQ_UCODE3,
 124     },
 125     [IN_SQ_UCODE1] = {
 126         ['0' ... '9'] = IN_SQ_UCODE2,
 127         ['a' ... 'f'] = IN_SQ_UCODE2,
 128         ['A' ... 'F'] = IN_SQ_UCODE2,
 129     },
 130     [IN_SQ_UCODE0] = {
 131         ['0' ... '9'] = IN_SQ_UCODE1,
 132         ['a' ... 'f'] = IN_SQ_UCODE1,
 133         ['A' ... 'F'] = IN_SQ_UCODE1,
 134     },
 135     [IN_SQ_STRING_ESCAPE] = {
 136         ['b'] = IN_SQ_STRING,
 137         ['f'] =  IN_SQ_STRING,
 138         ['n'] =  IN_SQ_STRING,
 139         ['r'] =  IN_SQ_STRING,
 140         ['t'] =  IN_SQ_STRING,
 141         ['/'] = IN_DQ_STRING,
 142         ['\\'] = IN_DQ_STRING,
 143         ['\''] = IN_SQ_STRING,
 144         ['\"'] = IN_SQ_STRING,
 145         ['u'] = IN_SQ_UCODE0,
 146     },
 147     [IN_SQ_STRING] = {
 148         [1 ... 0xBF] = IN_SQ_STRING,
 149         [0xC2 ... 0xF4] = IN_SQ_STRING,
 150         ['\\'] = IN_SQ_STRING_ESCAPE,
 151         ['\''] = JSON_STRING,
 152     },
 153
 154     /* Zero */
 155     [IN_ZERO] = {
 156         TERMINAL(JSON_INTEGER),
 157         ['0' ... '9'] = IN_ERROR,
 158         ['.'] = IN_MANTISSA,
 159     },
 160
 161     /* Float */
 162     [IN_DIGITS] = {
 163         TERMINAL(JSON_FLOAT),
 164         ['0' ... '9'] = IN_DIGITS,
 165     },
 166
 167     [IN_DIGIT] = {
 168         ['0' ... '9'] = IN_DIGITS,
 169     },
 170
 171     [IN_EXP_E] = {
 172         ['-'] = IN_DIGIT,
 173         ['+'] = IN_DIGIT,
 174         ['0' ... '9'] = IN_DIGITS,
 175     },
 176
 177     [IN_MANTISSA_DIGITS] = {
 178         TERMINAL(JSON_FLOAT),
 179         ['0' ... '9'] = IN_MANTISSA_DIGITS,
 180         ['e'] = IN_EXP_E,
 181         ['E'] = IN_EXP_E,
 182     },
 183
 184     [IN_MANTISSA] = {
 185         ['0' ... '9'] = IN_MANTISSA_DIGITS,
 186     },
 187
 188     /* Number */
 189     [IN_NONZERO_NUMBER] = {
 190         TERMINAL(JSON_INTEGER),
 191         ['0' ... '9'] = IN_NONZERO_NUMBER,
 192         ['e'] = IN_EXP_E,
 193         ['E'] = IN_EXP_E,
 194         ['.'] = IN_MANTISSA,
 195     },
 196
 197     [IN_NEG_NONZERO_NUMBER] = {
 198         ['0'] = IN_ZERO,
 199         ['1' ... '9'] = IN_NONZERO_NUMBER,
 200     },
 201
 202     /* keywords */
 203     [IN_KEYWORD] = {
 204         TERMINAL(JSON_KEYWORD),
 205         ['a' ... 'z'] = IN_KEYWORD,
 206     },
 207
 208     /* whitespace */
 209     [IN_WHITESPACE] = {
 210         TERMINAL(JSON_SKIP),
 211         [' '] = IN_WHITESPACE,
 212         ['\t'] = IN_WHITESPACE,
 213         ['\r'] = IN_WHITESPACE,
 214         ['\n'] = IN_WHITESPACE,
 215     },
 216
 217     /* escape */
 218     [IN_ESCAPE_LL] = {
 219         ['d'] = JSON_ESCAPE,
 220     },
 221
 222     [IN_ESCAPE_L] = {
 223         ['d'] = JSON_ESCAPE,
 224         ['l'] = IN_ESCAPE_LL,
 225     },
 226
 227     [IN_ESCAPE_I64] = {
 228         ['d'] = JSON_ESCAPE,
 229     },
 230
 231     [IN_ESCAPE_I6] = {
 232         ['4'] = IN_ESCAPE_I64,
 233     },
 234
 235     [IN_ESCAPE_I] = {
 236         ['6'] = IN_ESCAPE_I6,
 237     },
 238
 239     [IN_ESCAPE] = {
 240         ['d'] = JSON_ESCAPE,
 241         ['i'] = JSON_ESCAPE,
 242         ['p'] = JSON_ESCAPE,
 243         ['s'] = JSON_ESCAPE,
 244         ['f'] = JSON_ESCAPE,
 245         ['l'] = IN_ESCAPE_L,
 246         ['I'] = IN_ESCAPE_I,
 247     },
 248
 249     /* top level rule */
 250     [IN_START] = {
 251         ['"'] = IN_DQ_STRING,
 252         ['\''] = IN_SQ_STRING,
 253         ['0'] = IN_ZERO,
 254         ['1' ... '9'] = IN_NONZERO_NUMBER,
 255         ['-'] = IN_NEG_NONZERO_NUMBER,
 256         ['{'] = JSON_OPERATOR,
 257         ['}'] = JSON_OPERATOR,
 258         ['['] = JSON_OPERATOR,
 259         [']'] = JSON_OPERATOR,
 260         [','] = JSON_OPERATOR,
 261         [':'] = JSON_OPERATOR,
 262         ['a' ... 'z'] = IN_KEYWORD,
 263         ['%'] = IN_ESCAPE,
 264         [' '] = IN_WHITESPACE,
 265         ['\t'] = IN_WHITESPACE,
 266         ['\r'] = IN_WHITESPACE,
 267         ['\n'] = IN_WHITESPACE,
 268     },
 269 };
 270
 271 void json_lexer_init(JSONLexer *lexer, JSONLexerEmitter func)
 272 {
 273     lexer->emit = func;
 274     lexer->state = IN_START;
 275     lexer->token = qstring_new();
 276     lexer->x = lexer->y = 0;
 277 }
 278
 279 static int json_lexer_feed_char(JSONLexer *lexer, char ch, bool flush)
 280 {
 281     int char_consumed, new_state;
 282
 283     lexer->x++;
 284     if (ch == '\n') {
 285         lexer->x = 0;
 286         lexer->y++;
 287     }
 288
 289     do {
 290         new_state = json_lexer[lexer->state][(uint8_t)ch];
 291         char_consumed = !TERMINAL_NEEDED_LOOKAHEAD(lexer->state, new_state);
 292         if (char_consumed) {
 293             qstring_append_chr(lexer->token, ch);
 294         }
 295
 296         switch (new_state) {
 297         case JSON_OPERATOR:
 298         case JSON_ESCAPE:
 299         case JSON_INTEGER:
 300         case JSON_FLOAT:
 301         case JSON_KEYWORD:
 302         case JSON_STRING:
 303             lexer->emit(lexer, lexer->token, new_state, lexer->x, lexer->y);
 304             /* fall through */
 305         case JSON_SKIP:
 306             QDECREF(lexer->token);
 307             lexer->token = qstring_new();
 308             new_state = IN_START;
 309             break;
 310         case IN_ERROR:
 311             /* XXX: To avoid having previous bad input leaving the parser in an
 312              * unresponsive state where we consume unpredictable amounts of
 313              * subsequent "good" input, percolate this error state up to the
 314              * tokenizer/parser by forcing a NULL object to be emitted, then
 315              * reset state.
 316              *
 317              * Also note that this handling is required for reliable channel
 318              * negotiation between QMP and the guest agent, since chr(0xFF)
 319              * is placed at the beginning of certain events to ensure proper
 320              * delivery when the channel is in an unknown state. chr(0xFF) is
 321              * never a valid ASCII/UTF-8 sequence, so this should reliably
 322              * induce an error/flush state.
 323              */
 324             lexer->emit(lexer, lexer->token, JSON_ERROR, lexer->x, lexer->y);
 325             QDECREF(lexer->token);
 326             lexer->token = qstring_new();
 327             new_state = IN_START;
 328             lexer->state = new_state;
 329             return 0;
 330         default:
 331             break;
 332         }
 333         lexer->state = new_state;
 334     } while (!char_consumed && !flush);
 335
 336     /* Do not let a single token grow to an arbitrarily large size,
 337      * this is a security consideration.
 338      */
 339     if (lexer->token->length > MAX_TOKEN_SIZE) {
 340         lexer->emit(lexer, lexer->token, lexer->state, lexer->x, lexer->y);
 341         QDECREF(lexer->token);
 342         lexer->token = qstring_new();
 343         lexer->state = IN_START;
 344     }
 345
 346     return 0;
 347 }
 348
 349 int json_lexer_feed(JSONLexer *lexer, const char *buffer, size_t size)
 350 {
 351     size_t i;
 352
 353     for (i = 0; i < size; i++) {
 354         int err;
 355
 356         err = json_lexer_feed_char(lexer, buffer[i], false);
 357         if (err < 0) {
 358             return err;
 359         }
 360     }
 361
 362     return 0;
 363 }
 364
 365 int json_lexer_flush(JSONLexer *lexer)
 366 {
 367     return lexer->state == IN_START ? 0 : json_lexer_feed_char(lexer, 0, true);
 368 }
 369
 370 void json_lexer_destroy(JSONLexer *lexer)
 371 {
 372     QDECREF(lexer->token);
 373 }