*/
enum json_lexer_state {
- IN_ERROR = 0, /* must really be 0, see json_lexer[] */
+ IN_RECOVERY = 1,
IN_DQ_STRING_ESCAPE,
IN_DQ_STRING,
IN_SQ_STRING_ESCAPE,
IN_SIGN,
IN_KEYWORD,
IN_INTERP,
- IN_WHITESPACE,
IN_START,
IN_START_INTERP, /* must be IN_START + 1 */
};
+QEMU_BUILD_BUG_ON(JSON_ERROR != 0);
+QEMU_BUILD_BUG_ON(IN_RECOVERY != JSON_ERROR + 1);
QEMU_BUILD_BUG_ON((int)JSON_MIN <= (int)IN_START_INTERP);
+QEMU_BUILD_BUG_ON(JSON_MAX >= 0x80);
QEMU_BUILD_BUG_ON(IN_START_INTERP != IN_START + 1);
-#define TERMINAL(state) [0 ... 0x7F] = (state)
-
-/* Return whether TERMINAL is a terminal state and the transition to it
- from OLD_STATE required lookahead. This happens whenever the table
- below uses the TERMINAL macro. */
-#define TERMINAL_NEEDED_LOOKAHEAD(old_state, terminal) \
- (terminal != IN_ERROR && json_lexer[(old_state)][0] == (terminal))
+#define LOOKAHEAD 0x80
+#define TERMINAL(state) [0 ... 0xFF] = ((state) | LOOKAHEAD)
static const uint8_t json_lexer[][256] = {
/* Relies on default initialization to IN_ERROR! */
+ /* error recovery */
+ [IN_RECOVERY] = {
+ /*
+ * Skip characters until a structural character, an ASCII
+ * control character other than '\t', or impossible UTF-8
+ * bytes '\xFE', '\xFF'. Structural characters and line
+ * endings are promising resynchronization points. Clients
+ * may use the others to force the JSON parser into known-good
+ * state; see docs/interop/qmp-spec.rst.
+ */
+ [0 ... 0x1F] = IN_START | LOOKAHEAD,
+ [0x20 ... 0xFD] = IN_RECOVERY,
+ [0xFE ... 0xFF] = IN_START | LOOKAHEAD,
+ ['\t'] = IN_RECOVERY,
+ ['['] = IN_START | LOOKAHEAD,
+ [']'] = IN_START | LOOKAHEAD,
+ ['{'] = IN_START | LOOKAHEAD,
+ ['}'] = IN_START | LOOKAHEAD,
+ [':'] = IN_START | LOOKAHEAD,
+ [','] = IN_START | LOOKAHEAD,
+ },
+
/* double quote string */
[IN_DQ_STRING_ESCAPE] = {
[0x20 ... 0xFD] = IN_DQ_STRING,
/* Zero */
[IN_ZERO] = {
TERMINAL(JSON_INTEGER),
- ['0' ... '9'] = IN_ERROR,
+ ['0' ... '9'] = JSON_ERROR,
['.'] = IN_MANTISSA,
},
['a' ... 'z'] = IN_KEYWORD,
},
- /* whitespace */
- [IN_WHITESPACE] = {
- TERMINAL(JSON_SKIP),
- [' '] = IN_WHITESPACE,
- ['\t'] = IN_WHITESPACE,
- ['\r'] = IN_WHITESPACE,
- ['\n'] = IN_WHITESPACE,
- },
-
/* interpolation */
[IN_INTERP] = {
TERMINAL(JSON_INTERP),
[','] = JSON_COMMA,
[':'] = JSON_COLON,
['a' ... 'z'] = IN_KEYWORD,
- [' '] = IN_WHITESPACE,
- ['\t'] = IN_WHITESPACE,
- ['\r'] = IN_WHITESPACE,
- ['\n'] = IN_WHITESPACE,
+ [' '] = IN_START,
+ ['\t'] = IN_START,
+ ['\r'] = IN_START,
+ ['\n'] = IN_START,
},
[IN_START_INTERP]['%'] = IN_INTERP,
};
+static inline uint8_t next_state(JSONLexer *lexer, char ch, bool flush,
+ bool *char_consumed)
+{
+ uint8_t next;
+
+ assert(lexer->state < ARRAY_SIZE(json_lexer));
+ next = json_lexer[lexer->state][(uint8_t)ch];
+ *char_consumed = !flush && !(next & LOOKAHEAD);
+ return next & ~LOOKAHEAD;
+}
+
void json_lexer_init(JSONLexer *lexer, bool enable_interpolation)
{
lexer->start_state = lexer->state = enable_interpolation
static void json_lexer_feed_char(JSONLexer *lexer, char ch, bool flush)
{
- int char_consumed, new_state;
+ int new_state;
+ bool char_consumed = false;
lexer->x++;
if (ch == '\n') {
lexer->y++;
}
- do {
- assert(lexer->state <= ARRAY_SIZE(json_lexer));
- new_state = json_lexer[lexer->state][(uint8_t)ch];
- char_consumed = !TERMINAL_NEEDED_LOOKAHEAD(lexer->state, new_state);
- if (char_consumed && !flush) {
+ while (flush ? lexer->state != lexer->start_state : !char_consumed) {
+ new_state = next_state(lexer, ch, flush, &char_consumed);
+ if (char_consumed) {
+ assert(!flush);
g_string_append_c(lexer->token, ch);
}
json_message_process_token(lexer, lexer->token, new_state,
lexer->x, lexer->y);
/* fall through */
- case JSON_SKIP:
+ case IN_START:
g_string_truncate(lexer->token, 0);
new_state = lexer->start_state;
break;
- case IN_ERROR:
- /* XXX: To avoid having previous bad input leaving the parser in an
- * unresponsive state where we consume unpredictable amounts of
- * subsequent "good" input, percolate this error state up to the
- * parser by emitting a JSON_ERROR token, then reset lexer state.
- *
- * Also note that this handling is required for reliable channel
- * negotiation between QMP and the guest agent, since chr(0xFF)
- * is placed at the beginning of certain events to ensure proper
- * delivery when the channel is in an unknown state. chr(0xFF) is
- * never a valid ASCII/UTF-8 sequence, so this should reliably
- * induce an error/flush state.
- */
+ case JSON_ERROR:
json_message_process_token(lexer, lexer->token, JSON_ERROR,
lexer->x, lexer->y);
+ new_state = IN_RECOVERY;
+ /* fall through */
+ case IN_RECOVERY:
g_string_truncate(lexer->token, 0);
- lexer->state = lexer->start_state;
- return;
+ break;
default:
break;
}
lexer->state = new_state;
- } while (!char_consumed && !flush);
+ }
/* Do not let a single token grow to an arbitrarily large size,
* this is a security consideration.
void json_lexer_flush(JSONLexer *lexer)
{
- if (lexer->state != lexer->start_state) {
- json_lexer_feed_char(lexer, 0, true);
- }
+ json_lexer_feed_char(lexer, 0, true);
+ assert(lexer->state == lexer->start_state);
json_message_process_token(lexer, lexer->token, JSON_END_OF_INPUT,
lexer->x, lexer->y);
}
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