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implement optional lookahead in json lexer 

Not requiring one extra character when lookahead is not necessary
ensures that clients behave properly even if they, for example,
send QMP requests without a trailing newline.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
This commit is contained in:
Paolo Bonzini 2010-05-24 09:39:52 +02:00 committed by Luiz Capitulino
parent 7f8fca7c8a
commit f7c052747e
1 changed files with 35 additions and 23 deletions
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58
json-lexer.c
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@ -65,6 +65,12 @@ enum json_lexer_state {
#define TERMINAL(state) [0 ... 0x7F] = (state) #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) \
(json_lexer[(old_state)][0] == (terminal))
static const uint8_t json_lexer[][256] = { static const uint8_t json_lexer[][256] = {
[IN_DONE_STRING] = { [IN_DONE_STRING] = {
TERMINAL(JSON_STRING), TERMINAL(JSON_STRING),
@ -284,35 +290,41 @@ void json_lexer_init(JSONLexer *lexer, JSONLexerEmitter func)
static int json_lexer_feed_char(JSONLexer *lexer, char ch) static int json_lexer_feed_char(JSONLexer *lexer, char ch)
{ {
int char_consumed, new_state;
lexer->x++; lexer->x++;
if (ch == '\n') { if (ch == '\n') {
lexer->x = 0; lexer->x = 0;
lexer->y++; lexer->y++;
} }
lexer->state = json_lexer[lexer->state][(uint8_t)ch]; do {
new_state = json_lexer[lexer->state][(uint8_t)ch];
switch (lexer->state) { char_consumed = !TERMINAL_NEEDED_LOOKAHEAD(lexer->state, new_state);
case JSON_OPERATOR: if (char_consumed) {
case JSON_ESCAPE: qstring_append_chr(lexer->token, ch);
case JSON_INTEGER: }
case JSON_FLOAT:
case JSON_KEYWORD:
case JSON_STRING:
lexer->emit(lexer, lexer->token, lexer->state, lexer->x, lexer->y);
case JSON_SKIP:
lexer->state = json_lexer[IN_START][(uint8_t)ch];
QDECREF(lexer->token);
lexer->token = qstring_new();
break;
case ERROR:
return -EINVAL;
default:
break;
}
qstring_append_chr(lexer->token, ch);
switch (new_state) {
case JSON_OPERATOR:
case JSON_ESCAPE:
case JSON_INTEGER:
case JSON_FLOAT:
case JSON_KEYWORD:
case JSON_STRING:
lexer->emit(lexer, lexer->token, new_state, lexer->x, lexer->y);
case JSON_SKIP:
QDECREF(lexer->token);
lexer->token = qstring_new();
new_state = IN_START;
break;
case ERROR:
return -EINVAL;
default:
break;
}
lexer->state = new_state;
} while (!char_consumed);
return 0; return 0;
} }
@ -334,7 +346,7 @@ int json_lexer_feed(JSONLexer *lexer, const char *buffer, size_t size)
int json_lexer_flush(JSONLexer *lexer) int json_lexer_flush(JSONLexer *lexer)
{ {
return json_lexer_feed_char(lexer, 0); return lexer->state == IN_START ? 0 : json_lexer_feed_char(lexer, 0);
} }
void json_lexer_destroy(JSONLexer *lexer) void json_lexer_destroy(JSONLexer *lexer)