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authorPaolo Bonzini <pbonzini@redhat.com>2010-05-24 09:39:52 +0200
committerLuiz Capitulino <lcapitulino@redhat.com>2010-06-11 15:25:14 -0300
commitf7c052747e4b139df16e1d5b7851f4729acc2bb7 (patch)
treecbdef39614a22f702ace4b66be1d38661af69400 /json-lexer.c
parent7f8fca7c8add770d6533c44d2d001c0442ed0371 (diff)
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>
Diffstat (limited to 'json-lexer.c')
-rw-r--r--json-lexer.c58
1 files changed, 35 insertions, 23 deletions
diff --git a/json-lexer.c b/json-lexer.c
index 1d9b81fef4..5ea64a75a7 100644
--- a/json-lexer.c
+++ b/json-lexer.c
@@ -65,6 +65,12 @@ enum json_lexer_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] = {
[IN_DONE_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)
{
+ int char_consumed, new_state;
+
lexer->x++;
if (ch == '\n') {
lexer->x = 0;
lexer->y++;
}
- lexer->state = json_lexer[lexer->state][(uint8_t)ch];
-
- switch (lexer->state) {
- case JSON_OPERATOR:
- case JSON_ESCAPE:
- 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);
+ do {
+ new_state = json_lexer[lexer->state][(uint8_t)ch];
+ char_consumed = !TERMINAL_NEEDED_LOOKAHEAD(lexer->state, new_state);
+ if (char_consumed) {
+ 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;
}
@@ -334,7 +346,7 @@ int json_lexer_feed(JSONLexer *lexer, const char *buffer, size_t size)
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)