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qjson: Convert to parser to recursive descent

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We backtrack in parse_value(), even though JSON is LL(1) and thus can
be parsed by straightforward recursive descent.  Do exactly that.

Based on an almost-correct patch from Paolo Bonzini.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1448486613-17634-10-git-send-email-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Markus Armbruster 2015-11-25 22:23:30 +01:00
parent d2ca7c0b0d
commit d538b25543
1 changed files with 47 additions and 118 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

165
qobject/json-parser.c
View File

@ -265,23 +265,6 @@ static QObject *parser_context_peek_token(JSONParserContext *ctxt)
return token;
}
static JSONParserContext parser_context_save(JSONParserContext *ctxt)
{
JSONParserContext saved_ctxt = {0};
saved_ctxt.tokens.pos = ctxt->tokens.pos;
saved_ctxt.tokens.count = ctxt->tokens.count;
saved_ctxt.tokens.buf = ctxt->tokens.buf;
return saved_ctxt;
}
static void parser_context_restore(JSONParserContext *ctxt,
JSONParserContext saved_ctxt)
{
ctxt->tokens.pos = saved_ctxt.tokens.pos;
ctxt->tokens.count = saved_ctxt.tokens.count;
ctxt->tokens.buf = saved_ctxt.tokens.buf;
}
static void tokens_append_from_iter(QObject *obj, void *opaque)
{
JSONParserContext *ctxt = opaque;
@ -333,7 +316,6 @@ static void parser_context_free(JSONParserContext *ctxt)
static int parse_pair(JSONParserContext *ctxt, QDict *dict, va_list *ap)
{
QObject *key = NULL, *token = NULL, *value, *peek;
JSONParserContext saved_ctxt = parser_context_save(ctxt);
peek = parser_context_peek_token(ctxt);
if (peek == NULL) {
@ -371,7 +353,6 @@ static int parse_pair(JSONParserContext *ctxt, QDict *dict, va_list *ap)
return 0;
out:
parser_context_restore(ctxt, saved_ctxt);
qobject_decref(key);
return -1;
@ -381,16 +362,9 @@ static QObject *parse_object(JSONParserContext *ctxt, va_list *ap)
{
QDict *dict = NULL;
QObject *token, *peek;
JSONParserContext saved_ctxt = parser_context_save(ctxt);
token = parser_context_pop_token(ctxt);
if (token == NULL) {
goto out;
}
if (token_get_type(token) != JSON_LCURLY) {
goto out;
}
assert(token && token_get_type(token) == JSON_LCURLY);
dict = qdict_new();
@ -434,7 +408,6 @@ static QObject *parse_object(JSONParserContext *ctxt, va_list *ap)
return QOBJECT(dict);
out:
parser_context_restore(ctxt, saved_ctxt);
QDECREF(dict);
return NULL;
}
@ -443,16 +416,9 @@ static QObject *parse_array(JSONParserContext *ctxt, va_list *ap)
{
QList *list = NULL;
QObject *token, *peek;
JSONParserContext saved_ctxt = parser_context_save(ctxt);
token = parser_context_pop_token(ctxt);
if (token == NULL) {
goto out;
}
if (token_get_type(token) != JSON_LSQUARE) {
goto out;
}
assert(token && token_get_type(token) == JSON_LSQUARE);
list = qlist_new();
@ -506,109 +472,72 @@ static QObject *parse_array(JSONParserContext *ctxt, va_list *ap)
return QOBJECT(list);
out:
parser_context_restore(ctxt, saved_ctxt);
QDECREF(list);
return NULL;
}
static QObject *parse_keyword(JSONParserContext *ctxt)
{
QObject *token, *ret;
JSONParserContext saved_ctxt = parser_context_save(ctxt);
QObject *token;
const char *val;
token = parser_context_pop_token(ctxt);
if (token == NULL) {
goto out;
}
if (token_get_type(token) != JSON_KEYWORD) {
goto out;
}
assert(token && token_get_type(token) == JSON_KEYWORD);
val = token_get_value(token);
if (!strcmp(val, "true")) {
ret = QOBJECT(qbool_from_bool(true));
return QOBJECT(qbool_from_bool(true));
} else if (!strcmp(val, "false")) {
ret = QOBJECT(qbool_from_bool(false));
return QOBJECT(qbool_from_bool(false));
} else if (!strcmp(val, "null")) {
ret = qnull();
} else {
parse_error(ctxt, token, "invalid keyword '%s'", val);
goto out;
return qnull();
}
return ret;
out:
parser_context_restore(ctxt, saved_ctxt);
parse_error(ctxt, token, "invalid keyword '%s'", val);
return NULL;
}
static QObject *parse_escape(JSONParserContext *ctxt, va_list *ap)
{
QObject *token = NULL, *obj;
JSONParserContext saved_ctxt = parser_context_save(ctxt);
QObject *token;
const char *val;
if (ap == NULL) {
goto out;
return NULL;
}
token = parser_context_pop_token(ctxt);
if (token == NULL) {
goto out;
}
if (token_get_type(token) != JSON_ESCAPE) {
goto out;
}
assert(token && token_get_type(token) == JSON_ESCAPE);
val = token_get_value(token);
if (!strcmp(val, "%p")) {
obj = va_arg(*ap, QObject *);
return va_arg(*ap, QObject *);
} else if (!strcmp(val, "%i")) {
obj = QOBJECT(qbool_from_bool(va_arg(*ap, int)));
return QOBJECT(qbool_from_bool(va_arg(*ap, int)));
} else if (!strcmp(val, "%d")) {
obj = QOBJECT(qint_from_int(va_arg(*ap, int)));
return QOBJECT(qint_from_int(va_arg(*ap, int)));
} else if (!strcmp(val, "%ld")) {
obj = QOBJECT(qint_from_int(va_arg(*ap, long)));
return QOBJECT(qint_from_int(va_arg(*ap, long)));
} else if (!strcmp(val, "%lld") ||
!strcmp(val, "%I64d")) {
obj = QOBJECT(qint_from_int(va_arg(*ap, long long)));
return QOBJECT(qint_from_int(va_arg(*ap, long long)));
} else if (!strcmp(val, "%s")) {
obj = QOBJECT(qstring_from_str(va_arg(*ap, const char *)));
return QOBJECT(qstring_from_str(va_arg(*ap, const char *)));
} else if (!strcmp(val, "%f")) {
obj = QOBJECT(qfloat_from_double(va_arg(*ap, double)));
} else {
goto out;
return QOBJECT(qfloat_from_double(va_arg(*ap, double)));
}
return obj;
out:
parser_context_restore(ctxt, saved_ctxt);
return NULL;
}
static QObject *parse_literal(JSONParserContext *ctxt)
{
QObject *token, *obj;
JSONParserContext saved_ctxt = parser_context_save(ctxt);
QObject *token;
token = parser_context_pop_token(ctxt);
if (token == NULL) {
goto out;
}
assert(token);
switch (token_get_type(token)) {
case JSON_STRING:
obj = QOBJECT(qstring_from_escaped_str(ctxt, token));
break;
return QOBJECT(qstring_from_escaped_str(ctxt, token));
case JSON_INTEGER: {
/* A possibility exists that this is a whole-valued float where the
* fractional part was left out due to being 0 (.0). It's not a big
@ -627,46 +556,46 @@ static QObject *parse_literal(JSONParserContext *ctxt)
errno = 0; /* strtoll doesn't set errno on success */
value = strtoll(token_get_value(token), NULL, 10);
if (errno != ERANGE) {
obj = QOBJECT(qint_from_int(value));
break;
return QOBJECT(qint_from_int(value));
}
/* fall through to JSON_FLOAT */
}
case JSON_FLOAT:
/* FIXME dependent on locale */
obj = QOBJECT(qfloat_from_double(strtod(token_get_value(token), NULL)));
break;
return QOBJECT(qfloat_from_double(strtod(token_get_value(token),
NULL)));
default:
goto out;
abort();
}
return obj;
out:
parser_context_restore(ctxt, saved_ctxt);
return NULL;
}
static QObject *parse_value(JSONParserContext *ctxt, va_list *ap)
{
QObject *obj;
QObject *token;
obj = parse_object(ctxt, ap);
if (obj == NULL) {
obj = parse_array(ctxt, ap);
}
if (obj == NULL) {
obj = parse_escape(ctxt, ap);
}
if (obj == NULL) {
obj = parse_keyword(ctxt);
}
if (obj == NULL) {
obj = parse_literal(ctxt);
token = parser_context_peek_token(ctxt);
if (token == NULL) {
parse_error(ctxt, NULL, "premature EOI");
return NULL;
}
return obj;
switch (token_get_type(token)) {
case JSON_LCURLY:
return parse_object(ctxt, ap);
case JSON_LSQUARE:
return parse_array(ctxt, ap);
case JSON_ESCAPE:
return parse_escape(ctxt, ap);
case JSON_INTEGER:
case JSON_FLOAT:
case JSON_STRING:
return parse_literal(ctxt);
case JSON_KEYWORD:
return parse_keyword(ctxt);
default:
parse_error(ctxt, token, "expecting value");
return NULL;
}
}
QObject *json_parser_parse(QList *tokens, va_list *ap)