Pass the lookahead token down to the various functions implementing the
recursive descent, instead of first peeking and then getting the token
again multiple times.
The main purpose of this patch is to switch the argument passing style
for parse_* functions to something more desirable for a push parser,
which gets one and exactly one token at a time. However, there are
some minor improvement in code size and a bugfix as well.
In particular, because parse_array() and parse_object() can assume
that the opening bracket/brace is not anymore in the token stream, it
is now apparent that the first entry of an array incorrectly used the
'[' character (stored in "token") as its location. parse_pair, for
comparison, handled it correctly:
if (!key) {
parse_error(ctxt, peek, "key is not a string in object");
goto out;
}
Signed-off-by: Paolo Bonzini <[email protected]>
---
qobject/json-parser.c | 125 +++++++++++++++++++-----------------------
1 file changed, 55 insertions(+), 70 deletions(-)
diff --git a/qobject/json-parser.c b/qobject/json-parser.c
index 7483e582fea..eabc9f8358c 100644
--- a/qobject/json-parser.c
+++ b/qobject/json-parser.c
@@ -49,13 +49,13 @@ typedef struct JSONParserContext {
* 4) deal with premature EOI
*/
-static QObject *parse_value(JSONParserContext *ctxt);
+static QObject *parse_value(JSONParserContext *ctxt, const JSONToken *token);
/**
* Error handler
*/
static void G_GNUC_PRINTF(3, 4) parse_error(JSONParserContext *ctxt,
- JSONToken *token, const char *msg,
...)
+ const JSONToken *token, const char
*msg, ...)
{
va_list ap;
char message[1024];
@@ -126,7 +126,7 @@ static int cvt4hex(const char *s)
* - Invalid Unicode characters are rejected.
* - Control characters \x00..\x1F are rejected by the lexer.
*/
-static QString *parse_string(JSONParserContext *ctxt, JSONToken *token)
+static QString *parse_string(JSONParserContext *ctxt, const JSONToken *token)
{
const char *ptr = token->str;
GString *str;
@@ -235,42 +235,29 @@ out:
return NULL;
}
-/* Note: the token object returned by parser_context_peek_token or
- * parser_context_pop_token is deleted as soon as parser_context_pop_token
- * is called again.
+/* Note: the token object returned by parser_context_pop_token is
+ * deleted as soon as parser_context_pop_token is called again.
*/
-static JSONToken *parser_context_pop_token(JSONParserContext *ctxt)
+static const JSONToken *parser_context_pop_token(JSONParserContext *ctxt)
{
g_free(ctxt->current);
ctxt->current = g_queue_pop_head(ctxt->buf);
return ctxt->current;
}
-static JSONToken *parser_context_peek_token(JSONParserContext *ctxt)
-{
- return g_queue_peek_head(ctxt->buf);
-}
-
/**
* Parsing rules
*/
-static int parse_pair(JSONParserContext *ctxt, QDict *dict)
+static int parse_pair(JSONParserContext *ctxt, const JSONToken *token, QDict
*dict)
{
QObject *key_obj = NULL;
QString *key;
QObject *value;
- JSONToken *peek, *token;
- peek = parser_context_peek_token(ctxt);
- if (peek == NULL) {
- parse_error(ctxt, NULL, "premature EOI");
- goto out;
- }
-
- key_obj = parse_value(ctxt);
+ key_obj = parse_value(ctxt, token);
key = qobject_to(QString, key_obj);
if (!key) {
- parse_error(ctxt, peek, "key is not a string in object");
+ parse_error(ctxt, token, "key is not a string in object");
goto out;
}
@@ -285,7 +272,13 @@ static int parse_pair(JSONParserContext *ctxt, QDict *dict)
goto out;
}
- value = parse_value(ctxt);
+ token = parser_context_pop_token(ctxt);
+ if (token == NULL) {
+ parse_error(ctxt, NULL, "premature EOI");
+ goto out;
+ }
+
+ value = parse_value(ctxt, token);
if (value == NULL) {
parse_error(ctxt, token, "Missing value in dict");
goto out;
@@ -309,21 +302,18 @@ out:
static QObject *parse_object(JSONParserContext *ctxt)
{
QDict *dict = NULL;
- JSONToken *token, *peek;
-
- token = parser_context_pop_token(ctxt);
- assert(token && token->type == JSON_LCURLY);
+ const JSONToken *token;
dict = qdict_new();
- peek = parser_context_peek_token(ctxt);
- if (peek == NULL) {
+ token = parser_context_pop_token(ctxt);
+ if (token == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
- if (peek->type != JSON_RCURLY) {
- if (parse_pair(ctxt, dict) == -1) {
+ if (token->type != JSON_RCURLY) {
+ if (parse_pair(ctxt, token, dict) == -1) {
goto out;
}
@@ -339,7 +329,13 @@ static QObject *parse_object(JSONParserContext *ctxt)
goto out;
}
- if (parse_pair(ctxt, dict) == -1) {
+ token = parser_context_pop_token(ctxt);
+ if (token == NULL) {
+ parse_error(ctxt, NULL, "premature EOI");
+ goto out;
+ }
+
+ if (parse_pair(ctxt, token, dict) == -1) {
goto out;
}
@@ -349,8 +345,6 @@ static QObject *parse_object(JSONParserContext *ctxt)
goto out;
}
}
- } else {
- (void)parser_context_pop_token(ctxt);
}
return QOBJECT(dict);
@@ -363,23 +357,20 @@ out:
static QObject *parse_array(JSONParserContext *ctxt)
{
QList *list = NULL;
- JSONToken *token, *peek;
-
- token = parser_context_pop_token(ctxt);
- assert(token && token->type == JSON_LSQUARE);
+ const JSONToken *token;
list = qlist_new();
- peek = parser_context_peek_token(ctxt);
- if (peek == NULL) {
+ token = parser_context_pop_token(ctxt);
+ if (token == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
- if (peek->type != JSON_RSQUARE) {
+ if (token->type != JSON_RSQUARE) {
QObject *obj;
- obj = parse_value(ctxt);
+ obj = parse_value(ctxt, token);
if (obj == NULL) {
parse_error(ctxt, token, "expecting value");
goto out;
@@ -399,7 +390,13 @@ static QObject *parse_array(JSONParserContext *ctxt)
goto out;
}
- obj = parse_value(ctxt);
+ token = parser_context_pop_token(ctxt);
+ if (token == NULL) {
+ parse_error(ctxt, NULL, "premature EOI");
+ goto out;
+ }
+
+ obj = parse_value(ctxt, token);
if (obj == NULL) {
parse_error(ctxt, token, "expecting value");
goto out;
@@ -413,8 +410,6 @@ static QObject *parse_array(JSONParserContext *ctxt)
goto out;
}
}
- } else {
- (void)parser_context_pop_token(ctxt);
}
return QOBJECT(list);
@@ -424,11 +419,8 @@ out:
return NULL;
}
-static QObject *parse_keyword(JSONParserContext *ctxt)
+static QObject *parse_keyword(JSONParserContext *ctxt, const JSONToken *token)
{
- JSONToken *token;
-
- token = parser_context_pop_token(ctxt);
assert(token && token->type == JSON_KEYWORD);
if (!strcmp(token->str, "true")) {
@@ -442,11 +434,8 @@ static QObject *parse_keyword(JSONParserContext *ctxt)
return NULL;
}
-static QObject *parse_interpolation(JSONParserContext *ctxt)
+static QObject *parse_interpolation(JSONParserContext *ctxt, const JSONToken
*token)
{
- JSONToken *token;
-
- token = parser_context_pop_token(ctxt);
assert(token && token->type == JSON_INTERP);
if (!strcmp(token->str, "%p")) {
@@ -478,11 +467,8 @@ static QObject *parse_interpolation(JSONParserContext
*ctxt)
return NULL;
}
-static QObject *parse_literal(JSONParserContext *ctxt)
+static QObject *parse_literal(JSONParserContext *ctxt, const JSONToken *token)
{
- JSONToken *token;
-
- token = parser_context_pop_token(ctxt);
assert(token);
switch (token->type) {
@@ -530,29 +516,21 @@ static QObject *parse_literal(JSONParserContext *ctxt)
}
}
-static QObject *parse_value(JSONParserContext *ctxt)
+static QObject *parse_value(JSONParserContext *ctxt, const JSONToken *token)
{
- JSONToken *token;
-
- token = parser_context_peek_token(ctxt);
- if (token == NULL) {
- parse_error(ctxt, NULL, "premature EOI");
- return NULL;
- }
-
switch (token->type) {
case JSON_LCURLY:
return parse_object(ctxt);
case JSON_LSQUARE:
return parse_array(ctxt);
case JSON_INTERP:
- return parse_interpolation(ctxt);
+ return parse_interpolation(ctxt, token);
case JSON_INTEGER:
case JSON_FLOAT:
case JSON_STRING:
- return parse_literal(ctxt);
+ return parse_literal(ctxt, token);
case JSON_KEYWORD:
- return parse_keyword(ctxt);
+ return parse_keyword(ctxt, token);
default:
parse_error(ctxt, token, "expecting value");
return NULL;
@@ -575,8 +553,15 @@ QObject *json_parser_parse(GQueue *tokens, va_list *ap,
Error **errp)
{
JSONParserContext ctxt = { .buf = tokens, .ap = ap };
QObject *result;
+ const JSONToken *token;
- result = parse_value(&ctxt);
+ token = parser_context_pop_token(&ctxt);
+ if (token == NULL) {
+ parse_error(&ctxt, NULL, "premature EOI");
+ return NULL;
+ }
+
+ result = parse_value(&ctxt, token);
assert(ctxt.err || g_queue_is_empty(ctxt.buf));
error_propagate(errp, ctxt.err);
--
2.52.0
