From 2975abb487a54b49246646db9aa40ee6d1beaa97 Mon Sep 17 00:00:00 2001

From: Markus Armbruster <armbru@redhat.com>

Date: Wed, 27 Jul 2016 07:35:08 +0200

Subject: [PATCH 10/16] qjson: Convert to parser to recursive descent

RH-Author: Markus Armbruster <armbru@redhat.com>

Message-id: <1469604913-12442-12-git-send-email-armbru@redhat.com>

Patchwork-id: 71474

O-Subject: [RHEL-7.3 qemu-kvm PATCH v2 10/15] qjson: Convert to parser to recursive descent

Bugzilla: 1276036

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

RH-Acked-by: John Snow <jsnow@redhat.com>

RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>

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>

(cherry picked from commit d538b25543f4db026bb435066e2403a542522c40)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

Conflicts:

	qobject/json-parser.c

Straighforward conflicts because lacking commit fc48ffc "qobject: Use

'bool' for qbool", we still use qbool_from_int(), and we lack commit

e549e71 "json-parser: Accept 'null' in QMP".

Signed-off-by: Markus Armbruster <armbru@redhat.com>

---

 qobject/json-parser.c | 163 ++++++++++++++------------------------------------

 1 file changed, 46 insertions(+), 117 deletions(-)

diff --git a/qobject/json-parser.c b/qobject/json-parser.c

index 79f4173..b242fba 100644

--- a/qobject/json-parser.c

+++ b/qobject/json-parser.c

@@ -266,23 +266,6 @@ 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;

@@ -334,7 +317,6 @@ 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) {

@@ -372,7 +354,6 @@ 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;

@@ -382,16 +363,9 @@ 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();

@@ -435,7 +409,6 @@ static QObject *parse_object(JSONParserContext *ctxt, va_list *ap)

     return QOBJECT(dict);

 out:

-    parser_context_restore(ctxt, saved_ctxt);

     QDECREF(dict);

     return NULL;

 }

@@ -444,16 +417,9 @@ 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();

@@ -507,107 +473,70 @@ 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_int(true));

+        return QOBJECT(qbool_from_int(true));

     } else if (!strcmp(val, "false")) {

-        ret = QOBJECT(qbool_from_int(false));

-    } else {

-        parse_error(ctxt, token, "invalid keyword '%s'", val);

-        goto out;

+        return QOBJECT(qbool_from_int(false));

     }

-

-    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_int(va_arg(*ap, int)));

+        return QOBJECT(qbool_from_int(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

@@ -626,46 +555,46 @@ 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)

-- 

1.8.3.1