Commit d538b255 authored by Markus Armbruster's avatar Markus Armbruster
Browse files

qjson: Convert to parser to recursive descent 



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: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarMarkus Armbruster <armbru@redhat.com>
Message-Id: <1448486613-17634-10-git-send-email-armbru@redhat.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
parent d2ca7c0b

qobject/json-parser.c

+47 −118
Original line number Diff line number Diff line
@@ -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)