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qemu/qobject/json-parser.c

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/*
* JSON Parser
*
* Copyright IBM, Corp. 2009
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
* See the COPYING.LIB file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu-common.h"
#include "qapi/qmp/types.h"
#include "qapi/qmp/json-parser.h"
#include "qapi/qmp/json-lexer.h"
#include "qapi/qmp/json-streamer.h"
typedef struct JSONParserContext
{
Error *err;
JSONToken *current;
GQueue *buf;
} JSONParserContext;
#define BUG_ON(cond) assert(!(cond))
/**
* TODO
*
* 0) make errors meaningful again
* 1) add geometry information to tokens
* 3) should we return a parsed size?
* 4) deal with premature EOI
*/
static QObject *parse_value(JSONParserContext *ctxt, va_list *ap);
/**
* Error handler
*/
static void GCC_FMT_ATTR(3, 4) parse_error(JSONParserContext *ctxt,
JSONToken *token, const char *msg, ...)
{
va_list ap;
char message[1024];
va_start(ap, msg);
vsnprintf(message, sizeof(message), msg, ap);
va_end(ap);
if (ctxt->err) {
error_free(ctxt->err);
ctxt->err = NULL;
}
error_setg(&ctxt->err, "JSON parse error, %s", message);
}
/**
* String helpers
*
* These helpers are used to unescape strings.
*/
static void wchar_to_utf8(uint16_t wchar, char *buffer, size_t buffer_length)
{
if (wchar <= 0x007F) {
BUG_ON(buffer_length < 2);
buffer[0] = wchar & 0x7F;
buffer[1] = 0;
} else if (wchar <= 0x07FF) {
BUG_ON(buffer_length < 3);
buffer[0] = 0xC0 | ((wchar >> 6) & 0x1F);
buffer[1] = 0x80 | (wchar & 0x3F);
buffer[2] = 0;
} else {
BUG_ON(buffer_length < 4);
buffer[0] = 0xE0 | ((wchar >> 12) & 0x0F);
buffer[1] = 0x80 | ((wchar >> 6) & 0x3F);
buffer[2] = 0x80 | (wchar & 0x3F);
buffer[3] = 0;
}
}
static int hex2decimal(char ch)
{
if (ch >= '0' && ch <= '9') {
return (ch - '0');
} else if (ch >= 'a' && ch <= 'f') {
return 10 + (ch - 'a');
} else if (ch >= 'A' && ch <= 'F') {
return 10 + (ch - 'A');
}
return -1;
}
/**
* parse_string(): Parse a json string and return a QObject
*
* string
* ""
* " chars "
* chars
* char
* char chars
* char
* any-Unicode-character-
* except-"-or-\-or-
* control-character
* \"
* \\
* \/
* \b
* \f
* \n
* \r
* \t
* \u four-hex-digits
*/
static QString *qstring_from_escaped_str(JSONParserContext *ctxt,
JSONToken *token)
{
const char *ptr = token->str;
QString *str;
int double_quote = 1;
if (*ptr == '"') {
double_quote = 1;
} else {
double_quote = 0;
}
ptr++;
str = qstring_new();
while (*ptr &&
((double_quote && *ptr != '"') || (!double_quote && *ptr != '\''))) {
if (*ptr == '\\') {
ptr++;
switch (*ptr) {
case '"':
qstring_append(str, "\"");
ptr++;
break;
case '\'':
qstring_append(str, "'");
ptr++;
break;
case '\\':
qstring_append(str, "\\");
ptr++;
break;
case '/':
qstring_append(str, "/");
ptr++;
break;
case 'b':
qstring_append(str, "\b");
ptr++;
break;
case 'f':
qstring_append(str, "\f");
ptr++;
break;
case 'n':
qstring_append(str, "\n");
ptr++;
break;
case 'r':
qstring_append(str, "\r");
ptr++;
break;
case 't':
qstring_append(str, "\t");
ptr++;
break;
case 'u': {
uint16_t unicode_char = 0;
char utf8_char[4];
int i = 0;
ptr++;
for (i = 0; i < 4; i++) {
if (qemu_isxdigit(*ptr)) {
unicode_char |= hex2decimal(*ptr) << ((3 - i) * 4);
} else {
parse_error(ctxt, token,
"invalid hex escape sequence in string");
goto out;
}
ptr++;
}
wchar_to_utf8(unicode_char, utf8_char, sizeof(utf8_char));
qstring_append(str, utf8_char);
} break;
default:
parse_error(ctxt, token, "invalid escape sequence in string");
goto out;
}
} else {
char dummy[2];
dummy[0] = *ptr++;
dummy[1] = 0;
qstring_append(str, dummy);
}
}
return str;
out:
QDECREF(str);
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.
*/
static JSONToken *parser_context_pop_token(JSONParserContext *ctxt)
{
g_free(ctxt->current);
assert(!g_queue_is_empty(ctxt->buf));
ctxt->current = g_queue_pop_head(ctxt->buf);
return ctxt->current;
}
static JSONToken *parser_context_peek_token(JSONParserContext *ctxt)
{
assert(!g_queue_is_empty(ctxt->buf));
return g_queue_peek_head(ctxt->buf);
}
static JSONParserContext *parser_context_new(GQueue *tokens)
{
JSONParserContext *ctxt;
if (!tokens) {
return NULL;
}
ctxt = g_malloc0(sizeof(JSONParserContext));
ctxt->buf = tokens;
return ctxt;
}
/* to support error propagation, ctxt->err must be freed separately */
static void parser_context_free(JSONParserContext *ctxt)
{
if (ctxt) {
while (!g_queue_is_empty(ctxt->buf)) {
parser_context_pop_token(ctxt);
}
g_free(ctxt->current);
g_queue_free(ctxt->buf);
g_free(ctxt);
}
}
/**
* Parsing rules
*/
static int parse_pair(JSONParserContext *ctxt, QDict *dict, va_list *ap)
{
QObject *key = NULL, *value;
JSONToken *peek, *token;
peek = parser_context_peek_token(ctxt);
if (peek == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
key = parse_value(ctxt, ap);
if (!key || qobject_type(key) != QTYPE_QSTRING) {
parse_error(ctxt, peek, "key is not a string in object");
goto out;
}
token = parser_context_pop_token(ctxt);
if (token == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
if (token->type != JSON_COLON) {
parse_error(ctxt, token, "missing : in object pair");
goto out;
}
value = parse_value(ctxt, ap);
if (value == NULL) {
parse_error(ctxt, token, "Missing value in dict");
goto out;
}
qdict_put_obj(dict, qstring_get_str(qobject_to_qstring(key)), value);
qobject_decref(key);
return 0;
out:
qobject_decref(key);
return -1;
}
static QObject *parse_object(JSONParserContext *ctxt, va_list *ap)
{
QDict *dict = NULL;
JSONToken *token, *peek;
token = parser_context_pop_token(ctxt);
assert(token && token->type == JSON_LCURLY);
dict = qdict_new();
peek = parser_context_peek_token(ctxt);
if (peek == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
if (peek->type != JSON_RCURLY) {
if (parse_pair(ctxt, dict, ap) == -1) {
goto out;
}
token = parser_context_pop_token(ctxt);
if (token == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
while (token->type != JSON_RCURLY) {
if (token->type != JSON_COMMA) {
parse_error(ctxt, token, "expected separator in dict");
goto out;
}
if (parse_pair(ctxt, dict, ap) == -1) {
goto out;
}
token = parser_context_pop_token(ctxt);
if (token == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
}
} else {
(void)parser_context_pop_token(ctxt);
}
return QOBJECT(dict);
out:
QDECREF(dict);
return NULL;
}
static QObject *parse_array(JSONParserContext *ctxt, va_list *ap)
{
QList *list = NULL;
JSONToken *token, *peek;
token = parser_context_pop_token(ctxt);
assert(token && token->type == JSON_LSQUARE);
list = qlist_new();
peek = parser_context_peek_token(ctxt);
if (peek == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
if (peek->type != JSON_RSQUARE) {
QObject *obj;
obj = parse_value(ctxt, ap);
if (obj == NULL) {
parse_error(ctxt, token, "expecting value");
goto out;
}
qlist_append_obj(list, obj);
token = parser_context_pop_token(ctxt);
if (token == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
while (token->type != JSON_RSQUARE) {
if (token->type != JSON_COMMA) {
parse_error(ctxt, token, "expected separator in list");
goto out;
}
obj = parse_value(ctxt, ap);
if (obj == NULL) {
parse_error(ctxt, token, "expecting value");
goto out;
}
qlist_append_obj(list, obj);
token = parser_context_pop_token(ctxt);
if (token == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
}
} else {
(void)parser_context_pop_token(ctxt);
}
return QOBJECT(list);
out:
QDECREF(list);
return NULL;
}
static QObject *parse_keyword(JSONParserContext *ctxt)
{
JSONToken *token;
token = parser_context_pop_token(ctxt);
assert(token && token->type == JSON_KEYWORD);
if (!strcmp(token->str, "true")) {
return QOBJECT(qbool_from_bool(true));
} else if (!strcmp(token->str, "false")) {
return QOBJECT(qbool_from_bool(false));
} else if (!strcmp(token->str, "null")) {
return qnull();
}
parse_error(ctxt, token, "invalid keyword '%s'", token->str);
return NULL;
}
static QObject *parse_escape(JSONParserContext *ctxt, va_list *ap)
{
JSONToken *token;
if (ap == NULL) {
return NULL;
}
token = parser_context_pop_token(ctxt);
assert(token && token->type == JSON_ESCAPE);
if (!strcmp(token->str, "%p")) {
return va_arg(*ap, QObject *);
} else if (!strcmp(token->str, "%i")) {
return QOBJECT(qbool_from_bool(va_arg(*ap, int)));
} else if (!strcmp(token->str, "%d")) {
return QOBJECT(qint_from_int(va_arg(*ap, int)));
} else if (!strcmp(token->str, "%ld")) {
return QOBJECT(qint_from_int(va_arg(*ap, long)));
} else if (!strcmp(token->str, "%lld") ||
!strcmp(token->str, "%I64d")) {
return QOBJECT(qint_from_int(va_arg(*ap, long long)));
} else if (!strcmp(token->str, "%s")) {
return QOBJECT(qstring_from_str(va_arg(*ap, const char *)));
} else if (!strcmp(token->str, "%f")) {
return QOBJECT(qfloat_from_double(va_arg(*ap, double)));
}
return NULL;
}
static QObject *parse_literal(JSONParserContext *ctxt)
{
JSONToken *token;
token = parser_context_pop_token(ctxt);
assert(token);
switch (token->type) {
case JSON_STRING:
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
* deal to treat these as ints in the parser, so long as users of the
* resulting QObject know to expect a QInt in place of a QFloat in
* cases like these.
*
* However, in some cases these values will overflow/underflow a
* QInt/int64 container, thus we should assume these are to be handled
* as QFloats/doubles rather than silently changing their values.
*
* strtoll() indicates these instances by setting errno to ERANGE
*/
int64_t value;
errno = 0; /* strtoll doesn't set errno on success */
value = strtoll(token->str, NULL, 10);
if (errno != ERANGE) {
return QOBJECT(qint_from_int(value));
}
/* fall through to JSON_FLOAT */
}
case JSON_FLOAT:
/* FIXME dependent on locale; a pervasive issue in QEMU */
/* FIXME our lexer matches RFC 7159 in forbidding Inf or NaN,
* but those might be useful extensions beyond JSON */
return QOBJECT(qfloat_from_double(strtod(token->str, NULL)));
default:
abort();
}
}
static QObject *parse_value(JSONParserContext *ctxt, va_list *ap)
{
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, 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(GQueue *tokens, va_list *ap)
{
return json_parser_parse_err(tokens, ap, NULL);
}
QObject *json_parser_parse_err(GQueue *tokens, va_list *ap, Error **errp)
{
JSONParserContext *ctxt = parser_context_new(tokens);
QObject *result;
if (!ctxt) {
return NULL;
}
result = parse_value(ctxt, ap);
error_propagate(errp, ctxt->err);
parser_context_free(ctxt);
return result;
}
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