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qemu/qobject/json-parser.c
Eric Blake e549e7161f json-parser: Accept 'null' in QMP 
We document that in QMP, the client may send any json-value
for the optional "id" key, and then return that same value
on reply (both success and failures, insofar as the failure
happened after parsing the id).  [Note that the output may
not be identical to the input, as whitespace may change and
since we may reorder keys within a json-object, but that this
still constitutes the same json-value].  However, we were not
handling the JSON literal null, which counts as a json-value
per RFC 7159.

Also, down the road, given the QAPI schema of {'*foo':'str'} or
{'*foo':'ComplexType'}, we could decide to allow the QMP client
to pass { "foo":null } instead of the current representation of
{ } where omitting the key is the only way to get at the default
NULL value.  Such a change might be useful for argument
introspection (if a type in older qemu lacks 'foo' altogether,
then an explicit "foo":null probe will force an easily
distinguished error message for whether the optional "foo" key
is even understood in newer qemu).  And if we add default values
to optional arguments, allowing an explicit null would be
required for getting a NULL value associated with an optional
string that has a non-null default.  But all that can come at a
later day.

The 'check-unit' testsuite is enhanced to test that parsing
produces the same object as explicitly requesting a reference
to the special qnull object.  In addition, I tested with:

$ ./x86_64-softmmu/qemu-system-x86_64 -qmp stdio -nodefaults
{"QMP": {"version": {"qemu": {"micro": 91, "minor": 2, "major": 2}, "package": ""}, "capabilities": []}}
{"execute":"qmp_capabilities","id":null}
{"return": {}, "id": null}
{"id":{"a":null,"b":[1,null]},"execute":"quit"}
{"return": {}, "id": {"a": null, "b": [1, null]}}
{"timestamp": {"seconds": 1427742379, "microseconds": 423128}, "event": "SHUTDOWN"}

Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2015-05-11 08:59:07 -04:00

716 lines
17 KiB
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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 <stdarg.h>
#include "qemu-common.h"
#include "qapi/qmp/qstring.h"
#include "qapi/qmp/qint.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qlist.h"
#include "qapi/qmp/qfloat.h"
#include "qapi/qmp/qbool.h"
#include "qapi/qmp/json-parser.h"
#include "qapi/qmp/json-lexer.h"
#include "qapi/qmp/qerror.h"
typedef struct JSONParserContext
{
Error *err;
struct {
QObject **buf;
size_t pos;
size_t count;
} tokens;
} 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);
/**
* Token manipulators
*
* tokens are dictionaries that contain a type, a string value, and geometry information
* about a token identified by the lexer. These are routines that make working with
* these objects a bit easier.
*/
static const char *token_get_value(QObject *obj)
{
return qdict_get_str(qobject_to_qdict(obj), "token");
}
static JSONTokenType token_get_type(QObject *obj)
{
return qdict_get_int(qobject_to_qdict(obj), "type");
}
static int token_is_operator(QObject *obj, char op)
{
const char *val;
if (token_get_type(obj) != JSON_OPERATOR) {
return 0;
}
val = token_get_value(obj);
return (val[0] == op) && (val[1] == 0);
}
static int token_is_keyword(QObject *obj, const char *value)
{
if (token_get_type(obj) != JSON_KEYWORD) {
return 0;
}
return strcmp(token_get_value(obj), value) == 0;
}
static int token_is_escape(QObject *obj, const char *value)
{
if (token_get_type(obj) != JSON_ESCAPE) {
return 0;
}
return (strcmp(token_get_value(obj), value) == 0);
}
/**
* Error handler
*/
static void GCC_FMT_ATTR(3, 4) parse_error(JSONParserContext *ctxt,
QObject *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, QObject *token)
{
const char *ptr = token_get_value(token);
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;
}
static QObject *parser_context_pop_token(JSONParserContext *ctxt)
{
QObject *token;
g_assert(ctxt->tokens.pos < ctxt->tokens.count);
token = ctxt->tokens.buf[ctxt->tokens.pos];
ctxt->tokens.pos++;
return token;
}
/* Note: parser_context_{peek|pop}_token do not increment the
* token object's refcount. In both cases the references will continue
* to be tracked and cleaned up in parser_context_free(), so do not
* attempt to free the token object.
*/
static QObject *parser_context_peek_token(JSONParserContext *ctxt)
{
QObject *token;
g_assert(ctxt->tokens.pos < ctxt->tokens.count);
token = ctxt->tokens.buf[ctxt->tokens.pos];
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;
g_assert(ctxt->tokens.pos < ctxt->tokens.count);
ctxt->tokens.buf[ctxt->tokens.pos++] = obj;
qobject_incref(obj);
}
static JSONParserContext *parser_context_new(QList *tokens)
{
JSONParserContext *ctxt;
size_t count;
if (!tokens) {
return NULL;
}
count = qlist_size(tokens);
if (count == 0) {
return NULL;
}
ctxt = g_malloc0(sizeof(JSONParserContext));
ctxt->tokens.pos = 0;
ctxt->tokens.count = count;
ctxt->tokens.buf = g_malloc(count * sizeof(QObject *));
qlist_iter(tokens, tokens_append_from_iter, ctxt);
ctxt->tokens.pos = 0;
return ctxt;
}
/* to support error propagation, ctxt->err must be freed separately */
static void parser_context_free(JSONParserContext *ctxt)
{
int i;
if (ctxt) {
for (i = 0; i < ctxt->tokens.count; i++) {
qobject_decref(ctxt->tokens.buf[i]);
}
g_free(ctxt->tokens.buf);
g_free(ctxt);
}
}
/**
* Parsing rules
*/
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) {
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_is_operator(token, ':')) {
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:
parser_context_restore(ctxt, saved_ctxt);
qobject_decref(key);
return -1;
}
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_is_operator(token, '{')) {
goto out;
}
dict = qdict_new();
peek = parser_context_peek_token(ctxt);
if (peek == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
if (!token_is_operator(peek, '}')) {
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_is_operator(token, '}')) {
if (!token_is_operator(token, ',')) {
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:
parser_context_restore(ctxt, saved_ctxt);
QDECREF(dict);
return NULL;
}
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_is_operator(token, '[')) {
goto out;
}
list = qlist_new();
peek = parser_context_peek_token(ctxt);
if (peek == NULL) {
parse_error(ctxt, NULL, "premature EOI");
goto out;
}
if (!token_is_operator(peek, ']')) {
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_is_operator(token, ']')) {
if (!token_is_operator(token, ',')) {
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:
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);
token = parser_context_pop_token(ctxt);
if (token == NULL) {
goto out;
}
if (token_get_type(token) != JSON_KEYWORD) {
goto out;
}
if (token_is_keyword(token, "true")) {
ret = QOBJECT(qbool_from_int(true));
} else if (token_is_keyword(token, "false")) {
ret = QOBJECT(qbool_from_int(false));
} else if (token_is_keyword(token, "null")) {
ret = qnull();
} else {
parse_error(ctxt, token, "invalid keyword `%s'", token_get_value(token));
goto out;
}
return ret;
out:
parser_context_restore(ctxt, saved_ctxt);
return NULL;
}
static QObject *parse_escape(JSONParserContext *ctxt, va_list *ap)
{
QObject *token = NULL, *obj;
JSONParserContext saved_ctxt = parser_context_save(ctxt);
if (ap == NULL) {
goto out;
}
token = parser_context_pop_token(ctxt);
if (token == NULL) {
goto out;
}
if (token_is_escape(token, "%p")) {
obj = va_arg(*ap, QObject *);
} else if (token_is_escape(token, "%i")) {
obj = QOBJECT(qbool_from_int(va_arg(*ap, int)));
} else if (token_is_escape(token, "%d")) {
obj = QOBJECT(qint_from_int(va_arg(*ap, int)));
} else if (token_is_escape(token, "%ld")) {
obj = QOBJECT(qint_from_int(va_arg(*ap, long)));
} else if (token_is_escape(token, "%lld") ||
token_is_escape(token, "%I64d")) {
obj = QOBJECT(qint_from_int(va_arg(*ap, long long)));
} else if (token_is_escape(token, "%s")) {
obj = QOBJECT(qstring_from_str(va_arg(*ap, const char *)));
} else if (token_is_escape(token, "%f")) {
obj = QOBJECT(qfloat_from_double(va_arg(*ap, double)));
} else {
goto out;
}
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);
token = parser_context_pop_token(ctxt);
if (token == NULL) {
goto out;
}
switch (token_get_type(token)) {
case JSON_STRING:
obj = QOBJECT(qstring_from_escaped_str(ctxt, token));
break;
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_get_value(token), NULL, 10);
if (errno != ERANGE) {
obj = QOBJECT(qint_from_int(value));
break;
}
/* fall through to JSON_FLOAT */
}
case JSON_FLOAT:
/* FIXME dependent on locale */
obj = QOBJECT(qfloat_from_double(strtod(token_get_value(token), NULL)));
break;
default:
goto out;
}
return obj;
out:
parser_context_restore(ctxt, saved_ctxt);
return NULL;
}
static QObject *parse_value(JSONParserContext *ctxt, va_list *ap)
{
QObject *obj;
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);
}
return obj;
}
QObject *json_parser_parse(QList *tokens, va_list *ap)
{
return json_parser_parse_err(tokens, ap, NULL);
}
QObject *json_parser_parse_err(QList *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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