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qemu/qobject/json-lexer.c

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/*
* JSON lexer
*
* 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 "qemu-common.h"
#include "qapi/qmp/json-lexer.h"
#define MAX_TOKEN_SIZE (64ULL << 20)
/*
* Required by JSON (RFC 7159):
*
* \"([^\\\"]|\\[\"'\\/bfnrt]|\\u[0-9a-fA-F]{4})*\"
* -?(0|[1-9][0-9]*)(.[0-9]+)?([eE][-+]?[0-9]+)?
* [{}\[\],:]
* [a-z]+ # covers null, true, false
*
* Extension of '' strings:
*
* '([^\\']|\\[\"'\\/bfnrt]|\\u[0-9a-fA-F]{4})*'
*
* Extension for vararg handling in JSON construction:
*
* %((l|ll|I64)?d|[ipsf])
*
*/
enum json_lexer_state {
IN_ERROR = 0, /* must really be 0, see json_lexer[] */
IN_DQ_UCODE3,
IN_DQ_UCODE2,
IN_DQ_UCODE1,
IN_DQ_UCODE0,
IN_DQ_STRING_ESCAPE,
IN_DQ_STRING,
IN_SQ_UCODE3,
IN_SQ_UCODE2,
IN_SQ_UCODE1,
IN_SQ_UCODE0,
IN_SQ_STRING_ESCAPE,
IN_SQ_STRING,
IN_ZERO,
IN_DIGITS,
IN_DIGIT,
IN_EXP_E,
IN_MANTISSA,
IN_MANTISSA_DIGITS,
IN_NONZERO_NUMBER,
IN_NEG_NONZERO_NUMBER,
IN_KEYWORD,
IN_ESCAPE,
IN_ESCAPE_L,
IN_ESCAPE_LL,
IN_ESCAPE_I,
IN_ESCAPE_I6,
IN_ESCAPE_I64,
IN_WHITESPACE,
IN_START,
};
QEMU_BUILD_BUG_ON((int)JSON_MIN <= (int)IN_START);
#define TERMINAL(state) [0 ... 0x7F] = (state)
/* Return whether TERMINAL is a terminal state and the transition to it
from OLD_STATE required lookahead. This happens whenever the table
below uses the TERMINAL macro. */
#define TERMINAL_NEEDED_LOOKAHEAD(old_state, terminal) \
(json_lexer[(old_state)][0] == (terminal))
static const uint8_t json_lexer[][256] = {
/* Relies on default initialization to IN_ERROR! */
/* double quote string */
[IN_DQ_UCODE3] = {
['0' ... '9'] = IN_DQ_STRING,
['a' ... 'f'] = IN_DQ_STRING,
['A' ... 'F'] = IN_DQ_STRING,
},
[IN_DQ_UCODE2] = {
['0' ... '9'] = IN_DQ_UCODE3,
['a' ... 'f'] = IN_DQ_UCODE3,
['A' ... 'F'] = IN_DQ_UCODE3,
},
[IN_DQ_UCODE1] = {
['0' ... '9'] = IN_DQ_UCODE2,
['a' ... 'f'] = IN_DQ_UCODE2,
['A' ... 'F'] = IN_DQ_UCODE2,
},
[IN_DQ_UCODE0] = {
['0' ... '9'] = IN_DQ_UCODE1,
['a' ... 'f'] = IN_DQ_UCODE1,
['A' ... 'F'] = IN_DQ_UCODE1,
},
[IN_DQ_STRING_ESCAPE] = {
['b'] = IN_DQ_STRING,
['f'] = IN_DQ_STRING,
['n'] = IN_DQ_STRING,
['r'] = IN_DQ_STRING,
['t'] = IN_DQ_STRING,
['/'] = IN_DQ_STRING,
['\\'] = IN_DQ_STRING,
['\''] = IN_DQ_STRING,
['\"'] = IN_DQ_STRING,
['u'] = IN_DQ_UCODE0,
},
[IN_DQ_STRING] = {
[1 ... 0xBF] = IN_DQ_STRING,
[0xC2 ... 0xF4] = IN_DQ_STRING,
['\\'] = IN_DQ_STRING_ESCAPE,
['"'] = JSON_STRING,
},
/* single quote string */
[IN_SQ_UCODE3] = {
['0' ... '9'] = IN_SQ_STRING,
['a' ... 'f'] = IN_SQ_STRING,
['A' ... 'F'] = IN_SQ_STRING,
},
[IN_SQ_UCODE2] = {
['0' ... '9'] = IN_SQ_UCODE3,
['a' ... 'f'] = IN_SQ_UCODE3,
['A' ... 'F'] = IN_SQ_UCODE3,
},
[IN_SQ_UCODE1] = {
['0' ... '9'] = IN_SQ_UCODE2,
['a' ... 'f'] = IN_SQ_UCODE2,
['A' ... 'F'] = IN_SQ_UCODE2,
},
[IN_SQ_UCODE0] = {
['0' ... '9'] = IN_SQ_UCODE1,
['a' ... 'f'] = IN_SQ_UCODE1,
['A' ... 'F'] = IN_SQ_UCODE1,
},
[IN_SQ_STRING_ESCAPE] = {
['b'] = IN_SQ_STRING,
['f'] = IN_SQ_STRING,
['n'] = IN_SQ_STRING,
['r'] = IN_SQ_STRING,
['t'] = IN_SQ_STRING,
['/'] = IN_SQ_STRING,
['\\'] = IN_SQ_STRING,
['\''] = IN_SQ_STRING,
['\"'] = IN_SQ_STRING,
['u'] = IN_SQ_UCODE0,
},
[IN_SQ_STRING] = {
[1 ... 0xBF] = IN_SQ_STRING,
[0xC2 ... 0xF4] = IN_SQ_STRING,
['\\'] = IN_SQ_STRING_ESCAPE,
['\''] = JSON_STRING,
},
/* Zero */
[IN_ZERO] = {
TERMINAL(JSON_INTEGER),
['0' ... '9'] = IN_ERROR,
['.'] = IN_MANTISSA,
},
/* Float */
[IN_DIGITS] = {
TERMINAL(JSON_FLOAT),
['0' ... '9'] = IN_DIGITS,
},
[IN_DIGIT] = {
['0' ... '9'] = IN_DIGITS,
},
[IN_EXP_E] = {
['-'] = IN_DIGIT,
['+'] = IN_DIGIT,
['0' ... '9'] = IN_DIGITS,
},
[IN_MANTISSA_DIGITS] = {
TERMINAL(JSON_FLOAT),
['0' ... '9'] = IN_MANTISSA_DIGITS,
['e'] = IN_EXP_E,
['E'] = IN_EXP_E,
},
[IN_MANTISSA] = {
['0' ... '9'] = IN_MANTISSA_DIGITS,
},
/* Number */
[IN_NONZERO_NUMBER] = {
TERMINAL(JSON_INTEGER),
['0' ... '9'] = IN_NONZERO_NUMBER,
['e'] = IN_EXP_E,
['E'] = IN_EXP_E,
['.'] = IN_MANTISSA,
},
[IN_NEG_NONZERO_NUMBER] = {
['0'] = IN_ZERO,
['1' ... '9'] = IN_NONZERO_NUMBER,
},
/* keywords */
[IN_KEYWORD] = {
TERMINAL(JSON_KEYWORD),
['a' ... 'z'] = IN_KEYWORD,
},
/* whitespace */
[IN_WHITESPACE] = {
TERMINAL(JSON_SKIP),
[' '] = IN_WHITESPACE,
['\t'] = IN_WHITESPACE,
['\r'] = IN_WHITESPACE,
['\n'] = IN_WHITESPACE,
},
/* escape */
[IN_ESCAPE_LL] = {
['d'] = JSON_ESCAPE,
['u'] = JSON_ESCAPE,
},
[IN_ESCAPE_L] = {
['d'] = JSON_ESCAPE,
['l'] = IN_ESCAPE_LL,
['u'] = JSON_ESCAPE,
},
[IN_ESCAPE_I64] = {
['d'] = JSON_ESCAPE,
['u'] = JSON_ESCAPE,
},
[IN_ESCAPE_I6] = {
['4'] = IN_ESCAPE_I64,
},
[IN_ESCAPE_I] = {
['6'] = IN_ESCAPE_I6,
},
[IN_ESCAPE] = {
['d'] = JSON_ESCAPE,
['i'] = JSON_ESCAPE,
['p'] = JSON_ESCAPE,
['s'] = JSON_ESCAPE,
['u'] = JSON_ESCAPE,
['f'] = JSON_ESCAPE,
['l'] = IN_ESCAPE_L,
['I'] = IN_ESCAPE_I,
},
/* top level rule */
[IN_START] = {
['"'] = IN_DQ_STRING,
['\''] = IN_SQ_STRING,
['0'] = IN_ZERO,
['1' ... '9'] = IN_NONZERO_NUMBER,
['-'] = IN_NEG_NONZERO_NUMBER,
['{'] = JSON_LCURLY,
['}'] = JSON_RCURLY,
['['] = JSON_LSQUARE,
[']'] = JSON_RSQUARE,
[','] = JSON_COMMA,
[':'] = JSON_COLON,
['a' ... 'z'] = IN_KEYWORD,
['%'] = IN_ESCAPE,
[' '] = IN_WHITESPACE,
['\t'] = IN_WHITESPACE,
['\r'] = IN_WHITESPACE,
['\n'] = IN_WHITESPACE,
},
};
void json_lexer_init(JSONLexer *lexer, JSONLexerEmitter func)
{
lexer->emit = func;
lexer->state = IN_START;
lexer->token = g_string_sized_new(3);
lexer->x = lexer->y = 0;
}
static int json_lexer_feed_char(JSONLexer *lexer, char ch, bool flush)
{
int char_consumed, new_state;
lexer->x++;
if (ch == '\n') {
lexer->x = 0;
lexer->y++;
}
do {
assert(lexer->state <= ARRAY_SIZE(json_lexer));
new_state = json_lexer[lexer->state][(uint8_t)ch];
char_consumed = !TERMINAL_NEEDED_LOOKAHEAD(lexer->state, new_state);
if (char_consumed) {
g_string_append_c(lexer->token, ch);
}
switch (new_state) {
case JSON_LCURLY:
case JSON_RCURLY:
case JSON_LSQUARE:
case JSON_RSQUARE:
case JSON_COLON:
case JSON_COMMA:
case JSON_ESCAPE:
case JSON_INTEGER:
case JSON_FLOAT:
case JSON_KEYWORD:
case JSON_STRING:
lexer->emit(lexer, lexer->token, new_state, lexer->x, lexer->y);
/* fall through */
case JSON_SKIP:
g_string_truncate(lexer->token, 0);
new_state = IN_START;
break;
case IN_ERROR:
/* XXX: To avoid having previous bad input leaving the parser in an
* unresponsive state where we consume unpredictable amounts of
* subsequent "good" input, percolate this error state up to the
* tokenizer/parser by forcing a NULL object to be emitted, then
* reset state.
*
* Also note that this handling is required for reliable channel
* negotiation between QMP and the guest agent, since chr(0xFF)
* is placed at the beginning of certain events to ensure proper
* delivery when the channel is in an unknown state. chr(0xFF) is
* never a valid ASCII/UTF-8 sequence, so this should reliably
* induce an error/flush state.
*/
lexer->emit(lexer, lexer->token, JSON_ERROR, lexer->x, lexer->y);
g_string_truncate(lexer->token, 0);
new_state = IN_START;
lexer->state = new_state;
return 0;
default:
break;
}
lexer->state = new_state;
} while (!char_consumed && !flush);
/* Do not let a single token grow to an arbitrarily large size,
* this is a security consideration.
*/
if (lexer->token->len > MAX_TOKEN_SIZE) {
lexer->emit(lexer, lexer->token, lexer->state, lexer->x, lexer->y);
g_string_truncate(lexer->token, 0);
lexer->state = IN_START;
}
return 0;
}
int json_lexer_feed(JSONLexer *lexer, const char *buffer, size_t size)
{
size_t i;
for (i = 0; i < size; i++) {
int err;
err = json_lexer_feed_char(lexer, buffer[i], false);
if (err < 0) {
return err;
}
}
return 0;
}
int json_lexer_flush(JSONLexer *lexer)
{
return lexer->state == IN_START ? 0 : json_lexer_feed_char(lexer, 0, true);
}
void json_lexer_destroy(JSONLexer *lexer)
{
g_string_free(lexer->token, true);
}
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