qobject/json-streamer.c

   1 /*
   2  * JSON streaming support
   3  *
   4  * Copyright IBM, Corp. 2009
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qapi/qmp/qlist.h"
  15 #include "qapi/qmp/qstring.h"
  16 #include "qapi/qmp/qint.h"
  17 #include "qapi/qmp/qdict.h"
  18 #include "qemu-common.h"
  19 #include "qapi/qmp/json-lexer.h"
  20 #include "qapi/qmp/json-streamer.h"
  21
  22 #define MAX_TOKEN_SIZE (64ULL << 20)
  23 #define MAX_NESTING (1ULL << 10)
  24
  25 static void json_message_free_tokens(JSONMessageParser *parser)
  26 {
  27     if (parser->tokens) {
  28         g_queue_free(parser->tokens);
  29         parser->tokens = NULL;
  30     }
  31 }
  32
  33 static void json_message_process_token(JSONLexer *lexer, GString *input,
  34                                        JSONTokenType type, int x, int y)
  35 {
  36     JSONMessageParser *parser = container_of(lexer, JSONMessageParser, lexer);
  37     QDict *dict;
  38
  39     switch (type) {
  40     case JSON_LCURLY:
  41         parser->brace_count++;
  42         break;
  43     case JSON_RCURLY:
  44         parser->brace_count--;
  45         break;
  46     case JSON_LSQUARE:
  47         parser->bracket_count++;
  48         break;
  49     case JSON_RSQUARE:
  50         parser->bracket_count--;
  51         break;
  52     default:
  53         break;
  54     }
  55
  56     dict = qdict_new();
  57     qdict_put(dict, "type", qint_from_int(type));
  58     qdict_put(dict, "token", qstring_from_str(input->str));
  59     qdict_put(dict, "x", qint_from_int(x));
  60     qdict_put(dict, "y", qint_from_int(y));
  61
  62     parser->token_size += input->len;
  63
  64     g_queue_push_tail(parser->tokens, dict);
  65
  66     if (type == JSON_ERROR) {
  67         goto out_emit_bad;
  68     } else if (parser->brace_count < 0 ||
  69         parser->bracket_count < 0 ||
  70         (parser->brace_count == 0 &&
  71          parser->bracket_count == 0)) {
  72         goto out_emit;
  73     } else if (parser->token_size > MAX_TOKEN_SIZE ||
  74                parser->bracket_count + parser->brace_count > MAX_NESTING) {
  75         /* Security consideration, we limit total memory allocated per object
  76          * and the maximum recursion depth that a message can force.
  77          */
  78         goto out_emit_bad;
  79     }
  80
  81     return;
  82
  83 out_emit_bad:
  84     /*
  85      * Clear out token list and tell the parser to emit an error
  86      * indication by passing it a NULL list
  87      */
  88     json_message_free_tokens(parser);
  89 out_emit:
  90     /* send current list of tokens to parser and reset tokenizer */
  91     parser->brace_count = 0;
  92     parser->bracket_count = 0;
  93     /* parser->emit takes ownership of parser->tokens.  */
  94     parser->emit(parser, parser->tokens);
  95     parser->tokens = g_queue_new();
  96     parser->token_size = 0;
  97 }
  98
  99 void json_message_parser_init(JSONMessageParser *parser,
 100                               void (*func)(JSONMessageParser *, GQueue *))
 101 {
 102     parser->emit = func;
 103     parser->brace_count = 0;
 104     parser->bracket_count = 0;
 105     parser->tokens = g_queue_new();
 106     parser->token_size = 0;
 107
 108     json_lexer_init(&parser->lexer, json_message_process_token);
 109 }
 110
 111 int json_message_parser_feed(JSONMessageParser *parser,
 112                              const char *buffer, size_t size)
 113 {
 114     return json_lexer_feed(&parser->lexer, buffer, size);
 115 }
 116
 117 int json_message_parser_flush(JSONMessageParser *parser)
 118 {
 119     return json_lexer_flush(&parser->lexer);
 120 }
 121
 122 void json_message_parser_destroy(JSONMessageParser *parser)
 123 {
 124     json_lexer_destroy(&parser->lexer);
 125     json_message_free_tokens(parser);
 126 }