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/qint.h"
  16 #include "qapi/qmp/qdict.h"
  17 #include "qemu-common.h"
  18 #include "qapi/qmp/json-lexer.h"
  19 #include "qapi/qmp/json-streamer.h"
  20
  21 #define MAX_TOKEN_SIZE (64ULL << 20)
  22 #define MAX_NESTING (1ULL << 10)
  23
  24 static void json_message_process_token(JSONLexer *lexer, QString *token, JSONTokenType type, int x, int y)
  25 {
  26     JSONMessageParser *parser = container_of(lexer, JSONMessageParser, lexer);
  27     QDict *dict;
  28
  29     if (type == JSON_OPERATOR) {
  30         switch (qstring_get_str(token)[0]) {
  31         case '{':
  32             parser->brace_count++;
  33             break;
  34         case '}':
  35             parser->brace_count--;
  36             break;
  37         case '[':
  38             parser->bracket_count++;
  39             break;
  40         case ']':
  41             parser->bracket_count--;
  42             break;
  43         default:
  44             break;
  45         }
  46     }
  47
  48     dict = qdict_new();
  49     qdict_put(dict, "type", qint_from_int(type));
  50     QINCREF(token);
  51     qdict_put(dict, "token", token);
  52     qdict_put(dict, "x", qint_from_int(x));
  53     qdict_put(dict, "y", qint_from_int(y));
  54
  55     parser->token_size += token->length;
  56
  57     qlist_append(parser->tokens, dict);
  58
  59     if (type == JSON_ERROR) {
  60         goto out_emit_bad;
  61     } else if (parser->brace_count < 0 ||
  62         parser->bracket_count < 0 ||
  63         (parser->brace_count == 0 &&
  64          parser->bracket_count == 0)) {
  65         goto out_emit;
  66     } else if (parser->token_size > MAX_TOKEN_SIZE ||
  67                parser->bracket_count > MAX_NESTING ||
  68                parser->brace_count > MAX_NESTING) {
  69         /* Security consideration, we limit total memory allocated per object
  70          * and the maximum recursion depth that a message can force.
  71          */
  72         goto out_emit;
  73     }
  74
  75     return;
  76
  77 out_emit_bad:
  78     /* clear out token list and tell the parser to emit and error
  79      * indication by passing it a NULL list
  80      */
  81     QDECREF(parser->tokens);
  82     parser->tokens = NULL;
  83 out_emit:
  84     /* send current list of tokens to parser and reset tokenizer */
  85     parser->brace_count = 0;
  86     parser->bracket_count = 0;
  87     parser->emit(parser, parser->tokens);
  88     if (parser->tokens) {
  89         QDECREF(parser->tokens);
  90     }
  91     parser->tokens = qlist_new();
  92     parser->token_size = 0;
  93 }
  94
  95 void json_message_parser_init(JSONMessageParser *parser,
  96                               void (*func)(JSONMessageParser *, QList *))
  97 {
  98     parser->emit = func;
  99     parser->brace_count = 0;
 100     parser->bracket_count = 0;
 101     parser->tokens = qlist_new();
 102     parser->token_size = 0;
 103
 104     json_lexer_init(&parser->lexer, json_message_process_token);
 105 }
 106
 107 int json_message_parser_feed(JSONMessageParser *parser,
 108                              const char *buffer, size_t size)
 109 {
 110     return json_lexer_feed(&parser->lexer, buffer, size);
 111 }
 112
 113 int json_message_parser_flush(JSONMessageParser *parser)
 114 {
 115     return json_lexer_flush(&parser->lexer);
 116 }
 117
 118 void json_message_parser_destroy(JSONMessageParser *parser)
 119 {
 120     json_lexer_destroy(&parser->lexer);
 121     QDECREF(parser->tokens);
 122 }