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 "qemu/osdep.h"
  15 #include "qemu-common.h"
  16 #include "qapi/qmp/json-lexer.h"
  17 #include "qapi/qmp/json-parser.h"
  18 #include "qapi/qmp/json-streamer.h"
  19
  20 #define MAX_TOKEN_SIZE (64ULL << 20)
  21 #define MAX_TOKEN_COUNT (2ULL << 20)
  22 #define MAX_NESTING (1ULL << 10)
  23
  24 static void json_message_free_token(void *token, void *opaque)
  25 {
  26     g_free(token);
  27 }
  28
  29 static void json_message_free_tokens(JSONMessageParser *parser)
  30 {
  31     if (parser->tokens) {
  32         g_queue_foreach(parser->tokens, json_message_free_token, NULL);
  33         g_queue_free(parser->tokens);
  34         parser->tokens = NULL;
  35     }
  36 }
  37
  38 void json_message_process_token(JSONLexer *lexer, GString *input,
  39                                 JSONTokenType type, int x, int y)
  40 {
  41     JSONMessageParser *parser = container_of(lexer, JSONMessageParser, lexer);
  42     QObject *json = NULL;
  43     Error *err = NULL;
  44     JSONToken *token;
  45
  46     switch (type) {
  47     case JSON_LCURLY:
  48         parser->brace_count++;
  49         break;
  50     case JSON_RCURLY:
  51         parser->brace_count--;
  52         break;
  53     case JSON_LSQUARE:
  54         parser->bracket_count++;
  55         break;
  56     case JSON_RSQUARE:
  57         parser->bracket_count--;
  58         break;
  59     case JSON_ERROR:
  60         goto out_emit;
  61     default:
  62         break;
  63     }
  64
  65     token = g_malloc(sizeof(JSONToken) + input->len + 1);
  66     token->type = type;
  67     memcpy(token->str, input->str, input->len);
  68     token->str[input->len] = 0;
  69     token->x = x;
  70     token->y = y;
  71
  72     parser->token_size += input->len;
  73
  74     g_queue_push_tail(parser->tokens, token);
  75
  76     if (parser->brace_count < 0 ||
  77         parser->bracket_count < 0 ||
  78         (parser->brace_count == 0 &&
  79          parser->bracket_count == 0)) {
  80         json = json_parser_parse(parser->tokens, parser->ap, &err);
  81         parser->tokens = NULL;
  82         goto out_emit;
  83     }
  84
  85     if (parser->token_size > MAX_TOKEN_SIZE ||
  86                g_queue_get_length(parser->tokens) > MAX_TOKEN_COUNT ||
  87                parser->bracket_count + parser->brace_count > MAX_NESTING) {
  88         /* Security consideration, we limit total memory allocated per object
  89          * and the maximum recursion depth that a message can force.
  90          */
  91         goto out_emit;
  92     }
  93
  94     return;
  95
  96 out_emit:
  97     parser->brace_count = 0;
  98     parser->bracket_count = 0;
  99     json_message_free_tokens(parser);
 100     parser->tokens = g_queue_new();
 101     parser->token_size = 0;
 102     parser->emit(parser->opaque, json, err);
 103 }
 104
 105 void json_message_parser_init(JSONMessageParser *parser,
 106                               void (*emit)(void *opaque, QObject *json,
 107                                            Error *err),
 108                               void *opaque, va_list *ap)
 109 {
 110     parser->emit = emit;
 111     parser->opaque = opaque;
 112     parser->ap = ap;
 113     parser->brace_count = 0;
 114     parser->bracket_count = 0;
 115     parser->tokens = g_queue_new();
 116     parser->token_size = 0;
 117
 118     json_lexer_init(&parser->lexer, !!ap);
 119 }
 120
 121 void json_message_parser_feed(JSONMessageParser *parser,
 122                              const char *buffer, size_t size)
 123 {
 124     json_lexer_feed(&parser->lexer, buffer, size);
 125 }
 126
 127 void json_message_parser_flush(JSONMessageParser *parser)
 128 {
 129     json_lexer_flush(&parser->lexer);
 130 }
 131
 132 void json_message_parser_destroy(JSONMessageParser *parser)
 133 {
 134     json_lexer_destroy(&parser->lexer);
 135     json_message_free_tokens(parser);
 136 }