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 "qapi/error.h"
  16 #include "json-parser-int.h"
  17
  18 #define MAX_TOKEN_SIZE (64ULL << 20)
  19 #define MAX_TOKEN_COUNT (2ULL << 20)
  20 #define MAX_NESTING (1 << 10)
  21
  22 static void json_message_free_tokens(JSONMessageParser *parser)
  23 {
  24     JSONToken *token;
  25
  26     while ((token = g_queue_pop_head(&parser->tokens))) {
  27         g_free(token);
  28     }
  29 }
  30
  31 void json_message_process_token(JSONLexer *lexer, GString *input,
  32                                 JSONTokenType type, int x, int y)
  33 {
  34     JSONMessageParser *parser = container_of(lexer, JSONMessageParser, lexer);
  35     QObject *json = NULL;
  36     Error *err = NULL;
  37     JSONToken *token;
  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     case JSON_ERROR:
  53         error_setg(&err, "JSON parse error, stray '%s'", input->str);
  54         goto out_emit;
  55     case JSON_END_OF_INPUT:
  56         if (g_queue_is_empty(&parser->tokens)) {
  57             return;
  58         }
  59         json = json_parser_parse(&parser->tokens, parser->ap, &err);
  60         goto out_emit;
  61     default:
  62         break;
  63     }
  64
  65     /*
  66      * Security consideration, we limit total memory allocated per object
  67      * and the maximum recursion depth that a message can force.
  68      */
  69     if (parser->token_size + input->len + 1 > MAX_TOKEN_SIZE) {
  70         error_setg(&err, "JSON token size limit exceeded");
  71         goto out_emit;
  72     }
  73     if (g_queue_get_length(&parser->tokens) + 1 > MAX_TOKEN_COUNT) {
  74         error_setg(&err, "JSON token count limit exceeded");
  75         goto out_emit;
  76     }
  77     if (parser->bracket_count + parser->brace_count > MAX_NESTING) {
  78         error_setg(&err, "JSON nesting depth limit exceeded");
  79         goto out_emit;
  80     }
  81
  82     token = json_token(type, x, y, input);
  83     parser->token_size += input->len;
  84
  85     g_queue_push_tail(&parser->tokens, token);
  86
  87     if ((parser->brace_count > 0 || parser->bracket_count > 0)
  88         && parser->brace_count >= 0 && parser->bracket_count >= 0) {
  89         return;
  90     }
  91
  92     json = json_parser_parse(&parser->tokens, parser->ap, &err);
  93
  94 out_emit:
  95     parser->brace_count = 0;
  96     parser->bracket_count = 0;
  97     json_message_free_tokens(parser);
  98     parser->token_size = 0;
  99     parser->emit(parser->opaque, json, err);
 100 }
 101
 102 void json_message_parser_init(JSONMessageParser *parser,
 103                               void (*emit)(void *opaque, QObject *json,
 104                                            Error *err),
 105                               void *opaque, va_list *ap)
 106 {
 107     parser->emit = emit;
 108     parser->opaque = opaque;
 109     parser->ap = ap;
 110     parser->brace_count = 0;
 111     parser->bracket_count = 0;
 112     g_queue_init(&parser->tokens);
 113     parser->token_size = 0;
 114
 115     json_lexer_init(&parser->lexer, !!ap);
 116 }
 117
 118 void json_message_parser_feed(JSONMessageParser *parser,
 119                              const char *buffer, size_t size)
 120 {
 121     json_lexer_feed(&parser->lexer, buffer, size);
 122 }
 123
 124 void json_message_parser_flush(JSONMessageParser *parser)
 125 {
 126     json_lexer_flush(&parser->lexer);
 127     assert(g_queue_is_empty(&parser->tokens));
 128 }
 129
 130 void json_message_parser_destroy(JSONMessageParser *parser)
 131 {
 132     json_lexer_destroy(&parser->lexer);
 133     json_message_free_tokens(parser);
 134 }