netwerk/cache/nsCacheMetaData.cpp

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  *
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "nsCacheMetaData.h"
   8 #include "nsICacheEntryDescriptor.h"
   9
  10 const char* nsCacheMetaData::GetElement(const char* key) {
  11   const char* data = mBuffer;
  12   const char* limit = mBuffer + mMetaSize;
  13
  14   while (data < limit) {
  15     // Point to the value part
  16     const char* value = data + strlen(data) + 1;
  17     MOZ_ASSERT(value < limit, "Cache Metadata corrupted");
  18     if (strcmp(data, key) == 0) return value;
  19
  20     // Skip value part
  21     data = value + strlen(value) + 1;
  22   }
  23   MOZ_ASSERT(data == limit, "Metadata corrupted");
  24   return nullptr;
  25 }
  26
  27 nsresult nsCacheMetaData::SetElement(const char* key, const char* value) {
  28   const uint32_t keySize = strlen(key) + 1;
  29   char* pos = (char*)GetElement(key);
  30
  31   if (!value) {
  32     // No value means remove the key/value pair completely, if existing
  33     if (pos) {
  34       uint32_t oldValueSize = strlen(pos) + 1;
  35       uint32_t offset = pos - mBuffer;
  36       uint32_t remainder = mMetaSize - (offset + oldValueSize);
  37
  38       memmove(pos - keySize, pos + oldValueSize, remainder);
  39       mMetaSize -= keySize + oldValueSize;
  40     }
  41     return NS_OK;
  42   }
  43
  44   const uint32_t valueSize = strlen(value) + 1;
  45   uint32_t newSize = mMetaSize + valueSize;
  46   if (pos) {
  47     const uint32_t oldValueSize = strlen(pos) + 1;
  48     const uint32_t offset = pos - mBuffer;
  49     const uint32_t remainder = mMetaSize - (offset + oldValueSize);
  50
  51     // Update the value in place
  52     newSize -= oldValueSize;
  53     nsresult rv = EnsureBuffer(newSize);
  54     NS_ENSURE_SUCCESS(rv, rv);
  55
  56     // Move the remainder to the right place
  57     pos = mBuffer + offset;
  58     memmove(pos + valueSize, pos + oldValueSize, remainder);
  59   } else {
  60     // allocate new meta data element
  61     newSize += keySize;
  62     nsresult rv = EnsureBuffer(newSize);
  63     NS_ENSURE_SUCCESS(rv, rv);
  64
  65     // Add after last element
  66     pos = mBuffer + mMetaSize;
  67     memcpy(pos, key, keySize);
  68     pos += keySize;
  69   }
  70
  71   // Update value
  72   memcpy(pos, value, valueSize);
  73   mMetaSize = newSize;
  74
  75   return NS_OK;
  76 }
  77
  78 nsresult nsCacheMetaData::FlattenMetaData(char* buffer, uint32_t bufSize) {
  79   if (mMetaSize > bufSize) {
  80     NS_ERROR("buffer size too small for meta data.");
  81     return NS_ERROR_OUT_OF_MEMORY;
  82   }
  83
  84   if (!mBuffer) {
  85     MOZ_ASSERT(mMetaSize == 0);
  86     MOZ_ASSERT(bufSize == 0);
  87     return NS_OK;
  88   }
  89
  90   memcpy(buffer, mBuffer, mMetaSize);
  91   return NS_OK;
  92 }
  93
  94 nsresult nsCacheMetaData::UnflattenMetaData(const char* data, uint32_t size) {
  95   if (data && size) {
  96     // Check if the metadata ends with a zero byte.
  97     if (data[size - 1] != '\0') {
  98       NS_ERROR("Cache MetaData is not null terminated");
  99       return NS_ERROR_ILLEGAL_VALUE;
 100     }
 101     // Check that there are an even number of zero bytes
 102     // to match the pattern { key \0 value \0 }
 103     bool odd = false;
 104     for (uint32_t i = 0; i < size; i++) {
 105       if (data[i] == '\0') odd = !odd;
 106     }
 107     if (odd) {
 108       NS_ERROR("Cache MetaData is malformed");
 109       return NS_ERROR_ILLEGAL_VALUE;
 110     }
 111
 112     nsresult rv = EnsureBuffer(size);
 113     NS_ENSURE_SUCCESS(rv, rv);
 114
 115     memcpy(mBuffer, data, size);
 116     mMetaSize = size;
 117   }
 118   return NS_OK;
 119 }
 120
 121 nsresult nsCacheMetaData::VisitElements(nsICacheMetaDataVisitor* visitor) {
 122   const char* data = mBuffer;
 123   const char* limit = mBuffer + mMetaSize;
 124
 125   while (data < limit) {
 126     const char* key = data;
 127     // Skip key part
 128     data += strlen(data) + 1;
 129     MOZ_ASSERT(data < limit, "Metadata corrupted");
 130     bool keepGoing;
 131     nsresult rv = visitor->VisitMetaDataElement(key, data, &keepGoing);
 132     if (NS_FAILED(rv) || !keepGoing) return NS_OK;
 133
 134     // Skip value part
 135     data += strlen(data) + 1;
 136   }
 137   MOZ_ASSERT(data == limit, "Metadata corrupted");
 138   return NS_OK;
 139 }
 140
 141 nsresult nsCacheMetaData::EnsureBuffer(uint32_t bufSize) {
 142   if (mBufferSize < bufSize) {
 143     char* buf = (char*)realloc(mBuffer, bufSize);
 144     if (!buf) {
 145       return NS_ERROR_OUT_OF_MEMORY;
 146     }
 147     mBuffer = buf;
 148     mBufferSize = bufSize;
 149   }
 150   return NS_OK;
 151 }