netwerk/cache/nsCacheMetaData.cpp

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   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 *
  11 nsCacheMetaData::GetElement(const char * key)
  12 {
  13     const char * data = mBuffer;
  14     const char * limit = mBuffer + mMetaSize;
  15
  16     while (data < limit) {
  17         // Point to the value part
  18         const char * value = data + strlen(data) + 1;
  19         NS_ABORT_IF_FALSE(value < limit, "Cache Metadata corrupted");
  20         if (strcmp(data, key) == 0)
  21             return value;
  22
  23         // Skip value part
  24         data = value + strlen(value) + 1;
  25     }
  26     NS_ABORT_IF_FALSE(data == limit, "Metadata corrupted");
  27     return nullptr;
  28 }
  29
  30
  31 nsresult
  32 nsCacheMetaData::SetElement(const char * key,
  33                             const char * value)
  34 {
  35     const uint32_t keySize = strlen(key) + 1;
  36     char * pos = (char *)GetElement(key);
  37
  38     if (!value) {
  39         // No value means remove the key/value pair completely, if existing
  40         if (pos) {
  41             uint32_t oldValueSize = strlen(pos) + 1;
  42             uint32_t offset = pos - mBuffer;
  43             uint32_t remainder = mMetaSize - (offset + oldValueSize);
  44
  45             memmove(pos - keySize, pos + oldValueSize, remainder);
  46             mMetaSize -= keySize + oldValueSize;
  47         }
  48         return NS_OK;
  49     }
  50
  51     const uint32_t valueSize = strlen(value) + 1;
  52     uint32_t newSize = mMetaSize + valueSize;
  53     if (pos) {
  54         const uint32_t oldValueSize = strlen(pos) + 1;
  55         const uint32_t offset = pos - mBuffer;
  56         const uint32_t remainder = mMetaSize - (offset + oldValueSize);
  57
  58         // Update the value in place
  59         newSize -= oldValueSize;
  60         nsresult rv = EnsureBuffer(newSize);
  61         NS_ENSURE_SUCCESS(rv, rv);
  62
  63         // Move the remainder to the right place
  64         pos = mBuffer + offset;
  65         memmove(pos + valueSize, pos + oldValueSize, remainder);
  66     } else {
  67         // allocate new meta data element
  68         newSize += keySize;
  69         nsresult rv = EnsureBuffer(newSize);
  70         NS_ENSURE_SUCCESS(rv, rv);
  71
  72         // Add after last element
  73         pos = mBuffer + mMetaSize;
  74         memcpy(pos, key, keySize);
  75         pos += keySize;
  76     }
  77
  78     // Update value
  79     memcpy(pos, value, valueSize);
  80     mMetaSize = newSize;
  81
  82     return NS_OK;
  83 }
  84
  85 nsresult
  86 nsCacheMetaData::FlattenMetaData(char * buffer, uint32_t bufSize)
  87 {
  88     if (mMetaSize > bufSize) {
  89         NS_ERROR("buffer size too small for meta data.");
  90         return NS_ERROR_OUT_OF_MEMORY;
  91     }
  92
  93     memcpy(buffer, mBuffer, mMetaSize);
  94     return NS_OK;
  95 }
  96
  97 nsresult
  98 nsCacheMetaData::UnflattenMetaData(const char * data, uint32_t size)
  99 {
 100     if (data && size) {
 101         // Check if the metadata ends with a zero byte.
 102         if (data[size-1] != '\0') {
 103             NS_ERROR("Cache MetaData is not null terminated");
 104             return NS_ERROR_ILLEGAL_VALUE;
 105         }
 106         // Check that there are an even number of zero bytes
 107         // to match the pattern { key \0 value \0 }
 108         bool odd = false;
 109         for (uint32_t i = 0; i < size; i++) {
 110             if (data[i] == '\0')
 111                 odd = !odd;
 112         }
 113         if (odd) {
 114             NS_ERROR("Cache MetaData is malformed");
 115             return NS_ERROR_ILLEGAL_VALUE;
 116         }
 117
 118         nsresult rv = EnsureBuffer(size);
 119         NS_ENSURE_SUCCESS(rv, rv);
 120
 121         memcpy(mBuffer, data, size);
 122         mMetaSize = size;
 123     }
 124     return NS_OK;
 125 }
 126
 127 nsresult
 128 nsCacheMetaData::VisitElements(nsICacheMetaDataVisitor * visitor)
 129 {
 130     const char * data = mBuffer;
 131     const char * limit = mBuffer + mMetaSize;
 132
 133     while (data < limit) {
 134         const char * key = data;
 135         // Skip key part
 136         data += strlen(data) + 1;
 137         NS_ABORT_IF_FALSE(data < limit, "Metadata corrupted");
 138         bool keepGoing;
 139         nsresult rv = visitor->VisitMetaDataElement(key, data, &keepGoing);
 140         if (NS_FAILED(rv) || !keepGoing)
 141             return NS_OK;
 142
 143         // Skip value part
 144         data += strlen(data) + 1;
 145     }
 146     NS_ABORT_IF_FALSE(data == limit, "Metadata corrupted");
 147     return NS_OK;
 148 }
 149
 150 nsresult
 151 nsCacheMetaData::EnsureBuffer(uint32_t bufSize)
 152 {
 153     if (mBufferSize < bufSize) {
 154         char * buf = (char *)moz_realloc(mBuffer, bufSize);
 155         if (!buf) {
 156             return NS_ERROR_OUT_OF_MEMORY;
 157         }
 158         mBuffer = buf;
 159         mBufferSize = bufSize;
 160     }
 161     return NS_OK;
 162 }