xpcom/io/nsSegmentedBuffer.cpp

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  15  * The Original Code is mozilla.org code.
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  17  * The Initial Developer of the Original Code is
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  37
  38 #include "nsSegmentedBuffer.h"
  39 #include "nsCRT.h"
  40
  41 nsresult
  42 nsSegmentedBuffer::Init(PRUint32 segmentSize, PRUint32 maxSize,
  43                         nsIMemory* allocator)
  44 {
  45     if (mSegmentArrayCount != 0)
  46         return NS_ERROR_FAILURE;        // initialized more than once
  47     mSegmentSize = segmentSize;
  48     mMaxSize = maxSize;
  49     mSegAllocator = allocator;
  50     if (mSegAllocator == nsnull) {
  51         mSegAllocator = nsMemory::GetGlobalMemoryService();
  52     }
  53     else {
  54         NS_ADDREF(mSegAllocator);
  55     }
  56 #if 0 // testing...
  57     mSegmentArrayCount = 2;
  58 #else
  59     mSegmentArrayCount = NS_SEGMENTARRAY_INITIAL_COUNT;
  60 #endif
  61     return NS_OK;
  62 }
  63
  64 char*
  65 nsSegmentedBuffer::AppendNewSegment()
  66 {
  67     if (GetSize() >= mMaxSize)
  68         return nsnull;
  69
  70     if (mSegmentArray == nsnull) {
  71         PRUint32 bytes = mSegmentArrayCount * sizeof(char*);
  72         mSegmentArray = (char**)nsMemory::Alloc(bytes);
  73         if (mSegmentArray == nsnull)
  74             return nsnull;
  75         memset(mSegmentArray, 0, bytes);
  76     }
  77
  78     if (IsFull()) {
  79         PRUint32 newArraySize = mSegmentArrayCount * 2;
  80         PRUint32 bytes = newArraySize * sizeof(char*);
  81         char** newSegArray = (char**)nsMemory::Realloc(mSegmentArray, bytes);
  82         if (newSegArray == nsnull)
  83             return nsnull;
  84         mSegmentArray = newSegArray;
  85         // copy wrapped content to new extension
  86         if (mFirstSegmentIndex > mLastSegmentIndex) {
  87             // deal with wrap around case
  88             memcpy(&mSegmentArray[mSegmentArrayCount],
  89                    mSegmentArray,
  90                    mLastSegmentIndex * sizeof(char*));
  91             memset(mSegmentArray, 0, mLastSegmentIndex * sizeof(char*));
  92             mLastSegmentIndex += mSegmentArrayCount;
  93             memset(&mSegmentArray[mLastSegmentIndex], 0,
  94                    (newArraySize - mLastSegmentIndex) * sizeof(char*));
  95         }
  96         else {
  97             memset(&mSegmentArray[mLastSegmentIndex], 0,
  98                    (newArraySize - mLastSegmentIndex) * sizeof(char*));
  99         }
 100         mSegmentArrayCount = newArraySize;
 101     }
 102
 103     char* seg = (char*)mSegAllocator->Alloc(mSegmentSize);
 104     if (seg == nsnull) {
 105         return nsnull;
 106     }
 107     mSegmentArray[mLastSegmentIndex] = seg;
 108     mLastSegmentIndex = ModSegArraySize(mLastSegmentIndex + 1);
 109     return seg;
 110 }
 111
 112 PRBool
 113 nsSegmentedBuffer::DeleteFirstSegment()
 114 {
 115     NS_ASSERTION(mSegmentArray[mFirstSegmentIndex] != nsnull, "deleting bad segment");
 116     (void)mSegAllocator->Free(mSegmentArray[mFirstSegmentIndex]);
 117     mSegmentArray[mFirstSegmentIndex] = nsnull;
 118     PRInt32 last = ModSegArraySize(mLastSegmentIndex - 1);
 119     if (mFirstSegmentIndex == last) {
 120         mLastSegmentIndex = last;
 121         return PR_TRUE;
 122     }
 123     else {
 124         mFirstSegmentIndex = ModSegArraySize(mFirstSegmentIndex + 1);
 125         return PR_FALSE;
 126     }
 127 }
 128
 129 PRBool
 130 nsSegmentedBuffer::DeleteLastSegment()
 131 {
 132     PRInt32 last = ModSegArraySize(mLastSegmentIndex - 1);
 133     NS_ASSERTION(mSegmentArray[last] != nsnull, "deleting bad segment");
 134     (void)mSegAllocator->Free(mSegmentArray[last]);
 135     mSegmentArray[last] = nsnull;
 136     mLastSegmentIndex = last;
 137     return (PRBool)(mLastSegmentIndex == mFirstSegmentIndex);
 138 }
 139
 140 PRBool
 141 nsSegmentedBuffer::ReallocLastSegment(size_t newSize)
 142 {
 143     PRInt32 last = ModSegArraySize(mLastSegmentIndex - 1);
 144     NS_ASSERTION(mSegmentArray[last] != nsnull, "realloc'ing bad segment");
 145     char *newSegment =
 146         (char*)mSegAllocator->Realloc(mSegmentArray[last], newSize);
 147     if (newSegment) {
 148         mSegmentArray[last] = newSegment;
 149         return PR_TRUE;
 150     } else {
 151         return PR_FALSE;
 152     }
 153 }
 154
 155 void
 156 nsSegmentedBuffer::Empty()
 157 {
 158     if (mSegmentArray) {
 159         for (PRUint32 i = 0; i < mSegmentArrayCount; i++) {
 160             if (mSegmentArray[i])
 161                 mSegAllocator->Free(mSegmentArray[i]);
 162         }
 163         nsMemory::Free(mSegmentArray);
 164         mSegmentArray = nsnull;
 165     }
 166     mSegmentArrayCount = NS_SEGMENTARRAY_INITIAL_COUNT;
 167     mFirstSegmentIndex = mLastSegmentIndex = 0;
 168 }
 169
 170 #ifdef DEBUG
 171 NS_COM void
 172 TestSegmentedBuffer()
 173 {
 174     nsSegmentedBuffer* buf = new nsSegmentedBuffer();
 175     NS_ASSERTION(buf, "out of memory");
 176     buf->Init(4, 16);
 177     char* seg;
 178     PRBool empty;
 179     seg = buf->AppendNewSegment();
 180     NS_ASSERTION(seg, "AppendNewSegment failed");
 181     seg = buf->AppendNewSegment();
 182     NS_ASSERTION(seg, "AppendNewSegment failed");
 183     seg = buf->AppendNewSegment();
 184     NS_ASSERTION(seg, "AppendNewSegment failed");
 185     empty = buf->DeleteFirstSegment();
 186     NS_ASSERTION(!empty, "DeleteFirstSegment failed");
 187     empty = buf->DeleteFirstSegment();
 188     NS_ASSERTION(!empty, "DeleteFirstSegment failed");
 189     seg = buf->AppendNewSegment();
 190     NS_ASSERTION(seg, "AppendNewSegment failed");
 191     seg = buf->AppendNewSegment();
 192     NS_ASSERTION(seg, "AppendNewSegment failed");
 193     seg = buf->AppendNewSegment();
 194     NS_ASSERTION(seg, "AppendNewSegment failed");
 195     empty = buf->DeleteFirstSegment();
 196     NS_ASSERTION(!empty, "DeleteFirstSegment failed");
 197     empty = buf->DeleteFirstSegment();
 198     NS_ASSERTION(!empty, "DeleteFirstSegment failed");
 199     empty = buf->DeleteFirstSegment();
 200     NS_ASSERTION(!empty, "DeleteFirstSegment failed");
 201     empty = buf->DeleteFirstSegment();
 202     NS_ASSERTION(empty, "DeleteFirstSegment failed");
 203     delete buf;
 204 }
 205 #endif
 206
 207 ////////////////////////////////////////////////////////////////////////////////