pjs/xpcom/io/nsSegmentedBuffer.cpp

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#include "nsSegmentedBuffer.h"
#include "nsCRT.h"

nsSegmentedBuffer::nsSegmentedBuffer()
    : mSegmentSize(0), mMaxSize(0), 
      mSegAllocator(nsnull), mSegmentArray(nsnull),
      mSegmentArrayCount(0),
      mFirstSegmentIndex(0), mLastSegmentIndex(0)
{
}

nsSegmentedBuffer::~nsSegmentedBuffer()
{
    Empty();
    NS_IF_RELEASE(mSegAllocator);
}

nsresult
nsSegmentedBuffer::Init(PRUint32 segmentSize, PRUint32 maxSize,
                        nsIMemory* allocator)
{
    if (mSegmentArrayCount != 0)
        return NS_ERROR_FAILURE;        // initialized more than once
    mSegmentSize = segmentSize;
    mMaxSize = maxSize;
    mSegAllocator = allocator;
    if (mSegAllocator == nsnull) {
        mSegAllocator = nsMemory::GetGlobalMemoryService();
    }
    else {
        NS_ADDREF(mSegAllocator);
    }
#if 0 // testing...
    mSegmentArrayCount = 2;
#else
    mSegmentArrayCount = NS_SEGMENTARRAY_INITIAL_COUNT;
#endif
    return NS_OK;
}

char*
nsSegmentedBuffer::AppendNewSegment()
{
    if (GetSize() >= mMaxSize)
        return nsnull;

    if (mSegmentArray == nsnull) {
        PRUint32 bytes = mSegmentArrayCount * sizeof(char*);
        mSegmentArray = (char**)nsMemory::Alloc(bytes);
        if (mSegmentArray == nsnull)
            return nsnull;
        memset(mSegmentArray, 0, bytes);
    }
    
    if (IsFull()) {
        PRUint32 newArraySize = mSegmentArrayCount * 2;
        PRUint32 bytes = newArraySize * sizeof(char*);
        char** newSegArray = (char**)nsMemory::Realloc(mSegmentArray, bytes);
        if (newSegArray == nsnull)
            return nsnull;
        mSegmentArray = newSegArray;
        // copy wrapped content to new extension
        if (mFirstSegmentIndex > mLastSegmentIndex) {
            // deal with wrap around case
            memcpy(&mSegmentArray[mSegmentArrayCount],
                   mSegmentArray,
                   mLastSegmentIndex * sizeof(char*));
            memset(mSegmentArray, 0, mLastSegmentIndex * sizeof(char*));
            mLastSegmentIndex += mSegmentArrayCount;
            memset(&mSegmentArray[mLastSegmentIndex], 0,
                   (newArraySize - mLastSegmentIndex) * sizeof(char*));
        }
        else {
            memset(&mSegmentArray[mLastSegmentIndex], 0,
                   (newArraySize - mLastSegmentIndex) * sizeof(char*));
        }
        mSegmentArrayCount = newArraySize;
    }

    char* seg = (char*)mSegAllocator->Alloc(mSegmentSize);
    if (seg == nsnull) {
        return nsnull;
    }
    mSegmentArray[mLastSegmentIndex] = seg;
    mLastSegmentIndex = ModSegArraySize(mLastSegmentIndex + 1);
    return seg;
}

PRBool
nsSegmentedBuffer::DeleteFirstSegment()
{
    NS_ASSERTION(mSegmentArray[mFirstSegmentIndex] != nsnull, "deleting bad segment");
    (void)mSegAllocator->Free(mSegmentArray[mFirstSegmentIndex]);
    mSegmentArray[mFirstSegmentIndex] = nsnull;
    PRInt32 last = ModSegArraySize(mLastSegmentIndex - 1);
    if (mFirstSegmentIndex == last) {
        mLastSegmentIndex = last;
        return PR_TRUE;
    }
    else {
        mFirstSegmentIndex = ModSegArraySize(mFirstSegmentIndex + 1);
        return PR_FALSE;
    }
}

PRBool
nsSegmentedBuffer::DeleteLastSegment()
{
    PRInt32 last = ModSegArraySize(mLastSegmentIndex - 1);
    NS_ASSERTION(mSegmentArray[last] != nsnull, "deleting bad segment");
    (void)mSegAllocator->Free(mSegmentArray[last]);
    mSegmentArray[last] = nsnull;
    mLastSegmentIndex = last;
    return (PRBool)(mLastSegmentIndex == mFirstSegmentIndex);
}

PRBool
nsSegmentedBuffer::ReallocLastSegment(size_t newSize)
{
    PRInt32 last = ModSegArraySize(mLastSegmentIndex - 1);
    NS_ASSERTION(mSegmentArray[last] != nsnull, "realloc'ing bad segment");
    char *newSegment =
        (char*)mSegAllocator->Realloc(mSegmentArray[last], newSize);
    if (newSegment) {
        mSegmentArray[last] = newSegment;
        return PR_TRUE;
    } else {
        return PR_FALSE;
    }
}

void
nsSegmentedBuffer::Empty()
{
    if (mSegmentArray) {
        for (PRUint32 i = 0; i < mSegmentArrayCount; i++) {
            if (mSegmentArray[i])
                mSegAllocator->Free(mSegmentArray[i]);
        }
        nsMemory::Free(mSegmentArray);
        mSegmentArray = nsnull;
    }
    mSegmentArrayCount = NS_SEGMENTARRAY_INITIAL_COUNT;
    mFirstSegmentIndex = mLastSegmentIndex = 0;
}

#ifdef DEBUG
NS_COM void
TestSegmentedBuffer()
{
    nsSegmentedBuffer* buf = new nsSegmentedBuffer();
    NS_ASSERTION(buf, "out of memory");
    buf->Init(4, 16);
    char* seg;
    PRBool empty;
    seg = buf->AppendNewSegment();
    NS_ASSERTION(seg, "AppendNewSegment failed");
    seg = buf->AppendNewSegment();
    NS_ASSERTION(seg, "AppendNewSegment failed");
    seg = buf->AppendNewSegment();
    NS_ASSERTION(seg, "AppendNewSegment failed");
    empty = buf->DeleteFirstSegment();
    NS_ASSERTION(!empty, "DeleteFirstSegment failed");
    empty = buf->DeleteFirstSegment();
    NS_ASSERTION(!empty, "DeleteFirstSegment failed");
    seg = buf->AppendNewSegment();
    NS_ASSERTION(seg, "AppendNewSegment failed");
    seg = buf->AppendNewSegment();
    NS_ASSERTION(seg, "AppendNewSegment failed");
    seg = buf->AppendNewSegment();
    NS_ASSERTION(seg, "AppendNewSegment failed");
    empty = buf->DeleteFirstSegment();
    NS_ASSERTION(!empty, "DeleteFirstSegment failed");
    empty = buf->DeleteFirstSegment();
    NS_ASSERTION(!empty, "DeleteFirstSegment failed");
    empty = buf->DeleteFirstSegment();
    NS_ASSERTION(!empty, "DeleteFirstSegment failed");
    empty = buf->DeleteFirstSegment();
    NS_ASSERTION(empty, "DeleteFirstSegment failed");
    delete buf;
}
#endif

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