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//---------------------------------------------------------------------------
// ChunkedFile.cpp
//---------------------------------------------------------------------------
// -=* VPatch *=-
//---------------------------------------------------------------------------
// Copyright (C) 2001-2005 Koen van de Sande / Van de Sande Productions
//---------------------------------------------------------------------------
// Website: http://www.tibed.net/vpatch
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
// claim that you wrote the original software. If you use this software
// in a product, an acknowledgment in the product documentation would be
// appreciated but is not required.
// 2. Altered source versions must be plainly marked as such, and must not be
// misrepresented as being the original software.
// 3. This notice may not be removed or altered from any source distribution.
//
// Unicode support by Jim Park -- 08/29/2007
#include "ChunkedFile.h"
#include "tchar.h"
using namespace std;
ChunkedFile::ChunkedFile(bistream& f, TFileOffset fSize, TFileOffset chunkSize) :
chunks(NULL) {
chunkCount = fSize / chunkSize;
tout << _T("[ChunkedFile] Filesize of ") << static_cast<unsigned int>(fSize) << _T(" gives ") << static_cast<unsigned int>(chunkCount) << _T(" chunks.\n");
tout << _T("[ChunkedFile] Memory to be used by those chunks: ") << sizeof(FileChunk) * chunkCount << _T(" bytes...");
if(chunkCount == 0) {
chunks = NULL;
return;
}
chunks = new FileChunk[chunkCount];
tout << _T(" allocated.\n");
unsigned char* data = new unsigned char[chunkSize];
for(TFileOffset i = 0; i < chunkCount; i++) {
f.read(reinterpret_cast<char*>(data),chunkSize);
chunks[i].offset = i * chunkSize;
calculateChecksum(data,chunkSize,chunks[i].checksum);
}
delete[] data;
tout << _T("[ChunkedFile] Sorting chunks... ");
std::sort(chunks,chunks + chunkCount);
tout << _T("done.\n");
}
bool ChunkedFile::search(TChunkChecksum key, TFileOffset* start) {
// function:
// Searches sortedArray[first]..sortedArray[last] for key.
// returns: index of the matching element if it finds key,
// otherwise -(index where it could be inserted)-1.
// parameters:
// sortedArray in array of sorted (ascending) values.
// first, last in lower and upper subscript bounds
// key in value to search for.
// returns:
// index of key, or -insertion_position -1 if key is not
// in the array. This value can easily be
// transformed into the position to insert it.
if(chunkCount == 0) return false;
int first = 0;
int last = chunkCount - 1;
while (first <= last) {
int mid = (first + last) / 2; // compute mid point.
if(key == chunks[mid].checksum) {
while(true) {
if(mid == 0) break;
mid--;
if(!(key == chunks[mid].checksum)) {
mid++;
break;
}
}
*start = mid;
return true; // found it. return position
}
if (key < chunks[mid].checksum)
last = mid - 1; // repeat search in bottom half.
else
first = mid + 1; // repeat search in top half.
}
return false; // failed to find key
}
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