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#include <string.h>
#include "BlockCache.H"
int BlockCache::compare(unsigned int size, const unsigned char *data,
int overwrite)
{
int match = 0;
if (size == size_)
{
match = 1;
for (unsigned int i = 0; i < size_; i++)
if (data[i] != buffer_[i])
{
match = 0;
break;
}
}
if (!match && overwrite)
set(size, data);
return match;
}
void BlockCache::set(unsigned int size, const unsigned char *data)
{
if (size_ < size)
{
delete[]buffer_;
buffer_ = new unsigned char[size];
}
size_ = size;
memcpy(buffer_, data, size);
checksum_ = checksum(size, data);
}
unsigned int
BlockCache::checksum(unsigned int size, const unsigned char *data)
{
unsigned int sum = 0;
unsigned int shift = 0;
const unsigned char *next = data;
for (unsigned int i = 0; i < size; i++)
{
unsigned int value = (unsigned int) *next++;
sum += (value << shift);
shift++;
if (shift == 8)
shift = 0;
}
return sum;
}
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