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//-----------------------------------------------------------------------------
// Name: checksum.cpp
// Developer: Wolfire Games LLC
// Description:
// License: Read below
//-----------------------------------------------------------------------------
//
// Copyright 2022 Wolfire Games LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//-----------------------------------------------------------------------------
#include "checksum.h"
#include <Internal/error.h>
#include <Internal/profiler.h>
#include <Internal/common.h>
#include <Compat/fileio.h>
#include <Memory/allocation.h>
#include <stdio.h>
#include <string>
using std::endl;
using std::string;
// TODO: Maybe modifying this to be Adler32 would be a little better CRC32 even more so, lowering the risk for collisions for small changes.
//(If you make a 'b' a 'c' and another 'b' an 'a' in a file, this function will give you the same checksum value, i would consider this a possible common change)
unsigned short Checksum(const string& abs_path) {
PROFILER_ZONE(g_profiler_ctx, "Checksum");
unsigned short sum = 0;
FILE* pFile;
long lSize;
unsigned char* buffer;
size_t result;
pFile = my_fopen(abs_path.c_str(), "rb");
#ifndef NO_ERR
const int kBufSize = 512;
char error_msg[kBufSize];
while (pFile == NULL) {
FormatString(error_msg, kBufSize, "Could not open file: %s. Retry?", abs_path.c_str());
DisplayError("Error", error_msg, _ok_cancel);
pFile = my_fopen(abs_path.c_str(), "rb");
}
#endif
if (pFile) {
// obtain file size:
fseek(pFile, 0, SEEK_END);
lSize = ftell(pFile);
rewind(pFile);
// allocate memory to contain the whole file:
buffer = (unsigned char*)alloc.stack.Alloc(sizeof(char) * lSize);
if (buffer) {
#ifndef NO_ERR
if (buffer == NULL) {
FormatString(error_msg, kBufSize, "Could not allocate memory to checksum: %s.", abs_path.c_str());
FatalError("Error", error_msg);
}
#endif
// copy the file into the buffer:
result = fread(buffer, 1, lSize, pFile);
#ifndef NO_ERR
if (result != (size_t)lSize) {
FormatString(error_msg, kBufSize, "Could not read data from file: %s.", abs_path.c_str());
FatalError("Error", error_msg);
}
#endif
{
PROFILER_ZONE(g_profiler_ctx, "Actual summation");
size_t short_count = lSize / 2;
for (size_t i = 0; i < short_count; i++) {
// Might have trouble on wrong-endian machines, but those should probably just have different checksums built in anyhow, to keep this fast
sum += ((uint16_t*)buffer)[i];
}
}
alloc.stack.Free(buffer);
} else {
LOGE << "Failed to allocate data from stack allocator, size: " << lSize << endl;
}
// terminate
fclose(pFile);
} else {
LOGE << "Failed to open file " << abs_path << endl;
}
return sum;
}
// From http://www.cse.yorku.ca/~oz/hash.html
unsigned long djb2_string_hash(const char* cstr) {
unsigned long hash = 5381;
int c;
while ((c = *cstr++))
hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
return hash;
}
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