FilePointer.c

#include <windows.h>
#include <stdio.h>
#define BUF_SIZE 16384  /* 2^14 Optimal in several experiments. Small values such as 256 give very bad performance */

#if define UNICODE
	#define CreateFile  CreateFileW
#else
	#define CreateFile CreateFileA
#endif

int main(int argc, LPTSTR argv[])
{
	//Init File_Pointer, Counter, Buffer
	HANDLE hIn, hOut;
	DWORD nIn, nOut;
	CHAR buffer[BUF_SIZE];
	if (argc != 3) {
		fprintf(stderr, "Usage: cp file1 file2\n");
		return 1;
	}
	//Open File1
	hIn = CreateFile(
		argv[1], //LPCTSTR
		GENERIC_READ, // GENERIC_READ | GENERIC_WRITE
		FILE_SHARE_READ, // 0 , FILE_SHARE_READ , FILE_SHARE_WRITE
		NULL, // SECURITY_ATTR
		OPEN_EXISTING, //CREATE_NEW , CREATE_ALWAYS , OPEN_ALWAYS, TRUNCATE_EXISTING,
		FILE_ATTRIBUTE_NORMAL, //FILE_ATTRIBUTE_READONLY , FILE_FLAG_DELETE_ON_CLOSE
		NULL //TEMPLETE HANDLE
		);

	if (hIn == INVALID_HANDLE_VALUE) {
		fprintf(stderr, "Cannot open input file. Error: %x\n", GetLastError());
		return 2;
	}
	//Create File2
	hOut = CreateFile(argv[2], GENERIC_WRITE, 0, NULL,
		CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
	if (hOut == INVALID_HANDLE_VALUE) {
		fprintf(stderr, "Cannot open output file. Error: %x\n", GetLastError());
		CloseHandle(hIn);
		return 3;
	}
	//###################################################
	//###################################################
	//###################################################
	SetFilePointer(hIn //File Handle
		, 4 //  (+,-)distance
		, NULL // MAX distance
		, FILE_BEGIN //FILE_BEGIN, FILE_CURRENT , FILE_END
		);
	//###################################################
	//###################################################
	//###################################################
	//Loop
	//Read to Buffer and Write to File2
	while (ReadFile
		(hIn, // HANDLE
		buffer, //LPVIOD == CHAR[]
		BUF_SIZE, // DWOED
		&nIn, // LPDWORD
		NULL //LPOVERLAPPED
		) && nIn > 0) {

		WriteFile(hOut,
			buffer,
			nIn,
			&nOut,
			NULL);
		if (nIn != nOut) {
			fprintf(stderr, "Fatal write error: %x\n", GetLastError());
			CloseHandle(hIn); CloseHandle(hOut);
			return 4;
		}
	}
	//###################################################
	//###################################################
	//###################################################
	DWORD inSize = GetFileSize(hIn, NULL);
	DWORD outSize = GetFileSize(hOut, NULL);
	if (inSize != outSize)
		printf("Error: file size %d\n", outSize);
	else
		printf("OK");
	//###################################################
	//###################################################
	//###################################################
	//Close File1 and File2
	CloseHandle(hIn);
	CloseHandle(hOut);
	return 0;
}