C語言之文件的加密與解密

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#include<stdio.h>
#include<stdlib.h>

int getfilesize(char *path)
{
	FILE *pf = fopen(path, "r");
	if (pf == NULL)
	{
		return -1;
	}
	else
	{
		fseek(pf, 0, SEEK_END);
		int length = ftell(pf);
		return length;
	}
}
/*
void copy(char *oldpath, char *newpath)
{
	FILE *pfr, *pfw;
	pfr = fopen(oldpath, "rb");
	pfw = fopen(newpath, "wb");
	if (pfr == NULL || pfw == NULL)
	{
		fclose(pfr);
		fclose(pfw);
		return;
	}
	else
	{
		int length = getfilesize(oldpath);
		char *p = (char *)malloc(length*sizeof(char));
		fread(p, sizeof(char), length, pfr);
		fwrite(p, sizeof(char), length, pfw);
		fclose(pfr);
		fclose(pfw);
	}
}
*/
void EncryptFile(char *oldpath, char *newpath)
{
	int i = 0;
	FILE *pfr, *pfw;
	pfr = fopen(oldpath, "rb");
	pfw = fopen(newpath, "wb");
	if (pfr == NULL || pfw == NULL)
	{
		fclose(pfr);
		fclose(pfw);
		return;
	}
	else
	{
		int length = getfilesize(oldpath);
		char *p = (char *)malloc(length*sizeof(char));
		fread(p, sizeof(char), length, pfr);
		for (i = 0; i < length; i++)
		{
			p[i] ^= 'A';
		}
		fwrite(p, sizeof(char), length, pfw);
		fclose(pfr);
		fclose(pfw);
	}
}

void DecryptFile(char *oldpath, char *newpath)
{
	int i = 0;
	FILE *pfr, *pfw;
	pfr = fopen(oldpath, "rb");
	pfw = fopen(newpath, "wb");
	if (pfr == NULL || pfw == NULL)
	{
		fclose(pfr);
		fclose(pfw);
		return;
	}
	else
	{
		int length = getfilesize(oldpath);
		char *p = (char *)malloc(length*sizeof(char));
		fread(p, sizeof(char), length, pfr);
		for (i = 0; i < length; i++)
		{
			p[i] ^= 'A';
		}
		fwrite(p, sizeof(char), length, pfw);
		fclose(pfr);
		fclose(pfw);
	}
}

void main()
{       	
    char *oldpath = "tmAppAbDBB.db";
	char *newpath = "aa.db";
	char *newDecryptFilepath = "cc.db";
	EncryptFile(oldpath, newpath);
	DecryptFile(newpath, newDecryptFilepath);
}