求助：关于对文件BASE64加密解密

[wyangwo]

在下用ATL的Base64Encode及Base64Decode对文件进行加密解密操作时，遇到一点问题。先贴源码，编译环境VS2008

#include "stdafx.h"
#include "atlenc.h"
int _tmain(int argc, _TCHAR* argv[])
{	

	errno_t err;

	FILE *fr;
	if (err =(fopen_s(&fr, "a.txt", "rb")) != 0)
	{
		printf( "The file 'a.txt' was not opened\n" );
		return 0;

	}
	FILE *fw;
	if (err = (fopen_s(&fw, "b.txt", "w+")) != 0)
	{
		printf( "The file 'b.txt' was not opened\n" );
		return 0;
	}
	FILE *fd;
	if (err = (fopen_s(&fd, "c.txt", "w+")) != 0)
	{
		printf( "The file 'c.txt' was not opened\n" );
		return 0;
	}

	char srcbuf[50] = {0};	
	char dstbuf[50*2 + 1] = {0};
	char orgbuf[50] = {0};
	int nLen = 0;
	long nTotal1 = 0;
	long nTotal2 = 0;

         //文件加密处理，这里没问题
	while(!feof(fr))
	{
		nLen = fread(srcbuf, sizeof(char), sizeof(srcbuf), fr);
		int i = Base64EncodeGetRequiredLength(nLen);
		Base64Encode((BYTE*)srcbuf, nLen, dstbuf, &i, NULL);
		fwrite(dstbuf, sizeof(char), i, fw);
		nTotal1 += i;		
	}
	printf("total file encode: %d\n", nTotal1);

	fclose(fr);
	fclose(fw);

	memset(srcbuf, 0, sizeof(srcbuf));
	memset(dstbuf, 0, sizeof(dstbuf));
	memset(orgbuf, 0, sizeof(orgbuf));

	fopen_s(&fw, "b.txt", "rb");
         //文件解密处理，解密出来的文件跟原始文件有差距，文件越大，差距越明显
	while(!feof(fw))
	{
		nLen = fread(srcbuf, sizeof(char), sizeof(srcbuf), fw);
		printf("file read: %d\n", nLen);
		int i = Base64DecodeGetRequiredLength(nLen);
		printf("i encode: %d\n", i);
		Base64Decode(srcbuf, nLen, (BYTE*)orgbuf, &i);
		int m = fwrite(orgbuf, sizeof(char), i, fd);
		nTotal2 += m; 
	}

	printf("total file decode: %d\n", nTotal2);	

	fclose(fw);
	fclose(fd);

	return 0;
}

对文件加密后，再进行解密操作时出现了问题，解密后文件跟原始文件大小和内容均有差距，用UltraEdit打开也能发现不同，文件越大，差距越明显，请问这是为什么？

[wyangwo]

下面是两张测试图，源文件越大，加密解密后输出文件差别就越大。图中
a.txt是原始文件，b.txt是加密后文件，c.txt是解密后文件

[wyangwo]

贴图怎么这么小哦，算了，把文件大小贴一下

2012-09-28 17:04 42 a.txt
2012-09-28 17:24 56 b.txt
2012-09-28 17:24 49 c.txt

求高手指点！！[size=24px][/size]

[zgl7903]

"w+" 改成 "w" 试试，
不要追加

[zgl7903]

#include "atlenc.h"

errno_t fileBase64Encode(const char *srcFile, const char *dstFile)
{
  FILE *fr = NULL, *fw = NULL;
  errno_t err = 0;
  
  if(err == 0)
  {
    err= fopen_s(&fr, srcFile, "rb");
    if(err != 0)
    {
      printf( "The file '%s' can't be open\n", srcFile );
    }
  }
  
  if (err == 0)
  {
    err = fopen_s(&fw, dstFile, "wb");
    if(err != 0)
    {
      printf( "The file '%s' can't be open\n", dstFile );
    }
  }

  if(err == 0)
  {
    const int tLen = ATLSMTP_MAX_BASE64_LINE_LENGTH; // = 57
    BYTE srcBuf[tLen + 1];
    char dstBuf[tLen * 4 /3 + 5]; //+\r\n\r\n\0 //

    size_t nTotal = 0;
    while(!feof(fr))
    {
      int nLen = fread(srcBuf, 1, tLen, fr);
      int i = Base64EncodeGetRequiredLength(nLen);
      Base64Encode(srcBuf, nLen, dstBuf, &i);
      nTotal += fwrite(dstBuf, 1, i, fw);       
    }
  }

  if(fr)
    fclose(fr);
  if(fw)
    fclose(fw);

  return err;
}

errno_t fileBase64Decode(const char *srcFile, const char *dstFile)
{
  FILE *fr = NULL, *fw = NULL;
  errno_t err = 0;
  
  if(err == 0)
  {
    err= fopen_s(&fr, srcFile, "rb");
    if(err != 0)
    {
      printf( "The file '%s' can't be open\n", srcFile );
    }
  }
  
  if (err == 0)
  {
    err = fopen_s(&fw, dstFile, "wb");
    if(err != 0)
    {
      printf( "The file '%s' can't be open\n", dstFile );
    }
  }

  if(err == 0)
  {
    const int tLen = ATLSMTP_MAX_QP_LINE_LENGTH + 2; //76+2
    char srcBuf[tLen+1];
    BYTE dstBuf[tLen*3/4+1];

    size_t nTotal = 0;
    while(!feof(fr))
    {
      int nLen = fread(srcBuf, 1, tLen, fr);
      int i = Base64DecodeGetRequiredLength(nLen);
      Base64Decode(srcBuf, nLen, dstBuf, &i);
      nTotal += fwrite(dstBuf, 1, i, fw); 
    }
  }

  if(fr)
    fclose(fr);
  if(fw)
    fclose(fw);

  return err;
}

[Gloveing]

[Quote=引用 3 楼 的回复:]
"w+" 改成 "w" 试试，
不要追加
[/Quote]
最好还是：wb

[wyangwo]

感谢LS几位，确实，不用追加就可以了，我用的WB。

[mytsou]

VC6 下无法编译？求指导