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base64解码问题 [复制链接]

chunhui_true

丰衣足食

论坛徽章:: 0

电梯直达

1楼 [收藏(0)] [报告]

发表于 2006-11-30 20:52 |只看该作者 |倒序浏览

求解以下BASE64字符串的解码！哪位有现成的C函数希望能提供一下！我现在有2个函数但是
都不好使！
本来正常解码之后应该是这个样子：~tt.txt
但是我现在的函数解了之后如： ~<0x00>t<0x00>t<0x00>.<0x00>t<0x00>x<0x00>t
无缘无故地在字符之间加上了 0！这样当我打印的时候就打不出来了。
请问这是为何？如何解决？
各位有现成的解码函数吗？试着解一下这个字符串，看看你们的能正常解开么？
字符串如下：
fgIAAAMAAAACIQAAAAAAAAEAAAB0AHQALgB0AHgAdAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA/////wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=

jetrix

稍有积蓄

论坛徽章:: 0

2楼 [报告]

发表于 2006-12-01 12:42 |只看该作者

/***********************************************************************
Mady By ZwelL
2004.8.16
zwell@sohu.com
http://www.donews.net/zwell
Usage: base.exe <-e|-d> <string>
***********************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
const int BASE64_MAXLINE = 76;
const char EOL[] = "\r\n";
const char BASE64_TAB[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const char DeBase64Tab[] =
{
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
62, //'+'
0, 0, 0,
63, //'/'
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, //'0' - '9'
0, 0, 0, 0, 0, 0, 0,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, //'A' - 'Z'
0, 0, 0, 0, 0, 0,
26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, //'a' - 'z'
};
char *
enBase64(const char *szInANSI)
{
int nInLen = strlen(szInANSI);
char *szOutBase64;
char *returnstr;
//Set up the parameters prior to the main encoding loop
int nInPos = 0;
int nOutPos = 0;
int nLineLen = 0;
int c1, c2, c3;
int i;
szOutBase64 = (char *)malloc(nInLen * 4 / 3 + 1);
returnstr = szOutBase64;
memset(szOutBase64, 0, nInLen * 4 / 3 + 1);
//Input Parameter validation
if ((szInANSI == NULL) || (nInLen == 0) || (szOutBase64 == NULL))
return 0;
//Get three characters at a time from the input buffer and encode them
for (i = 0; i < nInLen / 3; ++i) {
//Get the next 2 characters
c1 = szInANSI[nInPos++] & 0xFF;
c2 = szInANSI[nInPos++] & 0xFF;
c3 = szInANSI[nInPos++] & 0xFF;
//Encode into the 4 6 bit characters
szOutBase64[nOutPos++] = BASE64_TAB[c1 >> 2];
szOutBase64[nOutPos++] = BASE64_TAB[((c1 << 4) | (c2 >> 4)) & 0x3F];
szOutBase64[nOutPos++] = BASE64_TAB[((c2 << 2) | (c3 >> 6)) & 0x3F];
szOutBase64[nOutPos++] = BASE64_TAB[c3 & 0x3F];
nLineLen += 4;
//Handle the case where we have gone over the max line boundary
if (nLineLen > BASE64_MAXLINE - 4) {
szOutBase64[nOutPos++] = EOL[0];
szOutBase64[nOutPos++] = EOL[1];
nLineLen = 0;
}
}
//Encode the remaining one or two characters in the input buffer
switch (nInLen % 3) {
case 0: {
szOutBase64[nOutPos++] = EOL[0];
szOutBase64[nOutPos++] = EOL[1];
break;
}
case 1: {
c1 = szInANSI[nInPos] & 0xFF;
szOutBase64[nOutPos++] = BASE64_TAB[(c1 & 0xFC) >> 2];
szOutBase64[nOutPos++] = BASE64_TAB[((c1 & 0x03) << 4)];
szOutBase64[nOutPos++] = '=';
szOutBase64[nOutPos++] = '=';
szOutBase64[nOutPos++] = EOL[0];
szOutBase64[nOutPos++] = EOL[1];
break;
}
case 2: {
c1 = szInANSI[nInPos++] & 0xFF;
c2 = szInANSI[nInPos] & 0xFF;
szOutBase64[nOutPos++] = BASE64_TAB[(c1 & 0xFC) >> 2];
szOutBase64[nOutPos++] = BASE64_TAB[((c1 & 0x03) << 4) | ((c2 & 0xF0) >> 4)];
szOutBase64[nOutPos++] = BASE64_TAB[((c2 & 0x0F) << 2)];
szOutBase64[nOutPos++] = '=';
szOutBase64[nOutPos++] = EOL[0];
szOutBase64[nOutPos++] = EOL[1];
break;
}
default:
{
return 0;
}
}
szOutBase64[nOutPos] = 0;
return returnstr;
}
char *
deBase64(const char *pSrc)
{
int nDstLen;
//Output string 's length
int nValue;
//decode used length
int i;
int nSrcLen;
unsigned char *pDst;
char *ptmpDst;
i = 0;
nDstLen = 0;
nSrcLen = strlen(pSrc);
pDst = (unsigned char *)malloc(nSrcLen * 3 / 4 + 1);
ptmpDst = (char *)pDst;
memset(pDst, 0, nSrcLen * 3 / 4 + 1);
//Get four characters at a time from the input buffer and decode them
while (i < nSrcLen) {
if (*pSrc != '\r' && *pSrc != '\n') {
nValue = DeBase64Tab[*pSrc++] << 18;
nValue += DeBase64Tab[*pSrc++] << 12;
*pDst++ = (nValue & 0x00ff0000) >> 16;
nDstLen++;
if (*pSrc != '=') {
nValue += DeBase64Tab[*pSrc++] << 6;
*pDst++ = (nValue & 0x0000ff00) >> 8;
nDstLen++;
if (*pSrc != '=') {
nValue += DeBase64Tab[*pSrc++];
*pDst++ = nValue & 0x000000ff;
nDstLen++;
}
}
i += 4;
} else
//CR LF not care
{
pSrc++;
i++;
}
}
//the end of the output string
* pDst = '\0';
return ptmpDst;
}
void
Usage(char *exename)
{
printf("Usage:%s -e|-d string\r\n", exename);
}
int
main(int argc, char **argv)
{
if (argc < 3) {
Usage(argv[0]);
return -1;
}
if (!strcmp(argv[1], "-e")) {
printf(enBase64(argv[2]));
printf("\n");
} else if (!strcmp(argv[1], "-d")) {
printf(deBase64(argv[2]));
printf("\n");
} else {
Usage(argv[0]);
return -1;
}
return 0;
}

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