Posted on 2010-10-29 10:37
午夜凉饭 阅读(529)
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Linux
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
//decode
const char Base64IdxTab[128] =
{
255,255,255,255, 255,255,255,255, 255,255,255,255, 255,255,255,255,
255,255,255,255, 255,255,255,255, 255,255,255,255, 255,255,255,255,
255,255,255,255, 255,255,255,255, 255,255,255,62, 255,255,255,63,
52,53,54,55, 56,57,58,59, 60,61,255,255, 255,255,255,255,
255,0,1,2, 3,4,5,6, 7,8,9,10, 11,12,13,14,
15,16,17,18, 19,20,21,22, 23,24,25,255, 255,255,255,255,
255,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
41,42,43,44, 45,46,47,48, 49,50,51,255, 255,255,255,255
};
#define BVal(x) Base64IdxTab[x]
int DecodeBase64(char * pInput, char * pOutput)
{
int i = 0;
int iCnt = 0;
int iSrcLen = (int)strlen(pInput);
char * p = pOutput;
for (i=0; i < iSrcLen; i++)
{
if (pInput[i] > 127) continue;
if (pInput[i] == '=') return p-pOutput+1;
char a = BVal(pInput[i]);
if (a == 255) continue;
switch (iCnt)
{
case 0:
{
*p = a << 2;
iCnt++;
}
break;
case 1:
{
*p++ |= a >> 4;
*p = a << 4;
iCnt++;
}
break;
case 2:
{
*p++ |= a >> 2;
*p = a << 6;
iCnt++;
}
break;
case 3:
{
*p++ |= a;
iCnt = 0;
}
break;
}
}
*p = 0x00;
return p-pOutput;
}
//encode
const char Base64ValTab[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
#define AVal(x) Base64ValTab[x]
int EncodeBase64(char * pInput, char * pOutput)
{
int i = 0;
int loop = 0;
int remain = 0;
int iDstLen = 0;
int iSrcLen = (int)strlen(pInput);
loop = iSrcLen/3;
remain = iSrcLen%3;
// also can encode native char one by one as decode method
// but because all of char in native string is to be encoded so encode 3-chars one time is easier.
for (i=0; i < loop; i++)
{
char a1 = (pInput[i*3] >> 2);
char a2 = ( ((pInput[i*3] & 0x03) << 4) | (pInput[i*3+1] >> 4) );
char a3 = ( ((pInput[i*3+1] & 0x0F) << 2) | ((pInput[i*3+2] & 0xC0) >> 6) );
char a4 = (pInput[i*3+2] & 0x3F);
pOutput[i*4] = AVal(a1);
pOutput[i*4+1] = AVal(a2);
pOutput[i*4+2] = AVal(a3);
pOutput[i*4+3] = AVal(a4);
}
iDstLen = i*4;
if (remain == 1)
{
// should pad two equal sign
i = iSrcLen-1;
char a1 = (pInput[i] >> 2);
char a2 = ((pInput[i] & 0x03) << 4);
pOutput[iDstLen++] = AVal(a1);
pOutput[iDstLen++] = AVal(a2);
pOutput[iDstLen++] = '=';
pOutput[iDstLen++] = '=';
pOutput[iDstLen] = 0x00;
}
else if (remain == 2)
{
// should pad one equal sign
i = iSrcLen-2;
char a1 = (pInput[i] >> 2);
char a2 = ( ((pInput[i] & 0x03) << 4) | (pInput[i+1] >> 4));
char a3 = ( (pInput[i+1] & 0x0F) << 2);
pOutput[iDstLen++] = AVal(a1);
pOutput[iDstLen++] = AVal(a2);
pOutput[iDstLen++] = AVal(a3);
pOutput[iDstLen++] = '=';
pOutput[iDstLen] = 0x00;
}
else
{
// just division by 3
pOutput[iDstLen] = 0x00;
}
return iDstLen;
}