Base64编码解码C代码实现

编码：

/*
*inHex:输入参数，待编码十六进制数据首地址，如果NULL表示计算输出需要缓冲大小
*inBytes:输入参数，待编码十六进制数据字节长度，如果<=0表示计算输出需要缓冲大小
*outStr:输出参数，编码之后的字符串数据
*outBufLen:输入参数，编码出来的缓存字节
*返回值：>=0表示成功编码，编码后数据长度；<0表示出错
*/
int Base64Encode(char* inHex, int inBytes, char* outStr, int outBufLen)
{/*  A-Z a-z 0-9 +/  */int i = 0;int charIndex = 0;switch (inBytes % 3) {case 0:i = (i / 3) * 4;break;case 1:i = (i / 3) * 4 + 1 + 1;i = i + 2;break;case 2:i = (i / 3) * 4 + 1 + 1 + 1;i = i + 1;break;}if (outStr == NULL || outBufLen <= 0) {i++;goto EXIT_FUN;}if (i >= outBufLen) {/* 缓冲不够 */i = -1;goto EXIT_FUN;}charIndex = 0;for (i = 0; i < inBytes; i++) {switch (i % 3) {case 0:charIndex = inHex[i] >> 2;        break;case 1:charIndex = inHex[i - 1] << 4;  charIndex &= 0x00000030;charIndex |= (inHex[i] >> 4) & 0x0F;break;case 2:charIndex = inHex[i - 1] << 2;  charIndex &= 0x0000003C;charIndex |= (inHex[i] >> 6) & 0x03;break;default:break;}charIndex &= 0x0000003F;if (charIndex >= 0 && charIndex < 26) {outStr[(i / 3) * 4 + (i % 3)] = 'A' + charIndex;} else if (charIndex >= 26 && charIndex < 52) {outStr[(i / 3) * 4 + (i % 3)] = 'a' + charIndex - 26;} else if (charIndex >= 52 && charIndex < 62) {outStr[(i / 3) * 4 + (i % 3)] = '0' + charIndex - 52;} else if (charIndex == 62) {outStr[(i / 3) * 4 + (i % 3)] = '+';} else if (charIndex == 63) {outStr[(i / 3) * 4 + (i % 3)] = '/';}if ((i % 3) == 2 || i + 1 >= inBytes) {if ((i % 3) == 2) {charIndex = inHex[i];charIndex &= 0x0000003F;} else if ((i % 3) == 0) {charIndex = inHex[i] << 4;    charIndex &= 0x00000030;} else if ((i % 3) == 1) {charIndex = inHex[i] << 2;  charIndex &= 0x0000003C;}if (charIndex >= 0 && charIndex < 26) {outStr[(i / 3) * 4 + (i % 3) + 1] = 'A' + charIndex;} else if (charIndex >= 26 && charIndex < 52) {outStr[(i / 3) * 4 + (i % 3) + 1] = 'a' + charIndex - 26;} else if (charIndex >= 52 && charIndex < 62) {outStr[(i / 3) * 4 + (i % 3) + 1] = '0' + charIndex - 52;} else if (charIndex == 62) {outStr[(i / 3) * 4 + (i % 3) + 1] = '+';} else if (charIndex == 63) {outStr[(i / 3) * 4 + (i % 3) + 1] = '/';}}}switch (inBytes % 3) {case 0:i = (i / 3) * 4;break;case 1:i = (i / 3) * 4 + 1 + 1;strcpy(outStr + i, "==");i = i + 2;break;case 2:i = (i / 3) * 4 + 1 + 1 + 1;strcpy(outStr + i, "=");i = i + 1;break;}outStr[i] = 0;EXIT_FUN:return i;
}

解码：

/*
*inStr:输入参数，待解码字符串数据首地址，如果NULL表示计算输出需要缓冲大小
*outHex:输出参数，解码之后的十六进制数据
*outBufLen:输入参数，解码出来的缓存字节
*返回值：>=0表示成功编码，编码后数据长度；<0表示出错
*/
int Base64Decode(char* inStr, char* outHex, int outBufLen)
{int i = 0;int equalSignCnt = 0;int inLen = strlen(inStr);int charIndex = 0;int validBase64Index = 0;char tmp[4];for (i = 0; i < inLen; i++) {if (inStr[i] >= 'A' && inStr[i] <= 'Z') {charIndex = inStr[i] - 'A';} else if (inStr[i] >= 'a' && inStr[i] <= 'z') {charIndex = inStr[i] - 'a' + 26;} else if (inStr[i] >= '0' && inStr[i] <= '9') {charIndex = inStr[i] - '0' + 52;} else if (inStr[i] == '+') {charIndex = 62;} else if (inStr[i] == '/') {charIndex = 63;} else if (inStr[i] == '=') {for (equalSignCnt = 0; i < inLen; i++) {if (inStr[i] == '=') {equalSignCnt++;}}   if (equalSignCnt > 2 || equalSignCnt < 1) {/* 数据格式错误 */i = -1;goto EXIT_FUN;}break;} else {continue;}if (outHex == NULL || outBufLen <= 0) {validBase64Index++;continue;}switch (validBase64Index % 4) {case 0:tmp[0] = charIndex << 2;tmp[0] &= (~0x03);break;case 1:tmp[0] |= (charIndex >> 4);tmp[1] = (charIndex << 4);tmp[1] &= 0xF0;break;case 2:tmp[1] |= (charIndex >> 2);tmp[2] = charIndex << 6;tmp[2] &= 0xC0;break;case 3:tmp[2] |= charIndex;        if ((validBase64Index / 4) * 3 + 3 >= outBufLen) {/* 缓冲不够 */i = -1;goto EXIT_FUN;}outHex[(validBase64Index / 4) * 3] = tmp[0];outHex[(validBase64Index / 4) * 3 + 1] = tmp[1];outHex[(validBase64Index / 4) * 3 + 2] = tmp[2];break;}validBase64Index++;}if ((validBase64Index % 4) == 0) {if (i >= inLen) {i = (validBase64Index / 4) * 3;goto EXIT_FUN;}/* 数据格式错误 */i = -1;goto EXIT_FUN;}/* if (inStr[i] == '=') */if (equalSignCnt == 1) {if (outHex != NULL && outBufLen > 0) {if ((validBase64Index / 4) * 3 + 2 >= outBufLen) {/* 缓冲不够 */i = -1;goto EXIT_FUN;}outHex[(validBase64Index / 4) * 3] = tmp[0];outHex[(validBase64Index / 4) * 3 + 1] = tmp[1];}i = (validBase64Index / 4) * 3 + 2;}if (equalSignCnt == 2) {if (outHex != NULL && outBufLen > 0) {if ((validBase64Index / 4) * 3 + 1 >= outBufLen) {/* 缓冲不够 */i = -1;goto EXIT_FUN;}outHex[(validBase64Index / 4) * 3] = tmp[0];}i = (validBase64Index / 4) * 3 + 1; }EXIT_FUN:return i;
}

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