自己实现一个小巧的base64编码解码

int Base64Encode(BYTE* input_data, DWORD cbData, TCHAR* OUT buffer) { if(!input_data || !cbData || !buffer) return 0; static char* table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; DWORD group_count = cbData / 3; DWORD remain_count = cbData - group_count * 3; DWORD dwTemp = 0; BYTE* pStore = (BYTE*)(&dwTemp); int r = 0; int w = 0; for(DWORD i = 0; i < group_count; i++) { pStore[2] = input_data[r++]; pStore[1] = input_data[r++]; pStore[0] = input_data[r++]; for(int j = 0; j < 4; j++) { dwTemp <<= 6; buffer[w++] = table[pStore[3] & 0x3F]; } } if(remain_count) { int k = 2; for(DWORD i = 0; i < remain_count; i++) pStore[k--] = input_data[r++]; int rcnt = remain_count == 1 ? 2 : 3; int pcnt = 4 - rcnt; for(int j = 0; j < rcnt; j++) { dwTemp <<= 6; buffer[w++] = table[pStore[3] & 0x3F]; } for(int j = 0; j < pcnt; j++) buffer[w++] = _T('='); } buffer[w] = 0; return w; } int Base64Decode(TCHAR* pBase64, DWORD cchChar, BYTE* pBuffer) { if(cchChar < 4 || !pBase64 || !pBuffer) return 0; static BYTE rtable[256] = { 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 64, 64, 64, 64, 64, 64, 64, 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, 64, 64, 64, 64, 64, 64, 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, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64 }; int group_cnt = cchChar / 4 - 1; DWORD dwTemp = 0; BYTE* pStore = (BYTE*)(&dwTemp); int r = 0; int w = 0; for(int i = 0; i < group_cnt; i++) { dwTemp = 0; for(int j = 0; j < 4; j++) { dwTemp <<= 6; BYTE ch = rtable[ pBase64[r++] ]; if(ch > 63) return -1; dwTemp |= ch ; } pBuffer[w++] = pStore[2]; pBuffer[w++] = pStore[1]; pBuffer[w++] = pStore[0]; } int cc = 3; if(pBase64[cchChar - 1] == '=') cc--; if(pBase64[cchChar - 2] == '=') cc--; dwTemp = 0; for(int j = 0; j < 4; j++) { dwTemp <<= 6; dwTemp |= (rtable[ pBase64[r++]] & 0x3F); } int k = 2; for(int j = 0; j < cc; j++) pBuffer[w++] = pStore[k--]; return w; }