iOS之Base64编码解码

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#pragma mark ----------加密----------- (NSString*) base64Encode:(NSData *)data{        static char base64EncodingTable[64] = {                'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',                'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',                'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',                'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'            };        int length = [data length];        unsigned long ixtext, lentext;        long ctremaining;        unsigned char input[3], output[4];        short i, charsonline = 0, ctcopy;        const unsigned char *raw;        NSMutableString *result;                lentext = [data length];        if (lentext < 1)                return @"";        result = [NSMutableString stringWithCapacity: lentext];        raw = [data bytes];        ixtext = 0;                while (true) {                ctremaining = lentext - ixtext;                if (ctremaining <= 0)                        break;                for (i = 0; i < 3; i++) {                        unsigned long ix = ixtext + i;                        if (ix < lentext)                                input[i] = raw[ix];                                else                                        input[i] = 0;                                        }                output[0] = (input[0] & 0xFC) >> 2;                output[1] = ((input[0] & 0x03) << 4) | ((input[1] & 0xF0) >> 4);                output[2] = ((input[1] & 0x0F) << 2) | ((input[2] & 0xC0) >> 6);                output[3] = input[2] & 0x3F;                ctcopy = 4;                switch (ctremaining) {                            case 1:                                ctcopy = 2;                                break;                            case 2:                                ctcopy = 3;                                break;                        }                                for (i = 0; i < ctcopy; i++)                        [result appendString: [NSString stringWithFormat: @"%c", base64EncodingTable[output[i]]]];                                for (i = ctcopy; i < 4; i++)                        [result appendString: @"="];                                ixtext += 3;                charsonline += 4;                                if ((length > 0) && (charsonline >= length))                        charsonline = 0;                        }        return result;    }#pragma mark ---------- 解密 ---------- (NSData*) base64Decode:(NSString *)string{        unsigned long ixtext, lentext;        unsigned char ch, inbuf[4], outbuf[4];        short i, ixinbuf;        Boolean flignore, flendtext = false;        const unsigned char *tempcstring;        NSMutableData *theData;        if (string == nil) {                return [NSData data];            }                ixtext = 0;                tempcstring = (const unsigned char *)[string UTF8String];                lentext = [string length];                theData = [NSMutableData dataWithCapacity: lentext];                ixinbuf = 0;                while (true) {                if (ixtext >= lentext){                        break;                    }                                ch = tempcstring [ixtext++];                                flignore = false;                                if ((ch >= 'A') && (ch <= 'Z')) {                        ch = ch - 'A';                    } else if ((ch >= 'a') && (ch <= 'z')) {                        ch = ch - 'a' + 26;                    } else if ((ch >= '0') && (ch <= '9')) {                        ch = ch - '0' + 52;                    } else if (ch == '+') {                        ch = 62;                    } else if (ch == '=') {                        flendtext = true;                    } else if (ch == '/') {                        ch = 63;                    } else {                        flignore = true;                    }                                if (!flignore) {                        short ctcharsinbuf = 3;                        Boolean flbreak = false;                                                if (flendtext) {                                if (ixinbuf == 0) {                                        break;                                    }                                                                if ((ixinbuf == 1) || (ixinbuf == 2)) {                                        ctcharsinbuf = 1;                                    } else {                                        ctcharsinbuf = 2;                                    }                                                                ixinbuf = 3;                                                                flbreak = true;                            }                                                inbuf [ixinbuf++] = ch;                                                if (ixinbuf == 4) {                                ixinbuf = 0;                                                                outbuf[0] = (inbuf[0] << 2) | ((inbuf[1] & 0x30) >> 4);                                outbuf[1] = ((inbuf[1] & 0x0F) << 4) | ((inbuf[2] & 0x3C) >> 2);                                outbuf[2] = ((inbuf[2] & 0x03) << 6) | (inbuf[3] & 0x3F);                                                                for (i = 0; i < ctcharsinbuf; i++) {                                        [theData appendBytes: &outbuf[i] length: 1];                                    }                            }                                                if (flbreak) {                                break;                            }                    }            }                return theData;    }
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