RSA+Base64之NSData+Base64

新建NSData+Base64扩展，代码如下：

//

//  NSData+Base64.h

//  rsa

//

//  Created by wzk on 2017/12/29.

//  Copyright © 2017年 lihe. All rights reserved.

//

#import

@interfaceNSData (Base64)

+ (NSData*)dataWithBase64EncodedString:(NSString*)string;

- (NSString*)base64EncodedStringWithWrapWidth:(NSUInteger)wrapWidth;

- (NSString*)base64EncodedString;

@end

//

//  NSData+Base64.m

//  rsa

//

//  Created by wzk on 2017/12/29.

//  Copyright © 2017年 lihe. All rights reserved.

//

#import "NSData+Base64.h"

@implementationNSData (Base64)

+ (NSData*)dataWithBase64EncodedString:(NSString*)string

{

    constcharlookup[] =

    {

        99,99,99,99,99,99,99,99,99,99,99,99,99,99,99,99,

        99,99,99,99,99,99,99,99,99,99,99,99,99,99,99,99,

        99,99,99,99,99,99,99,99,99,99,99,62,99,99,99,63,

        52,53,54,55,56,57,58,59,60,61,99,99,99,99,99,99,

        99,  0,  1,  2,  3,4,  5,  6,  7,  8,9,10,11,12,13,14,

        15,16,17,18,19,20,21,22,23,24,25,99,99,99,99,99,

        99,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,

        41,42,43,44,45,46,47,48,49,50,51,99,99,99,99,99

    };

    NSData *inputData = [string dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];

    longlonginputLength = [inputDatalength];

    constunsignedchar*inputBytes = [inputDatabytes];

    longlongmaxOutputLength = (inputLength /4+1) *3;

    NSMutableData*outputData = [NSMutableDatadataWithLength:maxOutputLength];

    unsignedchar*outputBytes = (unsignedchar*)[outputDatamutableBytes];

    intaccumulator =0;

    longlongoutputLength =0;

    unsignedcharaccumulated[] = {0,0,0,0};

    for(longlongi =0; i < inputLength; i++)

    {

        unsignedchardecoded = lookup[inputBytes[i] &0x7F];

        if(decoded !=99)

        {

            accumulated[accumulator] = decoded;

            if(accumulator ==3)

            {

                outputBytes[outputLength++] = (accumulated[0] <<2) | (accumulated[1] >>4);

                outputBytes[outputLength++] = (accumulated[1] <<4) | (accumulated[2] >>2);

                outputBytes[outputLength++] = (accumulated[2] <<6) | accumulated[3];

            }

            accumulator = (accumulator +1) %4;

        }

    }

    //handle left-over data

    if(accumulator >0) outputBytes[outputLength] = (accumulated[0] <<2) | (accumulated[1] >>4);

    if(accumulator >1) outputBytes[++outputLength] = (accumulated[1] <<4) | (accumulated[2] >>2);

    if(accumulator >2) outputLength++;

    //truncate data to match actual output length

    outputData.length= outputLength;

    returnoutputLength? outputData:nil;

}

- (NSString*)base64EncodedStringWithWrapWidth:(NSUInteger)wrapWidth

{

    //ensure wrapWidth is a multiple of 4

    wrapWidth = (wrapWidth /4) *4;

    const char lookup[] ="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    longlonginputLength = [selflength];

    constunsignedchar*inputBytes = [selfbytes];

    longlongmaxOutputLength = (inputLength /3+1) *4;

    maxOutputLength += wrapWidth? (maxOutputLength / wrapWidth) *2:0;

    unsignedchar*outputBytes = (unsignedchar*)malloc(maxOutputLength);

    long long i;

    longlongoutputLength =0;

    for(i =0; i < inputLength -2; i +=3)

    {

        outputBytes[outputLength++] = lookup[(inputBytes[i] &0xFC) >>2];

        outputBytes[outputLength++] = lookup[((inputBytes[i] &0x03) <<4) | ((inputBytes[i +1] &0xF0) >>4)];

        outputBytes[outputLength++] = lookup[((inputBytes[i +1] &0x0F) <<2) | ((inputBytes[i +2] &0xC0) >>6)];

        outputBytes[outputLength++] = lookup[inputBytes[i +2] &0x3F];

        //add line break

        if(wrapWidth && (outputLength +2) % (wrapWidth +2) ==0)

        {

            outputBytes[outputLength++] ='\r';

            outputBytes[outputLength++] ='\n';

        }

    }

    //handle left-over data

    if(i == inputLength -2)

    {

        // = terminator

        outputBytes[outputLength++] = lookup[(inputBytes[i] &0xFC) >>2];

        outputBytes[outputLength++] = lookup[((inputBytes[i] &0x03) <<4) | ((inputBytes[i +1] &0xF0) >>4)];

        outputBytes[outputLength++] = lookup[(inputBytes[i +1] &0x0F) <<2];

        outputBytes[outputLength++] =  '=';

    }

    elseif(i == inputLength -1)

    {

        // == terminator

        outputBytes[outputLength++] = lookup[(inputBytes[i] &0xFC) >>2];

        outputBytes[outputLength++] = lookup[(inputBytes[i] &0x03) <<4];

        outputBytes[outputLength++] ='=';

        outputBytes[outputLength++] ='=';

    }

    //truncate data to match actual output length

    outputBytes =realloc(outputBytes, outputLength);

    NSString *result = [[NSString alloc] initWithBytesNoCopy:outputBytes length:outputLength  encoding:NSASCIIStringEncoding freeWhenDone:YES];

#if !__has_feature(objc_arc)

    [resultautorelease];

#endif

    return(outputLength >=4)? result:nil;

}

- (NSString *)base64EncodedString

{

    return[selfbase64EncodedStringWithWrapWidth:0];

}

@end