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
