我想进行base64编码和解码,但我无法从iPhone SDK中找到任何支持。我怎么能做base64编码和解码与或没有一个库?
当前回答
iOS 7
NSData *data=[[NSData alloc]init];
[data base64Encoding];
其他回答
在这个问题最初发布的时候,人们可以理解地引导您使用第三方base64库,因为缺乏任何本地例程。但iOS 7引入了base64编码例程(这实际上只是暴露了iOS从iOS 4开始就有的私有方法)。
你可以使用NSData方法base64EncodedStringWithOptions:从NSData创建一个base-64字符串。
NSString *string = [data base64EncodedStringWithOptions:kNilOptions];
你可以使用initWithBase64EncodedString:options:将一个base-64字符串转换回NSData:
NSData *data = [[NSData alloc] initWithBase64EncodedString:string options:kNilOptions];
或者,在Swift中:
let string = data.base64EncodedString()
And
let data = Data(base64Encoded: string)
因为这似乎是在base64编码和iphone上排名第一的谷歌,我想用上面的代码片段分享我的经验。
它是有效的,但是非常慢。在本机iphone上对随机图像(0.4 mb)进行基准测试需要37秒。主要原因可能是OOP的魔力——单字符nsstring等,只有在编码完成后才会自动释放。
这里发布的另一个建议(ab)使用openssl库,这感觉也有点过分。
下面的代码需要70毫秒——这是500倍的加速。这只做base64编码(解码将遵循一旦我遇到它)
+ (NSString *) base64StringFromData: (NSData *)data length: (int)length {
int lentext = [data length];
if (lentext < 1) return @"";
char *outbuf = malloc(lentext*4/3+4); // add 4 to be sure
if ( !outbuf ) return nil;
const unsigned char *raw = [data bytes];
int inp = 0;
int outp = 0;
int do_now = lentext - (lentext%3);
for ( outp = 0, inp = 0; inp < do_now; inp += 3 )
{
outbuf[outp++] = base64EncodingTable[(raw[inp] & 0xFC) >> 2];
outbuf[outp++] = base64EncodingTable[((raw[inp] & 0x03) << 4) | ((raw[inp+1] & 0xF0) >> 4)];
outbuf[outp++] = base64EncodingTable[((raw[inp+1] & 0x0F) << 2) | ((raw[inp+2] & 0xC0) >> 6)];
outbuf[outp++] = base64EncodingTable[raw[inp+2] & 0x3F];
}
if ( do_now < lentext )
{
char tmpbuf[2] = {0,0};
int left = lentext%3;
for ( int i=0; i < left; i++ )
{
tmpbuf[i] = raw[do_now+i];
}
raw = tmpbuf;
outbuf[outp++] = base64EncodingTable[(raw[inp] & 0xFC) >> 2];
outbuf[outp++] = base64EncodingTable[((raw[inp] & 0x03) << 4) | ((raw[inp+1] & 0xF0) >> 4)];
if ( left == 2 ) outbuf[outp++] = base64EncodingTable[((raw[inp+1] & 0x0F) << 2) | ((raw[inp+2] & 0xC0) >> 6)];
}
NSString *ret = [[[NSString alloc] initWithBytes:outbuf length:outp encoding:NSASCIIStringEncoding] autorelease];
free(outbuf);
return ret;
}
我省略了行切割,因为我不需要它,但添加它是微不足道的。
对于那些对优化感兴趣的人来说:目标是最小化主循环中发生的事情。因此,处理最后3个字节的所有逻辑都在循环之外处理。
此外,尝试就地处理数据,而不需要额外地从缓冲区复制数据。把所有算术运算都简化到最小。
观察那些放在一起查找表中的条目的位,当它们被放在一起而不移动时,它们不会重叠。因此,一个主要的改进可能是使用4个单独的256字节查找表并消除移位,如下所示:
outbuf[outp++] = base64EncodingTable1[(raw[inp] & 0xFC)];
outbuf[outp++] = base64EncodingTable2[(raw[inp] & 0x03) | (raw[inp+1] & 0xF0)];
outbuf[outp++] = base64EncodingTable3[(raw[inp+1] & 0x0F) | (raw[inp+2] & 0xC0)];
outbuf[outp++] = base64EncodingTable4[raw[inp+2] & 0x3F];
当然,你可以更进一步,但这超出了这里的范围。
iOS8及以后使用- (NSString *)base64EncodedStringWithOptions:(NSDataBase64EncodingOptions) NSData的选项
根据您的要求,我已经使用Swift 4创建了一个示例演示,您可以根据您的要求编码/解码字符串和图像。
I have also added sample methods of relevant operations. // // Base64VC.swift // SOF_SortArrayOfCustomObject // // Created by Test User on 09/01/18. // Copyright © 2018 Test User. All rights reserved. // import UIKit import Foundation class Base64VC: NSObject { //---------------------------------------------------------------- // MARK:- // MARK:- String to Base64 Encode Methods //---------------------------------------------------------------- func sampleStringEncodingAndDecoding() { if let base64String = self.base64Encode(string: "TestString") { print("Base64 Encoded String: \n\(base64String)") if let originalString = self.base64Decode(base64String: base64String) { print("Base64 Decoded String: \n\(originalString)") } } } //---------------------------------------------------------------- func base64Encode(string: String) -> String? { if let stringData = string.data(using: .utf8) { return stringData.base64EncodedString() } return nil } //---------------------------------------------------------------- func base64Decode(base64String: String) -> String? { if let base64Data = Data(base64Encoded: base64String) { return String(data: base64Data, encoding: .utf8) } return nil } //---------------------------------------------------------------- // MARK:- // MARK:- Image to Base64 Encode Methods //---------------------------------------------------------------- func sampleImageEncodingAndDecoding() { if let base64ImageString = self.base64Encode(image: UIImage.init(named: "yourImageName")!) { print("Base64 Encoded Image: \n\(base64ImageString)") if let originaImage = self.base64Decode(base64ImageString: base64ImageString) { print("originalImageData \n\(originaImage)") } } } //---------------------------------------------------------------- func base64Encode(image: UIImage) -> String? { if let imageData = UIImagePNGRepresentation(image) { return imageData.base64EncodedString() } return nil } //---------------------------------------------------------------- func base64Decode(base64ImageString: String) -> UIImage? { if let base64Data = Data(base64Encoded: base64ImageString) { return UIImage(data: base64Data)! } return nil } }
QSUtilities库中的QSStrings类提供了一个非常非常快的实现,它从PHP Core库移植(并修改/改进)到原生Objective-C代码中。我做了一个快速的基准测试:一个5.3MB的图像(JPEG)文件编码用时少于50毫秒,解码用时约140毫秒。
整个库的代码(包括Base64方法)都可以在GitHub上找到。
或者,如果你想让代码只包含Base64方法本身,我把它贴在这里:
首先,你需要映射表:
static const char _base64EncodingTable[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const short _base64DecodingTable[256] = {
-2, -2, -2, -2, -2, -2, -2, -2, -2, -1, -1, -2, -1, -1, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-1, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 62, -2, -2, -2, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -2, -2, -2, -2, -2, -2,
-2, 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, -2, -2, -2, -2, -2,
-2, 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, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2
};
编码:
+ (NSString *)encodeBase64WithString:(NSString *)strData {
return [QSStrings encodeBase64WithData:[strData dataUsingEncoding:NSUTF8StringEncoding]];
}
+ (NSString *)encodeBase64WithData:(NSData *)objData {
const unsigned char * objRawData = [objData bytes];
char * objPointer;
char * strResult;
// Get the Raw Data length and ensure we actually have data
int intLength = [objData length];
if (intLength == 0) return nil;
// Setup the String-based Result placeholder and pointer within that placeholder
strResult = (char *)calloc((((intLength + 2) / 3) * 4) + 1, sizeof(char));
objPointer = strResult;
// Iterate through everything
while (intLength > 2) { // keep going until we have less than 24 bits
*objPointer++ = _base64EncodingTable[objRawData[0] >> 2];
*objPointer++ = _base64EncodingTable[((objRawData[0] & 0x03) << 4) + (objRawData[1] >> 4)];
*objPointer++ = _base64EncodingTable[((objRawData[1] & 0x0f) << 2) + (objRawData[2] >> 6)];
*objPointer++ = _base64EncodingTable[objRawData[2] & 0x3f];
// we just handled 3 octets (24 bits) of data
objRawData += 3;
intLength -= 3;
}
// now deal with the tail end of things
if (intLength != 0) {
*objPointer++ = _base64EncodingTable[objRawData[0] >> 2];
if (intLength > 1) {
*objPointer++ = _base64EncodingTable[((objRawData[0] & 0x03) << 4) + (objRawData[1] >> 4)];
*objPointer++ = _base64EncodingTable[(objRawData[1] & 0x0f) << 2];
*objPointer++ = '=';
} else {
*objPointer++ = _base64EncodingTable[(objRawData[0] & 0x03) << 4];
*objPointer++ = '=';
*objPointer++ = '=';
}
}
// Terminate the string-based result
*objPointer = '\0';
// Create result NSString object
NSString *base64String = [NSString stringWithCString:strResult encoding:NSASCIIStringEncoding];
// Free memory
free(strResult);
return base64String;
}
解码:
+ (NSData *)decodeBase64WithString:(NSString *)strBase64 {
const char *objPointer = [strBase64 cStringUsingEncoding:NSASCIIStringEncoding];
size_t intLength = strlen(objPointer);
int intCurrent;
int i = 0, j = 0, k;
unsigned char *objResult = calloc(intLength, sizeof(unsigned char));
// Run through the whole string, converting as we go
while ( ((intCurrent = *objPointer++) != '\0') && (intLength-- > 0) ) {
if (intCurrent == '=') {
if (*objPointer != '=' && ((i % 4) == 1)) {// || (intLength > 0)) {
// the padding character is invalid at this point -- so this entire string is invalid
free(objResult);
return nil;
}
continue;
}
intCurrent = _base64DecodingTable[intCurrent];
if (intCurrent == -1) {
// we're at a whitespace -- simply skip over
continue;
} else if (intCurrent == -2) {
// we're at an invalid character
free(objResult);
return nil;
}
switch (i % 4) {
case 0:
objResult[j] = intCurrent << 2;
break;
case 1:
objResult[j++] |= intCurrent >> 4;
objResult[j] = (intCurrent & 0x0f) << 4;
break;
case 2:
objResult[j++] |= intCurrent >>2;
objResult[j] = (intCurrent & 0x03) << 6;
break;
case 3:
objResult[j++] |= intCurrent;
break;
}
i++;
}
// mop things up if we ended on a boundary
k = j;
if (intCurrent == '=') {
switch (i % 4) {
case 1:
// Invalid state
free(objResult);
return nil;
case 2:
k++;
// flow through
case 3:
objResult[k] = 0;
}
}
// Cleanup and setup the return NSData
NSData * objData = [[[NSData alloc] initWithBytes:objResult length:j] autorelease];
free(objResult);
return objData;
}
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