关于 NSData 的数据类型(2进制,16进制之间)及深入剖析(转)

1. NSData 与 NSString
NSData－> NSString
NSString *aString = [[NSString alloc initWithData:adataencoding:NSUTF8StringEncoding];


NSString－>NSData
NSString *aString = @"1234abcd";
NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];

 
2.NSData 与 Byte
NSData－> Byte数组
NSString *testString = @"1234567890";
NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];
Byte *testByte = (Byte *)[testData bytes];
for(int i=0;i<[testData length];i++){
　　printf("testByte = %d
",testByte);
}

Byte数组－> NSData
Byte byte[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23};
NSData *adata = [[NSData alloc] initWithBytes:byte length:24];

Byte数组－>16进制数
Byte *bytes = (Byte *)[aData bytes];
NSString *hexStr=@"";
for(int i=0;i<[encryData length];i++)
{
　　NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes&0xff];///16进制数
　　if([newHexStr length]==1){
　　　　hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];
　　}else{
　　　　hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr];
　　}
}

NSLog(@"bytes 的16进制数为:%@",hexStr);

16进制数－>Byte数组
// 将16进制数据转化成Byte 数组
NSString *hexString = @"3e435fab9c34891f"; //16进制字符串
int j=0;
Byte bytes[128]; ///3ds key的Byte 数组， 128位
for(int i=0;i<[hexString length];i++)
{
　　int int_ch; /// 两位16进制数转化后的10进制数
　　unichar hex_char1 = [hexString characterAtIndex:i]; ////两位16进制数中的第一位(高位*16)
　　int int_ch1;
　　if(hex_char1 >= '0' && hex_char1 <='9')
　　　　int_ch1 = (hex_char1-48)*16;   //// 0 的Ascll - 48
　　else if(hex_char1 >= 'A' && hex_char1 <='F')
　　　　int_ch1 = (hex_char1-55)*16; //// A 的Ascll - 65
　　else
　　　　int_ch1 = (hex_char1-87)*16; //// a 的Ascll - 97
　　　　i++;
　　　　unichar hex_char2 = [hexString characterAtIndex:i]; ///两位16进制数中的第二位(低位)
　　　　int int_ch2;
　　if(hex_char2 >= '0' && hex_char2 <='9')
　　　　int_ch2 = (hex_char2-48); //// 0 的Ascll - 48
　　else if(hex_char1 >= 'A' && hex_char1 <='F')
　　　　int_ch2 = hex_char2-55; //// A 的Ascll - 65
　　else
　　　　int_ch2 = hex_char2-87; //// a 的Ascll - 97
　　　　int_ch = int_ch1+int_ch2;
　　NSLog(@"int_ch=%d",int_ch);
　　bytes[j] = int_ch;  ///将转化后的数放入Byte数组里
　　j++;
}

NSData *newData = [[NSData alloc] initWithBytes:bytes length:128];
NSLog(@"newData=%@",newData);

3. NSData 与 UIImage

NSData－>UIImage
UIImage *aimage = [UIImage imageWithData: imageData];
//例：从本地文件沙盒中取图片并转换为NSData
NSString *path = [[NSBundle mainBundle bundlePath];
NSString *name = [NSString stringWithFormat:@"ceshi.png"];
NSString *finalPath = [path stringByAppendingPathComponent:name];
NSData *imageData = [NSData dataWithContentsOfFile: finalPath];
UIImage *aimage = [UIImage imageWithData: imageData];

UIImage－> NSData
NSData *imageData = UIImagePNGRepresentation(aimae);