ios kb转m_iOS基础之字节处理(NSData,Byte,NSString转换)

漫步

TCP传输协议：前2个子节为一个固定的字符，这里以0x809B为例，接着为4个子节(存放content的长度)，然后为传输的内容content

TCP传输协议

以下内容都在Demo中，有兴趣可以下载

一、 拼接方式1---使用Byte数组

这里以传输一张图片为例

1.1前期准备---获取一张图片的大小

NSString *path= [[NSBundle mainBundle] pathForResource:@"ceshi" ofType:@"jpeg"];

NSData* content = [NSData dataWithContentsOfFile:path];

int value = (int)content.length;

1.2 将长度value转换为4个字节

Byte byteData[4] = {};

byteData[0] =(Byte)((value & 0xFF000000)>>24);

byteData[1] =(Byte)((value & 0x00FF0000)>>16);

byteData[2] =(Byte)((value & 0x0000FF00)>>8);

byteData[3] =(Byte)((value & 0x000000FF));

//转换为4个字节

1.3 拼接固定字符并转为NSData

Byte byte[] = {0x80,0x9B,byteData[0],byteData[1],byteData[2],byteData[3]};

NSData *temphead = [[NSData alloc]initWithBytes:byte length:6];

1.4 拼接传输的数据(图片)

//拼接content

NSMutableData *m_data = [[NSMutableData alloc] init];

[m_data appendData:temphead];

[m_data appendData:content];

二、 拼接方式2---使用十六进制转换

2.1前期准备---获取一张图片的大小

NSString *path= [[NSBundle mainBundle] pathForResource:@"ceshi" ofType:@"jpeg"];

NSData* content = [NSData dataWithContentsOfFile:path];

int value = (int)content.length;

2.2 将长度value转换十六进制string

//将长度转为十进制string

NSString* decimalString = [NSString stringWithFormat:@"%d",value];

//将十进制string转为十六进制并保证长度为8

NSString* firstHex = [decimalString decimalToHexWithLength:8];//私有方法(见Demo)

2.3 将十六进拼接固定字符并转为NSData

//将十六进制拼接上809B

NSString* hexString = [NSString stringWithFormat:@"809B%@",firstHex];

//将十六进制转为NSData

NSData* temphead = [hexString convertBytesStringToData];

2.4 拼接传输的数据(图片)

//拼接content

NSMutableData *m_data = [[NSMutableData alloc] init];

[m_data appendData:temphead];

[m_data appendData:content];

三、 解析数据

这里是模拟服务器返回的数据

因为发送给服务器内容的格式根服务器返回的内容的格式相同，所以这里我们直接解析我们发送给服务器的数据就可以

3.1 获取头部数据

NSData *head = [_receiveData subdataWithRange:NSMakeRange(0, 6)];//取得头部数据

NSData *lengthData = [head subdataWithRange:NSMakeRange(2, 4)];//取得长度数据

3.2 将4个字节的数据还原为content的长度

1 将lengthData转为16进制数

NSString* hexString = [lengthData convertDataToHexStr];

2 将16进制数转为10进制

NSInteger length = [[hexString hexToDecimal]integerValue];//得出content长度

3.3 取出content的内容

NSInteger complateDataLength = length + 6;//算出一个包完整的长度(内容长度＋头长度)

if (_receiveData.length >= complateDataLength)//如果缓存中数据够一个整包的长度

{

//这个data即为我们传出去的数据

NSData *data = [_receiveData subdataWithRange:NSMakeRange(6, length)];//截取一个包的长度(处理粘包)

//显示到程序上

[self.resultImage setImage:[UIImage imageWithData:data]];

}

image.png

image.png

四、 进制、Byte、Byte数组、NSData的相互转换(参考Demo)

#import "NSString+SwitchData.h"

@implementation NSString (SwitchData)

/**

带子节的string转为NSData

@return NSData类型

*/

-(NSData*) convertBytesStringToData {

NSMutableData* data = [NSMutableData data];

int idx;

for (idx = 0; idx+2 <= self.length; idx+=2) {

NSRange range = NSMakeRange(idx, 2);

NSString* hexStr = [self substringWithRange:range];

NSScanner* scanner = [NSScanner scannerWithString:hexStr];

unsigned int intValue;

[scanner scanHexInt:&intValue];

[data appendBytes:&intValue length:1];

}

return data;

}

/**

十进制转十六进制

@return 十六进制字符串

*/

- (NSString *)decimalToHex {

long long int tmpid = [self intValue];

NSString *nLetterValue;

NSString *str = @"";

long long int ttmpig;

for (int i = 0; i < 9; i++) {

ttmpig = tmpid % 16;

tmpid = tmpid / 16;

switch (ttmpig) {

case 10:

nLetterValue = @"A";

break;

case 11:

nLetterValue = @"B";

break;

case 12:

nLetterValue = @"C";

break;

case 13:

nLetterValue = @"D";

break;

case 14:

nLetterValue = @"E";

break;

case 15:

nLetterValue = @"F";

break;

default:

nLetterValue = [[NSString alloc]initWithFormat:@"%lli", ttmpig];

}

str = [nLetterValue stringByAppendingString:str];

if (tmpid == 0) {

break;

}

}

return str;

}

/**

十进制转十六进制

length 总长度，不足补0

@return 十六进制字符串

*/

- (NSString *)decimalToHexWithLength:(NSUInteger)length{

NSString* subString = [self decimalToHex];

NSUInteger moreL = length - subString.length;

if (moreL>0) {

for (int i = 0; i

subString = [NSString stringWithFormat:@"0%@",subString];

}

}

return subString;

}

/**

十六进制转十进制

@return 十进制字符串

*/

- (NSString *)hexToDecimal {

return [NSString stringWithFormat:@"%lu",strtoul([self UTF8String],0,16)];

}

/*

二进制转十进制

@return 十进制字符串

*/

- (NSString *)binaryToDecimal {

int ll = 0 ;

int temp = 0 ;

for (int i = 0; i < self.length; i ++) {

temp = [[self substringWithRange:NSMakeRange(i, 1)] intValue];

temp = temp * powf(2, self.length - i - 1);

ll += temp;

}

NSString * result = [NSString stringWithFormat:@"%d",ll];

return result;

}

/**

十进制转二进制

@return 二进制字符串

*/

- (NSString *)decimalToBinary {

NSInteger num = [self integerValue];

NSInteger remainder = 0; //余数

NSInteger divisor = 0; //除数

NSString * prepare = @"";

while (true) {

remainder = num%2;

divisor = num/2;

num = divisor;

prepare = [prepare stringByAppendingFormat:@"%d",(int)remainder];

if (divisor == 0) {

break;

}

}

NSString * result = @"";

for (NSInteger i = prepare.length - 1; i >= 0; i --) {

result = [result stringByAppendingFormat:@"%@",

[prepare substringWithRange:NSMakeRange(i , 1)]];

}

return [NSString stringWithFormat:@"%08d",[result intValue]];

}

@end

@implementation NSData (SwitchData)

/**

NSData 转 十六进制string

@return NSString类型的十六进制string

*/

- (NSString *)convertDataToHexStr{

if (!self || [self length] == 0) {

return @"";

}

NSMutableString *string = [[NSMutableString alloc] initWithCapacity:[self length]];

[self enumerateByteRangesUsingBlock:^(const void *bytes, NSRange byteRange, BOOL *stop) {

unsigned char *dataBytes = (unsigned char*)bytes;

for (NSInteger i = 0; i < byteRange.length; i++) {

NSString *hexStr = [NSString stringWithFormat:@"%x", (dataBytes[i]) & 0xff];

if ([hexStr length] == 2) {

[string appendString:hexStr];

} else {

[string appendFormat:@"0%@", hexStr];

}

}

}];

return string;

}

/**

NSData 转 NSString

@return NSString类型的字符串

*/

- (NSString *)dataToString {

Byte *bytes = (Byte *)[self bytes];

NSMutableString *string = [[NSMutableString alloc] init];

for(int i = 0; i< [self length]; i++) {

if (i == 0) {

[string appendString:[NSString stringWithFormat:@"%hhu",bytes[i]]];

}else {

[string appendString:[NSString stringWithFormat:@",%hhu",bytes[i]]];

}

}

return string;

}

@end

写在最后：

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