一：字节-Byte
1个字 =2个字节 = 16 bit
1Byte =1个字节 = 8 bit（1B = 1根数据总线= 1个字节 ）
1Byte = 8 bit （8个二进制位 0000 0000，即8个bit位，8位1个字节）
1B
1KB == 1024 Byte = 2 ^ 10 （10根地址总线) 00 0000 0000 ~ 11 1111 1111
1MB == 1024 * 1024 Byte = 2 ^ 20 （20根地址总线) 0000 0000 0000 0000 0000 ~ 1111 1111 1111 1111 1111
详情请看这里：地址总线-数据总线
“ 32位cup 对应的字节大小”
| 数据类型 | 储存空间大小(单位:字节) | 范围 |
|---|---|---|
| Byte(字节型) | 1 | 0 - 255 |
| Boolean(布尔型/逻辑型) | 2 | True 或 False |
| Integer(整数型) | 2 | -32,768 ~ 32767 |
Byte byte[] = {1,2,3,-255};
NSData *headerData = [[NSData alloc] initWithBytes:byte length:4];
字节数组 byte[]，这里有4个字节，每个字节8个二进制位（即：0000 0000~1111 1111，2^8 = 256）
每个字节可存放最大的数是255，
字节数组
二：Byte、char、NSData、NSString 相互转换
了解：字节、字符、字符串、二进制数据
//1.1、NSData --> Byte
NSString *testString = @"1234567890";
NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];
Byte *DataByte = (Byte *)[testData bytes];
//1.2、Byte --> 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 *Bytedata = [[NSData alloc] initWithBytes:byte length:24];
NSInteger byteLength2 = sizeof(byte2);
NSLog(@"字节长度_byteLength2= %zd",byteLength2);//byteLength2= 24
NSLog(@"---<2.2>testByte: %s", DataByte);
NSLog(@"---<2.2>Bytedata: %@\n ", Bytedata);
//2.1、 NSString 转化为 char*
NSString *strr = @"Test转化123";
const char * charA = [strr UTF8String];
NSLog(@"charA = %s",charA);
//2.2、char* 转化为 NSString
NSString *charToString = [NSString stringWithUTF8String:charA];
NSLog(@"charToString= %@ \n ",charToString);
//3.1、：NSString --> NSData
NSString * str1 = @"hello, world!";
NSData * data = [str1 dataUsingEncoding:NSUTF8StringEncoding];
//3.2、NSData --> NSString
NSString * dataString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(@"---<2.1>data.bytes: %s", data.bytes);
NSLog(@"---<2.1>dataString: %@\n ", dataString);
三：NSMutableData 的拼接、删除、插入
NSData *strData = [@"testdata" dataUsingEncoding:NSUTF8StringEncoding];
NSMutableData *data = [NSMutableData data];
[data appendData:strData];
NSLog(@"data length= %ld",data.length);
// delete
[data replaceBytesInRange:NSMakeRange(0, 4) withBytes:NULL length:0];
NSLog(@"data length= %ld",data.length);
// insert
[data replaceBytesInRange:NSMakeRange(0, 0) withBytes:strData.bytes length:strData.length];
NSLog(@"data length= %ld",data.length);
}
四：socket 组装发送消息
- (void)zmTest {
//NSData－> Byte数组
// 消息正文
NSString *contentStr = @"abcdEFG";
for (int i=0; i<10; i++) {
contentStr = [contentStr stringByAppendingString:@"1234567890-"];
}
//NSLog(@"contentStr= %@ ",contentStr);
NSData *contentData = [contentStr dataUsingEncoding: NSUTF8StringEncoding];
NSLog(@"contentStr_长度= %zd ",contentStr.length);
//计算正文长度
NSUInteger a1 = contentStr.length%256; //0~255
NSUInteger a2 = contentStr.length%16777216%65536/256; //256~65535
NSUInteger a3 = contentStr.length%16777216/65536; //65536~16777215
NSUInteger a4 = contentStr.length/16777216; //16777216~4294967295
NSLog(@"(a1,a2,a3,a4) = (%zd,%zd,%zd,%zd) ",a1,a2,a3,a4);
// 消息头
Byte byte[] = {a4,a3,a2,a1}; //4个字节
NSData *headerData = [[NSData alloc] initWithBytes:byte length:4];
// 消息组装体（总消息、总长度）
NSMutableData *mutData = [[NSMutableData alloc] init];
[mutData appendData:headerData];
[mutData appendData:contentData];
//------以下为测试------
NSLog(@"测试：1、消息正文 ------------------------------- ");
Byte *contentByte = (Byte *)[contentData bytes];
for(int i=0;i<[contentData length];i++){
printf("体_contentByte = %d\n",contentByte[i]);
}
NSLog(@"测试：2、消息头------------------------------- ");
Byte *headerByte = (Byte *)[headerData bytes];
for(int i=0;i<[headerData length];i++){
printf("头_headerByte = %d\n",headerByte[i]);
}
NSLog(@"测试：3、总消息------------------------------- ");
NSString *ByteString = @"[";
Byte *mutByte = (Byte *)[mutData bytes];
for(int i=0;i<[mutData length];i++){
//printf("mutByte = %d\n",mutByte[i]);
ByteString = [NSString stringWithFormat:@"%@%d,",ByteString,mutByte[i]];
}
NSLog(@"---All：ByteString_1= %@\n ", ByteString);
NSLog(@"---mutData.length_11= %zd\n ", mutData.length);
NSLogline(@" ");
//截取数据
[mutData subdataWithRange:NSMakeRange(0, 110)];//删除索引0到索引50的数据
NSLog(@"---mutData.length_22= %zd ", mutData.length);
NSLog(@"---[mutData length]_22= %zd ", [mutData length]);
Byte *mutByte2 = (Byte *)[mutData bytes];
NSString *ByteString2 = @"[";
for(int i=0;i<[mutData length];i++){
if (i==([mutData length]-1)) {
ByteString2 = [NSString stringWithFormat:@"%@%d]",ByteString2,mutByte2[i]];
}else{
ByteString2 = [NSString stringWithFormat:@"%@%d,",ByteString2,mutByte2[i]];
}
}
NSLog(@"---截取：ByteString_2= %@ ", ByteString2);
NSLog(@"---mutData.length_22= %zd \n ", mutData.length);
//删除数据
[mutData replaceBytesInRange:NSMakeRange(0, 117) withBytes:NULL length:0];//删除索引0到索引50的数据
NSLog(@"---mutData.length_33= %zd ", mutData.length);
NSLog(@"---[mutData length]_33= %zd ", [mutData length]);
Byte *mutByte3 = (Byte *)[mutData bytes];
NSString *ByteString3 = @"[";
for(int i=0;i<[mutData length];i++){
if (i==([mutData length]-1)) {
ByteString3 = [NSString stringWithFormat:@"%@%d]",ByteString3,mutByte3[i]];
}else{
ByteString3 = [NSString stringWithFormat:@"%@%d,",ByteString3,mutByte3[i]];
}
}
NSLog(@"---删除：ByteString_3= %@ ", ByteString3);
NSLog(@"---mutData.length_33= %zd \n ", mutData.length);