How to read bytes from NSData

Question

任何人都可以建议一种从NSData读取字节的方法（例如@interface NSInputStream读取函数： NSStream ）

Answer 1

How to read binary bytes in NSData? may help you:

NSString *path = @"…put the path to your file here…";
NSData * fileData = [NSData dataWithContentsOfFile: path];
const char* fileBytes = (const char*)[fileData bytes];
NSUInteger length = [fileData length];
NSUInteger index;

for (index = 0; index<length; index++) {
   char aByte = fileBytes[index];
   //Do something with each byte
}

Answer 2

You can also create an NSInputStream from an NSData object, if you need the read interface:

NSData *data = ...;
NSInputStream *readData = [[NSInputStream alloc] initWithData:data];
[readData open];

However, you should be aware that initWithData copies the contents of data.

Answer 3

One of the simplest ways is to use NSData getBytes:range: .

NSData *data = ...;
char buffer[numberOfBytes];
[data getBytes:buffer range:NSMakeRange(position, numberOfBytes)];

where position and length is the position you want to read from in NSData and the length is how many bytes you want to read. No need to copy.

Answer 4

Alex already mentioned NSData getBytes:range: but there is also NSData getBytes:length: which starts from the first byte.

NSData *data = ...;
char buffer[numberOfBytes];
[data getBytes:buffer length:numberOfBytes];

Answer 5

May way of doing that.. do not forget to free byte array after usage.

NSData* dat = //your code
NSLog(@"Receive from Peripheral: %@",dat);
NSUInteger len = [dat length];
Byte *bytedata = (Byte*)malloc(len);
[dat getBytes:bytedata length:len];
int p = 0;
while(p < len)
{
    printf("%02x",bytedata[p]);
    if(p!=len-1)
    {
     printf("-");
    }//printf("%c",bytedata[p]);
    p++;
}
printf("\n");
// byte array manipulation

free(bytedata);