how to extract only the 1st 2 bytes of data from CFReadStream in Objective-C for iPhone programming

Question

Hello,

1) How to read the data from read stream in Objective-C, Below code would give me how many bytes are read from stream, but how to know what data is read from stream?

CFIndex cf = CFReadStreameRead(Stream, buffer, length);

2) How to extract only the 1st 2bytes of data in the read stream in Objective-C For Ex: If this is the data from stream

 017MacApp

1st byte has 0 in it, and 2nd byte has 17 in it.

how do i extract o and 17 into byte array?

I know that the below code would give me back the byte array to int value.

((b[0] & 0xFF) << 8)+ (b[1] & 0xFF);

but how to put 0 into b[0] and 17 into b[1]?

plz help me to solve this.

Answer 1

uint8_t buffer[2];
CFIndex cf = CFReadStreameRead(Stream, buffer, 2);
if (cf == 2)
{
    uint8_t firstByte = buffer[0];
    uint8_t secondByte = buffer[1];
}
else
{
    // cf == -1 => error, cf == 0 => end of file, cf == 1 => you need to call again to get the second byte
}

Here is the Apple doc.