arrays - Convert Bytes to Int / uint in C

Question

I have a unsigned char array[248]; filled with bytes. Like 2F AF FF 00 EB AB CD EF ..... This Array is my Byte Stream which I store my Data from the UART (RS232) as a Buffer.

Now I want to convert the bytes back to my uint16's and int32's.

In C# I used the BitConverter Class to do this. e.g:

byte[] Array = { 0A, AB, CD, 25 };
int myint1 = BitConverter.ToInt32(bytes, 0);
int myint2 = BitConverter.ToInt32(bytes, 4);
int myint3 = BitConverter.ToInt32(bytes, 8);
int myint4 = BitConverter.ToInt32(bytes, 12);
//...
enter code here
Console.WriteLine("int: {0}", myint1); //output Data...

Is there a similiar Function in C ? (no .net , I use the KEIL compiler because code is running on a microcontroller)

With Regards Sam

Answer 1

There's no standard function to do it for you in C. You'll have to assemble the bytes back into your 16- and 32-bit integers yourself. Be careful about endianness!

Here's a simple little-endian example:

extern uint8_t *bytes;
uint32_t myInt1 = bytes[0] + (bytes[1] << 8) + (bytes[2] << 16) + (bytes[3] << 24);

For a big-endian system, it's just the opposite order:

uint32_t myInt1 = (bytes[0] << 24) + (bytes[1] << 16) + (bytes[2] << 8) + bytes[3];

You might be able to get away with:

uint32_t myInt1 = *(uint32_t *)bytes;

If you're careful about alignment issues.