Question

I have an array of ushorts, with each ushort representing a 12-bit word. This needs to be tightly packed into an array of bytes. It should look like this in the end:

|  word1    |  word2    |  word3    |  word4   |
| byte1 | byte2 | byte3 | byte4 | byte5 | byte6|

Since each word only uses 12 bits, 2 words will be packed into 3 bytes.

Could someone help? I’m a bit stuck on how to do this in C#.

Answer 1

You’re probably going to have to brute-force it.

I’m not a C# guy, but you are looking at something along the lines of (in C):

unsigned incursor, outcursor;
unsigned inlen = length(inputarray);  // not literally
for(incursor=0,outcursor=0;incursor < inlen; incursor+=2,outcursor+=3{
   outputarray[outcursor+0] = ((inputarray[incursor+0]) >> 4) & 0xFF;
   outputarray[outcursor+1] = ((inputarray[incursor+0] & 0x0F)<<4 | ((inputarray[incursor+1]>>8) & 0x0F);
   outputarray[outcursor+2] = inputarray[incursor+1] & 0xFF;
}