Strip parity bits in C -

say have stream of bits 8 bits of data followed 2 parity bits (pattern repeats).

example (x parity bits):

0001 0001 xx00 0100 01xx 0001 0001 xx00 ...

should become

0001 0001 0001 0001 0001 0001 ...

i feel should easy , i'm on thinking it, how go stripping these parity bits?

the tricky bit here c doesn't let work bits easily, bytes. going assume char holds 8 bits (check char_bit in limits.h) -- case on modern systems. least common multiple of 8 , 10 40, want work in buffer of @ least 40 bits can integer arithmetic on whole -- in practice means 64-bit type. here's 1 way it, reading stdin , writing stdout. handling streams not multiple of 40 bits in length left exercise.

#include <stdint.h> #include <stdio.h>  int main(void) {     int c;     uint_least64_t buffer;      (;;)     {        buffer = 0;        /* read in 4 10-bit units = 5 8-bit units */        c = getchar(); if (c == eof) break;        buffer = ((buffer << 8) | c);        c = getchar(); if (c == eof) break;        buffer = ((buffer << 8) | c);        c = getchar(); if (c == eof) break;        buffer = ((buffer << 8) | c);        c = getchar(); if (c == eof) break;        buffer = ((buffer << 8) | c);        c = getchar(); if (c == eof) break;        buffer = ((buffer << 8) | c);         /* write out non-parity bits */        putchar((buffer & 0xff00000000ull) >> 32);        putchar((buffer & 0x003fc00000ull) >> 22);        putchar((buffer & 0x00000ff000ull) >> 12);        putchar((buffer & 0x00000003fcull) >>  2);     }     /* deal incomplete block here */     return 0; } 

... if wanted clever check parity bits before threw them away, although have come constructive when (not if) checksum failed.