Name: Anonymous 2014-07-22 13:29
Can be yours or not, I just want to see something good.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <stdbool.h>
typedef struct {
unsigned char *p, *q;
size_t n, tmp, bits;
} bitptr;
void bitinit(bitptr *, void *, size_t, size_t);
void bitnext(bitptr *);
void bitprev(bitptr *);
void bitset(bitptr *, bool);
bool bitval(bitptr *);
void bitrewind(bitptr *);
size_t bitsize(bitptr *);
void bitpack(bitptr *, bitptr *, size_t, size_t);
void bitunpack(bitptr *, bitptr *, size_t, size_t);
void bitinit(bitptr *p, void *q, size_t n, size_t bits) {
p->p = p->q = q;
p->tmp = n;
p->bits = bits;
p->n = 0;
while(n--) bitnext(p);
}
void bitnext(bitptr *p) {
if(++p->n == CHAR_BIT) {
p->n = 0;
p->q++;
}
}
void bitprev(bitptr *p) {
if(p->n-- == 0) {
p->n = CHAR_BIT - 1;
p->q--;
}
}
void bitset(bitptr *p, bool b) {
if(b)
*p->q |= (b << p->n);
else
*p->q &= ~(b << p->n);
}
bool bitval(bitptr *p) {
return *p->q & (1 << p->n);
}
void bitrewind(bitptr *p) {
size_t n;
p->q = p->p;
p->n = p->tmp;
for(n = p->tmp; n--; bitnext(p));
}
size_t bitsize(bitptr *p) {
return p->bits;
}
#define bitsize(p) ((p)->bits)
void bitpack(bitptr *p, bitptr *q, size_t size, size_t nmemb) {
size_t n;
while(nmemb--) {
n = size;
while(n--) {
bitset(p, bitval(q));
bitnext(p);
bitnext(q);
}
if((n = bitsize(q) - size) != 0)
while(n--) bitnext(q);
}
}
void bitunpack(bitptr *p, bitptr *q, size_t size, size_t nmemb) {
size_t n;
while(nmemb--) {
n = size;
while(n--) {
bitset(p, bitval(q));
bitnext(p);
bitnext(q);
}
if((n = bitsize(p) - size) != 0)
while(n--) bitnext(p);
}
}
#define objsize(obj) (sizeof obj * CHAR_BIT)
static const char map[] = "abcdefghijklmnopqrstuvwxyz";
#define mapletter(x) (strchr(map, x) - map)
int main(void) {
bitptr p, s;
char buf[3] = {0}, x[] = { mapletter('h'), mapletter('e'), mapletter('l'), mapletter('l'), mapletter('o'), 0 };
size_t n;
bitinit(&p, buf, 0, objsize(buf[0]));
bitinit(&s, x, 0, objsize(x[0]));
bitpack(&p, &s, 4, sizeof x - 1);
bitrewind(&p);
bitrewind(&s);
printf("Message 'hello' stored in 3 bytes array. contents of s.p:\n");
memset(x, 0, sizeof x);
bitunpack(&s, &p, 4, sizeof x - 1);
for(n = 0; n < sizeof x - 1; n++)
s.p[n] = map[s.p[n]];
puts((void *)s.p);
return 0;
}