// Gets the next integer from the rl2 encoding. Returns EOF at end.
static int rl2unpacker_getc(Rl2Unpacker *rl2) {
if (rl2->b == EOF) {
return EOF;
}
// First, count the number of zero chunks until we come to a nonzero chunk.
int zero_count = 0;
int bmask = (1 << rl2->n) - 1;
int bv = (rl2->b & (bmask << (rl2->bi - rl2->n)));
if (rl2->zero_expands) {
while (bv == 0) {
++zero_count;
rl2->bi -= rl2->n;
if (rl2->bi <= 0) {
rl2->b = rbuffer_getc(rl2->rb);
rl2->bi = 8;
if (rl2->b == EOF) {
return EOF;
}
}
bv = (rl2->b & (bmask << (rl2->bi - rl2->n)));
}
}
// Infer from that the number of chunks, and hence the number of
// bits, that make up the value we will extract.
int num_chunks = (zero_count + 1);
int bit_count = num_chunks * rl2->n;
// OK, now we need to extract the next bitCount bits into a word.
int result = 0;
while (bit_count >= rl2->bi) {
int mask = (1 << rl2->bi) - 1;
int value = (rl2->b & mask);
result = (result << rl2->bi) | value;
bit_count -= rl2->bi;
rl2->b = rbuffer_getc(rl2->rb);
rl2->bi = 8;
if (rl2->b == EOF) {
break;
}
}
if (bit_count > 0) {
// A partial word in the middle of the byte.
int bottom_count = rl2->bi - bit_count;
assert(bottom_count > 0);
int mask = ((1 << bit_count) - 1);
int value = ((rl2->b >> bottom_count) & mask);
result = (result << bit_count) | value;
rl2->bi -= bit_count;
}
void rl2unpacker_init(Rl2Unpacker *rl2, RBuffer *rb, int n) {
// assumption: n is an integer divisor of 8.
assert(n * (8 / n) == 8);
rl2->rb = rb;
rl2->n = n;
rl2->b = rbuffer_getc(rb);
rl2->bi = 8;
}
static void rl2unpacker_init(Rl2Unpacker *rl2, RBuffer *rb, int n, bool zero_expands) {
// assumption: n is an integer divisor of 8.
assert(n * (8 / n) == 8);
rl2->rb = rb;
rl2->n = n;
rl2->b = rbuffer_getc(rb);
rl2->bi = 8;
rl2->zero_expands = zero_expands;
}
