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#include <stdlib.h>
#include <stddef.h>
// This GETBIT is supposed to work on little endian
// 32bit systems. The algorithm will definitely need
// some fixing on other systems, but it might not be
// a problem since the nrv2b binary behaves the same..
#define GETBIT(bb, src, ilen) \
(bc > 0 ? ((bb>>--bc)&1) : (bc=31,\
bb=*(const uint32_t *)((src)+ilen),ilen+=4,(bb>>31)&1))
static void unrv2b(uint8_t * src, uint8_t * dst)
{
unsigned long ilen = 0, olen = 0, last_m_off = 1;
uint32_t bb = 0;
unsigned bc = 0;
const uint8_t *m_pos;
// skip length
src += 4;
for (;;) {
unsigned int m_off, m_len;
while (GETBIT(bb, src, ilen)) {
dst[olen++] = src[ilen++];
}
m_off = 1;
do {
m_off = m_off * 2 + GETBIT(bb, src, ilen);
} while (!GETBIT(bb, src, ilen));
if (m_off == 2) {
m_off = last_m_off;
} else {
m_off = (m_off - 3) * 256 + src[ilen++];
if (m_off == 0xffffffffU)
break;
last_m_off = ++m_off;
}
m_len = GETBIT(bb, src, ilen);
m_len = m_len * 2 + GETBIT(bb, src, ilen);
if (m_len == 0) {
m_len++;
do {
m_len = m_len * 2 + GETBIT(bb, src, ilen);
} while (!GETBIT(bb, src, ilen));
m_len += 2;
}
m_len += (m_off > 0xd00);
m_pos = dst + olen - m_off;
dst[olen++] = *m_pos++;
do {
dst[olen++] = *m_pos++;
} while (--m_len > 0);
}
}
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