87 lines
2.0 KiB
C
87 lines
2.0 KiB
C
#include <libpayload.h>
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// This GETBIT is supposed to work on little endian
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// 32bit systems. The algorithm will definitely need
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// some fixing on other systems, but it might not be
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// a problem since the nrv2b binary behaves the same..
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#ifndef ENDIAN
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#define ENDIAN 0
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#endif
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#ifndef BITSIZE
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#define BITSIZE 32
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#endif
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#define GETBIT_8(bb, src, ilen) \
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(((bb = bb & 0x7f ? bb*2 : ((unsigned)src[ilen++]*2+1)) >> 8) & 1)
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#define GETBIT_LE16(bb, src, ilen) \
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(bb*=2,bb&0xffff ? (bb>>16)&1 : (ilen+=2,((bb=(src[ilen-2]+src[ilen-1]*256u)*2+1)>>16)&1))
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#define GETBIT_LE32(bb, src, ilen) \
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(bc > 0 ? ((bb>>--bc)&1) : (bc=31,\
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bb=*(const u32 *)((src)+ilen),ilen+=4,(bb>>31)&1))
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#if ENDIAN == 0 && BITSIZE == 8
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#define GETBIT(bb, src, ilen) GETBIT_8(bb, src, ilen)
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#endif
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#if ENDIAN == 0 && BITSIZE == 16
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#define GETBIT(bb, src, ilen) GETBIT_LE16(bb, src, ilen)
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#endif
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#if ENDIAN == 0 && BITSIZE == 32
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#define GETBIT(bb, src, ilen) GETBIT_LE32(bb, src, ilen)
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#endif
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unsigned long unrv2b(u8 *src, u8 *dst, unsigned long *ilen_p)
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{
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unsigned long ilen = 0, olen = 0, last_m_off = 1;
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u32 bb = 0;
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unsigned bc = 0;
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const u8 *m_pos;
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// skip length
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src += 4;
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/* FIXME: check olen with the length stored in first 4 bytes */
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for (;;) {
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unsigned int m_off, m_len;
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while (GETBIT(bb, src, ilen)) {
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dst[olen++] = src[ilen++];
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}
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m_off = 1;
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do {
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m_off = m_off * 2 + GETBIT(bb, src, ilen);
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} while (!GETBIT(bb, src, ilen));
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if (m_off == 2) {
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m_off = last_m_off;
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} else {
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m_off = (m_off - 3) * 256 + src[ilen++];
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if (m_off == 0xffffffffU)
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break;
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last_m_off = ++m_off;
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}
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m_len = GETBIT(bb, src, ilen);
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m_len = m_len * 2 + GETBIT(bb, src, ilen);
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if (m_len == 0) {
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m_len++;
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do {
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m_len = m_len * 2 + GETBIT(bb, src, ilen);
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} while (!GETBIT(bb, src, ilen));
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m_len += 2;
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}
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m_len += (m_off > 0xd00);
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m_pos = dst + olen - m_off;
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dst[olen++] = *m_pos++;
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do {
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dst[olen++] = *m_pos++;
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} while (--m_len > 0);
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}
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*ilen_p = ilen;
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return olen;
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}
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