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codelength.h
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1 /* $Id: codelength.h,v 1.3 2011/07/30 13:10:05 nanard Exp $ */
2 /* Project : miniupnp
3  * Author : Thomas BERNARD
4  * copyright (c) 2005-2015 Thomas Bernard
5  * This software is subjet to the conditions detailed in the
6  * provided LICENCE file. */
7 #ifndef CODELENGTH_H_INCLUDED
8 #define CODELENGTH_H_INCLUDED
9 
10 /* Encode length by using 7bit per Byte :
11  * Most significant bit of each byte specifies that the
12  * following byte is part of the code */
13 
14 /* n : unsigned
15  * p : unsigned char *
16  */
17 #define DECODELENGTH(n, p) n = 0; \
18  do { n = (n << 7) | (*p & 0x7f); } \
19  while((*(p++)&0x80) && (n<(1<<25)));
20 
21 /* n : unsigned
22  * READ : function/macro to read one byte (unsigned char)
23  */
24 #define DECODELENGTH_READ(n, READ) \
25  n = 0; \
26  do { \
27  unsigned char c; \
28  READ(c); \
29  n = (n << 7) | (c & 0x07f); \
30  if(!(c&0x80)) break; \
31  } while(n<(1<<25));
32 
33 /* n : unsigned
34  * p : unsigned char *
35  * p_limit : unsigned char *
36  */
37 #define DECODELENGTH_CHECKLIMIT(n, p, p_limit) \
38  n = 0; \
39  do { \
40  if((p) >= (p_limit)) break; \
41  n = (n << 7) | (*(p) & 0x7f); \
42  } while((*((p)++)&0x80) && (n<(1<<25)));
43 
44 
45 /* n : unsigned
46  * p : unsigned char *
47  */
48 #define CODELENGTH(n, p) if(n>=268435456) *(p++) = (n >> 28) | 0x80; \
49  if(n>=2097152) *(p++) = (n >> 21) | 0x80; \
50  if(n>=16384) *(p++) = (n >> 14) | 0x80; \
51  if(n>=128) *(p++) = (n >> 7) | 0x80; \
52  *(p++) = n & 0x7f;
53 
54 #endif /* CODELENGTH_H_INCLUDED */
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