Subversion Repositories tendra.SVN

Rev

Rev 2 | Go to most recent revision | Details | Compare with Previous | Last modification | View Log | RSS feed

Rev Author Line No. Line
2 7u83 1 
/*
2 
    		 Crown Copyright (c) 1997
3 
 
4 
    This TenDRA(r) Computer Program is subject to Copyright
5 
    owned by the United Kingdom Secretary of State for Defence
6 
    acting through the Defence Evaluation and Research Agency
7 
    (DERA).  It is made available to Recipients with a
8 
    royalty-free licence for its use, reproduction, transfer
9 
    to other parties and amendment for any purpose not excluding
10 
    product development provided that any such use et cetera
11 
    shall be deemed to be acceptance of the following conditions:-
12 
 
13 
        (1) Its Recipients shall ensure that this Notice is
14 
        reproduced upon any copies or amended versions of it;
15 
 
16 
        (2) Any amended version of it shall be clearly marked to
17 
        show both the nature of and the organisation responsible
18 
        for the relevant amendment or amendments;
19 
 
20 
        (3) Its onward transfer from a recipient to another
21 
        party shall be deemed to be that party's acceptance of
22 
        these conditions;
23 
 
24 
        (4) DERA gives no warranty or assurance as to its
25 
        quality or suitability for any purpose and DERA accepts
26 
        no liability whatsoever in relation to any use to which
27 
        it may be put.
28 
*/
29 
 
30 
 
31 
#include "config.h"
32 
#include "file.h"
33 
#include "types.h"
34 
#include "utility.h"
35 
 
36 
 
37 
/*
38 
    CURRENT FILE POINTER
39 
 
40 
    As they are read from the input file bits are stored in input_buff.
41 
    The current number of bits in the buffer is bits_in_buff.  bytes_read
42 
    records the position in the input file.
43 
*/
44 
 
45 
unsigned bits_in_buff = 0 ;
46 
long bytes_read = 0 ;
47 
static unsigned long input_buff = 0 ;
48 
 
49 
 
50 
/*
51 
    ALIGN TO NEXT BYTE BOUNDARY
52 
 
53 
    Any bits remaining in the current byte are ignored.
54 
*/
55 
 
56 
void byte_align
57 
    PROTO_Z ()
58 
{
59 
    bits_in_buff = 0 ;
60 
    return ;
61 
}
62 
 
63 
 
64 
/*
65 
    FETCH A NUMBER OF BITS
66 
 
67 
    This routine reads the next n bits from the input file and returns
68 
    them as a long.
69 
*/
70 
 
71 
long fetch
72 
    PROTO_N ( ( n ) )
73 
    PROTO_T ( int n )
74 
{
75 
    unsigned long s ;
76 
    unsigned long r = 0 ;
77 
    unsigned b = ( unsigned ) n ;
78 
    while ( b ) {
79 
	unsigned m ;
80 
	if ( bits_in_buff == 0 ) {
81 
	    int c = getc ( input ) ;
82 
	    bytes_read++ ;
83 
	    if ( c == EOF ) {
84 
		input_error ( "Premature end of file" ) ;
85 
		c = 0xff ;
86 
	    }
87 
	    bits_in_buff = BYTESIZE ;
88 
	    input_buff = ( unsigned long ) ( c & 0xff ) ;
89 
	}
90 
	m = ( b <= bits_in_buff ? b : bits_in_buff ) ;
91 
	s = ( input_buff << m ) ;
92 
	r = ( ( r << m ) | ( ( s >> BYTESIZE ) & 0xff ) ) ;
93 
	b -= m ;
94 
	bits_in_buff -= m ;
95 
	input_buff = ( s & 0xff ) ;
96 
    }
97 
    return ( ( long ) r ) ;
98 
}
99 
 
100 
 
101 
/*
102 
    FIND CURRENT POSITION IN FILE
103 
 
104 
    The current position in the input file (in bits) is returned.
105 
*/
106 
 
107 
long input_posn
108 
    PROTO_Z ()
109 
{
110 
    return ( BYTESIZE * bytes_read - ( long ) bits_in_buff ) ;
111 
}
112 
 
113 
 
114 
/*
115 
    GO TO A POSITION IN FILE
116 
 
117 
    The position in the input file is set to the nth bit.
118 
*/
119 
 
120 
void input_goto
121 
    PROTO_N ( ( n ) )
122 
    PROTO_T ( long n )
123 
{
124 
    int b = ( int ) ( n % BYTESIZE ) ;
125 
    bytes_read = ( n / BYTESIZE ) ;
126 
    bits_in_buff = 0 ;
127 
    if ( fseek ( input, bytes_read, SEEK_SET ) ) {
128 
	bits_in_buff = ( unsigned ) b ;
129 
	input_error ( "Illegal seek command" ) ;
130 
	return ;
131 
    }
132 
    if ( b ) IGNORE fetch ( b ) ;
133 
    return ;
134 
}
135 
 
136 
 
137 
/*
138 
    SKIP A NUMBER OF BITS
139 
 
140 
    The next n bits in the input file are ignored.
141 
*/
142 
 
143 
void input_skip
144 
    PROTO_N ( ( n ) )
145 
    PROTO_T ( long n )
146 
{
147 
    if ( n <= 4 * BYTESIZE ) {
148 
	IGNORE fetch ( ( int ) n ) ;
149 
    } else {
150 
	long m = input_posn () + n ;
151 
	input_goto ( m ) ;
152 
    }
153 
    return ;
154 
}