blob: 14d44fcbc1c81968575a1b39d64ed44cf83aa484 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
|
/* -*-C-*- signex.h */
/*-->signex*/
/**********************************************************************/
/******************************* signex *******************************/
/**********************************************************************/
INT32
signex(fp, n) /* return n byte quantity from file fd */
register FILE *fp; /* file pointer */
register BYTE n; /* number of bytes */
{
register BYTE n1; /* number of bytes */
register INT32 number; /* number being constructed */
number = (INT32)getc(fp);/* get first (high-order) byte */
#if PCC_20
if (number > 127) /* sign bit is set, pad top of word with sign bit */
number |= 0xfffffff00;
/* this constant could be written for any */
/* 2's-complement machine as -1 & ~0xff, but */
/* PCC-20 does not collapse constant expressions */
/* at compile time, sigh... */
#endif /* PCC_20 */
#if (OS_ATARI | OS_UNIX) /* 4.1BSD C compiler uses logical shift too */
if (number > 127) /* sign bit is set, pad top of word with sign bit */
number |= 0xffffff00;
#endif /* OS_UNIX */
n1 = n--;
while (n--)
{
number <<= 8;
number |= (INT32)getc(fp);
}
#if (OS_ATARI | PCC_20 | OS_UNIX)
#else /* NOT (OS_ATARI | PCC_20 | OS_UNIX) */
/* NOTE: This code assumes that the right-shift is an arithmetic, rather
than logical, shift which will propagate the sign bit right. According
to Kernighan and Ritchie, this is compiler dependent! */
number<<=HOST_WORD_SIZE-8*n1;
#if ARITHRSHIFT
number>>=HOST_WORD_SIZE-8*n1; /* sign extend */
#else /* NOT ARITHRSHIFT */
(void)fatal("signex(): no code implemented for logical right shift");
#endif /* ARITHRSHIFT */
#endif /* (OS_ATARI | PCC_20 | OS_UNIX) */
return((INT32)number);
}
|
