1 /*****************************************************************************/
5 /* Safe shift routines */
9 /* (C) 2003 Ullrich von Bassewitz */
11 /* D-70794 Filderstadt */
12 /* EMail: uz@cc65.org */
15 /* This software is provided 'as-is', without any expressed or implied */
16 /* warranty. In no event will the authors be held liable for any damages */
17 /* arising from the use of this software. */
19 /* Permission is granted to anyone to use this software for any purpose, */
20 /* including commercial applications, and to alter it and redistribute it */
21 /* freely, subject to the following restrictions: */
23 /* 1. The origin of this software must not be misrepresented; you must not */
24 /* claim that you wrote the original software. If you use this software */
25 /* in a product, an acknowledgment in the product documentation would be */
26 /* appreciated but is not required. */
27 /* 2. Altered source versions must be plainly marked as such, and must not */
28 /* be misrepresented as being the original software. */
29 /* 3. This notice may not be removed or altered from any source */
32 /*****************************************************************************/
36 /* According to the C standard, shifting a data type by the number of bits it
37 * has causes undefined behaviour. So
39 * unsigned long l = 1;
43 * maybe illegal. The functions in this module behave safely in this respect,
44 * and they use proper casting to distinguish signed from unsigned shifts.
45 * They are not a general purpose replacement for the shift operator!
57 /*****************************************************************************/
59 /*****************************************************************************/
63 long asl_l (long l, unsigned count)
64 /* Arithmetic shift left l by count. */
67 if (count >= CHAR_BIT * sizeof (l)) {
68 l <<= (CHAR_BIT * sizeof (l) - 1);
69 count -= (CHAR_BIT * sizeof (l) - 1);
80 long asr_l (long l, unsigned count)
81 /* Arithmetic shift right l by count */
84 if (count >= CHAR_BIT * sizeof (l)) {
85 l >>= (CHAR_BIT * sizeof (l) - 1);
86 count -= (CHAR_BIT * sizeof (l) - 1);
97 unsigned long shl_l (unsigned long l, unsigned count)
98 /* Logical shift left l by count */
101 if (count >= CHAR_BIT * sizeof (l)) {
102 l <<= (CHAR_BIT * sizeof (l) - 1);
103 count -= (CHAR_BIT * sizeof (l) - 1);
114 unsigned long shr_l (unsigned long l, unsigned count)
115 /* Logical shift right l by count */
118 if (count >= CHAR_BIT * sizeof (l)) {
119 l >>= (CHAR_BIT * sizeof (l) - 1);
120 count -= (CHAR_BIT * sizeof (l) - 1);