source: trunk/essentials/dev-lang/python/Python/mystrtoul.c@ 3437

Last change on this file since 3437 was 3225, checked in by bird, 19 years ago

Python 2.5
File size: 5.5 KB
Line 
1
2#include "Python.h"
3
4#if defined(__sgi) && defined(WITH_THREAD) && !defined(_SGI_MP_SOURCE)
5#define _SGI_MP_SOURCE
6#endif
7
8/* Convert a possibly signed character to a nonnegative int */
9/* XXX This assumes characters are 8 bits wide */
10#ifdef __CHAR_UNSIGNED__
11#define Py_CHARMASK(c) (c)
12#else
13#define Py_CHARMASK(c) ((c) & 0xff)
14#endif
15
16/* strtol and strtoul, renamed to avoid conflicts */
17
18
19#include <ctype.h>
20#ifdef HAVE_ERRNO_H
21#include <errno.h>
22#endif
23
24/* Static overflow check values for bases 2 through 36.
25 * smallmax[base] is the largest unsigned long i such that
26 * i * base doesn't overflow unsigned long.
27 */
28static unsigned long smallmax[] = {
29 0, /* bases 0 and 1 are invalid */
30 0,
31 ULONG_MAX / 2,
32 ULONG_MAX / 3,
33 ULONG_MAX / 4,
34 ULONG_MAX / 5,
35 ULONG_MAX / 6,
36 ULONG_MAX / 7,
37 ULONG_MAX / 8,
38 ULONG_MAX / 9,
39 ULONG_MAX / 10,
40 ULONG_MAX / 11,
41 ULONG_MAX / 12,
42 ULONG_MAX / 13,
43 ULONG_MAX / 14,
44 ULONG_MAX / 15,
45 ULONG_MAX / 16,
46 ULONG_MAX / 17,
47 ULONG_MAX / 18,
48 ULONG_MAX / 19,
49 ULONG_MAX / 20,
50 ULONG_MAX / 21,
51 ULONG_MAX / 22,
52 ULONG_MAX / 23,
53 ULONG_MAX / 24,
54 ULONG_MAX / 25,
55 ULONG_MAX / 26,
56 ULONG_MAX / 27,
57 ULONG_MAX / 28,
58 ULONG_MAX / 29,
59 ULONG_MAX / 30,
60 ULONG_MAX / 31,
61 ULONG_MAX / 32,
62 ULONG_MAX / 33,
63 ULONG_MAX / 34,
64 ULONG_MAX / 35,
65 ULONG_MAX / 36,
66};
67
68/* maximum digits that can't ever overflow for bases 2 through 36,
69 * calculated by [int(math.floor(math.log(2**32, i))) for i in range(2, 37)].
70 * Note that this is pessimistic if sizeof(long) > 4.
71 */
72#if SIZEOF_LONG == 4
73static int digitlimit[] = {
74 0, 0, 32, 20, 16, 13, 12, 11, 10, 10, /* 0 - 9 */
75 9, 9, 8, 8, 8, 8, 8, 7, 7, 7, /* 10 - 19 */
76 7, 7, 7, 7, 6, 6, 6, 6, 6, 6, /* 20 - 29 */
77 6, 6, 6, 6, 6, 6, 6}; /* 30 - 36 */
78#elif SIZEOF_LONG == 8
79/* [int(math.floor(math.log(2**64, i))) for i in range(2, 37)] */
80static int digitlimit[] = {
81 0, 0, 64, 40, 32, 27, 24, 22, 21, 20, /* 0 - 9 */
82 19, 18, 17, 17, 16, 16, 16, 15, 15, 15, /* 10 - 19 */
83 14, 14, 14, 14, 13, 13, 13, 13, 13, 13, /* 20 - 29 */
84 13, 12, 12, 12, 12, 12, 12}; /* 30 - 36 */
85#else
86#error "Need table for SIZEOF_LONG"
87#endif
88
89/*
90** strtoul
91** This is a general purpose routine for converting
92** an ascii string to an integer in an arbitrary base.
93** Leading white space is ignored. If 'base' is zero
94** it looks for a leading 0, 0x or 0X to tell which
95** base. If these are absent it defaults to 10.
96** Base must be 0 or between 2 and 36 (inclusive).
97** If 'ptr' is non-NULL it will contain a pointer to
98** the end of the scan.
99** Errors due to bad pointers will probably result in
100** exceptions - we don't check for them.
101*/
102unsigned long
103PyOS_strtoul(register char *str, char **ptr, int base)
104{
105 register unsigned long result = 0; /* return value of the function */
106 register int c; /* current input character */
107 register int ovlimit; /* required digits to overflow */
108
109 /* skip leading white space */
110 while (*str && isspace(Py_CHARMASK(*str)))
111 ++str;
112
113 /* check for leading 0 or 0x for auto-base or base 16 */
114 switch (base) {
115 case 0: /* look for leading 0, 0x or 0X */
116 if (*str == '0') {
117 ++str;
118 if (*str == 'x' || *str == 'X') {
119 ++str;
120 base = 16;
121 }
122 else
123 base = 8;
124 }
125 else
126 base = 10;
127 break;
128
129 case 16: /* skip leading 0x or 0X */
130 if (*str == '0') {
131 ++str;
132 if (*str == 'x' || *str == 'X')
133 ++str;
134 }
135 break;
136 }
137
138 /* catch silly bases */
139 if (base < 2 || base > 36) {
140 if (ptr)
141 *ptr = str;
142 return 0;
143 }
144
145 /* skip leading zeroes */
146 while (*str == '0')
147 ++str;
148
149 /* base is guaranteed to be in [2, 36] at this point */
150 ovlimit = digitlimit[base];
151
152 /* do the conversion until non-digit character encountered */
153 while ((c = _PyLong_DigitValue[Py_CHARMASK(*str)]) < base) {
154 if (ovlimit > 0) /* no overflow check required */
155 result = result * base + c;
156 else { /* requires overflow check */
157 register unsigned long temp_result;
158
159 if (ovlimit < 0) /* guaranteed overflow */
160 goto overflowed;
161
162 /* there could be an overflow */
163 /* check overflow just from shifting */
164 if (result > smallmax[base])
165 goto overflowed;
166
167 result *= base;
168
169 /* check overflow from the digit's value */
170 temp_result = result + c;
171 if (temp_result < result)
172 goto overflowed;
173
174 result = temp_result;
175 }
176
177 ++str;
178 --ovlimit;
179 }
180
181 /* set pointer to point to the last character scanned */
182 if (ptr)
183 *ptr = str;
184
185 return result;
186
187overflowed:
188 if (ptr) {
189 /* spool through remaining digit characters */
190 while (_PyLong_DigitValue[Py_CHARMASK(*str)] < base)
191 ++str;
192 *ptr = str;
193 }
194 errno = ERANGE;
195 return (unsigned long)-1;
196}
197
198/* Checking for overflow in PyOS_strtol is a PITA since C doesn't define
199 * anything about what happens when a signed integer operation overflows,
200 * and some compilers think they're doing you a favor by being "clever"
201 * then. Python assumes a 2's-complement representation, so that the bit
202 * pattern for the largest postive signed long is LONG_MAX, and for
203 * the smallest negative signed long is LONG_MAX + 1.
204 */
205
206long
207PyOS_strtol(char *str, char **ptr, int base)
208{
209 long result;
210 unsigned long uresult;
211 char sign;
212
213 while (*str && isspace(Py_CHARMASK(*str)))
214 str++;
215
216 sign = *str;
217 if (sign == '+' || sign == '-')
218 str++;
219
220 uresult = PyOS_strtoul(str, ptr, base);
221
222 if (uresult <= (unsigned long)LONG_MAX) {
223 result = (long)uresult;
224 if (sign == '-')
225 result = -result;
226 }
227 else if (sign == '-' && uresult == (unsigned long)LONG_MAX + 1) {
228 assert(LONG_MIN == -LONG_MAX-1);
229 result = LONG_MIN;
230 }
231 else {
232 errno = ERANGE;
233 result = LONG_MAX;
234 }
235 return result;
236}
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