1 /* $NetBSD: off_cvt.c,v 1.2 2020/03/18 19:05:16 christos Exp $ */
2
3 /*++
4 /* NAME
5 /* off_cvt 3
6 /* SUMMARY
7 /* off_t conversions
8 /* SYNOPSIS
9 /* #include <off_cvt.h>
10 /*
11 /* off_t off_cvt_string(string)
12 /* const char *string;
13 /*
14 /* VSTRING *off_cvt_number(result, offset)
15 /* VSTRING *result;
16 /* off_t offset;
17 /* DESCRIPTION
18 /* This module provides conversions between \fIoff_t\fR and string.
19 /*
20 /* off_cvt_string() converts a string, containing a non-negative
21 /* offset, to numerical form. The result is -1 in case of problems.
22 /*
23 /* off_cvt_number() converts a non-negative offset to string form.
24 /*
25 /* Arguments:
26 /* .IP string
27 /* String with non-negative number to be converted to off_t.
28 /* .IP result
29 /* Buffer for storage of the result of conversion to string.
30 /* .IP offset
31 /* Non-negative off_t value to be converted to string.
32 /* DIAGNOSTICS
33 /* Panic: negative offset
34 /* LICENSE
35 /* .ad
36 /* .fi
37 /* The Secure Mailer license must be distributed with this software.
38 /* AUTHOR(S)
39 /* Wietse Venema
40 /* IBM T.J. Watson Research
41 /* P.O. Box 704
42 /* Yorktown Heights, NY 10598, USA
43 /*
44 /* Wietse Venema
45 /* Google, Inc.
46 /* 111 8th Avenue
47 /* New York, NY 10011, USA
48 /*--*/
49
50 /* System library. */
51
52 #include <sys_defs.h>
53 #include <sys/types.h>
54 #include <ctype.h>
55
56 /* Utility library. */
57
58 #include <msg.h>
59 #include <vstring.h>
60
61 /* Global library. */
62
63 #include "off_cvt.h"
64
65 /* Application-specific. */
66
67 #define STR vstring_str
68 #define END vstring_end
69 #define SWAP(type, a, b) { type temp; temp = a; a = b; b = temp; }
70
71 /* off_cvt_string - string to number */
72
off_cvt_string(const char * str)73 off_t off_cvt_string(const char *str)
74 {
75 int ch;
76 off_t result;
77 off_t digit_value;
78
79 /*
80 * Detect overflow before it happens. Code that attempts to detect
81 * overflow after-the-fact makes assumptions about undefined behavior.
82 * Compilers may invalidate such assumptions.
83 */
84 for (result = 0; (ch = *(unsigned char *) str) != 0; str++) {
85 if (!ISDIGIT(ch))
86 return (-1);
87 digit_value = ch - '0';
88 if (result > OFF_T_MAX / 10
89 || (result *= 10) > OFF_T_MAX - digit_value)
90 return (-1);
91 result += digit_value;
92 }
93 return (result);
94 }
95
96 /* off_cvt_number - number to string */
97
off_cvt_number(VSTRING * buf,off_t offset)98 VSTRING *off_cvt_number(VSTRING *buf, off_t offset)
99 {
100 static char digs[] = "0123456789";
101 char *start;
102 char *last;
103 int i;
104
105 /*
106 * Sanity checks
107 */
108 if (offset < 0)
109 msg_panic("off_cvt_number: negative offset -%s",
110 STR(off_cvt_number(buf, -offset)));
111
112 /*
113 * First accumulate the result, backwards.
114 */
115 VSTRING_RESET(buf);
116 while (offset != 0) {
117 VSTRING_ADDCH(buf, digs[offset % 10]);
118 offset /= 10;
119 }
120 VSTRING_TERMINATE(buf);
121
122 /*
123 * Then, reverse the result.
124 */
125 start = STR(buf);
126 last = END(buf) - 1;
127 for (i = 0; i < VSTRING_LEN(buf) / 2; i++)
128 SWAP(int, start[i], last[-i]);
129 return (buf);
130 }
131
132 #ifdef TEST
133
134 /*
135 * Proof-of-concept test program. Read a number from stdin, convert to
136 * off_t, back to string, and print the result.
137 */
138 #include <vstream.h>
139 #include <vstring_vstream.h>
140
main(int unused_argc,char ** unused_argv)141 int main(int unused_argc, char **unused_argv)
142 {
143 VSTRING *buf = vstring_alloc(100);
144 off_t offset;
145
146 while (vstring_fgets_nonl(buf, VSTREAM_IN)) {
147 if (STR(buf)[0] == '#' || STR(buf)[0] == 0)
148 continue;
149 if ((offset = off_cvt_string(STR(buf))) < 0) {
150 msg_warn("bad input %s", STR(buf));
151 } else {
152 vstream_printf("%s\n", STR(off_cvt_number(buf, offset)));
153 }
154 vstream_fflush(VSTREAM_OUT);
155 }
156 vstring_free(buf);
157 return (0);
158 }
159
160 #endif
161