libsyscall/mach/string.c

   1 /*
   2  * Copyright (c) 2010 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 #include "string.h"
  30
  31 static const char hex[] = "0123456789abcdef";
  32
  33 static int
  34 _mach_strlen(const char *str)
  35 {
  36         const char *p;
  37         for (p = str; p; p++) {
  38                 if (*p == '\0') {
  39                         return (int)(p - str);
  40                 }
  41         }
  42         /* NOTREACHED */
  43         return 0;
  44 }
  45
  46 static void
  47 _mach_hex(char **buffer, int *length, unsigned long long n)
  48 {
  49         char buf[32];
  50         char *cp = buf + sizeof(buf);
  51
  52         if (n) {
  53                 *--cp = '\0';
  54                 while (n) {
  55                         *--cp = hex[n & 0xf];
  56                         n >>= 4;
  57                 }
  58
  59                 int width = _mach_strlen(cp);
  60                 while (width > 0 && length > 0) {
  61                         *(*buffer)++ = *cp++;
  62                         (*length)--;
  63                         width--;
  64                 }
  65         }
  66 }
  67
  68 int
  69 _mach_vsnprintf(char *buffer, int length, const char *fmt, va_list ap)
  70 {
  71         int width, max = length;
  72         char *out_ptr = buffer;
  73
  74         // we only ever write n-1 bytes so we can put a \0 at the end
  75         length--;
  76         while (length > 0 && *fmt) {
  77                 if (*fmt == '\0') {
  78                         break;
  79                 }
  80                 if (*fmt != '%') {
  81                         *(out_ptr++) = *(fmt++);
  82                         length--;
  83                         continue;
  84                 }
  85                 fmt++;
  86                 // only going to support a specific subset of sprintf flags
  87                 // namely %s, %x, with no padding modifiers
  88                 switch (*fmt++) {
  89                         case 's':
  90                         {
  91                                 char *cp = va_arg(ap, char*);
  92                                 width = _mach_strlen(cp);
  93                                 while (width > 0 && length > 0) {
  94                                         *(out_ptr++) = *(cp++);
  95                                         width--;
  96                                         length--;
  97                                 }
  98                                 break;
  99                         }
 100                         case 'x':
 101                         {
 102                                 _mach_hex(&out_ptr, &length, va_arg(ap, unsigned int));
 103                                 break;
 104                         }
 105                 }
 106         }
 107         *out_ptr = '\0';
 108         return max - length;
 109 }
 110
 111 int
 112 _mach_snprintf(char *buffer, int length, const char *fmt, ...)
 113 {
 114         int ret;
 115         va_list ap;
 116         va_start(ap, fmt);
 117         ret = _mach_vsnprintf(buffer, length, fmt, ap);
 118         va_end(ap);
 119         return ret;
 120 }