xapian-core/common/str.cc

   1 /** @file
   2  * @brief Convert types to std::string
   3  */
   4 /* Copyright (C) 2009,2012,2015,2017 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  19  */
  20
  21 #include <config.h>
  22
  23 #include "str.h"
  24
  25 #include "negate_unsigned.h"
  26 #include "omassert.h"
  27
  28 #include <cstdio> // For snprintf().
  29 #include <cstdlib> // For abort().
  30 #include <string>
  31 #include <type_traits>
  32
  33 using namespace std;
  34
  35 // Much faster than snprintf() - also less generated code!
  36 template<class T>
  37 static inline string
  38 tostring_unsigned(T value)
  39 {
  40     static_assert(std::is_unsigned_v<T>, "Unsigned type required");
  41     // Special case single digit positive numbers.
  42     // FIXME: is this actually worthwhile?
  43     if (value < 10) return string(1, '0' + char(value));
  44     char buf[(sizeof(T) * 5 + 1) / 2];
  45     char * p = buf + sizeof(buf);
  46     do {
  47         AssertRel(p,>,buf);
  48         char ch = static_cast<char>(value % 10);
  49         value /= 10;
  50         *(--p) = ch + '0';
  51     } while (value);
  52     return string(p, buf + sizeof(buf) - p);
  53 }
  54
  55 template<class T>
  56 static inline string
  57 tostring(T value)
  58 {
  59     // Special case single digit positive numbers.
  60     // FIXME: is this actually worthwhile?
  61     if (value < 10 && value >= 0) return string(1, '0' + char(value));
  62
  63     bool negative = (value < 0);
  64
  65     typedef typename std::make_unsigned_t<T> unsigned_type;
  66     unsigned_type val(value);
  67     if (negative) {
  68         val = negate_unsigned(val);
  69     }
  70
  71     char buf[(sizeof(unsigned_type) * 5 + 1) / 2 + 1];
  72     char * p = buf + sizeof(buf);
  73     do {
  74         AssertRel(p,>,buf);
  75         char ch = static_cast<char>(val % 10);
  76         val /= 10;
  77         *(--p) = ch + '0';
  78     } while (val);
  79
  80     if (negative) {
  81         AssertRel(p,>,buf);
  82         *--p = '-';
  83     }
  84     return string(p, buf + sizeof(buf) - p);
  85 }
  86
  87 namespace Xapian {
  88 namespace Internal {
  89
  90 string
  91 str(int value)
  92 {
  93     return tostring(value);
  94 }
  95
  96 string
  97 str(unsigned int value)
  98 {
  99     return tostring_unsigned(value);
 100 }
 101
 102 string
 103 str(long value)
 104 {
 105     return tostring(value);
 106 }
 107
 108 string
 109 str(unsigned long value)
 110 {
 111     return tostring_unsigned(value);
 112 }
 113
 114 string
 115 str(long long value)
 116 {
 117     return tostring(value);
 118 }
 119
 120 string
 121 str(unsigned long long value)
 122 {
 123     return tostring_unsigned(value);
 124 }
 125
 126 template<class T>
 127 static inline string
 128 format(const char * fmt, T value)
 129 {
 130     char buf[128];
 131     // If -1 is returned (as pre-ISO snprintf does if the buffer is too small,
 132     // it will be cast to > sizeof(buf) and handled appropriately.
 133     size_t size = snprintf(buf, sizeof(buf), fmt, value);
 134     AssertRel(size,<=,sizeof(buf));
 135     if (size > sizeof(buf)) size = sizeof(buf);
 136     return string(buf, size);
 137 }
 138
 139 string
 140 str(double value)
 141 {
 142     return format("%.20g", value);
 143 }
 144
 145 string
 146 str(const void * value)
 147 {
 148     return format("%p", value);
 149 }
 150
 151 }
 152 }