feedc0de/boost_conversion
1
0
Fork 0
forked from boostorg/conversion
Code Pull Requests Activity

Fixes #5576, adds performance section to the lexical_cast documentation, fixes misprint in tests/

Browse Source 
[SVN r72224]
This commit is contained in:
Antony Polukhin
2011-05-27 18:19:38 +00:00
parent 98d24e04f4
commit b0b1ce9453
3 changed files with 74 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

73
include/boost/lexical_cast.hpp
View File

@@ -555,6 +555,10 @@ namespace boost
BOOST_STATIC_ASSERT(!std::numeric_limits<T>::is_signed);
#endif
typedef typename Traits::int_type int_type;
CharT const czero = lcast_char_constants<CharT>::zero;
int_type const zero = Traits::to_int_type(czero);
#ifndef BOOST_LEXICAL_CAST_ASSUME_C_LOCALE
// TODO: use BOOST_NO_STD_LOCALE
std::locale loc;
@@ -562,47 +566,54 @@ namespace boost
numpunct const& np = BOOST_USE_FACET(numpunct, loc);
std::string const& grouping = np.grouping();
std::string::size_type const grouping_size = grouping.size();
CharT thousands_sep = grouping_size ? np.thousands_sep() : 0;
std::string::size_type group = 0; // current group number
char last_grp_size =
grouping_size == 0 || grouping[0] <= 0 ? CHAR_MAX : grouping[0];
if ( grouping_size && grouping[0] > 0 )
{
#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
// Check that ulimited group is unreachable:
BOOST_STATIC_ASSERT(std::numeric_limits<T>::digits10 < CHAR_MAX);
#endif
CharT thousands_sep = np.thousands_sep();
std::string::size_type group = 0; // current group number
char last_grp_size = grouping[0];
char left = last_grp_size;
char left = last_grp_size;
#endif
typedef typename Traits::int_type int_type;
CharT const czero = lcast_char_constants<CharT>::zero;
int_type const zero = Traits::to_int_type(czero);
do
{
#ifndef BOOST_LEXICAL_CAST_ASSUME_C_LOCALE
if(left == 0)
do
{
++group;
if(group < grouping_size)
if(left == 0)
{
char const grp_size = grouping[group];
last_grp_size = grp_size <= 0 ? CHAR_MAX : grp_size;
++group;
if(group < grouping_size)
{
char const grp_size = grouping[group];
last_grp_size = grp_size <= 0 ? CHAR_MAX : grp_size;
}
left = last_grp_size;
--finish;
Traits::assign(*finish, thousands_sep);
}
left = last_grp_size;
--left;
--finish;
Traits::assign(*finish, thousands_sep);
}
int_type const digit = static_cast<int_type>(n % 10U);
Traits::assign(*finish, Traits::to_char_type(zero + digit));
n /= 10;
} while(n);
--left;
} else
#endif
--finish;
int_type const digit = static_cast<int_type>(n % 10U);
Traits::assign(*finish, Traits::to_char_type(zero + digit));
n /= 10;
} while(n);
{
do
{
--finish;
int_type const digit = static_cast<int_type>(n % 10U);
Traits::assign(*finish, Traits::to_char_type(zero + digit));
n /= 10;
} while(n);
}
return finish;
}
@@ -638,10 +649,10 @@ namespace boost
/* According to [22.2.2.1.2] of Programming languages - C++
* we MUST check for correct grouping
*/
if (grouping_size)
if (grouping_size && grouping[0] > 0)
{
unsigned char current_grouping = 0;
CharT const thousands_sep = grouping_size ? np.thousands_sep() : 0;
CharT const thousands_sep = np.thousands_sep();
char remained = grouping[current_grouping] - 1;
for(;end>=begin; --end)

34
lexical_cast.htm
View File

@@ -26,6 +26,8 @@
<a href="#references">References</a></li>
<li>
<a href="#changes">Changes</a></li>
<li>
<a href="#performance">Performance</a></li>
</ul>
<hr>
<h2><a name="motivation">Motivation</a></h2>
@@ -87,7 +89,7 @@
For a good discussion of the options and issues involved in string-based
formatting, including comparison of <code>stringstream</code>, <code>lexical_cast</code>,
and others, see Herb Sutter's article, <a href="http://www.gotw.ca/publications/mill19.htm">
<i>The String Formatters of Manor Farm</i></a>.
<i>The String Formatters of Manor Farm</i></a>. Also, take a look at the <a href="#performance">Performance</a> section.
<p>
<hr>
<h2><a name="examples">Examples</a></h2>
@@ -267,6 +269,7 @@ Eliminate an overhead of <code>std::locale</code> if your program runs in the "C
<h2><a name="changes">Changes</a></h2>
<h3>May 2011:</h3>
<ul type="square">
<li>Optimizations for "C" and other locales without number grouping.</li>
<li>Better performance and less memory usage for unsigned char and signed char conversions.</li>
<li>Better performance and less memory usage for conversions to arithmetic types.</li>
<li>Better performance and less memory usage for conversions from arithmetic type to arithmetic type.</li>
@@ -313,7 +316,34 @@ Eliminate an overhead of <code>std::locale</code> if your program runs in the "C
</ul>
<p>
<hr>
<h2><a name="performance">Performance</a></h2>
This table shows the execution speed for 100000 iterations in milliseconds of the following code blocks:
<table border="1" width="100%">
<tr>
<td>From->To</td><td> <code>target = lexical_cast&lt;Target&gt;(source);</code> </td>
<td><code>std::stringstream ss;<br>ss &lt;&lt; source;<br> ss &gt;&gt; target;</code></td>
<td><code>ss &lt;&lt; source;<br> ss &gt;&gt; target;<br>ss.str(std::string());<br>ss.clear();</code></td>
<td><code>sscanf( (const char*)source, <...>, &amp;target);</code> <br>OR<br> <code>sprintf( (char*)buffer, <...>, source);<br>
target = buffer;</code></td></tr>
<tr><td>string->char</td><td bgcolor="#00C000"><1</td><td>91</td><td>7</td><td>10</td></tr>
<tr><td>string->int</td><td bgcolor="#00C000">7</td><td>115</td><td>23</td><td>18</td></tr>
<tr><td>string->unsigned int</td><td bgcolor="#00C000">7</td><td>117</td><td>22</td><td>17</td></tr>
<tr><td>string->bool</td><td bgcolor="#00C000"><1</td><td>104</td><td>19</td><td>10</td></tr>
<tr><td>string->float</td><td>85</td><td>172</td><td>60</td><td bgcolor="#00C000">33</td></tr>
<tr><td>char->string</td><td bgcolor="#00C000">7</td><td>105</td><td>16</td><td>12</td></tr>
<tr><td>int->string</td><td bgcolor="#00C000">15</td><td>131</td><td>21</td><td>17</td></tr>
<tr><td>unsigned int->string</td><td bgcolor="#00C000">14</td><td>125</td><td>21</td><td>17</td></tr>
<tr><td>bool->string</td><td bgcolor="#00C000">7</td><td>122</td><td>24</td><td>12</td></tr>
<tr><td>float->string</td><td>124</td><td>223</td><td>115</td><td bgcolor="#00C000">48</td></tr>
<tr><td>char*->string</td><td bgcolor="#00C000">9</td><td>123</td><td>20</td><td>---</td></tr>
<tr><td>int->int</td><td bgcolor="#00C000"><1</td><td>120</td><td>26</td><td>---</td></tr>
<tr><td>float->float</td><td bgcolor="#00C000"><1</td><td>262</td><td>142</td><td>---</td></tr>
</table>
Fastest results are highlitened with green.
<hr>
<div align="right"><small><i>Copyright &copy; Kevlin Henney, 2000-2005</i></small></div>
<div align="right"><small><i>Copyright &copy; Alexander Nasonov, 2006-2010</i></small></div>
<div align="right"><small><i>Copyright &copy; Antony Polukhin, 2011</i></small></div>

1
lexical_cast_test.cpp
View File

@@ -937,7 +937,6 @@ void test_wallocator()
#endif
#include <iostream>
void test_char_types_conversions()
{
const char c_arr[] = "Test array of chars";