blocks|key|1514744|text|对于同时使用C和C%2B%2B的方法，您可能需要考虑使用标准库函数strtol()。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1514745|#include+<cstdlib>
#include+<iostream>
using+namespace+std;

int+main()+{
++++string+s+=+"abcd";
++++char+*+p;
++++long+n+=+strtol(+s.c_str(),+&+p,+16+);
++++if+(+*+p+!=+0+)+{+//my+bad+edit+was+here
++++++++cout+<<+"not+a+number"+<<+endl;
++++}
++++else+{
++++++++cout+<<+n+<<+endl;
++++}
}|code-block|syntax|javascript|1514746|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

For a method that works with both C and C++, you might want to consider using the standard library function strtol().

<pre><code>#include &lt;cstdlib&gt;
#include &lt;iostream&gt;
using namespace std;

int main() {
 string s = "abcd";
 char * p;
 long n = strtol( s.c_str(), &amp; p, 16 );
 if ( * p != 0 ) { //my bad edit was here
 cout &lt;&lt; "not a number" &lt;&lt; endl;
 }
 else {
 cout &lt;&lt; n &lt;&lt; endl;
 }
}
</code></pre>

blocks|key|1300038|text|使用strtoul的工作示例如下：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1300039|#include+<cstdlib>
#include+<iostream>
using+namespace+std;

int+main()+{+
++++string+s+=+"fffefffe";
++++char+*+p;
++++long+n+=+strtoul(+s.c_str(),+&+p,+16+);+
++++if+(+*+p+!=+0+)+{++
++++++++cout+<<+"not+a+number"+<<+endl;
++++}++++else+{++
++++++++cout+<<+n+<<+endl;
++++}
}|code-block|syntax|javascript|1300040|strtol将string转换为long。在我的电脑上，numeric_limits<long>::max()给了0x7fffffff。显然，0xfffefffe比0x7fffffff更重要。因此，strtol返回MAX_LONG而不是所需的值。strtoul将string转换为unsigned+long，这就是在这种情况下没有溢出的原因。|1300041|好的，在转换之前，strtol正在考虑输入字符串，而不是32位有符号整数。strtol的有趣示例|1300042|#include+<cstdlib>
#include+<iostream>
using+namespace+std;

int+main()+{+
++++string+s+=+"-0x10002";
++++char+*+p;
++++long+n+=+strtol(+s.c_str(),+&+p,+16+);+
++++if+(+*+p+!=+0+)+{++
++++++++cout+<<+"not+a+number"+<<+endl;
++++}++++else+{++
++++++++cout+<<+n+<<+endl;
++++}
}|1300043|上面的代码在控制台中打印-65538。|1300044|entityMap^0|2|7|0|0|0|6|7|6|G|4|S|R|1L|A|1Z|A|2A|A|2R|6|2Z|8|3F|7|3N|6|3W|D|0|9|6|11|6|0|0|C|6|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]|$9|19|A|1A|B|C]|$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]|$9|1F|A|1G|B|C]|$9|1H|A|1I|B|C]|$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|1N|8|@$9|1O|A|1P|B|C]|$9|1Q|A|1R|B|C]]|D|@]|E|$]]|$1|O|3|P|5|H|7|1S|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|6|7|1T|8|@$9|1U|A|1V|B|C]]|D|@]|E|$]]|$1|S|3|-4|5|6|7|1W|8|@]|D|@]|E|$]]]|T|$]]

Working example with <code>strtoul</code> will be:

<pre><code>#include &lt;cstdlib>
#include &lt;iostream>
using namespace std;

int main() { 
 string s = "fffefffe";
 char * p;
 long n = strtoul( s.c_str(), & p, 16 ); 
 if ( * p != 0 ) { 
 cout &lt;&lt; "not a number" &lt;&lt; endl;
 } else { 
 cout &lt;&lt; n &lt;&lt; endl;
 }
}
</code></pre>

<code>strtol</code> converts <code>string</code> to <code>long</code>. On my computer <code>numeric_limits&lt;long&gt;::max()</code> gives <code>0x7fffffff</code>. Obviously that <code>0xfffefffe</code> is greater than <code>0x7fffffff</code>. So <code>strtol</code> returns <code>MAX_LONG</code> instead of wanted value. <code>strtoul</code> converts <code>string</code> to <code>unsigned long</code> that's why no overflow in this case.

Ok, <code>strtol</code> is considering input string not as 32-bit signed integer before convertation. Funny sample with <code>strtol</code>:

<pre><code>#include &lt;cstdlib>
#include &lt;iostream>
using namespace std;

int main() { 
 string s = "-0x10002";
 char * p;
 long n = strtol( s.c_str(), & p, 16 ); 
 if ( * p != 0 ) { 
 cout &lt;&lt; "not a number" &lt;&lt; endl;
 } else { 
 cout &lt;&lt; n &lt;&lt; endl;
 }
}
</code></pre>

The code above prints <code>-65538</code> in console.

blocks|key|1300092|text|我今天遇到了同样的问题，下面是我如何解决它的，这样我就可以保留lexical_cast<>|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1300093|typedef+unsigned+int++++uint32;
typedef+signed+int++++++int32;

class+uint32_from_hex+++//+For+use+with+boost::lexical_cast
{
++++uint32+value;
public:
++++operator+uint32()+const+{+return+value;+}
++++friend+std::istream&+operator>>(+std::istream&+in,+uint32_from_hex&+outValue+)
++++{
++++++++in+>>+std::hex+>>+outValue.value;
++++}
};

class+int32_from_hex+++//+For+use+with+boost::lexical_cast
{
++++uint32+value;
public:
++++operator+int32()+const+{+return+static_cast<int32>(+value+);+}
++++friend+std::istream&+operator>>(+std::istream&+in,+int32_from_hex&+outValue+)
++++{
++++++++in+>>+std::hex+>>+outvalue.value;
++++}
};

uint32+material0+=+lexical_cast<uint32_from_hex>(+"0x4ad"+);
uint32+material1+=+lexical_cast<uint32_from_hex>(+"4ad"+);
uint32+material2+=+lexical_cast<uint32>(+"1197"+);

int32+materialX+=+lexical_cast<int32_from_hex>(+"0xfffefffe"+);
int32+materialY+=+lexical_cast<int32_from_hex>(+"fffefffe"+);
//+etc...|code-block|syntax|javascript|1300094|(当我正在寻找一种不那么糟糕的方式时，发现了这个页面:-)|1300095|干杯A。|1300096|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I had the same problem today, here's how I solved it so I could keep lexical_cast&lt;> 

<pre><code>typedef unsigned int uint32;
typedef signed int int32;

class uint32_from_hex // For use with boost::lexical_cast
{
 uint32 value;
public:
 operator uint32() const { return value; }
 friend std::istream&amp; operator&gt;&gt;( std::istream&amp; in, uint32_from_hex&amp; outValue )
 {
 in &gt;&gt; std::hex &gt;&gt; outValue.value;
 }
};

class int32_from_hex // For use with boost::lexical_cast
{
 uint32 value;
public:
 operator int32() const { return static_cast&lt;int32&gt;( value ); }
 friend std::istream&amp; operator&gt;&gt;( std::istream&amp; in, int32_from_hex&amp; outValue )
 {
 in &gt;&gt; std::hex &gt;&gt; outvalue.value;
 }
};

uint32 material0 = lexical_cast&lt;uint32_from_hex&gt;( "0x4ad" );
uint32 material1 = lexical_cast&lt;uint32_from_hex&gt;( "4ad" );
uint32 material2 = lexical_cast&lt;uint32&gt;( "1197" );

int32 materialX = lexical_cast&lt;int32_from_hex&gt;( "0xfffefffe" );
int32 materialY = lexical_cast&lt;int32_from_hex&gt;( "fffefffe" );
// etc...
</code></pre>

(Found this page when I was looking for a less sucky way :-)

Cheers,
A.

blocks|key|1514881|text|Andy+Buchanan，就坚持使用C%2B%2B而言，我喜欢你的，但我有几个mod：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1514882|template+<typename+ElemT>
struct+HexTo+{
++++ElemT+value;
++++operator+ElemT()+const+{return+value;}
++++friend+std::istream&+operator>>(std::istream&+in,+HexTo&+out)+{
++++++++in+>>+std::hex+>>+out.value;
++++++++return+in;
++++}
};|code-block|syntax|javascript|1514883|使用方式如下|1514884|uint32_t+value+=+boost::lexical_cast<HexTo<uint32_t>+>("0x2a");|1514885|这样，您就不需要为每个int类型执行一次impl。|1514886|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Andy Buchanan, as far as sticking to C++ goes, I liked yours, but I have a few mods:

<pre><code>template &lt;typename ElemT&gt;
struct HexTo {
 ElemT value;
 operator ElemT() const {return value;}
 friend std::istream&amp; operator&gt;&gt;(std::istream&amp; in, HexTo&amp; out) {
 in &gt;&gt; std::hex &gt;&gt; out.value;
 return in;
 }
};
</code></pre>

Used like

<pre><code>uint32_t value = boost::lexical_cast&lt;HexTo&lt;uint32_t&gt; &gt;("0x2a");
</code></pre>

That way you don't need one impl per int type.

blocks|key|1300189|text|这对我很有效：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1300190|string+string_test+=+"80123456";
unsigned+long+x;
signed+long+val;

std::stringstream+ss;
ss+<<+std::hex+<<+string_test;
ss+>>+x;
//+ss+>>+val;++//+if+I+try+this+val+=+0
val+=+(signed+long)x;++//+However,+if+I+cast+the+unsigned+result+I+get+val+=+0x80123456+|code-block|syntax|javascript|1300191|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This worked for me: 

<pre><code>string string_test = "80123456";
unsigned long x;
signed long val;

std::stringstream ss;
ss &lt;&lt; std::hex &lt;&lt; string_test;
ss &gt;&gt; x;
// ss &gt;&gt; val; // if I try this val = 0
val = (signed long)x; // However, if I cast the unsigned result I get val = 0x80123456 
</code></pre>

blocks|key|1300269|text|下面是我在其他地方找到的一个简单有效的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1300270|string+hexString+=+"7FF";
int+hexNumber;
sscanf(hexString.c_str(),+"%25x",+&hexNumber);|code-block|syntax|javascript|1300271|请注意，您可能更喜欢使用无符号长整型/长整型来接收值。另请注意，c_str()函数只是将std::string转换为const+char*。|1300272|因此，如果您已经准备好const+char*，那么只需继续直接使用该变量名，如下所示，我还展示了无符号长变量对于较大十六进制数的用法。不要将其与使用const+char*而不是string的情况混淆|1300273|const+char+*hexString+=+"7FFEA5";+//Just+to+show+the+conversion+of+a+bigger+hex+number
unsigned+long+hexNumber;+//In+case+your+hex+number+is+going+to+be+sufficiently+big.
sscanf(hexString,+"%25x",+&hexNumber);|1300274|这可以很好地工作(如果您根据需要使用适当的数据类型)。|1300275|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Here's a simple and working method I found elsewhere:

<pre><code>string hexString = "7FF";
int hexNumber;
sscanf(hexString.c_str(), "%x", &amp;hexNumber);
</code></pre>

Please note that you might prefer using unsigned long integer/long integer, to receive the value.
Another note, the c_str() function just converts the std::string to const char* .

So if you have a const char* ready, just go ahead with using that variable name directly, as shown below [I am also showing the usage of the unsigned long variable for a larger hex number. Do not confuse it with the case of having const char* instead of string]:

<pre><code>const char *hexString = "7FFEA5"; //Just to show the conversion of a bigger hex number
unsigned long hexNumber; //In case your hex number is going to be sufficiently big.
sscanf(hexString, "%x", &amp;hexNumber);
</code></pre>

This works just perfectly fine (provided you use appropriate data types per your need).

blocks|key|1515089|text|尝尝这个。这个解决方案有点冒险。没有支票。字符串必须仅具有十六进制值，并且字符串长度必须与返回类型大小匹配。但不需要额外的报头。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1515090|char+hextob(char+ch)
{
++++if+(ch+>=+'0'+&&+ch+<=+'9')+return+ch+-+'0';
++++if+(ch+>=+'A'+&&+ch+<=+'F')+return+ch+-+'A'+%2B+10;
++++if+(ch+>=+'a'+&&+ch+<=+'f')+return+ch+-+'a'+%2B+10;
++++return+0;
}
template<typename+T>
T+hextot(char*+hex)
{
++++T+value+=+0;
++++for+(size_t+i+=+0;+i+<+sizeof(T)*2;+%2B%2Bi)
++++++++value+%7C=+hextob(hex[i])+<<+(8*sizeof(T)-4*(i%2B1));
++++return+value;
};|code-block|syntax|javascript|1515091|用法：|1515092|int+main()
{
++++char+str[4]+=+{'f','f','f','f'};
++++std::cout+<<+hextot<int16_t>(str)++<<+"\n";
}|1515093|注意:字符串的长度必须能被2整除|1515094|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Try this. This solution is a bit risky. There are no checks. The string must only have hex values and the string length must match the return type size. But no need for extra headers.

<pre><code>char hextob(char ch)
{
 if (ch &gt;= '0' &amp;&amp; ch &lt;= '9') return ch - '0';
 if (ch &gt;= 'A' &amp;&amp; ch &lt;= 'F') return ch - 'A' + 10;
 if (ch &gt;= 'a' &amp;&amp; ch &lt;= 'f') return ch - 'a' + 10;
 return 0;
}
template&lt;typename T&gt;
T hextot(char* hex)
{
 T value = 0;
 for (size_t i = 0; i &lt; sizeof(T)*2; ++i)
 value |= hextob(hex[i]) &lt;&lt; (8*sizeof(T)-4*(i+1));
 return value;
};
</code></pre>

Usage:

<pre><code>int main()
{
 char str[4] = {'f','f','f','f'};
 std::cout &lt;&lt; hextot&lt;int16_t&gt;(str) &lt;&lt; "\n";
}
</code></pre>

Note: the length of the string must be divisible by 2

blocks|key|1515155|text|例如，只需使用stoi/stol/stoll：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1515156|std::cout+<<+std::stol("fffefffe",+nullptr,+16)+<<+std::endl;|code-block|syntax|javascript|1515157|输出:+4294901758|1515158|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

just use stoi/stol/stoll
for example:
<pre><code>std::cout &lt;&lt; std::stol(&quot;fffefffe&quot;, nullptr, 16) &lt;&lt; std::endl;
</code></pre>
output: 4294901758

I want to convert a hex string to a 32 bit signed integer in C++. 

So, for example, I have the hex string "fffefffe". The binary representation of this is 11111111111111101111111111111110. The signed integer representation of this is: -65538. 

How do I do this conversion in C++? This also needs to work for non-negative numbers. For example, the hex string "0000000A", which is 00000000000000000000000000001010 in binary, and 10 in decimal.

C++ convert hex string to signed integer

我想在C++中将十六进制字符串转换为32位有符号整数。例如，我有一个十六进制字符串"fffefffe“。它的二进制表示是1111111111111010111111111111111111111110。它的带符号整数表示是：-65538。如何在C++中执行此转换？这也需要对非负数起作用。例如，十六进制字符串"00000...

问C++将十六进制字符串转换为有符号整数
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