如何在 C++ 中将 char* 转换为 unsigned short
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How to convert char* to unsigned short in C++
提问by Elpezmuerto
I have a char* namewhich is a string representation of the short I want, such as "15" and need to output this as unsigned short unitIdto a binary file. This cast must also be cross-platform compatible.
我有一个char* name它是我想要的短的字符串表示形式，例如“15”，并且需要将其输出为unsigned short unitId二进制文件。此演员表还必须是跨平台兼容的。
Is this the correct cast: unitId = unsigned short(temp);
这是正确的演员阵容： unitId = unsigned short(temp);
Please note that I am at an beginner level in understanding binary.
请注意，我在理解二进制方面处于初级水平。
回答by JSB????
I assume that your char* namecontains a stringrepresentation of the short that you want, i.e. "15".
我假设您char* name包含您想要的短的字符串表示形式，即"15".
Do notcast a char*directly to a non-pointer type. Casts in C don't actually change the data at all (with a few exceptions)--they just inform the compiler that you want to treat one type into another type. If you cast a char*to an unsigned short, you'll be taking the value of the pointer(which has nothing to do with the contents), chopping off everything that doesn't fit into a short, and then throwing away the rest. This is absolutely not what you want.
千万不能一投char*直接到非指针类型。C 中的强制转换实际上根本不更改数据（有一些例外）——它们只是通知编译器您想将一种类型处理为另一种类型。如果您将 a 转换char*为 an unsigned short，您将获取指针的值（与内容无关），切掉不适合 a 的所有内容short，然后丢弃其余部分。这绝对不是你想要的。
Instead use the std::strtoulfunction, which parses a string and gives you back the equivalent number:
而是使用std::strtoul解析字符串并返回等效数字的函数：
unsigned short number = (unsigned short) strtoul(name, NULL, 0);
(You still need to use a cast, because strtoulreturns an unsigned long. This cast is between two different integer types, however, and so is valid. The worst that can happen is that the number inside nameis too big to fit into a short--a situation that you can check for elsewhere.)
（您仍然需要使用强制转换，因为strtoul返回一个unsigned long。但是，此强制转换介于两种不同的整数类型之间，因此是有效的。可能发生的最坏情况是里面的数字name太大而无法适应short--a 情况您可以在其他地方检查。）
回答by fredoverflow
#include <boost/lexical_cast.hpp>
unitId = boost::lexical_cast<unsigned short>(temp);
回答by Amardeep AC9MF
To convert a string to binary in C++ you can use stringstream.
要将字符串转换为 C++ 中的二进制，您可以使用 stringstream。
#include <sstream>
. . .
int somefunction()
{
unsigned short num;
char *name = "123";
std::stringstream ss(name);
ss >> num;
if (ss.fail() == false)
{
// You can write out the binary value of num. Since you mention
// cross platform in your question, be sure to enforce a byte order.
}
}
回答by Chris Card
that cast will give you (a truncated) integer version of the pointer, assuming temp is also a char*. This is almost certainly not what you want (and the syntax is wrong too). Take a look at the function atoi, it may be what you need, e.g. unitId = (unsigned short)(atoi(temp)); Note that this assumes that (a) temp is pointing to a string of digits and (b) the digits represent a number that can fit into an unsigned short
该转换将为您提供（截断的）整数版本的指针，假设 temp 也是一个 char*。这几乎肯定不是你想要的（而且语法也是错误的）。看看函数atoi，它可能是你需要的，例如unitId = (unsigned short)(atoi(temp)); 请注意，这假设 (a) temp 指向一串数字并且 (b) 数字代表一个可以放入无符号短整型的数字
回答by Tim Schaeffer
Is the pointernamethe id, or the string of chars pointed to by name? That is if namecontains "1234", do you need to output 1234to the file? I will assume this is the case, since the other case, which you would do with unitId = unsigned short(name), is certainly wrong.
是指针name的ID，或者指向字符的字符串name？也就是说如果namecontains "1234"，是否需要输出1234到文件中？我会假设是这种情况，因为您将使用的另一种情况unitId = unsigned short(name)肯定是错误的。
What you want then is the strtoul()function.
那么你想要的是strtoul()功能。
char * endp
unitId = (unsigned short)strtoul(name, &endp, 0);
if (endp == name) {
/* The conversion failed. The string pointed to by name does not look like a number. */
}
Be careful about writing binary values to a file; the result of doing the obvious thing may work now but will likely not be portable.
将二进制值写入文件时要小心；做显而易见的事情的结果现在可能会奏效，但可能无法移植。
回答by Nick Smith
If you have a string (char* in C) representation of a number you must use the appropriate function to convert that string to the numeric value it represents.
如果您有一个数字的字符串（C 中的 char*）表示，您必须使用适当的函数将该字符串转换为它所表示的数值。
There are several functions for doing this. They are documented here: http://www.cplusplus.com/reference/clibrary/cstdlib
有几个函数可以做到这一点。它们记录在此处：http: //www.cplusplus.com/reference/clibrary/cstdlib
