C ++我的字节数组到int以及从int到字节数组转换器的问题是什么？

Question

i know there is a lot of questions about it, but most of them uses fixed sized converters, like 4 bytes to int and etc.
I have an templated functions to convert bytes to numbers and etc, but have a problem :D

template <typename IntegerType>
     static IntegerType bitsToInt(BYTE* bits, bool little_endian = true)
     {
         IntegerType result = 0;

         if (little_endian)
             for (int n = sizeof(IntegerType); n >= 0; n--)
                 result = (result << 8) + bits[n];
         else
             for (int n = 0; n < sizeof(IntegerType); n++)
                 result = (result << 8) + bits[n];

         return result;
     }

     template <typename IntegerType>
     static BYTE *intToBits(IntegerType value)
     {
         BYTE result[sizeof(IntegerType)] = { 0 };

         for (int i = 0; i < sizeof(IntegerType); i++)
             result = (value >> (i * 8));

         return result;
     }

     static void TestConverters()
     {
         short int test = 12345;

         BYTE *bytes = intToBits<short int>(test);

         short int test2 = bitsToInt<short int>(bytes); //<--i getting here different number, then 12345, so something goes wrong at conversion
     }

So, could anyone say what's wrong here?

Answer 1

static BYTE *intToBits(IntegerType value)

这将返回一个指向本地分配的内存的指针，一旦函数返回，该指针将超出范围，并且不再有效。

Answer 2

There are several bugs in the function intsToBits 1. Insted of

result = (value >> (i * 8)); 

there should be

result[i] = 0xFF & (value >> (i * 8)); 

More serious one you return the pointer to the memory on the stack, which is generally incorrect after you exit the function. You shoul allocate the memory with the new operator.

BYTE * result = new BYTE[sizeof(IntegerType)];

The you'll be needed to release the memory

Answer 3

这可能不是您唯一的问题，但是intToBits返回了一个指向局部变量的指针，该变量是未定义的行为。

Answer 4

尝试使用new分配返回的字节数组