C# 指针和固定大小的缓冲区只能在不安全的上下文中使用
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原文地址: http://stackoverflow.com/questions/10269748/
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Pointers and fixed size buffers may only be used in an unsafe context
提问by user1277070
I have 2 functions within a class and getting error on the call for ParseBits() function i.e. "int num_elements = ParseBits(bits, buffer);" because of the "buffer" arguement I am passing "public int ParseBits(string bits, int* buffer)":
我在一个类中有 2 个函数，并且在调用 ParseBits() 函数时出现错误，即“ int num_elements = ParseBits(bits, buffer);”，因为我正在传递“ public int ParseBits(string bits, int* buffer)”的“缓冲区”争论：
Function 1:
功能一：
public float AssignFitness(string bits, int target_value)
{
//holds decimal values of gene sequence
int[] buffer = new int[(VM_Placement.AlgorithmParameters.chromo_length / VM_Placement.AlgorithmParameters.gene_length)];
int num_elements = ParseBits(bits, buffer);
// ok, we have a buffer filled with valid values of: operator - number - operator - number..
// now we calculate what this represents.
float result = 0.0f;
for (int i=0; i < num_elements-1; i+=2)
{
switch (buffer[i])
{
case 10:
result += buffer[i+1];
break;
case 11:
result -= buffer[i+1];
break;
case 12:
result *= buffer[i+1];
break;
case 13:
result /= buffer[i+1];
break;
}//end switch
}
// Now we calculate the fitness. First check to see if a solution has been found
// and assign an arbitarily high fitness score if this is so.
if (result == (float)target_value)
return 999.0f;
else
return 1/(float)fabs((double)(target_value - result));
// return result;
}
Function 2:
功能二：
public int ParseBits(string bits, int* buffer)
{
//counter for buffer position
int cBuff = 0;
// step through bits a gene at a time until end and store decimal values
// of valid operators and numbers. Don't forget we are looking for operator -
// number - operator - number and so on... We ignore the unused genes 1111
// and 1110
//flag to determine if we are looking for an operator or a number
bool bOperator = true;
//storage for decimal value of currently tested gene
int this_gene = 0;
for (int i = 0; i < VM_Placement.AlgorithmParameters.chromo_length; i += VM_Placement.AlgorithmParameters.gene_length)
{
//convert the current gene to decimal
this_gene = BinToDec(bits.Substring(i, VM_Placement.AlgorithmParameters.gene_length));
//find a gene which represents an operator
if (bOperator)
{
if ((this_gene < 10) || (this_gene > 13))
continue;
else
{
bOperator = false;
buffer[cBuff++] = this_gene;
continue;
}
}
//find a gene which represents a number
else
{
if (this_gene > 9)
continue;
else
{
bOperator = true;
buffer[cBuff++] = this_gene;
continue;
}
}
}//next gene
// now we have to run through buffer to see if a possible divide by zero
// is included and delete it. (ie a '/' followed by a '0'). We take an easy
// way out here and just change the '/' to a '+'. This will not effect the
// evolution of the solution
for (int i = 0; i < cBuff; i++)
{
if ((buffer[i] == 13) && (buffer[i + 1] == 0))
buffer[i] = 10;
}
return cBuff;
}
I am getting 2 errors for this functions on the highlighted lines:
我在突出显示的行上收到此函数的 2 个错误：
Error 1: The best overloaded method match for 'VM_Placement.Program.ParseBits(string, int*)' has some invalid arguments
Error 2: Pointers and fixed size buffers may only be used in an unsafe context
采纳答案by Iridium
Perhaps I've missed it, but you don't appear to be doing anything that actually requires the use of a int*. Why not simply pass it an int array and change the ParseBits function signature to:
也许我错过了它，但您似乎没有做任何实际上需要使用int*. 为什么不简单地传递一个 int 数组并将 ParseBits 函数签名更改为：
public int ParseBits(string bits, int[]buffer)
public int ParseBits(string bits, int[]buffer)
and remove the unsafe{ ... }blocks altogether.
并unsafe{ ... }完全删除块。
回答by Tony The Lion
You need to enclose your function using raw pointers in an unsafeblock.
您需要使用unsafe块中的原始指针将您的函数括起来。
unsafe
{
//your code
}
回答by MD-7
I had the same problem, but it wasn't solved by any of the other answers up here. I kept getting different errors.
我遇到了同样的问题，但这里的任何其他答案都没有解决。我不断收到不同的错误。
Whatever functions use unsafe code simply need to be declared with the "unsafe" keyword.
For example:
任何使用不安全代码的函数都只需要使用“unsafe”关键字进行声明。
例如：
static unsafe void myFunction(int* myInt, float* myFloat)
{
// Function definition
}
Personally, I was trying to do this when making a wrapper class.
For those interested, it ended up looking something like this:
就个人而言，我在制作包装类时试图这样做。
对于那些感兴趣的人，它最终看起来像这样：
using System.Runtime.InteropServices;
namespace myNamespace
{
public class myClass
{
[DllImport("myLib.so", EntryPoint = "myFunction")]
public static extern unsafe void myFunction(float* var1, float* var2);
}
}
Theres a lot of great information in the MSDN "Unsafe Code Tutorial":
https://msdn.microsoft.com/en-us/library/aa288474(v=vs.71).aspx
MSDN“不安全代码教程”中有很多很棒的信息：https: //msdn.microsoft.com/en-us/library/aa288474(v=vs.71).aspx
It's probably worth a read, I found it quite useful.
它可能值得一读，我发现它非常有用。
