我可以强制`const`通过引用（也就是`````````参数） [英] Can I force `const` to pass by reference (aka the missing `in` parameter)

问题描述

Delphi有：

var ：通过引用传递;参数是输入和输出。

out ：通过引用传递;参数只能输出。

const ：pass by ..... well it depends;参数只能输入。

in ： pass by reference;参数仅输入，不会更改没有in。

var : pass by reference; parameter is both input and output.
out : pass by reference; parameter is output only.
const: pass by ..... well it depends; parameter is input only.
in : pass by reference; parameter is input only and will not be changed there is no "in".

我不介意 没有勺子 ，但是我错过了 >;考虑以下代码，是否有更干净的方法？

I don't mind that there is no spoon, but I miss in; considering the following code, is there a cleaner way of doing this?

type TFastDiv = record 
strict private
  FBuffer: Int64;
  other fields
....

//Must be `var` because `const` would pass a Int64 by value
//                      |||
//                      VVV
function DivideFixedI32(var Buffer: Int64; x: integer): integer;
asm  
  mov  r9,rcx                   
  imul dword ptr[rcx]    // do stuff with the buffer
  ..
  mov     ecx, [r9+4]    // do other stuff with the rest of the buffer  

_{{将代码更改为 imul ecx; ...; shr r9,32; mov ecx，r9d 将允许通过值，但让我们假设代码不能更改。} / sub>}

_{{Changing the code to imul ecx;...;shr r9,32;mov ecx,r9d would allow pass by value, but let's assume the code must not be changed.}}

class operator TFastDiv.IntDivide(x:integer; const buffer:TFastDiv):integer;
begin
  Result:= DivideFixedI32(Int64((@buffer.FBuffer)^), abs(x)); <<-- Ugly
  if (x < 0) then Result:= - Result;
end;

DivideFixed 永远不会更改缓冲区。例程的全部要点是缓冲区是一个预先计算的值，不会更改。

DivideFixed will never change the buffer. The whole point of the routine is that buffer is a precalculated value that does not change.

在类运算符我将缓冲区声明为const，因为记录不能更改。

In the class operator I declare buffer as const, because the record must not change.

问题是：

如果我坚持声明缓冲区参数IntDivide 作为 const 是一种更干净的编码方式，或者我卡在pointer_to / points_to黑客

The question is:
If I insist on declaring the buffer parameter in IntDivide as const is there a cleaner way of coding or am I stuck in the pointer_to/points_to hack?

推荐答案

较新的编译器版本支持 [Ref] decorator： p>

Newer compiler versions support the [Ref] decorator:

procedure Foo(const [Ref] Arg1: Integer; [Ref] const Arg2: Byte);

从文档，其中强调 [Ref] 可以在之前或之后 const 关键字。

Example adapted from the documentation, which emphasises the [Ref] can go either before or after the const keyword.

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