从C ++到Delphi的转换（简单） [英] Conversion from C++ to Delphi (simple)

问题描述

我在C ++中有一个函数，我试图在delphi中复制：

I have a function in C++ that I am attempting to replicate in delphi:

typedef double  ANNcoord;        // coordinate data type
typedef ANNcoord* ANNpoint;      // a point     
typedef ANNpoint* ANNpointArray; // an array of points 

bool readPt(istream &in, ANNpoint p) // read point (false on EOF)
{
    for (int i = 0; i < dim; i++) {
        if(!(in >> p[i])) return false;
    }
    return true;
}

在Delphi中，我相信我已经正确地声明了数据类型。可能是错误的）：

In Delphi I believe that I have correctly declared the data types.. (I could be wrong):

type
  IPtr =  ^IStream; // pointer to Istream
  ANNcoord = Double;
  ANNpoint = ^ANNcoord;

function readPt(inpt: IPtr; p: ANNpoint): boolean;
var
  i: integer;
begin

  for i := 0 to dim do
  begin

  end;

end; 

但我不知道如何模仿C ++函数的行为（可能是因为我不明白位移算子）。

But I cannot figure out how to mimic the behavior in the C++ function (probably because I do not understand the bitshift operator).

此外，我需要最终找出如何将一组点从Zeos TZQuery 对象传输到相同的数据类型 - 所以如果任何人有一些任何输入，我会真的很感激。

Also, I need to eventually figure out how to transfer the set of points from a Zeos TZQuery object to the same datatype - so if anyone has some any input on that I would really appreciate it.

推荐答案

尝试：

type
  ANNcoord = Double;
  ANNpoint = ^ANNcoord;

function readPt(inStr: TStream; p: ANNpoint): boolean;
var
  Size: Integer; // number of bytes to read
begin
  Size := SizeOf(ANNcoord) * dim; 
  Result := inStr.Read(p^, Size) = Size;
end;

不需要分别阅读每个ANNcoord。注意，istream是一个流类，而不是一个IStream接口，在C + +。 Delphi的等价是TStream。代码假定流被打开以进行读取（使用合适的参数创建Create-d），并且当前流指针指向一个数字（dim）的ANNcoords，就像C ++代码一样。

There is no need to read each ANNcoord separately. Note that istream is a stream class, not an IStream interface, in C++. Delphi's equivalent is TStream. The code assumes the stream is opened for reading (Create-d with the proper parameters) and the current stream pointer points to a number (dim) of ANNcoords, just like the C++ code does.

FWIW 在>> p [i] 从输入流中读取到<$ c $>中的 ANNcoord c> p [i] ，将 p 解释为指向数组 ANNcoords

FWIW in >> p[i] reads an ANNcoord from the input stream in to p[i], interpreting p as a pointer to an array of ANNcoords.

Rob Kennedy指出， myDouble 从输入流读取一个double，但是流被解释为 流，而不是二进制，即：

As Rob Kennedy pointed out, in >> myDouble reads a double from the input stream, but the stream is interpreted as text stream, not binary, i.e. it looks like:

1.345 3.56845 2.452345
3.234 5.141 3.512
7.81234 2.4123 514.1234

etc...   

AFAIK在Delphi中没有类似的方法或操作。为此目的只有 System.Read 和 System.Readln 。显然， Peter Below 曾写过一个单元StreamIO ，可以使用 System.Read 和 System.Readln 。我只能找到一个版本，在新闻组帖子。

There is, AFAIK, no equivalent method or operation in Delphi for streams. There is only System.Read and System.Readln for this purpose. Apparently Peter Below once wrote a unit StreamIO which makes it possible to use System.Read and System.Readln for streams. I could only find one version, in a newsgroup post.

对于可以从其文本表示中读取双精度，整数，单数等的流，编写一个包装器可能是有意义的。我还没有看到。

It would probably make sense to write a wrapper for streams that can read doubles, integers, singles, etc. from their text representations. I haven't seen one yet.

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