如何使用EncdDec库编码字符串 [英] How to encode strings with EncdDec library

问题描述

我有这个基本的代码，应该编码一个字符串，然后把它拿回来。但是，解码的文本是垃圾。

  procedure TForm5.Button2Click（Sender：TObject）; 
 VAR s1，s2，s3：String; 
 i：整数; 
 begin 
 for i：= 1 to 200 
 DO s1：= s1 + char（Random（255））; 
 
 s1：= EncdDecd.EncodeString（s1）; 
 s3：= EncdDecd.DecodeString（s2）; 
 
如果s1 = s3 
那么Caption：='Equal'
 else Caption：='不等于' 
结束
  

---

更新： br>
如果我做char（Random（128））而不是255，它可以工作

解决方案

问题是这里，在 Soap.EncdDecd 单位：

 函数EncodeString（const输入：string）：string; 
 var 
 InStr，OutStr：TStringStream; 
 begin 
 InStr：= TStringStream.Create（Input）; 
 try 
 OutStr：= TStringStream.Create（''）; 
 try 
 EncodeStream（InStr，OutStr）; 
结果：= OutStr.DataString; 
 finally 
 OutStr.Free; 
结束
 finally 
 InStr.Free; 
结束
结束
  

此代码尚未更新为Unicode。问题在于使用 TStringStream <？c $ c> InStr 而不指定编码。没有指定编码，ANSI用于对字节数组进行解码。因此，只有本地ANSI代码页中的字符才能正确解码。

在 DecodeString 中的另一个方向也犯了同样的错误。

您可以通过创建指定完整的Unicode编码的变体来解决这个问题。例如：

  function EncodeString（const Input：string）：string; 
 var 
 InStr，OutStr：TStringStream; 
 begin 
 InStr：= TStringStream.Create（Input，TEncoding.UTF8）; 
 try 
 OutStr：= TStringStream.Create（''）; 
 try 
 EncodeStream（InStr，OutStr）; 
结果：= OutStr.DataString; 
 finally 
 OutStr.Free; 
结束
 finally 
 InStr.Free; 
结束
结束
 
函数DecodeString（const Input：string）：string; 
 var 
 InStr，OutStr：TStringStream; 
 begin 
 InStr：= TStringStream.Create（Input）; 
 try 
 OutStr：= TStringStream.Create（''，TEncoding.UTF8）; 
 try 
 DecodeStream（InStr，OutStr）; 
结果：= OutStr.DataString; 
 finally 
 OutStr.Free; 
结束
 finally 
 InStr.Free; 
结束
结束
  

只要是完整的Unicode编码，您指定的编码无关紧要，而您在双向使用相同的编码！

应该鼓励Embarcadero对其代码进行更改。

此程序表明该修复工作正常工作：

  {$ APPTYPE CONSOLE} 
 
使用
 System.SysUtils，System.Classes，Soap.EncdDecd; 
 
函数EncodeString（const Input：string）：string; 
 var 
 InStr，OutStr：TStringStream; 
 begin 
 InStr：= TStringStream.Create（Input，TEncoding.UTF8）; 
 try 
 OutStr：= TStringStream.Create（''）; 
 try 
 EncodeStream（InStr，OutStr）; 
结果：= OutStr.DataString; 
 finally 
 OutStr.Free; 
结束
 finally 
 InStr.Free; 
结束
结束
 
函数DecodeString（const Input：string）：string; 
 var 
 InStr，OutStr：TStringStream; 
 begin 
 InStr：= TStringStream.Create（Input）; 
 try 
 OutStr：= TStringStream.Create（''，TEncoding.UTF8）; 
 try 
 DecodeStream（InStr，OutStr）; 
结果：= OutStr.DataString; 
 finally 
 OutStr.Free; 
结束
 finally 
 InStr.Free; 
结束
结束
 
 const 
 N = 256; 
 
 var 
 i：整数; 
 s1，s2：string; 
 
 begin 
 SetLength（s1，N）; 
 for i：= 1 to N do 
 s1 [i]：= Chr（i-1）; 
 
 s2：= Soap.EncdDecd.EncodeString（s1）; 
 s2：= Soap.EncdDecd.DecodeString（s2）; 
 Writeln（s1 = s2）; 
 
 s2：= EncodeString（s1）; 
 s2：= DecodeString（s2）; 
 Writeln（s1 = s2）; 
结束。 
  

输出：

 
 FALSE 
 TRUE 
 

I have this basic code that should encode a string and then get it back. However, the decoded text is garbage.

procedure TForm5.Button2Click(Sender: TObject);
VAR s1, s2, s3: String;
    i: Integer;
begin
 for i:= 1 to 200
  DO s1:= s1+ char(Random(255));

 s1:= EncdDecd.EncodeString(s1);
 s3:= EncdDecd.DecodeString(s2);

 if s1= s3
 then Caption:= 'Equal'
 else Caption:= 'Not equal';
end;

---

Update:
It works if I do char(Random(128)) instead of 255!

解决方案

The problem is here, in the Soap.EncdDecd unit:

function EncodeString(const Input: string): string;
var
  InStr, OutStr: TStringStream;
begin
  InStr := TStringStream.Create(Input);
  try
    OutStr := TStringStream.Create('');
    try
      EncodeStream(InStr, OutStr);
      Result := OutStr.DataString;
    finally
      OutStr.Free;
    end;
  finally
    InStr.Free;
  end;
end;

This code has not been updated for Unicode. The use of TStringStream for InStr without specifying an encoding is the problem. With no encoding specified, ANSI is used to decode to a byte array. And so only characters in the local ANSI code page are decoded correctly.

The same mistake is made in the other direction in DecodeString.

You can fix this readily enough by creating variants that specify a full Unicode encoding. For example:

function EncodeString(const Input: string): string;
var
  InStr, OutStr: TStringStream;
begin
  InStr := TStringStream.Create(Input, TEncoding.UTF8);
  try
    OutStr := TStringStream.Create('');
    try
      EncodeStream(InStr, OutStr);
      Result := OutStr.DataString;
    finally
      OutStr.Free;
    end;
  finally
    InStr.Free;
  end;
end;

function DecodeString(const Input: string): string;
var
  InStr, OutStr: TStringStream;
begin
  InStr := TStringStream.Create(Input);
  try
    OutStr := TStringStream.Create('', TEncoding.UTF8);
    try
      DecodeStream(InStr, OutStr);
      Result := OutStr.DataString;
    finally
      OutStr.Free;
    end;
  finally
    InStr.Free;
  end;
end;

It doesn't matter which encoding you specify so long as it is a full Unicode encoding, and you use the same encoding in both directions!

Clearly Embarcadero should be encouraged to make this change to their code.

This program demonstrates that the fix works:

{$APPTYPE CONSOLE}

uses
  System.SysUtils, System.Classes, Soap.EncdDecd;

function EncodeString(const Input: string): string;
var
  InStr, OutStr: TStringStream;
begin
  InStr := TStringStream.Create(Input, TEncoding.UTF8);
  try
    OutStr := TStringStream.Create('');
    try
      EncodeStream(InStr, OutStr);
      Result := OutStr.DataString;
    finally
      OutStr.Free;
    end;
  finally
    InStr.Free;
  end;
end;

function DecodeString(const Input: string): string;
var
  InStr, OutStr: TStringStream;
begin
  InStr := TStringStream.Create(Input);
  try
    OutStr := TStringStream.Create('', TEncoding.UTF8);
    try
      DecodeStream(InStr, OutStr);
      Result := OutStr.DataString;
    finally
      OutStr.Free;
    end;
  finally
    InStr.Free;
  end;
end;

const
  N = 256;

var
  i: Integer;
  s1, s2: string;

begin
  SetLength(s1, N);
  for i := 1 to N do
    s1[i] := Chr(i-1);

  s2 := Soap.EncdDecd.EncodeString(s1);
  s2 := Soap.EncdDecd.DecodeString(s2);
  Writeln(s1=s2);

  s2 := EncodeString(s1);
  s2 := DecodeString(s2);
  Writeln(s1=s2);
end.

Output:

FALSE
TRUE

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