在Delphi 2009中将TMemoryStream转换为’String’

发布时间：2020-12-15 05:21:47 所属栏目：大数据来源：网络整理

导读：我们在Delphi 2009之前有以下代码： span style="font: 10pt Courier New;"span class="pas1-reservedword"function/spanspan class="pas1-space" /spanspan class="pas1-identifier"MemoryStreamToString(M:/spanspan class="pas1-space" /spanspan class="

我们在Delphi 2009之前有以下代码：

<span style="font: 10pt Courier New;"><span class="pas1-reservedword">function</span><span class="pas1-space"> </span><span class="pas1-identifier">MemoryStreamToString(M:</span><span class="pas1-space"> </span><span class="pas1-identifier">TMemoryStream):</span><span class="pas1-space"> </span><span class="pas1-reservedword">String</span><span class="pas1-symbol">;
</span><span class="pas1-reservedword">var
</span><span class="pas1-space">  </span><span class="pas1-identifier">NewCapacity:</span><span class="pas1-space"> </span><span class="pas1-identifier">Longint;
</span><span class="pas1-reservedword">begin
</span><span class="pas1-space">  </span><span class="pas1-reservedword">if</span><span class="pas1-space"> </span><span class="pas1-symbol">(M.Size</span><span class="pas1-space"> </span><span class="pas1-symbol">=</span><span class="pas1-space"> </span><span class="pas1-number">0)</span><span class="pas1-space"> </span><span class="pas1-reservedword">or</span><span class="pas1-space"> </span><span class="pas1-symbol">(M.Memory</span><span class="pas1-space"> </span><span class="pas1-symbol">=</span><span class="pas1-space"> </span><span class="pas1-reservedword">nil</span><span class="pas1-symbol">)</span><span class="pas1-space"> </span><span class="pas1-reservedword">then
</span><span class="pas1-space">    </span><span class="pas1-identifier">Result:=</span><span class="pas1-space"> </span><span class="pas1-string">''
</span><span class="pas1-space">  </span><span class="pas1-reservedword">else
</span><span class="pas1-space">  </span><span class="pas1-reservedword">begin
</span><span class="pas1-space">    </span><span class="pas1-reservedword">if</span><span class="pas1-space"> </span><span class="pas1-identifier">TMemoryStreamProtected(M).Capacity</span><span class="pas1-space"> </span><span class="pas1-symbol">=</span><span class="pas1-space"> </span><span class="pas1-identifier">M.Size</span><span class="pas1-space"> </span><span class="pas1-reservedword">then
</span><span class="pas1-space">    </span><span class="pas1-reservedword">begin
</span><span class="pas1-space">      </span><span class="pas1-identifier">NewCapacity:=</span><span class="pas1-space"> </span><span class="pas1-identifier">M.Size+1;
</span><span class="pas1-space">      </span><span class="pas1-identifier">TMemoryStreamProtected(M).Realloc(NewCapacity);
</span><span class="pas1-space">    </span><span class="pas1-reservedword">end</span><span class="pas1-symbol">;
</span><span class="pas1-space">    </span><span class="pas1-identifier">NullString(M.Memory^)[M.Size]:=</span><span class="pas1-space"> </span><span class="pas1-character">#0;
</span><span class="pas1-space">    </span><span class="pas1-identifier">Result:=</span><span class="pas1-space"> </span><span class="pas1-identifier">StrPas(M.Memory);
</span><span class="pas1-space">  </span><span class="pas1-reservedword">end</span><span class="pas1-symbol">;
</span><span class="pas1-reservedword">end</span><span class="pas1-symbol">;
</span></span>

我们如何转换这个代码以支持Unicode现在与Delphi 2009？

解决方法

你的代码是不必要的复杂，即使对于老版本的Delphi版本。为什么获取字符串版本的流强迫流的内存被重新分配？

function MemoryStreamToString(M: TMemoryStream): string;
begin
  SetString(Result,PChar(M.Memory),M.Size div SizeOf(Char));
end;

它适用于所有的Delphi版本，而不仅仅是Delphi 2009。当流是空的没有任何特殊情况下工作。 SetString是一个不起眼的功能。

如果您的流的内容没有更改为Unicode，切换到Delphi 2009，那么您应该使用此功能代替：

function MemoryStreamToString(M: TMemoryStream): AnsiString;
begin
  SetString(Result,PAnsiChar(M.Memory),M.Size);
end;

这相当于你的原始代码，但跳过特殊情况。

（编辑：李大同）

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