delphi - Copy 有 ANSI 版本吗？

Question

在Delphi XE下，Copy有ANSI版本吗？我经常使用 Copy 来复制 ANSI 字符串的片段。

Answer 1

祭坛Copy Delphi 中的函数是内部函数，这意味着它由编译器而不是运行时库处理。根据传递给该函数的参数，调用LStrCopy或UStrCopy内部函数

检查此示例:

{$APPTYPE CONSOLE}

uses
  SysUtils;
Var
   s : AnsiString;
   u : string;
begin
  try
   s:='this is a ansi string';
   s:= Copy(s,1,5);
   Writeln(s);
   u:='this is a unicode string';
   u:= Copy(u,1,5);
   Writeln(u);
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
  Readln;
end.

现在检查汇编代码

Project91.dpr.12: s:='this is a ansi string';
004111DC B8787E4100       mov eax,$00417e78
004111E1 BA04134100       mov edx,$00411304
004111E6 E8314FFFFF       call @LStrAsg
Project91.dpr.13: s:= Copy(s,1,5);
004111EB 68787E4100       push $00417e78
004111F0 B905000000       mov ecx,$00000005
004111F5 BA01000000       mov edx,$00000001
004111FA A1787E4100       mov eax,[$00417e78]
004111FF E8A050FFFF       call @LStrCopy //call the ansi version of copy
Project91.dpr.14: Writeln(s);
00411204 A1EC2C4100       mov eax,[$00412cec]
00411209 8B15787E4100     mov edx,[$00417e78]
0041120F E84033FFFF       call @Write0LString
00411214 E8DF33FFFF       call @WriteLn
00411219 E8D22AFFFF       call @_IOTest
Project91.dpr.15: u:='this is a unicode string';
0041121E B87C7E4100       mov eax,$00417e7c
00411223 BA28134100       mov edx,$00411328
00411228 E8534EFFFF       call @UStrAsg
Project91.dpr.16: u:= Copy(u,1,5);
0041122D 687C7E4100       push $00417e7c
00411232 B905000000       mov ecx,$00000005
00411237 BA01000000       mov edx,$00000001
0041123C A17C7E4100       mov eax,[$00417e7c]
00411241 E8C654FFFF       call @UStrCopy //call the unicode version of copy
Project91.dpr.17: Writeln(u);
00411246 A1EC2C4100       mov eax,[$00412cec]