SysUtils.StrCopy、SysUtils.StrECopy

StrCopy 和 StrECopy 都是复制源 PChar 串到目标 PChar 串, 只是返回值不同;
StrCopy 返回结果的首地址, StrECopy 返回结果的尾(#0)地址.

1unit Unit1;
2
3interface
4
5uses
6  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
7  Dialogs, StdCtrls;
8
9type
10  TForm1 = class(TForm)
11    Button1: TButton;
12    Button2: TButton;
13    Button3: TButton;
14    Button4: TButton;
15    procedure Button1Click(Sender: TObject);
16    procedure Button2Click(Sender: TObject);
17    procedure Button3Click(Sender: TObject);
18    procedure Button4Click(Sender: TObject);
19  end;
20
21var
22  Form1: TForm1;
23
24implementation
25
26{$R *.dfm}
27
28//一般用法, 看不出 StrCopy 与 StrECopy 的区别
29procedure TForm1.Button1Click(Sender: TObject);
30var
31  arr: array[0..3] of Char; {假如 PChar 长度是 3, 这里数组要大出一个, PChar 最后还有一个 #0}
32begin
33  StrCopy(arr, 'ABC');
34  ShowMessage(arr);    {ABC}
35  
36  StrCopy(arr, '123');
37  ShowMessage(arr);    {123}
38
39  StrECopy(arr, 'ABC');
40  ShowMessage(arr);    {ABC}
41  
42  StrECopy(arr, '123');
43  ShowMessage(arr);    {123}
44end;
45
46//测试 StrCopy 及其返回值:
47procedure TForm1.Button2Click(Sender: TObject);
48var
49  p1,p2,p3,p: PChar;
50begin
51  p1 := '123456789';
52  p2 := 'ABC';
53
54  p3 := PChar(StringOfChar(#0, 9)); {这里用 StringOfChar 代替了 GetMem}
55  
56  p := StrCopy(p3, p1);
57  ShowMessageFmt('%s, %s', [p3, p]); {123456789, 123456789}
58
59  p := StrCopy(p3, p2);
60  ShowMessageFmt('%s, %s', [p3, p]); {ABC, ABC}
61
62  ShowMessageFmt('%s, %s', [p3+4, p+4]); {56789, 56789}
63end;
64
65//测试 StrECopy 及其返回值:
66procedure TForm1.Button3Click(Sender: TObject);
67var
68  p1,p2,p3,p: PChar;
69begin
70  p1 := '123456789';
71  p2 := 'ABC';
72
73  p3 := PChar(StringOfChar(#0, 9)); {这里用 StringOfChar 代替了 GetMem}
74  
75  p := StrECopy(p3, p1);
76  ShowMessageFmt('%s, %s', [p3, p]); {123456789, }
77
78  p := StrECopy(p3, p2);
79  ShowMessageFmt('%s, %s', [p3, p+1]); {ABC, 56789}
80end;
81
82
83//可以巧妙利用 StrECopy 的返回值:
84procedure TForm1.Button4Click(Sender: TObject);
85var
86  p: PChar;
87begin
88  GetMem(p, 10);
89
90  StrECopy(StrECopy(p,'12345'), '67890');
91  ShowMessage(p); {1234567890}
92  
93  FreeMem(p);
94end;
95
96end.
97
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SysUtils 单元下的公用函数目录