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delphi 字符串查找替换函数
山炮   ·  2021.0423 14:17:49
Stat:445v. 0r. 0u. 0d. 0f 
#0. (Normal)

1.       提取字符串中指定子字符串前的字符串

Function Before( Src:string ; S:string ): string ;
  Var
    F: Word ;
  begin
    F:= POS(Src,S) ;
    if F=0 then
      Before := S
     else
      Before := COPY(S,1,F-1) ;
  end ;

eg: Before('123','helloworld_123')  返回结果:helloworld_

2.       提取字符串中指定子字符串后的字符串

function After(Src: string; S: string):string;
  var
    F: Word;
  begin
    F:= Pos(Src, S);
    if F = 0 then
      After:= ''
    else
      After:= Copy(S, F+Length(Src), Length(S));
  end;

3.       Delphi 替换函数

procedure Replace(var s:string;const SourceChar:pchar;const RChar:pchar);
  //第一个参数是原串,第二个是模式串,第三个是替换串
  var
    ta,i,j:integer;
    m,n,pn,sn:integer;
    SLen,SCLen,RCLen:integer;//SLen表示原串的长度,SCLen表示模式传的长度,RCLen表示替换串的长度
    IsSame:integer;
    newp:array of char;//用来保存替换后的字符数组
  begin
    SLen:=strlen(pchar(s));SCLen:=strlen(SourceChar);RCLen:=strlen(RChar);
    j:=pos(string(SourceChar),s);
    s:=s+chr(0);ta:=0;i:=j;
    while s[i]<>chr(0) do //这个循环用ta统计模式串在原串中出现的次数
    begin
      n:=0;IsSame:=1;
    for m:=i to i+SCLen-1 do
      begin
        if m>SLen then begin
          IsSame:=0;break;
        end;
        if s[m]<>sourceChar[n] then begin
          IsSame:=0;break;
        end;
        n:=n+1;
      end;
      if IsSame=1 then begin
        ta:=ta+1;i:=m;
      end
      else
        i:=i+1;
    end;
    if j>0 then
    begin
      pn:=0;sn:=1;
      setlength(newp,SLen-ta*SCLen+ta*RCLen+1);//分配newp的长度,+1表示后面还有一个#0结束符
      while s[sn]<>chr(0) do //主要循环,开始替换
      begin
        n:=0;IsSame:=1;
        for m:=sn to sn+SCLen-1 do //比较子串是否和模式串相同
        begin
          if m>SLen then begin IsSame:=0;break; end;
          if s[m]<>sourceChar[n] then begin IsSame:=0;break; end;
          n:=n+1;
        end;
        if IsSame=1 then//相同
        begin
          for m:=0 to RCLen-1 do
          begin
            newp[pn]:=RChar[m];pn:=pn+1;
          end;
          sn:=sn+SCLen;
        end
        else
        begin //不同
          newp[pn]:=s[sn];
          pn:=pn+1;sn:=sn+1;
        end;
      end;
      newp[pn]:=#0;
      s:=string(newp); //重置s,替换完成!
    end;
  end;

4.       Delphi StringReplace() 替换字符串的用法

str:= '{"UserName":"helloworld","UserPass":"helloworld_123","UserEmail":"[email protected]"}';
  str:= StringReplace(str,'"','"',[rfReplaceAll]);
  StringReplace(源字符串,'被替换字符','替换后字符',[rfReplaceAll]);

5.       查找字符串中指定字符及字符串最后一次出现的位置

function RightPosEx(const Substr,S: string): Integer;
  var
    iPos: Integer;
    TmpStr: string;
    i,j,len: Integer;
    PCharS,PCharSub: PChar;
  begin
    PCharS:=PChar(s); //将字符串转化为PChar格式 
    PCharSub:=PChar(Substr);
    Result:=0;
    len:=length(Substr);
    for i:=0 to length(S)-1 do begin
      for j:=0 to len-1 do begin
        if PCharS[i+j]<>PCharSub[j] then break;
      end;
      if j=len then Result:=i+1;
    end;
  end;
调用方式:RightPosEx(‘’,’1234567’);
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Tag:   Delphi   字符串函数   
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