一步步教你優化Delphi字串查找(2)

這個函數裡，用到了Delete函數，我們再來看一看System.pas文件裡Delete函數的實現過程，請看下面代碼：

procedure _LStrDelete{ var s : AnsiString; index, count : Integer };
asm
{ EAX Pointer to s }
{ EDX index }
{ ECX count }
PUSH EBX
PUSH ESI
PUSH EDI
MOV EBX,EAX
MOV ESI,EDX
MOV EDI,ECX
CALL UniqueString
MOV EDX,[EBX]
TEST EDX,EDX { source already empty:
nothing to do }
JE @@exit
MOV ECX,[EDX-skew].StrRec.length
{ make index 0-based, if not in [0 .. Length(s)-1]
do nothing }
DEC ESI
JL @@exit
CMP ESI,ECX
JGE @@exit
{ limit count to [0 .. Length(s) - index] }
TEST EDI,EDI
JLE @@exit
SUB ECX,ESI { ECX = Length(s) - index
}
CMP EDI,ECX
JLE @@1
MOV EDI,ECX
@@1:
{ move length - index - count characters from
s+index+count to s+index }
SUB ECX,EDI { ECX = Length(s) - index
- count }
ADD EDX,ESI { EDX = s+index }
LEA EAX,[EDX+EDI] { EAX = s+index+count }
CALL Move
{ set length(s) to length(s) - count }
MOV EDX,[EBX]
MOV EAX,EBX
MOV EDX,[EDX-skew].StrRec.length
SUB EDX,EDI
CALL _LStrSetLength
@@exit:
POP EDI
POP ESI
POP EBX
end;