FreeBasic

Данный поиск работает по алгоритму Boyer–Moore. Unicode не поддерживает. Обгоняет стандартный InStr приблизительно в 10 раз.

Платформы: Windows, Linux
Автор: MichaelW

#INCLUDE "crt.bi"

Function InStrZ naked( start As Integer, _
    s1 As Zstring Ptr, _
    s2 As Zstring Ptr ) As Integer
    Asm
        mov ecx, [esp+8]            '' get pointer to s1
        mov edx, [esp+12]           '' get pointer to s2
        movzx eax, Byte Ptr [ecx]   '' get first char
        test eax, eax               '' test for null string
        jz 0f                       '' return zero
        movzx eax, Byte Ptr [edx]   '' get first char
        test eax, eax               '' test for null string
        jz 0f                       '' return zero
        push ecx                    '' preserve ecx around call
        ''--------------------------------------------
        '' The extra '+4' below is to correct for the
        '' effect of the 'push ecx' above on ESP.
        ''--------------------------------------------
        Add ecx, [esp+4+4]          '' correct for start position
        dec ecx                     '' correct for change in base
        push edx                    '' push pointer to s2
        push ecx                    '' push corrected pointer to s1
        Call StrStr                 '' call CRT strstr function
        Add esp, 8                  '' remove parameters from stack
        pop ecx                     '' recover ecx
        test eax, eax               '' test for substring not found
        jz 0f                       '' return zero
        Sub eax, ecx                '' subtract address of s1 data
        inc eax                     '' adjust return value to base 1
        0:
        ret 12                      '' return and remove parameters from stack
    End Asm
End Function