'===========================================================================
' Subject: BINARY SEARCH SUBROUTINE          Date: 03-10-00 (13:16)       
' Author:  Randall L. Glass                  Code: PB                     
' Origin:  rlglass@yahoo.com               Packet: PB.ABC
'===========================================================================
'------------------------------------------------------------------------
'  Correction For PowerBasic Inline Assembly Search Subroutines
'
'  Assembly binary search subroutine correction
'
'  Donated to Public Domain By Randall Glass
'  E-Mail Address rlglass@yahoo.com
'
'
'----------------------------------------------------------------------------
' For some reason i decided to retest my assembly search programs.
' This time I added a test routine to let my computer look for problems.
' all of them work perfectly except for my binary search program
' it worked perfectly except it did not find the very last string in
' in the string array.
'
'--------------------------------------------------------------------------


' corrected Binary search subroutine

FUNCTION BinSearch% (byval Lower%,byval Upper%,Find$,a$(),BYVAL ArrayHandleAddr???) Public
DIM FindPtr AS DWORD,Middle AS INTEGER,Ln AS WORD
! LES BX,Find$
! MOV AX,ES:[BX]
! PUSH AX
! CALL GetStrLoc           ; find where the data is located
! JCXZ BinSearchDone1
! JMP Continue
BinSearchDone1:
! JMP BinSearchDone
Continue:
! MOV  FindPtr???[2],DX    ; put segment in ES
! MOV  FindPtr???[0],AX    ; put segment in ES
! MOV Ln??,CX

'WHILE Lower% < Upper%
BinaryWhile:
!      MOV BX,Lower%
!      MOV DX,Upper%
!      cmp  BX,DX
!      ja BinSearchDone    ; !!!! this was jae caused my problem
'if    Upper% >= Lower%  then Quit
!       MOV AX,BX        ;CX = Upper%
!       ADD AX,DX
!       shr AX,1         ;AX = Middle%
'  Middle% = (Upper% + Lower%) \ 2         'start testing in middle
! MOV Middle%,AX
! LES DI,ArrayHandleAddr???
! SHL AX,1
! ADD DI,AX
! MOV AX,ES:[DI]
! PUSH AX
! call GetStrLoc           ; find where the data is located
! JCXZ BinSearchDone
! mov  ES, DX              ; put segment in ES
! mov  DI, AX              ; put offset in DI
! MOV DX,Ln??
! MOV BX,CX
! CMP DX,CX
! JG  NoMin
! MOV CX,DX
NoMin:
! PUSH DS
! LDS SI,FindPtr???
NeMinLen:
! CMPSB
! JA AisGTFind
! JB AisLTFind
! LOOP NeMinLen
! CMP BX,DX
! Jl AisGtFind
! Je BinaryFoundIt
AisLTFind:
! POP DS
! MOV AX,Middle%
! MOV Upper%,AX
! JMP BinaryWhile
AisGtFind:
! POP DS
! MOV AX,Middle%
! INC AX
! MOV Lower%,AX
!JMP BinaryWhile
BinaryFoundIt:
! POP DS
! MOV AX,Middle%
! MOV FUNCTION,AX
BinSearchDone:
END FUNCTION