***************************************
 
* Pattern Search

* OTHER MODULES REQUIRED: COMPARE

* ENTRY: X=start of memory to search
*        U=end of memory
*        Y=start of pattern
*        D=size of pattern
*        CASEMTCH (a global variable in COMPARE) =0 if A<>a, -1 if A=a

* EXIT: X=address of match if found, unchanged if no match
*       CC zero set if match, clear for no-match
*       A,B,U,Y preserved


 nam Pattern Search
 ttl Assembler Library Module


 section .data

pattend rmb 2 end of pattern in memory
memend  rmb 2 realend-pattern size
patsize rmb 2 saved <D>
memstrt rmb 2 saved <X>
patstrt rmb 2 saved <Y>
realend rmb 2 saved <U>

 endsect

 section .text

* set up stack frame for variables

PTSEARCH:
 pshs d,x,y,u
 leas -4,s room for temps
 tfr u,d end of memory to check
 subd patsize,s end-pattern size
 std memend,s where we stop looking
 ldd patstrt,s
 addd patsize,s
 std pattend,s

* loop here looking for a match of the first characters

inmatch
 cmpx memend,s raeched end of memory
 bhs nomatch
 lda ,x+ get char from memory
 ldb ,y compare to pattern
 lbsr COMPARE compare them
 bne inmatch keep looking for inital match

* see if rest of pattern matches

more
 tfr x,u save pointer
 leay 1,y already matched that one

more1
 cmpy pattend,s all chars matched, go home happy
 beq match
 lda ,x+
 ldb ,y+
 lbsr COMPARE
 beq more1 keep matching
 tfr u,x match fails, backup and do more
 ldy patstrt,s start of pattern
 bra inmatch


nomatch
 lda #1 clear zero
 bra exit

match
 leau -1,u start of match
 stu memstrt,s where pattern starts
 clra set zero flag=found

exit
 leas 4,s clean stack
 puls d,x,y,u,pc

 endsect