/*
 * Lookup a primitive within a given table
 *
 * to compile:	`as lookup.s -o lookup.o; ld lookup.o -o lookup' 
 *
 * to execute:	`./lookup; echo $?'
 *
 * returns `1' if found, `0' if not
 *			  
 */		

.data					/* data section */

/* primitives' lookup table */	
primitives:	.ascii "input", "erasechar", "quit", "bye", "exit", "\0"

/* primitive to match */
ptest:		.asciz	"bye"
ptest_len = .- ptest-1
	
.text					/* text section */
									
.globl _start
.type _start, @function			/* main */
_start:

	pushl	$ptest
	call	LookUp
	addl	$4, %esp

	movl	%eax, %ebx		/* exit */
	movl	$1, %eax
	int	$0x80

	
.type LookUp, @function			/* lookup function */
.globl LookUp
LookUp:	
	pushl	%ebp
	movl	%esp, %ebp

	movl	0x8(%ebp), %ebx		# pointer to string to match
	movl	$primitives, %ecx	# primitives' buffer

	movb	(%ebx, 1), %dl		# store %bl into %dl
	
.LookUp_search:	
	cmpb	$0x0, (%ecx,1)		# watch out for end of buffer
	je	.LookUp_done

	cmpb	%dl, (%ecx,1)		# compare first pointer char with current ecx
	je	.LookUp_match

	incl	%ecx			# increment ecx

	jmp	.LookUp_search

.LookUp_match:
	pushl	%ebx			# save & send ebx as func's arg
	pushl	%ecx			# save & send ecx as func's arg
	call	StrCmp

	popl	%ecx			# pop it
	popl	%ebx			# pop it

	incl	%ecx			# increment ecx

	cmpl	$0x1, %eax		# check StrCmp's result
	je	.LookUp_done

	jmp	.LookUp_search

.LookUp_done:	
	movl	%ebp, %esp
	popl	%ebp
	ret

.type StrCmp, @function			/* strcmp function */
.globl StrCmp
StrCmp:
	pushl	%ebp
	movl	%esp, %ebp

	movl	0x8(%ebp), %esi		# pointer to primitive's buffer
	movl	0xc(%ebp), %edi		# pointer to the string to match
	movl	$ptest_len, %ecx	# requested primitive's len

	cld
	repe  cmpsb
	jg   .StrCmp_no

	movl $1,%eax
	jmp  .StrCmp_end

.StrCmp_no:
	movl $0,%eax

.StrCmp_end:
	movl	%ebp, %esp
	popl	%ebp
	ret