#	;; ls.s
#

#
#

#include <asm/unistd_64.h>

	.file	"ls.s"

	.data
dirname:
	.string "/usr/lib"
open_flags:
	.quad	00200000
#	.quad	O_DIRECTORY | O_RDONLY
eoln:
	.string "\n"
separator:
	.string " "

	.align	4
direntries:
	.space	4096,0

	.text
	.global	ls

ls:
	# walk through arglist, see if you can open files...
	
	nop
	pop     %r13 		# %r8 keeps the argc
	pop	%rsi		# remove command

	dec	%r8
	jz	_finish

_nextarg:
	pop	%rdi		# load directory name into %rdi
	mov	open_flags,%rsi
	mov	$__NR_open,%rax
	syscall

	cmp	$0,%rax
	jl	_next

	# save the file descriptor in %r15
	mov	%rax,%r15
	lea	direntries,%r14
	# clear %r8 - %r9
	xor	%r8,%r8		# going to use this to walk direntries
	xor	%r9,%r9		# going to calculate offset to next dirent
	xor	%r10,%r10	# going to use save how many bytes did we receive from getdents

_read_entries:
	mov 	%r15,%rdi	# recover file descriptor from %r15
	mov	%r14,%rsi	# point %rsi at direntries
	mov	$4096,%rdx
	mov	$__NR_getdents,%rax
	syscall

	cmp	$0,%rax
	jle	_finish

	mov	%rax,%r10
	call	_process_entries

	# close the file descriptor...
	mov	%r15,%rdi
	mov	$__NR_close,%rax
	syscall

_next:	
	dec	%r13
	jnz	_nextarg

_finish:	
	mov	$0,%rdi	# and exit with a zero status
	mov	$__NR_exit,%rax	# syscall = 60 is exit
	syscall

#
#  process_entries
#
#
#	we have been handed a block of entries in 'direntries'
#
#       step through each one, and call appropriate handler for
#	each individual one...
#

_process_entries:
	lea	direntries,%r8	# %r8 has the current dirent
_around:	
	call	_entry_raw
	# is there a next?
	mov	16(%r8),%r9w	# okay, %r9w has distance to next
	add	%r9,%r8

	mov	%r8,%r12	# check to see if we have processed all bytes...
	sub	%r14,%r12	# %r14 should have value of direntries
	cmp	%r10,%r12
	jl	_around

	ret
	
#
#   entry_raw
#	
#	this is the most basic handler --> all that it does is send an
#	entry out to stdout
#

_entry_raw:
	mov	$1,%rdi
	lea	18(%r8),%rsi
	call	writestr
	mov	$1,%rdi
	lea	eoln,%rsi
	call	writestr
	ret