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global _start
section .text
process_fd:
; rax = fd
; read(rax, buf, bufSize)
mov rbx, rax
mov rdi, rax
mov rsi, buf
mov rdx, bufSize
mov rax, 0
syscall
; check if stuff was read
cmp rax, 1
jl .ret
; TODO flag handling
; write(1, buf, rax)
mov rdi, 1
mov rsi, buf
mov rdx, rax
mov rax, 1
syscall
; continue loop
mov rax, rbx
jmp process_fd
.ret:
; return rax
mov rax, rbx
ret
_start:
; r12 = argc
mov rbp, rsp
mov r12, [rbp]
cmp r12, 2
jl final.stdin
; r13 = our flag holder
xor r13, r13
add rbp, 8 * 2
; flag consumer loop
.loop:
cmp r12, 2
jl final
mov r11, [rbp]
mov r11, [r11]
and r11, 0xff
cmp r11, "-"
jne .cont
; solid - is stdin
; shouldnt be consumed
mov r11, [rbp]
add r11, 1
mov r11, [r11]
and r11, 0xff
cmp r11, 0x00
je .cont
mov r11, [rbp]
xor r9, r9
mov [rbp], r9 ; consume argument (should be ignored in final loop)
; inner loop to process all flags
.inloop:
inc r11
mov r10, [r11]
and r10, 0xff
cmp r10, 0x00
je .cont
; basically switch() { case }
cmp r10, "b"
je .numbernonblankonly
cmp r10, "E"
je .showends
cmp r10, "n"
je .numberlines
cmp r10, "s"
je .squeezeblanks
cmp r10, "T"
je .showtabs
cmp r10, "v"
je .shownonprinting
cmp r10, "A"
je .showall
cmp r10, "e"
je .ve
cmp r10, "t"
je .vt
cmp r10, "u"
je .inloop
jmp usage
.numbernonblankonly:
or r13, numbernonblankonly
jmp .inloop
.showends:
or r13, showends
jmp .inloop
.numberlines:
or r13, numberlines
jmp .inloop
.squeezeblanks:
or r13, squeezeblanks
jmp .inloop
.showtabs:
or r13, showtabs
jmp .inloop
.shownonprinting:
or r13, shownonprinting
jmp .inloop
.showall:
or r13, shownonprinting
or r13, showends
or r13, showtabs
jmp .inloop
.ve:
or r13, shownonprinting
or r13, showends
jmp .inloop
.vt:
or r13, shownonprinting
or r13, showtabs
jmp .inloop
.cont:
add rbp, 8
sub r12, 1
jmp .loop
; actual FD processor loop
final:
; fix rbp and r12
mov rbp, rsp
mov r12, [rbp]
add rbp, 8 * 2 ; jump past 1st arg
.loop:
; if no more entries; exit
cmp r12, 2
jl exit
mov r10, [rbp]
cmp r10, 1
jl .cont
; at this point, all arguments starting with -
; should only be -\0 (stdin)
; (we can be lazy and skip checking)
mov r11, [rbp]
mov r11, [r11]
and r11, 0xff
cmp r11, "-"
je .stdin
; open(rbp, 0, 0)
mov rax, 2
mov rdi, [rbp]
mov rsi, 0
mov rdx, 0
syscall
; make sure fd exists
cmp rax, 1
jl error
; print file
call process_fd
; returns input
; close(rax)
mov rdi, rax
mov rax, 3
syscall
; prepare registers for next loop
.cont:
add rbp, 8
sub r12, 1
jmp .loop
.stdin:
mov rax, 0
call process_fd
jmp .cont
usage:
; TODO: usage message
mov rax, usagemsg
call pstring
jmp errorexit
error:
;exit(1)
; TODO: process RAX to print meaningful message
mov rax, errormsg
call pstring
errorexit:
mov rax, 60
mov rdi, 1
syscall
; function to print null terminated string
; arg: rax is pointer
pstring:
; r8 is length
; r9 is a cached buffer for operations
xor r8, r8
mov r9, rax
.loop:
mov r10, [r9]
and r10, 0xff
cmp r10, 0x00
je .fin
inc r8
inc r9
jmp .loop
.fin:
; print to stderr
mov rdx, r8
mov rsi, rax
mov rdi, 2
mov rax, 1
syscall
ret
exit:
mov rax, r13
mov [reg], rax
mov rax, 1
mov rdi, 2
mov rsi, reg
mov rdx, 8
syscall
;exit(0)
mov rax, 60
mov rdi, 0
syscall
section .data
usagemsg: db "Usage: % [-AbeEnstTuv] [file ...]", 10, 00
errormsg: db "An error has occured! Unfortunately, this program isnt complex enough to display the error yet. Try using strace!", 10, 00
section .bss
reg: resb 8
bufSize: equ 65536
buf: resb bufSize
numbernonblankonly: equ 0b000001 ; -b
showends: equ 0b000010 ; -E
numberlines: equ 0b000100 ; -n
squeezeblanks: equ 0b001000 ; -s
showtabs: equ 0b010000 ; -T
shownonprinting: equ 0b100000 ; -v
; -A = -vET
; -e = -vE
; -t = -vT
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