From dd4a3f3f53ac0e577975debb8658a7aef2877831 Mon Sep 17 00:00:00 2001
From: turret <turret@duck.com>
Date: Fri, 8 Sep 2023 10:56:03 -0500
Subject: cat: error notifs, flag parsing complete

---
 cat.s | 147 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 137 insertions(+), 10 deletions(-)

diff --git a/cat.s b/cat.s
index 279164f..831dea8 100644
--- a/cat.s
+++ b/cat.s
@@ -38,6 +38,11 @@ _start:
     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
@@ -45,14 +50,90 @@ _start:
     mov r11, [rbp]
     mov r11, [r11]
     and r11, 0xff
-    cmp r11, 0x2d ;'-'
+    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
@@ -67,11 +148,13 @@ final:
     cmp r10, 1
     jl .cont
 
-    ; arguments starting with "-" are special cases
+    ; 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, 0x2d ;'-'
+    cmp r11, "-"
     je .stdin
 
     ; open(rbp, 0, 0)
@@ -105,29 +188,73 @@ final:
 
 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
-showends:               equ 0b000010
-numberlines:            equ 0b000100
-squeezeblanks:          equ 0b001000
-showtabs:               equ 0b010000
-shownonprinting:        equ 0b100000
-
+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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