feat: read text from a file and dump to screen

asmatrix.asm

@@ -1,6 +1,10 @@
 global main
 
+; -------------------------------------------------
 ; imports
+; -------------------------------------------------
+
+; ncurses
 extern initscr
 extern cbreak
 extern noecho
@@ -11,16 +15,59 @@ extern endwin
 extern keypad
 extern stdscr
 
+; libc
+extern fopen
+extern fread
+extern fclose
+extern strerror
+%ifdef MACOS
+extern __error
+%else
+extern __errno_location
+%endif
+
 section .data
-    ; msg = ["a", "s", "s", "\n" (10), "\0" (0)]
-    msg db "ass", 10, 0
+    rmode   db "r", 0
+    err_msg db "Error: %s", 10, 0
+    usage   db "Usage: %s <filename>", 10, 0
+
+section .bss
+    ; 4KB buffer
+    buffer  resb 4096
 
 section .text
 default rel
 
+; -------------------------------------------------
+; Utility function: print string to screen
+; rdi = string address
+; -------------------------------------------------
+print_screen:
+    ; since printw is a variadic function,
+    ; we must declare number of registers used.
+    ; xor eax, eax := 0 since we are using
+    ; printw with 0 arguments
+    xor eax, eax
+    jmp printw
+
+; -------------------------------------------------
+; Main entry point: program initialization and execution
+; rdi = argc (argument count)
+; rsi = argv (argument vector)
+; -------------------------------------------------
 main:
-    ; stack alignment
+    ; save argc/argv
+    push rbp
+    mov rbp, rsp
+
+    ; Save argc and argv in callee-saved registers
+    mov r12, rdi            ; r12 = argc
+    mov r13, rsi            ; r13 = argv
+
+    ; stack alignment (16-byte align before calls)
     sub rsp, 8
+    push r12
+    push r13
 
     ; initialise the screen
     call initscr
@@ -37,20 +84,86 @@ main:
     mov esi, 1
     call keypad
 
-    ; load address of msg
-    lea rdi, [msg]
+    ; -------------------------------------------------
+    ; Check arguments
+    ; -------------------------------------------------
+    ; argc == 2?
+    cmp r12, 2
+    jne .show_usage
 
-    ; since printw is a variadic function,
-    ; we must declare number of registers used.
-    ; xor eax, eax := 0 since we are using
-    ; printw with 0 arguments
+    ; -------------------------------------------------
+    ; Open File: fopen(argv[1], "r")
+    ; -------------------------------------------------
+    mov rdi, [r13 + 8]          ; rdi = argv[1]
+    lea rsi, [rmode]            ; rsi = "r"
+    call fopen
+    test rax, rax               ; Check for NULL
+    jz .show_strerror           ; If null, display error
+    mov rbx, rax                ; Save FILE* in rbx
+
+    ; -------------------------------------------------
+    ; Read File: fread(buffer, 1, 4096, file)
+    ; -------------------------------------------------
+    lea rdi, [buffer]
+    mov rsi, 1
+    mov rdx, 4096
+    mov rcx, rbx
+    call fread
+
+    ; Null-terminate the string
+    mov rcx, rax                ; Save bytes read
+    lea rdi, [buffer]           ; Load buffer address
+    mov byte [rdi + rcx], 0     ; Null terminate using saved count
+
+    ; Close file
+    mov rdi, rbx
+    call fclose
+
+    ; -------------------------------------------------
+    ; Print content and exit
+    ; -------------------------------------------------
+    lea rdi, [buffer]
+    call print_screen
+    jmp .cleanup
+
+; -------------------------------------------------
+; Utility function: display usage message
+; Shows program usage instructions when arguments are invalid
+; -------------------------------------------------
+.show_usage:
+    lea rdi, [usage]
+    mov rsi, [r13]              ; argv[0]
     xor eax, eax
     call printw
+    jmp .cleanup
+
+; -------------------------------------------------
+; Utility function: display system error message
+; Retrieves errno value and displays corresponding error string
+; -------------------------------------------------
+.show_strerror:
+%ifdef MACOS
+    call __error              ; rax = &errno
+%else
+    call __errno_location     ; rax = &errno
+%endif
+    mov edi, [rax]            ; edi = errno value
+    call strerror             ; rax = error string
+    lea rdi, [err_msg]
+    mov rsi, rax
+    xor eax, eax
+    call printw
+
+; -------------------------------------------------
+; Utility function: cleanup and exit
+; Handles ncurses cleanup, waits for user input, and exits
+; Restores stack and returns with exit code 0
+; -------------------------------------------------
+.cleanup:
     call refresh
     call getch
     call endwin
-
-    ; restore stack pointer
-    add rsp, 8
     xor eax, eax
+    add rsp, 24               ; Clean up stack (8 + 16 for pushed registers)
+    pop rbp
     ret

assets/hackers-manifesto.txt

@@ -0,0 +1,56 @@
+Another one got caught today, it's all over the papers.  "Teenager
+Arrested in Computer Crime Scandal", "Hacker Arrested after Bank Tampering"...
+        Damn kids.  They're all alike.
+
+        But did you, in your three-piece psychology and 1950's technobrain,
+ever take a look behind the eyes of the hacker?  Did you ever wonder what
+made him tick, what forces shaped him, what may have molded him?
+        I am a hacker, enter my world...
+        Mine is a world that begins with school... I'm smarter than most of
+the other kids, this crap they teach us bores me...
+        Damn underachiever.  They're all alike.
+
+        I'm in junior high or high school.  I've listened to teachers explain
+for the fifteenth time how to reduce a fraction.  I understand it.  "No, Ms.
+Smith, I didn't show my work.  I did it in my head..."
+        Damn kid.  Probably copied it.  They're all alike.
+
+        I made a discovery today.  I found a computer.  Wait a second, this is
+cool.  It does what I want it to.  If it makes a mistake, it's because I
+screwed it up.  Not because it doesn't like me...
+                Or feels threatened by me...
+                Or thinks I'm a smart ass...
+                Or doesn't like teaching and shouldn't be here...
+        Damn kid.  All he does is play games.  They're all alike.
+
+        And then it happened... a door opened to a world... rushing through
+the phone line like heroin through an addict's veins, an electronic pulse is
+sent out, a refuge from the day-to-day incompetencies is sought... a board is
+found.
+        "This is it... this is where I belong..."
+        I know everyone here... even if I've never met them, never talked to
+them, may never hear from them again... I know you all...
+        Damn kid.  Tying up the phone line again.  They're all alike...
+
+        You bet your ass we're all alike... we've been spoon-fed baby food at
+school when we hungered for steak... the bits of meat that you did let slip
+through were pre-chewed and tasteless.  We've been dominated by sadists, or
+ignored by the apathetic.  The few that had something to teach found us will-
+ing pupils, but those few are like drops of water in the desert.
+
+        This is our world now... the world of the electron and the switch, the
+beauty of the baud.  We make use of a service already existing without paying
+for what could be dirt-cheap if it wasn't run by profiteering gluttons, and
+you call us criminals.  We explore... and you call us criminals.  We seek
+after knowledge... and you call us criminals.  We exist without skin color,
+without nationality, without religious bias... and you call us criminals.
+You build atomic bombs, you wage wars, you murder, cheat, and lie to us
+and try to make us believe it's for our own good, yet we're the criminals.
+
+        Yes, I am a criminal.  My crime is that of curiosity.  My crime is
+that of judging people by what they say and think, not what they look like.
+My crime is that of outsmarting you, something that you will never forgive me
+for.
+
+        I am a hacker, and this is my manifesto.  You may stop this individual,
+but you can't stop us all... after all, we're all alike.