diff options
| author | hachem <im@hachem.wtf> | 2026-08-25 11:26:54 +0200 |
|---|---|---|
| committer | hachem <im@hachem.wtf> | 2026-08-25 11:26:54 +0200 |
| commit | 2b0dad9d87b2b663ddc008876a4dbc3d17993d27 (patch) | |
| tree | 7394aef05e1ca7c0518a0f7ff6d785c0304e1863 /aoc-2025/day1.asm | |
| parent | 2806ed7d55266ececb197196af2fb84ae8c3cb35 (diff) | |
chore: refactor repository
Diffstat (limited to 'aoc-2025/day1.asm')
| -rw-r--r-- | aoc-2025/day1.asm | 314 |
1 files changed, 314 insertions, 0 deletions
diff --git a/aoc-2025/day1.asm b/aoc-2025/day1.asm new file mode 100644 index 0000000..8ba8f0e --- /dev/null +++ b/aoc-2025/day1.asm @@ -0,0 +1,314 @@ +; Advent of Code 2025 - Day 1
+
+bits 64
+default rel
+
+global _start
+
+%define SYS_EXIT 60
+%define SYS_READ 0
+%define SYS_WRITE 1
+%define SYS_OPEN 2
+%define SYS_CLOSE 3
+
+%define O_RDONLY 0
+%define STDOUT 1
+
+section .data
+ inputPath db "input/day1.txt", 0
+ newline db 10
+
+ label1 db "Password 1: ", 0
+ label2 db "Password 2: ", 0
+
+ angle1 dd 50
+ angle2 dd 50
+
+ password1 dd 0
+ password2 dd 0
+
+section .bss
+ buffer resb 4096
+ lineBuffer resb 256
+ numberBuffer resb 16
+ lineLen resd 1
+
+section .text
+
+_start:
+ ; open file
+ mov rax, SYS_OPEN
+ mov rdi, inputPath
+ mov rsi, O_RDONLY
+ xor rdx, rdx
+ syscall
+
+ mov r12, rax ; fd in R12
+ mov dword [lineLen], 0 ; no chars in current line yet
+
+ReadLoop:
+ ; read up to 4096 bytes
+ mov rax, SYS_READ
+ mov rdi, r12
+ mov rsi, buffer
+ mov rdx, 4096
+ syscall
+
+ cmp rax, 0
+ jle EOF ; <=0 -> EOF or error
+
+ mov rdi, buffer ; scan pointer
+ mov rbp, rax ; bytes remaining in this chunk
+
+ScanChunk:
+ cmp rbp, 0
+ je ReadLoop ; chunk done, read next
+
+ mov al, [rdi]
+
+ ; windows can be a fucking bitch
+ ; handle (CR) -> just skip
+ cmp al, 13
+ je SkipCR
+
+ ; handle LF (10) -> end of line
+ cmp al, 10
+ je EndOfLine
+
+ ; normal character -> append to lineBuffer if space left
+ mov edx, [lineLen]
+ cmp edx, 255 ; leave 1 byte for NULL
+ jae SkipStore ; ignore extra characters if too long
+ mov [lineBuffer+rdx], al
+ inc edx
+ mov [lineLen], edx
+
+SkipStore:
+ inc rdi
+ dec rbp
+ jmp ScanChunk
+
+SkipCR:
+ inc rdi
+ dec rbp
+ jmp ScanChunk
+
+EndOfLine:
+ ; terminate current line
+ mov edx, [lineLen]
+ mov byte [lineBuffer+rdx], 0
+
+ ; if line isn't empty, process it
+ cmp edx, 0
+ je LineDone
+
+ push rdi
+ mov rsi, lineBuffer
+ call HandleLine
+ pop rdi
+
+LineDone:
+ mov dword [lineLen], 0 ; reset line length
+ inc rdi
+ dec rbp
+ jmp ScanChunk
+
+; process last line if not newline-terminated, then print result
+EOF:
+ ; if there is a partial line at EOF, process it
+ mov edx, [lineLen]
+ cmp edx, 0
+ jle PrintResults
+ mov byte [lineBuffer+rdx], 0
+
+ mov rsi, lineBuffer
+ call HandleLine
+
+PrintResults:
+ mov rcx, label1
+ call PrintString
+ mov eax, [password1]
+ call PrintInt
+
+ ; newline
+ mov rax, SYS_WRITE
+ mov rdi, STDOUT
+ mov rsi, newline
+ mov rdx, 1
+ syscall
+
+ mov rcx, label2
+ call PrintString
+ mov eax, [password2]
+ call PrintInt
+
+ ; new linhe
+ mov rax, SYS_WRITE
+ mov rdi, STDOUT
+ mov rsi, newline
+ mov rdx, 1
+ syscall
+
+ mov rax, SYS_CLOSE
+ mov rdi, r12
+ syscall
+ mov rax, SYS_EXIT
+ xor rdi, rdi
+ syscall
+
+; Handle one line: RSI -> "L123" or "R45"
+HandleLine:
+ mov al, [rsi]
+ cmp al, 'L'
+ je .left
+ mov ebx, 1 ; direction = +1 for 'R' or anything else
+ jmp .after
+.left:
+ mov ebx, -1 ; direction = -1 for 'L'
+.after:
+ inc rsi ; skip 'L' or 'R'
+ call ParseInt ; EAX = steps
+ mov ecx, eax
+
+; Part 1
+P1_Start:
+ mov eax, ecx
+ imul eax, ebx
+ add eax, [angle1]
+ call NormalizeAngle
+ mov [angle1], eax
+ cmp eax, 0
+ jne P2_Start
+ mov rdi, password1
+ mov edx, [rdi]
+ inc edx
+ mov [rdi], edx
+
+; Part 2
+P2_Start:
+ mov rdi, password2
+.loop:
+ test ecx, ecx
+ jle P2_Exit
+ dec ecx
+
+ mov eax, [angle2]
+ call UpdateAngleCount
+ mov [angle2], eax
+
+ jmp .loop
+P2_Exit:
+ ret
+
+; normalize eax to 0..99
+NormalizeAngle:
+ cmp eax, 0
+ jl .add
+ cmp eax, 100
+ jl .done
+ sub eax, 100
+ jmp NormalizeAngle
+.add:
+ add eax, 100
+ jmp NormalizeAngle
+.done:
+ ret
+
+; eax = angle, ebx = direction, rdi = password counter addr
+UpdateAngleCount:
+ add eax, ebx
+ call NormalizeAngle
+
+ cmp eax, 0
+ jne .done
+ mov edx, [rdi]
+ inc edx
+ mov [rdi], edx
+.done:
+ ret
+
+; parse ASCII integer into EAX
+ParseInt:
+ xor eax, eax ; result = 0
+.parseLoop:
+ mov dl, [rsi]
+ cmp dl, '0'
+ jl .done
+ cmp dl, '9'
+ jg .done
+
+ sub dl, '0' ; digit value 0..9
+ movzx edx, dl
+
+ imul eax, eax, 10 ; result *= 10
+ add eax, edx ; result += digit
+
+ inc rsi
+ jmp .parseLoop
+.done:
+ ret
+
+PrintInt:
+ mov edi, numberBuffer+15 ; write digits from the end
+ mov byte [rdi], 0 ; terminator
+ dec rdi
+
+ cmp eax, 0
+ jne .convert
+ mov byte [rdi], '0'
+ jmp .finish
+.convert:
+ ; we will repeatedly compute:
+ ; q = eax / 10
+ ; r = eax % 10
+ ; using only subtraction
+.nextDigit:
+ mov edx, eax ; tmp = current value
+ mov ecx, 0 ; q = 0
+
+ cmp edx, 10 ; if < 0, q=0, r=edx
+ jb .lastDigit
+.subLoop:
+ sub edx, 10
+ inc ecx ; q++
+ cmp edx, 10
+ jae .subLoop ; while tmp >= 10
+.lastDigit:
+ ; now:
+ ; ecx = quotient
+ ; edx = remainder (0..9)
+ add dl, '0'
+ mov [rdi], dl ; store digit
+ dec rdi
+ mov eax, ecx ; eax = quotient
+ test eax, eax
+ jnz .nextDigit ; more digits to extract?
+
+ inc rdi ; move to first digit
+.finish:
+ mov rax, SYS_WRITE
+ mov rsi, rdi ; buffer pointer
+ mov rdi, STDOUT
+ mov rdx, numberBuffer+15
+ sub rdx, rsi ; length
+ syscall
+ ret
+
+PrintString:
+ push rcx
+ push rdx
+ mov rdx, 0
+.count:
+ cmp byte [rcx+rdx], 0
+ je .doneCount
+ inc rdx
+ jmp .count
+.doneCount:
+ mov rax, SYS_WRITE
+ mov rdi, STDOUT
+ mov rsi, rcx
+ syscall
+
+ pop rdx
+ pop rcx
+ ret
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