fix: add utilities

14 files changed, 182 insertions, 1152 deletions

diff --git a/aoc-2025/day1.asm b/aoc-2025/day1.asm
index f130675..928e7a5 100644
--- a/aoc-2025/day1.asm
+++ b/aoc-2025/day1.asm
@@ -5,18 +5,10 @@ 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

+%include "utils/io.asm"

 

 section .data

     input_path db "input/day1.txt", 0

-    newline   db 10

 

     label1 db "Password 1: ", 0

     label2 db "Password 2: ", 0

@@ -30,7 +22,6 @@ section .data
 section .bss

     buffer       resb 4096

     line_buffer   resb 256

-    number_buffer resb 16

     line_len      resd 1

 

 section .text

@@ -128,26 +119,14 @@ print_results:
     mov     rcx, label1

     call    print_string

     mov     eax, [password1]

-    call    print_int

-

-    ; newline

-    mov     rax, SYS_WRITE

-    mov     rdi, STDOUT

-    mov     rsi, newline

-    mov     rdx, 1

-    syscall

+    call    print_int64

+    call    print_newline

 

     mov     rcx, label2

     call    print_string

     mov     eax, [password2]

-    call    print_int

-

-    ; new linhe

-    mov     rax, SYS_WRITE

-    mov     rdi, STDOUT

-    mov     rsi, newline

-    mov     rdx, 1

-    syscall

+    call    print_int64

+    call    print_newline

 

     mov     rax, SYS_CLOSE

     mov     rdi, r12

@@ -247,68 +226,3 @@ parse_int:
     jmp     .parse_loop

 .done:

     ret

-

-print_int:

-    mov     edi, number_buffer+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

-.next_digit:

-    mov     edx, eax  ; tmp = current value

-    mov     ecx, 0    ; q = 0

-

-    cmp     edx, 10  ; if < 0,  q=0, r=edx

-    jb      .last_digit

-.sub_loop:

-    sub     edx, 10

-    inc     ecx  ; q++

-    cmp     edx, 10

-    jae     .sub_loop  ; while tmp >= 10

-.last_digit:

-    ; 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     .next_digit  ; 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, number_buffer+15

-    sub     rdx, rsi  ; length

-    syscall

-    ret

-

-print_string:

-    push    rcx

-    push    rdx

-    mov     rdx, 0

-.count:

-    cmp     byte [rcx+rdx], 0

-    je      .done_count

-    inc     rdx

-    jmp     .count

-.done_count:

-    mov     rax, SYS_WRITE

-    mov     rdi, STDOUT

-    mov     rsi, rcx

-    syscall

-

-    pop     rdx

-    pop     rcx

-    ret

diff --git a/aoc-2025/day10.asm b/aoc-2025/day10.asm
index 02582b2..456752c 100644
--- a/aoc-2025/day10.asm
+++ b/aoc-2025/day10.asm
@@ -5,14 +5,7 @@ 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
+%include "utils/io.asm"
 
 %define RAW_SIZE   262144
 %define MAXB       16
@@ -23,8 +16,6 @@ global _start
 section .data
     input_path db "input/day10.txt", 0
 
-    newline    db 10
-
     label1     db "Part 1: ", 0
     label2     db "Part 2: ", 0
 
@@ -57,35 +48,14 @@ section .bss
     total1        resq 1
     total2        resq 1
 
-    number_buffer resb 32
-
 section .text
 
 _start:
-    mov     rax, SYS_OPEN
     mov     rdi, input_path
-    mov     rsi, O_RDONLY
-    xor     rdx, rdx
-    syscall
-    mov     r12, rax
-
-    xor     r13, r13
-read_loop:
-    mov     rax, SYS_READ
-    mov     rdi, r12
-    lea     rsi, [raw + r13]
+    lea     rsi, [raw]
     mov     rdx, RAW_SIZE
-    sub     rdx, r13
-    syscall
-    cmp     rax, 0
-    jle     read_done
-    add     r13, rax
-    jmp     read_loop
-read_done:
-    mov     [raw_len], r13
-    mov     rax, SYS_CLOSE
-    mov     rdi, r12
-    syscall
+    call    read_file
+    mov     [raw_len], rax
 
     lea     rsi, [raw]
     mov     rax, [raw_len]
@@ -723,62 +693,3 @@ reduce_row:
     jmp     .divl
 .done:
     ret
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
-
-
diff --git a/aoc-2025/day11.asm b/aoc-2025/day11.asm
index bf92fad..c3cd930 100644
--- a/aoc-2025/day11.asm
+++ b/aoc-2025/day11.asm
@@ -5,14 +5,7 @@ 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
+%include "utils/io.asm"
 
 %define RAW_SIZE   262144
 %define NCODES     17576        ; 26^3 possible 3-letter names
@@ -26,8 +19,6 @@ global _start
 section .data
     input_path db "input/day11.txt", 0
 
-    newline    db 10
-
     label1     db "Part 1: ", 0
     label2     db "Part 2: ", 0
 
@@ -43,35 +34,14 @@ section .bss
     t1            resq 1
     t2            resq 1
 
-    number_buffer resb 32
-
 section .text
 
 _start:
-    mov     rax, SYS_OPEN
     mov     rdi, input_path
-    mov     rsi, O_RDONLY
-    xor     rdx, rdx
-    syscall
-    mov     r12, rax
-
-    xor     r13, r13
-read_loop:
-    mov     rax, SYS_READ
-    mov     rdi, r12
-    lea     rsi, [raw + r13]
+    lea     rsi, [raw]
     mov     rdx, RAW_SIZE
-    sub     rdx, r13
-    syscall
-    cmp     rax, 0
-    jle     read_done
-    add     r13, rax
-    jmp     read_loop
-read_done:
-    mov     [raw_len], r13
-    mov     rax, SYS_CLOSE
-    mov     rdi, r12
-    syscall
+    call    read_file
+    mov     [raw_len], rax
 
     ; memo = -1 everywhere
     mov     rax, -1
@@ -261,60 +231,3 @@ count:
     xor     eax, eax
 .ret:
     ret
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
diff --git a/aoc-2025/day12.asm b/aoc-2025/day12.asm
index 6eb64a9..8931a2b 100644
--- a/aoc-2025/day12.asm
+++ b/aoc-2025/day12.asm
@@ -5,14 +5,8 @@ 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
+%include "utils/io.asm"
+%include "utils/parse.asm"
 
 %define RAW_SIZE   262144
 %define GRID_SIZE  4096          ; regions are at most 50x50
@@ -20,8 +14,6 @@ global _start
 section .data
     input_path db "input/day12.txt", 0
 
-    newline    db 10
-
     label1     db "Part 1: ", 0
 
 section .bss
@@ -54,35 +46,14 @@ section .bss
     left          resq 1
     count_feasible resq 1
 
-    number_buffer resb 32
-
 section .text
 
 _start:
-    mov     rax, SYS_OPEN
     mov     rdi, input_path
-    mov     rsi, O_RDONLY
-    xor     rdx, rdx
-    syscall
-    mov     r12, rax
-
-    xor     r13, r13
-read_loop:
-    mov     rax, SYS_READ
-    mov     rdi, r12
-    lea     rsi, [raw + r13]
+    lea     rsi, [raw]
     mov     rdx, RAW_SIZE
-    sub     rdx, r13
-    syscall
-    cmp     rax, 0
-    jle     read_done
-    add     r13, rax
-    jmp     read_loop
-read_done:
-    mov     [raw_len], r13
-    mov     rax, SYS_CLOSE
-    mov     rdi, r12
-    syscall
+    call    read_file
+    mov     [raw_len], rax
 
     ; parse shapes and regions
     lea     rsi, [raw]
@@ -106,7 +77,7 @@ pline:
     cmp     al, '9'
     jg      maybe_grid
     ; a number begins the line
-    call    parse_num
+    call    parse_u64
     mov     r10, rax
     mov     al, [rsi]
     cmp     al, 'x'
@@ -127,7 +98,7 @@ region_line:
     mov     qword [orients_done], 1
 .have:
     inc     rsi                 ; skip 'x'
-    call    parse_num
+    call    parse_u64
     mov     r11, rax            ; L
 .find_colon:
     mov     al, [rsi]
@@ -145,7 +116,7 @@ region_line:
     inc     rsi
     jmp     .rsp
 .rsp_done:
-    call    parse_num
+    call    parse_u64
     mov     [counts + rcx*8], rax
     inc     rcx
     jmp     .rcounts
@@ -215,24 +186,6 @@ pdone:
     xor     rdi, rdi
     syscall
 
-; parse_num: read decimal at [RSI], advancing RSI. Clobbers RAX, RDX.
-parse_num:
-    xor     rax, rax
-.d:
-    mov     dl, [rsi]
-    cmp     dl, '0'
-    jl      .done
-    cmp     dl, '9'
-    jg      .done
-    sub     dl, '0'
-    movzx   rdx, dl
-    imul    rax, rax, 10
-    add     rax, rdx
-    inc     rsi
-    jmp     .d
-.done:
-    ret
-
 ; gen_orients: build the 8 dihedral orientations of every shape as offset lists
 ; anchored at their row-major-first cell.
 gen_orients:
@@ -531,60 +484,3 @@ rec:
     pop     rbp
     pop     rbx
     ret
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
diff --git a/aoc-2025/day2.asm b/aoc-2025/day2.asm
index c1ae232..987fbf9 100644
--- a/aoc-2025/day2.asm
+++ b/aoc-2025/day2.asm
@@ -5,18 +5,11 @@ 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
+%include "utils/io.asm"
+%include "utils/parse.asm"
 
 section .data
     input_path db "input/day2.txt", 0
-    newline   db 10
 
     label1 db "Part 1: ", 0
     label2 db "Part 2: ", 0
@@ -29,8 +22,6 @@ section .bss
     sum1         resq 1
     sum2         resq 1
 
-    number_buffer resb 32  ; for printing and number_to_string
-
 section .text
 
 _start:
@@ -139,7 +130,7 @@ print_results:
 handle_line:
 next_range:
     ; parse start
-    call    parse_int64
+    call    parse_u64
     mov     r13, rax
 
     cmp     byte [rsi], '-'
@@ -147,7 +138,7 @@ next_range:
     inc     rsi
 
     ; parse end
-    call    parse_int64
+    call    parse_u64
     mov     r14, rax
 
 range_loop:
@@ -186,26 +177,6 @@ after_range:
 done_line:
     ret
 
-; RSI points at decimal digits; stops on first non-digit
-parse_int64:
-    xor     rax, rax
-.parse:
-    mov     dl, [rsi]
-    cmp     dl, '0'
-    jl      .done
-    cmp     dl, '9'
-    jg      .done
-
-    sub     dl, '0'
-    movzx   rdx, dl
-    imul    rax, rax, 10
-    add     rax, rdx
-
-    inc     rsi
-    jmp     .parse
-.done:
-    ret
-
 ; number_to_string: convert RAX to decimal ASCII, MSB-first
 ;   Output:
 ;     RSI = pointer to first digit
@@ -351,60 +322,3 @@ check_invalid2:
     pop     rdx
     pop     rbx
     ret
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
diff --git a/aoc-2025/day3.asm b/aoc-2025/day3.asm
index c8b8b75..8330755 100644
--- a/aoc-2025/day3.asm
+++ b/aoc-2025/day3.asm
@@ -5,20 +5,11 @@ 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
+%include "utils/io.asm"
 
 section .data
     input_path db "input/day3.txt", 0
 
-    newline   db 10
-
     label1 db "Part 1: ", 0
     label2 db "Part 2: ", 0
 
@@ -31,7 +22,6 @@ section .bss
     sum2         resq 1
 
     work_digits   resb 64  ; stack for greedy subsequence
-    number_buffer resb 32  ; for printing
 
 section .text
 
@@ -242,60 +232,3 @@ get_max_for_k:
     jmp     .convert_loop
 .done:
     ret
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
diff --git a/aoc-2025/day4.asm b/aoc-2025/day4.asm
index 57867b1..60e53ec 100644
--- a/aoc-2025/day4.asm
+++ b/aoc-2025/day4.asm
@@ -5,14 +5,7 @@ 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
+%include "utils/io.asm"
 
 %define RAW_SIZE   4194304  ; 4 MiB scratch for the raw file
 %define GRID_SIZE  4194304  ; 4 MiB for the padded grid / mark buffers
@@ -20,8 +13,6 @@ global _start
 section .data
     input_path db "input/day4.txt", 0
 
-    newline    db 10
-
     label1     db "Part 1: ", 0
     label2     db "Part 2: ", 0
 
@@ -38,37 +29,14 @@ section .bss
     part1         resq 1
     part2         resq 1
 
-    number_buffer resb 32  ; for printing
-
 section .text
 
 _start:
-    mov     rax, SYS_OPEN
     mov     rdi, input_path
-    mov     rsi, O_RDONLY
-    xor     rdx, rdx
-    syscall
-    mov     r12, rax  ; fd
-
-    xor     r13, r13  ; bytes read so far
-read_loop:
-    mov     rax, SYS_READ
-    mov     rdi, r12
-    lea     rsi, [raw + r13]
+    lea     rsi, [raw]
     mov     rdx, RAW_SIZE
-    sub     rdx, r13  ; remaining capacity
-    syscall
-
-    cmp     rax, 0
-    jle     read_done
-    add     r13, rax
-    jmp     read_loop
-read_done:
-    mov     [raw_len], r13
-
-    mov     rax, SYS_CLOSE
-    mov     rdi, r12
-    syscall
+    call    read_file
+    mov     [raw_len], rax
 
     xor     rcx, rcx  ; column scanner
 width_scan:
@@ -266,60 +234,3 @@ count_neighbors:
     movzx   r8d, byte [grid + rdx + 1]
     add     eax, r8d
     ret
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
diff --git a/aoc-2025/day5.asm b/aoc-2025/day5.asm
index 4f395a0..4718343 100644
--- a/aoc-2025/day5.asm
+++ b/aoc-2025/day5.asm
@@ -5,14 +5,8 @@ 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
+%include "utils/io.asm"
+%include "utils/parse.asm"
 
 %define RAW_SIZE   1048576  ; 1 MiB scratch for the raw file
 %define MAX_RANGES 8192     ; plenty for the ~177 input ranges
@@ -20,8 +14,6 @@ global _start
 section .data
     input_path db "input/day5.txt", 0
 
-    newline    db 10
-
     label1     db "Part 1: ", 0
     label2     db "Part 2: ", 0
 
@@ -38,36 +30,14 @@ section .bss
     part1         resq 1
     part2         resq 1
 
-    number_buffer resb 32
-
 section .text
 
 _start:
-    mov     rax, SYS_OPEN
     mov     rdi, input_path
-    mov     rsi, O_RDONLY
-    xor     rdx, rdx
-    syscall
-    mov     r12, rax  ; fd
-
-    xor     r13, r13
-read_loop:
-    mov     rax, SYS_READ
-    mov     rdi, r12
-    lea     rsi, [raw + r13]
+    lea     rsi, [raw]
     mov     rdx, RAW_SIZE
-    sub     rdx, r13
-    syscall
-    cmp     rax, 0
-    jle     read_done
-    add     r13, rax
-    jmp     read_loop
-read_done:
-    mov     [raw_len], r13
-
-    mov     rax, SYS_CLOSE
-    mov     rdi, r12
-    syscall
+    call    read_file
+    mov     [raw_len], rax
 
     ; RSI = cursor, R14 = end pointer (both preserved across helper calls)
     lea     rsi, [raw]
@@ -146,25 +116,6 @@ print_results:
     xor     rdi, rdi
     syscall
 
-; parse_u64: read decimal digits at [RSI], advancing RSI past them.
-;   Output: RAX = value. Stops on the first non-digit. Clobbers RAX, RDX.
-parse_u64:
-    xor     rax, rax
-.digit:
-    mov     dl, [rsi]
-    cmp     dl, '0'
-    jl      .done
-    cmp     dl, '9'
-    jg      .done
-    sub     dl, '0'
-    movzx   rdx, dl
-    imul    rax, rax, 10
-    add     rax, rdx
-    inc     rsi
-    jmp     .digit
-.done:
-    ret
-
 ; is_fresh: test membership of an ID in the merged intervals.
 ;   Input:  RDI = id
 ;   Output: RAX = 1 if the id lies in any interval, else 0
@@ -272,60 +223,3 @@ finalize_ranges:
     inc     rdx  ; end - start + 1
     add     r12, rdx
     ret
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
diff --git a/aoc-2025/day6.asm b/aoc-2025/day6.asm
index 774ca4c..728b8b0 100644
--- a/aoc-2025/day6.asm
+++ b/aoc-2025/day6.asm
@@ -5,14 +5,7 @@ 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
+%include "utils/io.asm"
 
 %define RAW_SIZE   1048576
 %define MAX_W      8192
@@ -22,8 +15,6 @@ global _start
 section .data
     input_path db "input/day6.txt", 0
 
-    newline    db 10
-
     label1     db "Part 1: ", 0
     label2     db "Part 2: ", 0
 
@@ -42,36 +33,14 @@ section .bss
     part1         resq 1
     part2         resq 1
 
-    number_buffer resb 32
-
 section .text
 
 _start:
-    mov     rax, SYS_OPEN
     mov     rdi, input_path
-    mov     rsi, O_RDONLY
-    xor     rdx, rdx
-    syscall
-    mov     r12, rax
-
-    xor     r13, r13
-read_loop:
-    mov     rax, SYS_READ
-    mov     rdi, r12
-    lea     rsi, [raw + r13]
+    lea     rsi, [raw]
     mov     rdx, RAW_SIZE
-    sub     rdx, r13
-    syscall
-    cmp     rax, 0
-    jle     read_done
-    add     r13, rax
-    jmp     read_loop
-read_done:
-    mov     [raw_len], r13
-
-    mov     rax, SYS_CLOSE
-    mov     rdi, r12
-    syscall
+    call    read_file
+    mov     [raw_len], rax
 
     ; width = length of the first line
     xor     rcx, rcx
@@ -360,60 +329,3 @@ process_block:
     add     [part2], r13
 .ret:
     ret
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
diff --git a/aoc-2025/day7.asm b/aoc-2025/day7.asm
index 40d700d..1d990a7 100644
--- a/aoc-2025/day7.asm
+++ b/aoc-2025/day7.asm
@@ -5,14 +5,7 @@ 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
+%include "utils/io.asm"
 
 %define RAW_SIZE   1048576
 %define MAX_W      1024
@@ -22,8 +15,6 @@ global _start
 section .data
     input_path db "input/day7.txt", 0
 
-    newline    db 10
-
     label1     db "Part 1: ", 0
     label2     db "Part 2: ", 0
 
@@ -43,36 +34,14 @@ section .bss
     part1         resq 1
     part2         resq 1
 
-    number_buffer resb 32
-
 section .text
 
 _start:
-    mov     rax, SYS_OPEN
     mov     rdi, input_path
-    mov     rsi, O_RDONLY
-    xor     rdx, rdx
-    syscall
-    mov     r12, rax
-
-    xor     r13, r13
-read_loop:
-    mov     rax, SYS_READ
-    mov     rdi, r12
-    lea     rsi, [raw + r13]
+    lea     rsi, [raw]
     mov     rdx, RAW_SIZE
-    sub     rdx, r13
-    syscall
-    cmp     rax, 0
-    jle     read_done
-    add     r13, rax
-    jmp     read_loop
-read_done:
-    mov     [raw_len], r13
-
-    mov     rax, SYS_CLOSE
-    mov     rdi, r12
-    syscall
+    call    read_file
+    mov     [raw_len], rax
 
     ; width = length of the first line
     xor     rcx, rcx
@@ -331,60 +300,3 @@ print_results:
     mov     rax, SYS_EXIT
     xor     rdi, rdi
     syscall
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
diff --git a/aoc-2025/day8.asm b/aoc-2025/day8.asm
index 407d0e4..6a4ecec 100644
--- a/aoc-2025/day8.asm
+++ b/aoc-2025/day8.asm
@@ -5,14 +5,8 @@ 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
+%include "utils/io.asm"
+%include "utils/parse.asm"
 
 %define RAW_SIZE   262144
 %define MAXN       1024
@@ -22,8 +16,6 @@ global _start
 section .data
     input_path db "input/day8.txt", 0
 
-    newline    db 10
-
     label1     db "Part 1: ", 0
     label2     db "Part 2: ", 0
 
@@ -49,36 +41,14 @@ section .bss
     part1         resq 1
     part2         resq 1
 
-    number_buffer resb 32
-
 section .text
 
 _start:
-    mov     rax, SYS_OPEN
     mov     rdi, input_path
-    mov     rsi, O_RDONLY
-    xor     rdx, rdx
-    syscall
-    mov     r12, rax
-
-    xor     r13, r13
-read_loop:
-    mov     rax, SYS_READ
-    mov     rdi, r12
-    lea     rsi, [raw + r13]
+    lea     rsi, [raw]
     mov     rdx, RAW_SIZE
-    sub     rdx, r13
-    syscall
-    cmp     rax, 0
-    jle     read_done
-    add     r13, rax
-    jmp     read_loop
-read_done:
-    mov     [raw_len], r13
-
-    mov     rax, SYS_CLOSE
-    mov     rdi, r12
-    syscall
+    call    read_file
+    mov     [raw_len], rax
 
     ; parse "X,Y,Z" lines into x/y/z, counting boxes
     lea     rsi, [raw]
@@ -354,78 +324,3 @@ compute_part1:
     imul    rax, r10
     mov     [part1], rax
     ret
-
-; parse_u64: read decimal digits at [RSI], advancing RSI. Clobbers RAX, RDX.
-parse_u64:
-    xor     rax, rax
-.digit:
-    mov     dl, [rsi]
-    cmp     dl, '0'
-    jl      .done
-    cmp     dl, '9'
-    jg      .done
-    sub     dl, '0'
-    movzx   rdx, dl
-    imul    rax, rax, 10
-    add     rax, rdx
-    inc     rsi
-    jmp     .digit
-.done:
-    ret
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
diff --git a/aoc-2025/day9.asm b/aoc-2025/day9.asm
index 8b0edcf..e5a7d0d 100644
--- a/aoc-2025/day9.asm
+++ b/aoc-2025/day9.asm
@@ -5,14 +5,8 @@ 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
+%include "utils/io.asm"
+%include "utils/parse.asm"
 
 %define RAW_SIZE   262144
 %define MAXN       512
@@ -23,8 +17,6 @@ global _start
 section .data
     input_path db "input/day9.txt", 0
 
-    newline    db 10
-
     label1     db "Part 1: ", 0
     label2     db "Part 2: ", 0
 
@@ -62,35 +54,14 @@ section .bss
     best1         resq 1
     best2         resq 1
 
-    number_buffer resb 32
-
 section .text
 
 _start:
-    mov     rax, SYS_OPEN
     mov     rdi, input_path
-    mov     rsi, O_RDONLY
-    xor     rdx, rdx
-    syscall
-    mov     r12, rax
-
-    xor     r13, r13
-read_loop:
-    mov     rax, SYS_READ
-    mov     rdi, r12
-    lea     rsi, [raw + r13]
+    lea     rsi, [raw]
     mov     rdx, RAW_SIZE
-    sub     rdx, r13
-    syscall
-    cmp     rax, 0
-    jle     read_done
-    add     r13, rax
-    jmp     read_loop
-read_done:
-    mov     [raw_len], r13
-    mov     rax, SYS_CLOSE
-    mov     rdi, r12
-    syscall
+    call    read_file
+    mov     [raw_len], rax
 
     ; parse "X,Y" vertices in order
     lea     rsi, [raw]
@@ -567,78 +538,3 @@ dedup_q:
     jmp     .loop
 .done:
     ret
-
-; parse_u64: read decimal digits at [RSI], advancing RSI. Clobbers RAX, RDX.
-parse_u64:
-    xor     rax, rax
-.digit:
-    mov     dl, [rsi]
-    cmp     dl, '0'
-    jl      .done
-    cmp     dl, '9'
-    jg      .done
-    sub     dl, '0'
-    movzx   rdx, dl
-    imul    rax, rax, 10
-    add     rax, rdx
-    inc     rsi
-    jmp     .digit
-.done:
-    ret
-
-print_newline:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, newline
-    mov     rdx, 1
-    syscall
-    ret
-
-print_int64:
-    mov     rdi, number_buffer+31
-    mov     byte [rdi], 0
-    dec     rdi
-
-    cmp     rax, 0
-    jne     .conv
-
-    mov     byte [rdi], '0'
-    jmp     .done
-.conv:
-    mov     rbx, 10
-.next:
-    xor     rdx, rdx
-    div     rbx
-    add     dl, '0'
-    mov     [rdi], dl
-    dec     rdi
-    test    rax, rax
-    jnz     .next
-
-    inc     rdi
-.done:
-    mov     rax, SYS_WRITE
-    mov     rsi, rdi
-    mov     rdi, STDOUT
-    mov     rdx, number_buffer+31
-    sub     rdx, rsi
-    syscall
-    ret
-
-print_string:
-    push    rcx
-    push    rdx
-    mov     rdx, 0
-.length:
-    cmp     byte [rcx+rdx], 0
-    je      .submit
-    inc     rdx
-    jmp     .length
-.submit:
-    mov     rax, SYS_WRITE
-    mov     rdi, STDOUT
-    mov     rsi, rcx
-    syscall
-    pop     rdx
-    pop     rcx
-    ret
diff --git a/aoc-2025/utils/io.asm b/aoc-2025/utils/io.asm
new file mode 100644
index 0000000..2081671
--- /dev/null
+++ b/aoc-2025/utils/io.asm
@@ -0,0 +1,107 @@
+; utils/io.asm - shared syscall constants, file reading, and output helpers.
+; This file is %included (not linked) by each day's solution.
+
+%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
+    newline db 10
+
+section .bss
+    number_buffer resb 32
+
+section .text
+
+; read_file: open the path in RDI read-only, read up to RDX bytes into the
+; buffer in RSI, close, and return the number of bytes read in RAX.
+read_file:
+    mov     r8, rsi         ; buffer base
+    mov     r9, rdx         ; capacity
+    mov     rax, SYS_OPEN
+    mov     rsi, O_RDONLY
+    xor     rdx, rdx
+    syscall
+    mov     r10, rax        ; fd
+    xor     r11, r11        ; bytes read so far
+.loop:
+    mov     rax, SYS_READ
+    mov     rdi, r10
+    lea     rsi, [r8 + r11]
+    mov     rdx, r9
+    sub     rdx, r11
+    syscall
+    cmp     rax, 0
+    jle     .done
+    add     r11, rax
+    jmp     .loop
+.done:
+    mov     rax, SYS_CLOSE
+    mov     rdi, r10
+    syscall
+    mov     rax, r11
+    ret
+
+print_newline:
+    mov     rax, SYS_WRITE
+    mov     rdi, STDOUT
+    mov     rsi, newline
+    mov     rdx, 1
+    syscall
+    ret
+
+; print_int64: print the unsigned integer in RAX in decimal.
+print_int64:
+    mov     rdi, number_buffer+31
+    mov     byte [rdi], 0
+    dec     rdi
+
+    cmp     rax, 0
+    jne     .conv
+
+    mov     byte [rdi], '0'
+    jmp     .done
+.conv:
+    mov     rbx, 10
+.next:
+    xor     rdx, rdx
+    div     rbx
+    add     dl, '0'
+    mov     [rdi], dl
+    dec     rdi
+    test    rax, rax
+    jnz     .next
+
+    inc     rdi
+.done:
+    mov     rax, SYS_WRITE
+    mov     rsi, rdi
+    mov     rdi, STDOUT
+    mov     rdx, number_buffer+31
+    sub     rdx, rsi
+    syscall
+    ret
+
+; print_string: print the NUL-terminated string pointed to by RCX.
+print_string:
+    push    rcx
+    push    rdx
+    mov     rdx, 0
+.length:
+    cmp     byte [rcx+rdx], 0
+    je      .submit
+    inc     rdx
+    jmp     .length
+.submit:
+    mov     rax, SYS_WRITE
+    mov     rdi, STDOUT
+    mov     rsi, rcx
+    syscall
+    pop     rdx
+    pop     rcx
+    ret
diff --git a/aoc-2025/utils/parse.asm b/aoc-2025/utils/parse.asm
new file mode 100644
index 0000000..833cb4e
--- /dev/null
+++ b/aoc-2025/utils/parse.asm
@@ -0,0 +1,22 @@
+; utils/parse.asm - decimal parsing helper.
+
+section .text
+
+; parse_u64: read decimal digits at [RSI] into RAX, advancing RSI past them.
+; Stops on the first non-digit. Clobbers RAX, RDX.
+parse_u64:
+    xor     rax, rax
+.digit:
+    mov     dl, [rsi]
+    cmp     dl, '0'
+    jl      .done
+    cmp     dl, '9'
+    jg      .done
+    sub     dl, '0'
+    movzx   rdx, dl
+    imul    rax, rax, 10
+    add     rax, rdx
+    inc     rsi
+    jmp     .digit
+.done:
+    ret