refactor: clean up repository layout

1 files changed, 302 insertions, 0 deletions

diff --git a/2025/day7.asm b/2025/day7.asm
new file mode 100644
index 0000000..1d990a7
--- /dev/null
+++ b/2025/day7.asm
@@ -0,0 +1,302 @@
+; Advent of Code 2025 - Day 7
+
+bits 64
+default rel
+
+global _start
+
+%include "utils/io.asm"
+
+%define RAW_SIZE   1048576
+%define MAX_W      1024
+%define MAX_H      1024
+%define GRID_SIZE  (MAX_W * MAX_H)
+
+section .data
+    input_path db "input/day7.txt", 0
+
+    label1     db "Part 1: ", 0
+    label2     db "Part 2: ", 0
+
+section .bss
+    raw           resb RAW_SIZE
+    grid          resb GRID_SIZE          ; height x width, '.'-filled
+    g             resq (MAX_W * MAX_H)     ; part 2 timeline counts
+    cur           resb MAX_W               ; part 1 active columns (this row)
+    nxt           resb MAX_W               ; part 1 active columns (next row)
+
+    raw_len       resq 1
+    width         resq 1
+    height        resq 1
+    srow          resq 1
+    scol          resq 1
+
+    part1         resq 1
+    part2         resq 1
+
+section .text
+
+_start:
+    mov     rdi, input_path
+    lea     rsi, [raw]
+    mov     rdx, RAW_SIZE
+    call    read_file
+    mov     [raw_len], rax
+
+    ; width = length of the first line
+    xor     rcx, rcx
+width_scan:
+    cmp     rcx, [raw_len]
+    jge     width_done
+    mov     al, [raw + rcx]
+    cmp     al, 10
+    je      width_done
+    cmp     al, 13
+    je      width_done
+    inc     rcx
+    jmp     width_scan
+width_done:
+    mov     [width], rcx
+
+    ; height = number of lines
+    xor     rcx, rcx
+    xor     r8, r8
+height_scan:
+    cmp     rcx, [raw_len]
+    jge     height_tail
+    mov     al, [raw + rcx]
+    cmp     al, 10
+    jne     height_next
+    inc     r8
+height_next:
+    inc     rcx
+    jmp     height_scan
+height_tail:
+    mov     rax, [raw_len]
+    test    rax, rax
+    jz      height_store
+    mov     dl, [raw + rax - 1]
+    cmp     dl, 10
+    je      height_store
+    inc     r8
+height_store:
+    mov     [height], r8
+
+    ; '.'-fill the grid, then copy the raw bytes into it
+    mov     rax, [height]
+    imul    rax, [width]
+    mov     rcx, rax
+    lea     rdi, [grid]
+    mov     al, '.'
+    rep     stosb
+
+    xor     r8, r8   ; raw index
+    xor     r9, r9   ; row
+    xor     r10, r10 ; col
+fill_loop:
+    cmp     r8, [raw_len]
+    jge     fill_done
+    mov     al, [raw + r8]
+    inc     r8
+    cmp     al, 10
+    je      fill_newline
+    cmp     al, 13
+    je      fill_loop
+    cmp     r10, [width]
+    jge     fill_loop
+    mov     rdx, r9
+    imul    rdx, [width]
+    add     rdx, r10
+    mov     [grid + rdx], al
+    inc     r10
+    jmp     fill_loop
+fill_newline:
+    inc     r9
+    xor     r10, r10
+    jmp     fill_loop
+fill_done:
+
+    ; locate S
+    xor     r8, r8
+    mov     rax, [height]
+    imul    rax, [width]
+    mov     r9, rax
+find_s:
+    cmp     r8, r9
+    jge     s_done
+    mov     al, [grid + r8]
+    cmp     al, 'S'
+    je      s_found
+    inc     r8
+    jmp     find_s
+s_found:
+    mov     rax, r8
+    xor     rdx, rdx
+    div     qword [width]
+    mov     [srow], rax
+    mov     [scol], rdx
+s_done:
+
+    ; part 1: flood a set of active columns, counting splitter hits
+    lea     rdi, [cur]
+    mov     rcx, MAX_W
+    xor     al, al
+    rep     stosb
+    mov     rax, [scol]
+    mov     byte [cur + rax], 1
+
+    xor     r15, r15   ; row
+p1_row:
+    cmp     r15, [height]
+    jge     p1_done
+    lea     rdi, [nxt]
+    mov     rcx, MAX_W
+    xor     al, al
+    rep     stosb
+
+    mov     rax, r15
+    imul    rax, [width]
+    mov     r14, rax   ; row offset
+    xor     r13, r13   ; col
+    xor     r12, r12   ; any beam alive?
+p1_col:
+    cmp     r13, [width]
+    jge     p1_col_done
+    mov     al, [cur + r13]
+    test    al, al
+    jz      p1_next
+    mov     rdx, r14
+    add     rdx, r13
+    mov     al, [grid + rdx]
+    cmp     al, '^'
+    jne     p1_pass
+    inc     qword [part1]
+    mov     rbx, r13   ; left neighbor
+    test    rbx, rbx
+    jz      p1_no_left
+    dec     rbx
+    mov     byte [nxt + rbx], 1
+    mov     r12, 1
+p1_no_left:
+    mov     rbx, r13   ; right neighbor
+    inc     rbx
+    cmp     rbx, [width]
+    jge     p1_no_right
+    mov     byte [nxt + rbx], 1
+    mov     r12, 1
+p1_no_right:
+    jmp     p1_next
+p1_pass:
+    mov     byte [nxt + r13], 1
+    mov     r12, 1
+p1_next:
+    inc     r13
+    jmp     p1_col
+p1_col_done:
+    lea     rsi, [nxt]
+    lea     rdi, [cur]
+    mov     rcx, MAX_W
+    rep     movsb
+    test    r12, r12
+    jz      p1_done
+    inc     r15
+    jmp     p1_row
+p1_done:
+
+    ; part 2: bottom-up DP of timeline counts, g[r][c]
+    mov     r15, [height]
+    dec     r15        ; row, counting down
+p2_row:
+    cmp     r15, 0
+    jl      p2_done
+    mov     rax, r15
+    imul    rax, [width]
+    mov     r14, rax   ; row offset
+    xor     r13, r13   ; col
+p2_col:
+    cmp     r13, [width]
+    jge     p2_col_done
+    mov     rdx, r14
+    add     rdx, r13   ; idx = r*W + c
+    mov     al, [grid + rdx]
+    cmp     al, '^'
+    je      p2_split
+
+    ; pass straight down: g = (r+1 in grid ? g[r+1][c] : 1)
+    mov     rbx, r15
+    inc     rbx
+    cmp     rbx, [height]
+    jge     p2_pass_exit
+    mov     rcx, rdx
+    add     rcx, [width]
+    mov     rax, [g + rcx*8]
+    jmp     p2_store
+p2_pass_exit:
+    mov     rax, 1
+    jmp     p2_store
+
+p2_split:
+    ; left child enters (r+1, c-1)
+    mov     rbx, r15
+    inc     rbx
+    cmp     rbx, [height]
+    jge     p2_left_one
+    cmp     r13, 0
+    jle     p2_left_one
+    mov     rcx, rdx
+    add     rcx, [width]
+    dec     rcx
+    mov     r8, [g + rcx*8]
+    jmp     p2_left_done
+p2_left_one:
+    mov     r8, 1
+p2_left_done:
+    ; right child enters (r+1, c+1)
+    mov     rbx, r15
+    inc     rbx
+    cmp     rbx, [height]
+    jge     p2_right_one
+    mov     rbx, r13
+    inc     rbx
+    cmp     rbx, [width]
+    jge     p2_right_one
+    mov     rcx, rdx
+    add     rcx, [width]
+    inc     rcx
+    mov     r9, [g + rcx*8]
+    jmp     p2_right_done
+p2_right_one:
+    mov     r9, 1
+p2_right_done:
+    mov     rax, r8
+    add     rax, r9
+p2_store:
+    mov     [g + rdx*8], rax
+    inc     r13
+    jmp     p2_col
+p2_col_done:
+    dec     r15
+    jmp     p2_row
+p2_done:
+    mov     rax, [srow]
+    imul    rax, [width]
+    add     rax, [scol]
+    mov     rax, [g + rax*8]
+    mov     [part2], rax
+
+print_results:
+    mov     rcx, label1
+    call    print_string
+    mov     rax, [part1]
+    call    print_int64
+    call    print_newline
+
+    mov     rcx, label2
+    call    print_string
+    mov     rax, [part2]
+    call    print_int64
+    call    print_newline
+
+    mov     rax, SYS_EXIT
+    xor     rdi, rdi
+    syscall