write_file

stdlib/io.sl

@@ -0,0 +1,134 @@
+
+# L2 IO Primitives
+
+# : read_file ( path_ptr path_len -- len addr | 0 0 )
+#   Reads the file at the given path (pointer+length, not null-terminated),
+#   returns (len addr) of mapped file, or (0 0) on error.
+
+:asm read_file {
+	; stack: path_ptr (top), path_len (next)
+	mov rsi, [r12]        ; path_ptr
+	mov rdx, [r12 + 8]    ; path_len
+	add r12, 16           ; pop args
+
+	; open(path_ptr, O_RDONLY=0, mode=0)
+	mov rax, 2            ; syscall: open
+	mov rdi, rsi          ; filename
+	xor rsi, rsi          ; flags = O_RDONLY
+	xor rdx, rdx          ; mode = 0
+	syscall
+	mov r10, rax          ; save open() result
+	cmp rax, 0
+	jl .fail_open
+	mov r8, rax           ; fd
+
+	; use lseek to determine file size: lseek(fd, 0, SEEK_END)
+	mov rax, 8            ; syscall: lseek
+	mov rdi, r8           ; fd
+	xor rsi, rsi          ; offset = 0
+	mov rdx, 2            ; SEEK_END
+	syscall
+	mov r11, rax          ; save lseek() result
+	cmp rax, 0
+	jl .close_fail_lseek
+	mov rsi, rax          ; length = size
+
+	; mmap(NULL, size, PROT_READ=1, MAP_PRIVATE=2, fd, 0)
+	mov rax, 9            ; syscall: mmap
+	xor rdi, rdi          ; addr = NULL
+	; rsi already holds length
+	mov rdx, 1            ; PROT_READ
+	mov r10, 2            ; MAP_PRIVATE
+	mov r8, r8            ; fd
+	xor r9, r9            ; offset = 0
+	syscall
+	mov rbx, rax          ; addr
+	mov r12, r12          ; (no-op, for debug)
+	mov rax, 3            ; syscall: close
+	mov rdi, r8           ; fd
+	syscall
+	cmp rbx, -4095
+	jae .fail_mmap
+	sub r12, 16
+	mov [r12], rsi        ; len (rsi held length across syscall)
+	mov [r12 + 8], rbx    ; addr
+	ret
+
+.close_fail_lseek:
+	mov rax, 3
+	mov rdi, r8
+	syscall
+	mov rax, r11          ; return lseek() error code
+	sub r12, 16
+	mov [r12], rax
+	mov qword [r12 + 8], -1
+	ret
+
+.fail_open:
+	mov rax, r10          ; return open() error code
+	sub r12, 16
+	mov [r12], rax
+	mov qword [r12 + 8], -2
+	ret
+
+.fail_mmap:
+	mov rax, -1           ; return mmap() error
+	sub r12, 16
+	mov [r12], rax
+	mov qword [r12 + 8], -3
+	ret
+}
+;
+
+# : write_file ( path_ptr path_len buf_ptr buf_len -- bytes_written | neg_errno )
+:asm write_file {
+	; stack: path_ptr (top), path_len, buf_ptr, buf_len
+	mov rsi, [r12]        ; path_ptr
+	mov rdx, [r12 + 8]    ; path_len
+	mov r15, [r12 + 16]   ; buf_ptr (save in callee-saved r15)
+	mov r13, [r12 + 24]   ; buf_len (save in callee-saved r13)
+	add r12, 32           ; pop 4 args (we saved buf info)
+
+	; open(path_ptr, O_WRONLY|O_CREAT|O_TRUNC, 0666)
+	mov rdi, rsi          ; filename
+	mov rsi, 577          ; flags = O_WRONLY|O_CREAT|O_TRUNC
+	mov rdx, 438          ; mode = 0o666
+	mov rax, 2            ; syscall: open
+	syscall
+	cmp rax, 0
+	jl .fail_open
+	mov r9, rax           ; save fd
+
+	; write(fd, buf_ptr, buf_len) -- use preserved r15/r13 which survive syscalls
+	mov rax, 1            ; syscall: write
+	mov rdi, r9           ; fd
+	mov rsi, r15          ; buf_ptr
+	mov rdx, r13          ; buf_len
+	syscall
+	mov r10, rax          ; save write result
+	cmp r10, 0
+	jl .fail_write
+
+	; close(fd)
+	mov rax, 3            ; syscall: close
+	mov rdi, r9
+	syscall
+
+	sub r12, 8
+	mov [r12], r10
+	ret
+
+.fail_write:
+	mov rax, 3
+	mov rdi, r9
+	syscall
+	sub r12, 8
+	mov [r12], r10
+	ret
+
+.fail_open:
+	sub r12, 8
+	mov [r12], rax
+	ret
+}
+;