function file_error
	argument name
	fputs(2, .str_file_error)
	fputs(2, name)
	fputc(2, 10)
	exit(1)
	
:str_file_error
	string Error opening file:
	byte 32
	byte 0

function malloc
	argument size
	local total_size
	local memory
	total_size = size + 8
	memory = syscall(9, 0, total_size, 3, 0x22, -1, 0)
	if memory ] 0xffffffffffff0000 goto malloc_failed
	*8memory = total_size
	return memory + 8

:malloc_failed
	fputs(2, .str_out_of_memory)
	exit(1)
	
:str_out_of_memory
	string Out of memory.
	byte 10
	byte 0

function free
	argument memory
	local psize
	local size
	psize = memory - 8
	size = *8psize
	syscall(11, psize, size)
	return

; returns a pointer to a null-terminated string containing the number given
function itos
	global 32 itos_string
	argument x
	local c
	local p
	p = &itos_string
	p += 30
	:itos_loop
		c = x % 10
		c += '0
		*1p = c
		x /= 10
		if x == 0 goto itos_loop_end
		p -= 1
		goto itos_loop
	:itos_loop_end
	return p


; returns the number at the start of the given string
function stoi
	argument s
	local p
	local n
	local c
	n = 0
	p = s
	:stoi_loop
		c = *1p
		if c < '0 goto stoi_loop_end
		if c > '9 goto stoi_loop_end
		n *= 10
		n += c - '0
		p += 1
		goto stoi_loop
	:stoi_loop_end
	return n

function memchr
	argument mem
	argument c
	local p
	local a
	p = mem
	:memchr_loop
		a = *1p
		if a == c goto memchr_loop_end
		p += 1
		goto memchr_loop
	:memchr_loop_end
	return p

function strlen
	argument s
	local c
	local p
	p = s
	:strlen_loop
		c = *1p
		if c == 0 goto strlen_loop_end
		p += 1
		goto strlen_loop
	:strlen_loop_end
	return p - s

function strcpy
	argument dest
	argument src
	local p
	local q
	local c
	p = dest
	q = src
	:strcpy_loop
		c = *1q
		*1p = c
		if c == 0 goto strcpy_loop_end
		p += 1
		q += 1
		goto strcpy_loop
	:strcpy_loop_end
	return p
	
function str_startswith
	argument s
	argument prefix
	local p
	local q
	local c1
	local c2
	p = s
	q = prefix
	:str_startswith_loop
		c1 = *1p
		c2 = *1q
		if c2 == 0 goto return_1
		if c1 != c2 goto return_0
		p += 1
		q += 1
		goto str_startswith_loop

function fputs
	argument fd
	argument s
	local length
	length = strlen(s)
	syscall(1, fd, s, length)
	return

function puts
	argument s
	fputs(1, s)
	return

function fputn
	argument fd
	argument n
	local s
	s = itos(n)
	fputs(fd, s)
	return

function fputc
	argument fd
	argument c
	local p
	p = &c
	syscall(1, fd, p, 1)
	return

function putc
	argument c
	fputc(1, c)
	return

; returns 0 at end of file
function fgetc
	argument fd
	local c
	local p
	c = 0
	p = &c
	syscall(0, fd, p, 1)
	return c

; read a line from fd as a null-terminated string
; returns 0 at end of file, 1 otherwise
function fgets
	argument fd
	argument buf
	argument size
	local p
	local end
	local c
	p = buf
	end = buf + size
	
	:fgets_loop
		c = fgetc(fd)
		if c == 0 goto fgets_eof
		if c == 10 goto fgets_eol
		*1p = c
		p += 1
		if p == end goto fgets_eob
		goto fgets_loop
		
	:fgets_eol ; end of line
	*1p = 0
	return 1
	:fgets_eof ; end of file
	*1p = 0
	return 0
	:fgets_eob ; end of buffer
	p -= 1
	*1p = 0
	return 1

; open the given file for reading
function open_r
	argument filename
	local fd
	fd = syscall(2, filename, 0)
	if fd < 0 goto open_r_error
		return fd
	:open_r_error
		file_error(filename)
		return -1

; open the given file for writing with the given mode
function open_w
	argument filename
	argument mode
	local fd
	fd = syscall(2, filename, 0x241, mode)
	if fd < 0 goto open_w_error
		return fd
	:open_w_error
		file_error(filename)
		return -1
	
function close
	argument fd
	syscall(3, fd)
	return

function isupper
	argument c
	if c < 'A goto return_0
	if c <= 'Z goto return_1
	goto return_0

function exit
	argument status_code
	syscall(0x3c, status_code)

:return_0
	return 0
:return_1
	return 1

function syscall
	; I've done some testing, and this should be okay even if
	; rbp-56 goes beyond the end of the stack.
	; mov rax, [rbp-16]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xf0
	byte 0xff
	byte 0xff
	byte 0xff
	; mov rdi, rax
	byte 0x48
	byte 0x89
	byte 0xc7
	
	; mov rax, [rbp-24]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xe8
	byte 0xff
	byte 0xff
	byte 0xff
	; mov rsi, rax
	byte 0x48
	byte 0x89
	byte 0xc6
	
	; mov rax, [rbp-32]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xe0
	byte 0xff
	byte 0xff
	byte 0xff
	; mov rdx, rax
	byte 0x48
	byte 0x89
	byte 0xc2
	
	; mov rax, [rbp-40]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xd8
	byte 0xff
	byte 0xff
	byte 0xff
	; mov r10, rax
	byte 0x49
	byte 0x89
	byte 0xc2
	
	; mov rax, [rbp-48]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xd0
	byte 0xff
	byte 0xff
	byte 0xff
	; mov r8, rax
	byte 0x49
	byte 0x89
	byte 0xc0
	
	; mov rax, [rbp-56]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xc8
	byte 0xff
	byte 0xff
	byte 0xff
	; mov r9, rax
	byte 0x49
	byte 0x89
	byte 0xc1
	
	; mov rax, [rbp-8]
	byte 0x48
	byte 0x8b
	byte 0x85
	byte 0xf8
	byte 0xff
	byte 0xff
	byte 0xff
	
	; syscall
	byte 0x0f
	byte 0x05
	
	return