path: root/04b/in03

; initialize global_variables_end
C=:global_variables_end
D=:global_variables
8C=D
; initialize static_memory_end
C=:static_memory_end
D=x500000

I=8S
A=d3
?I!A:usage_error
; open input file
	J=S
	; argv[1] is at *(rsp+16)
	J+=d16
	J=8J
	I=d0
	syscall x2
	J=A
	?J<0:input_file_error
; open output file
	J=S
	; argv[2] is at *(rsp+24)
	J+=d24
	J=8J
	I=x241
	D=x1ed
	syscall x2
	J=A
	?J<0:output_file_error

:read_line
; increment line number
D=:line_number
C=8D
C+=d1
8D=C

; use rbp to store line pointer
R=:line
:read_line_loop
	; read 1 byte into rbp
	J=d3
	I=R
	D=d1
	syscall x0
	D=A
	?D=0:eof
	
	; check if the character was a newline:
	C=1R
	D=xa
	?C=D:read_line_loop_end
	; check if the character was a tab:
	D=x9
	; if so, don't increment rbp
	?C=D:read_line
	; check if the character was a semicolon:
	D=';
	; if so, it's a comment
	?C=D:handle_comment
	
	R+=d1
	!:read_line_loop

	:handle_comment
		; read out rest of line from file
		J=d3
		I=R
		D=d1
		syscall x0
		D=A
		?D=0:eof
		C=1R
		D=xa
		; if we didn't reach the end of the line, keep going
		?C!D:handle_comment
		
		!:read_line_loop_end
:read_line_loop_end

; remove whitespace (specifically, ' ' characters) at end of line
I=R
:remove_terminal_whitespace_loop
	I-=d1
	C=1I
	D=x20
	?C!D:remove_terminal_whitespace_loop_end
	; replace ' ' with a newline
	D=xa
	1I=D
	!:remove_terminal_whitespace_loop
:remove_terminal_whitespace_loop_end

; check if this is a blank line
C=:line
D=1C
C=xa
?C=D:read_line

I=:line
J=:"global"
C=x20
call :string=
D=A
?D!0:handle_global


!:read_line

:eof
	J=d0
	syscall x3c

:handle_global
	I=:line
	; skip "global "
	I+=d7
	call :read_type
	; put type in R
	R=A
	; skip ' ' after type
	I+=d1
	J=:global_variables_end
	J=8J
	call :ident_copy
	; store type
	1J=R
	J+=d1
	; store address
	D=:static_memory_end
	D=8D
	8J=D
	; update :static_memory_end
	D=:static_memory_end
	C=8D
	C+=d8
	8D=C
	; update :global_variables_end
	I=:global_variables_end
	8I=J
	; go read the next line
	!:read_line

:"global"
	str global
	x20

; copy the newline-terminated identifier from rsi to rdi
:ident_copy
	C=1I
	B=C
	call :isident
	D=A
	?D=0:bad_identifier
	
	:ident_loop
		C=1I
		D=xa
		?C=D:ident_loop_end
		B=C
		call :isident
		D=A
		?D=0:bad_identifier
		C=1I
		1J=C
		I+=d1
		J+=d1
		!:ident_loop
	:ident_loop_end
	return
		

; can the character in rbx appear in an identifier?
:isident
	A='0
	?B<A:return_0
	; note: 58 = '9' + 1
	A=d58
	?B<A:return_1
	A='A
	?B<A:return_0
	; note: 91 = 'z' + 1
	A=d91
	?B<A:return_1
	A='z
	?B>A:return_0
	; 96 = 'a' - 1
	A=d96
	?B>A:return_1
	A='_
	?B=A:return_1
	!:return_0

; read the space-terminated type from rsi, advance rsi, and set rax to the corresponding type number:
;    0 for non-pointer types
;    1 for pointer to char
;    2 for pointer to short
;    4 for pointer to int
;    8 for pointer to long
:read_type
	C=1I
	D='*
	?C=D:read_pointer_type
		; it's not a pointer
		call :read_simple_type
		A=d0
		return
	:read_pointer_type
		; it's a pointer!
		I+=d1
		!:read_simple_type
	
; returns 1 for char, 2 for short, 4 for int, 8 for long
:read_simple_type
	R=I
	C=x20
	I=R
	J=:"char"
	call :string=
	D=A
	?D!0:return_1
	I=R
	J=:"short"
	call :string=
	D=A
	?D!0:return_2
	I=R
	J=:"int"
	call :string=
	D=A
	?D!0:return_4
	I=R
	J=:"long"
	call :string=
	D=A
	?D!0:return_8
	!:bad_type

:"char"
	str char
	x20
:"short"
	str short
	x20
:"int"
	str int
	x20
:"long"
	str long
	x20


:usage_error
	B=:usage_error_message
	call :general_error
	
:usage_error_message
	str Please provide an input and an output file.
	xa
	x0

:input_file_error
	B=:input_file_error_message
	!:general_error

:input_file_error_message
	str Couldn't open input file.
	xa
	x0

:output_file_error
	B=:output_file_error_message
	!:general_error

:output_file_error_message
	str Couldn't open output file.
	xa
	x0

:bad_identifier
	B=:bad_identifier_error_message
	!:program_error

:bad_identifier_error_message
	str Bad identifier.
	xa
	x0
	
:bad_type
	B=:bad_type_error_message
	!:program_error

:bad_type_error_message
	str Bad type.
	xa
	x0

:general_error
	call :eputs
	J=d1
	syscall x3c

:program_error
	R=B
	
	B=:"Line"
	call :eputs
	
	D=:line_number
	D=8D
	B=D
	call :eputn
	
	B=:line_number_separator
	call :eputs
	
	B=R
	call :eputs
	J=d1
	syscall x3c

:"Line"
	str Line
	x20
	x0

:line_number_separator
	str :
	x20
	x0
	
:strlen
	I=B
	D=B
	:strlen_loop
	C=1I
	?C=0:strlen_ret
	I+=d1
	!:strlen_loop
	:strlen_ret
	I-=D
	A=I
	return

; check if strings in rdi and rsi are equal, up to terminator in rcx
:string=
	D=1I
	A=1J
	?D!A:return_0
	?D=C:return_1
	I+=d1
	J+=d1
	!:string=

; check if strings in rdi and rsi are equal, up to the first non-identifier character
:ident=
	D=1I
	B=D
	call :isident
	; I ended
	?A=0:ident=_I_end
	
	D=1J
	B=D
	call :isident
	; J ended, but I didn't
	?A=0:return_0
	
	; we haven't reached the end of either
	D=1I
	A=1J
	?D!A:return_0
	I+=d1
	J+=d1
	!:ident=
:ident=_I_end
	D=1J
	B=D
	call :isident
	; check if J also ended
	?A=0:return_1
	; J didn't end
	!:return_0
	
:return_0
	A=d0
	return
:return_1
	A=d1
	return
:return_2
	A=d2
	return
:return_3
	A=d3
	return
:return_4
	A=d4
	return
:return_5
	A=d5
	return
:return_6
	A=d6
	return
:return_7
	A=d7
	return
:return_8
	A=d8
	return

; write the character in rbx to the file in rdi.
:fputc
	C=B
	I=S
	I-=d1
	1I=C
	D=d1
	syscall x1
	return

; write the string in rbx to stderr
:eputs
	J=B
	call :strlen
	D=A
	I=J
	J=d2
	syscall x1
	return
	
; write rbx in decimal to stderr
:eputn
	I=B
	J=S
	J-=d1
	:eputn_loop
		D=d0
		; divide by 10
		B=d10
		A=I
		div
		; quotient is new number
		I=A
		; add remainder to string
		D+='0
		1J=D
		J-=d1
		?I!0:eputn_loop
	D=S
	D-=J
	I=J
	J=d2
	syscall x1
	return

; copy rdx bytes from rsi to rdi.
; this copies from the left: if you're doing an overlapped copy, rsi should be greater than rdi
:memcpy
	?D=0:return_0
	A=1I
	1J=A
	I+=d1
	J+=d1
	D-=d1
	!:memcpy

; put a 0 byte before the line (this is important for removing whitespace at the end of the line,
; specifically, we don't want this to be a space character)
x0
:line
	reserve d1000
	
align
:global_variables_end
	reserve d8
:static_memory_end
	reserve d8
:line_number
	reserve d8
:global_variables
	reserve d50000
	
; we shouldn't end the file with a reserve; we don't handle that properly	
x00