;; vim: syntax=fasm
-format ELF64 executable
+include "uefi.asm"
;; "Syscalls" {{{
;;
;; Clobbers: RAX, RCX, R11, RDI, RSI
macro sys_print_string {
- mov rax, 1
- mov rdi, 1
- mov rsi, rcx
- syscall
+ push r8
+ push r9
+ push r10
+
+ call uefi_print_string
+
+ pop r10
+ pop r9
+ pop r8
+}
+
+;; Read a character from the user into the given buffer.
+;;
+;; Input:
+;; - RSI = Character buffer
+;;
+;; Output:
+;; - BYTE [RSI] = Character
+;;
+;; Clobbers: RAX, RCX, R11, RDI, RSI, RDX
+macro sys_read_char {
+ push rbx
+ push r8
+ push r9
+ push r10
+ push r15
+
+ mov rcx, rsi
+ call uefi_read_char
+
+ pop r15
+ pop r10
+ pop r9
+ pop r8
+ pop rbx
+}
+
+macro sys_terminate code {
+ mov rax, code
+ call uefi_terminate
}
;; }}}
.start:
}
-segment readable executable
-
-entry main
+section '.text' code readable executable
include "impl.asm" ; Misc. subroutines
include "bootstrap.asm" ; Forth words encoded in Assembly
cld ; Clear direction flag so LODSQ does the right thing.
mov rbp, return_stack_top ; Initialize return stack
+ call uefi_initialize
+
mov rax, MAIN
jmp qword [rax]
popr rsi
next
-;; Read a word and push it onto the stack as a pointer and a size. The pointer
-;; is valid until the next call to READ_WORD.
-forth_asm READ_WORD, 'READ-WORD'
+;; Read a single character from the current input stream. Usually, this will wait
+;; for the user to press a key, and then return the corresponding character. When
+;; reading from a special buffer, it will instead return the next characater from
+;; that buffer.
+;;
+;; The ASCII character code is placed on the stack.
+forth_asm KEY, 'KEY'
+ call .impl
+ push rax
+ next
+
+;; Result in RAX
+.impl:
;; Are we reading from user input or from the input buffer?
cmp [input_buffer], 0
jne .from_buffer
;; Reading user input
- mov [.rsi], rsi
+ push rsi
+ mov rsi, .buffer
+ sys_read_char
+ pop rsi
- call read_word
- push rdi ; Buffer
- push rdx ; Length
-
- mov rsi, [.rsi]
- next
+ movzx rax, byte [.buffer]
+ ret
.from_buffer:
;; Reading from buffer
- mov [.rsi], rsi
+ mov rax, [input_buffer]
+ movzx rax, byte [rax]
- mov rsi, [input_buffer]
- mov rcx, [input_buffer_length]
+ inc [input_buffer]
+ dec [input_buffer_length]
+ ret
- call pop_word
+;; Read a word and push it onto the stack as a pointer and a size. The pointer
+;; is valid until the next call to READ_WORD.
+forth_asm READ_WORD, 'READ-WORD'
+ push rsi
+.skip_whitespace:
+ ;; Read characters until one of them is not whitespace.
+ call KEY.impl
+ ;; We consider newlines and spaces to be whitespace.
+ cmp al, ' '
+ je .skip_whitespace
+ cmp al, $A
+ je .skip_whitespace
+
+ ;; We got a character that wasn't whitespace. Now read the actual word.
+ mov [.length], 0
- mov [input_buffer], rsi ; Updated buffer
- mov [input_buffer_length], rcx ; Length of updated buffer
- push rdi ; Word buffer
- push rdx ; Length of word buffer
+.read_alpha:
+ movzx rbx, [.length]
+ mov rsi, .buffer
+ add rsi, rbx
+ mov [rsi], al
+ inc [.length]
+
+ call KEY.impl
+
+ cmp al, ' '
+ je .end
+ cmp al, $A
+ jne .read_alpha
+
+.end:
+ pop rsi
+ push .buffer
+ movzx rax, [.length]
+ push rax
- mov rsi, [.rsi]
next
;; Takes a string on the stack and replaces it with the decimal number that the
;; Exit the program cleanly.
forth_asm TERMINATE, 'TERMINATE'
- mov rax, $3C
- mov rdi, 0
- syscall
+ sys_terminate 0
;; Duplicate a pair of elements.
forth_asm PAIRDUP, '2DUP'
mov [.length], 0
.read_char:
- mov rax, 0
- mov rdi, 0
mov rsi, .char_buffer
- mov rdx, 1
- syscall
+ sys_read_char
mov al, [.char_buffer]
cmp al, '"'
;; We borrow READ_STRING's buffer. They won't mind.
mov [READ_STRING.length], 0
- ;; Skip space ([TODO]: Shouldn't we do this while parsing instead?)
- inc [input_buffer]
- dec [input_buffer_length]
-
.read_char:
mov rbx, [input_buffer]
mov al, [rbx]
dq LIT, input_buffer_length
dq EXIT
-segment readable writable
+section '.data' readable writable
;; The LATEST variable holds a pointer to the word that was last added to the
;; dictionary. This pointer is updated as new words are added, and its value is
DOTU.length dq ?
DOTU.printed_length dq ?
+KEY.buffer dq ?
+
+READ_WORD.buffer rb $FF
+READ_WORD.length db ?
+
;; Reserve space for compiled words, accessed through HERE.
here dq here_top
here_top rq $4000
rq $2000
return_stack_top:
-segment readable
-
;; We store some Forth code in sys.f that defined common words that the user
;; would expect to have available at startup. To execute these words, we just
;; include the file directly in the binary, and then interpret it at startup.
projects / rrq / jonasforth.git / blobdiff