X-Git-Url: https://git.rrq.au/?a=blobdiff_plain;f=main.asm;h=537d0e8e6fe3e3728bc06704d8925001e27f739e;hb=4170f15b09ccd8bcafc00bb960a6e56670252256;hp=a4db7329bb1f8ed39570b1196f0df2556f75e761;hpb=f0df53c35124c9a5e2b045aba60b513faa344567;p=rrq%2Fjonasforth.git

diff --git a/main.asm b/main.asm
index a4db732..537d0e8 100644
--- a/main.asm
+++ b/main.asm
@@ -1,6 +1,6 @@
 ;; vim: syntax=fasm
 
-format ELF64 executable
+include "uefi.asm"
 
 ;; "Syscalls" {{{
 
@@ -22,10 +22,46 @@ format ELF64 executable
 ;;
 ;; 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
 }
 
 ;; }}}
@@ -87,9 +123,7 @@ macro forth_asm label, name, immediate {
 .start:
 }
 
-segment readable executable
-
-entry main
+section '.text' code readable executable
 
 include "impl.asm"      ; Misc. subroutines
 include "bootstrap.asm" ; Forth words encoded in Assembly
@@ -98,6 +132,8 @@ main:
   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]
 
@@ -195,35 +231,77 @@ forth_asm EMIT, 'EMIT'
   popr rsi
   next
 
-;; Read a word from standard input 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'
-  mov [.rsi], rsi
+;; 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
 
-  call read_word
-  push rdi                      ; Buffer
-  push rdx                      ; Length
+;; Result in RAX
+.impl:
+  ;; Are we reading from user input or from the input buffer?
+  cmp [input_buffer], 0
+  jne .from_buffer
 
-  mov rsi, [.rsi]
-  next
+  ;; Reading user input
+  push rsi
+  mov rsi, .buffer
+  sys_read_char
+  pop rsi
 
-;; Read a word from a buffer. Expects (buffer buffer-length) on the stack.
-;; Updates buffer and buffer-length, such that the word has been removed from
-;; the buffer. Appends (word-buffer word-buffer-length) to the stack.
-forth_asm POP_WORD, 'POP-WORD'
-  pushr rsi
+  movzx rax, byte [.buffer]
+  ret
+
+.from_buffer:
+  ;; Reading from buffer
+  mov rax, [input_buffer]
+  movzx rax, byte [rax]
 
-  pop rcx ; Length
-  pop rsi ; Buffer
+  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
 
-  push rsi ; Updated buffer
-  push 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
 
-  popr rsi
   next
 
 ;; Takes a string on the stack and replaces it with the decimal number that the
@@ -255,9 +333,7 @@ forth_asm TELL, 'TELL'
 
 ;; 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'
@@ -406,23 +482,21 @@ forth_asm TIMESMOD, '/MOD'
   push rdx                      ; a % b
   next
 
-;; Read user input until next " character is found. Push a string containing the
+;; Read input until next " character is found. Push a string containing the
 ;; input on the stack as (buffer length). Note that the buffer is only valid
 ;; until the next call to S" and that no more than 255 characters can be read.
-;;
-;; [TODO] We want to be able to use this when reading from buffers (e.g. in
-;; INTERPRET-STRING) too!
 forth_asm READ_STRING, 'S"'
+  ;; If the input buffer is set, we should read from there instead.
+  cmp [input_buffer], 0
+  jne read_string_buffer
+
   push rsi
 
   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, '"'
@@ -442,19 +516,12 @@ forth_asm READ_STRING, 'S"'
 
   next
 
-;; BUF" works a bit like S, but it reads the string from the current input
-;; buffer described in INPUT-BUFFER and INPUT-LENGTH. We use this fucntion in
-;; sys.f to store strings.
-forth_asm BUF_READ_STRING, 'BUF"'
+read_string_buffer:
   push rsi
 
   ;; 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]
@@ -583,7 +650,7 @@ forth INPUT_LENGTH, 'INPUT-LENGTH'
   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
@@ -594,6 +661,12 @@ latest_entry dq initial_latest_entry
 ;; it is compiling.
 var_STATE dq 0
 
+;; The interpreter can read either from standard input or from a buffer. When
+;; input-buffer is set (non-null), words like READ-WORD and S" will use this
+;; buffer instead of reading user input.
+input_buffer dq 0
+input_buffer_length dq 0
+
 FIND.rsi dq ?
 
 READ_WORD.rsi dq ?
@@ -609,22 +682,19 @@ DOTU.rbuffer rq 16
 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
 
-;; Pointer to input buffer and its length. Used as local variable in
-;; INTERPRET-STRING (see bootstrap.asm). [TODO] The code organization is a bit
-;; awkward here.
-input_buffer dq ?
-input_buffer_length dq ?
-
 ;; Return stack
 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.