X-Git-Url: https://git.rrq.au/?a=blobdiff_plain;f=main.asm;h=0190d18ae34525e0cb67aa3bb7e29827f484efa7;hb=d0a849ffeb541a8c285a92558cedcd6611072540;hp=cb2e0d5deb2b08c33e1d7ea4a2bfdc100ae39d12;hpb=3e21454c3e1e006a38d2a05d856e4651d099b668;p=rrq%2Fjonasforth.git

diff --git a/main.asm b/main.asm
index cb2e0d5..0190d18 100644
--- a/main.asm
+++ b/main.asm
@@ -1,4 +1,56 @@
-format ELF64 executable
+;; vim: syntax=fasm
+
+include '%OS_INCLUDE%'
+
+;; Print a string of a given length.
+;;
+;; Input:
+;; - RCX = Pointer to buffer
+;; - RDX = Buffer length
+;;
+;; Clobbers: RAX, RCX, R11, RDI, RSI
+macro sys_print_string {
+  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
+}
 
 ;; The code in this macro is placed at the end of each Forth word. When we are
 ;; executing a definition, this code is what causes execution to resume at the
@@ -57,23 +109,17 @@ macro forth_asm label, name, immediate {
 .start:
 }
 
-;; Define a Forth word that is implemented in Forth. (The body will be a list of
-;; 'dq' statements.)
-macro forth label, name, immediate {
-  header label, name, immediate
-  dq DOCOL
-}
+section '.text' code readable executable
 
-segment readable executable
-
-entry main
-
-include "impl.asm"
+include "impl.asm"      ; Misc. subroutines
+include "bootstrap.asm" ; Forth words encoded in Assembly
 
 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]
 
@@ -100,6 +146,17 @@ forth_asm LIT, 'LIT'
   push rax
   next
 
+;; When LITSTRING is encountered while executing a word, it instead reads a
+;; string from the definition of that word, and places that string on the stack
+;; as (buffer, length).
+forth_asm LITSTRING, 'LITSTRING'
+  lodsb
+  push rsi ; Buffer
+  movzx rax, al
+  push rax ; Length
+  add rsi, rax ; Skip over string before resuming execution
+  next
+
 ;; Given a string (a pointer following by a size), return the location of the
 ;; dictionary entry for that word. If no such word exists, return 0.
 forth_asm FIND, 'FIND'
@@ -161,38 +218,87 @@ forth_asm EXEC, 'EXEC'
 forth_asm EMIT, 'EMIT'
   pushr rsi
   pushr rax
-  mov rax, 1
-  mov rdi, 1
-  lea rsi, [rsp]
+
+  lea rcx, [rsp]
   mov rdx, 1
-  syscall
+  sys_print_string
+
   add rsp, 8
   popr rax
   popr rsi
   next
 
-;; Prints a newline to standard output.
-forth NEWLINE, 'NEWLINE'
-  dq LIT, $A
-  dq EMIT
-  dq EXIT
+;; 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
 
-;; Prints a space to standard output.
-forth SPACE, 'SPACE'
-  dq LIT, ' '
-  dq EMIT
-  dq EXIT
+;; 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
+  push rsi
+  mov rsi, .buffer
+  sys_read_char
+  pop rsi
+
+  movzx rax, byte [.buffer]
+  ret
 
-;; 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.
+.from_buffer:
+  ;; Reading from buffer
+  mov rax, [input_buffer]
+  movzx rax, byte [rax]
+
+  inc [input_buffer]
+  dec [input_buffer_length]
+  ret
+
+;; 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'
-  mov [.rsi], rsi
+  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
 
-  call read_word
-  push rdi                      ; Buffer
-  push rdx                      ; Length
+.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
@@ -208,42 +314,23 @@ forth_asm PARSE_NUMBER, 'PARSE-NUMBER'
   push rax                      ; Result
   next
 
-forth READ_NUMBER, 'READ-NUMBER'
-  dq READ_WORD
-  dq PARSE_NUMBER
-  dq EXIT
-
 ;; Takes a string (in the form of a pointer and a length on the stack) and
 ;; prints it to standard output.
 forth_asm TELL, 'TELL'
-  mov rbx, rsi
-  mov rcx, rax
+  pushr rax
+  pushr rsi
 
-  mov rax, 1
-  mov rdi, 1
-  pop rdx     ; Length
-  pop rsi     ; Buffer
-  syscall
+  pop rdx ; Length
+  pop rcx ; Buffer
+  sys_print_string
 
-  mov rax, rcx
-  mov rsi, rbx
+  popr rsi
+  popr rax
   next
 
 ;; Exit the program cleanly.
 forth_asm TERMINATE, 'TERMINATE'
-  mov rax, $3C
-  mov rdi, 0
-  syscall
-
-forth HELLO, 'HELLO'
-  dq LIT, 'H', EMIT
-  dq LIT, 'e', EMIT
-  dq LIT, 'l', EMIT
-  dq LIT, 'l', EMIT
-  dq LIT, 'o', EMIT
-  dq LIT, '!', EMIT
-  dq NEWLINE
-  dq EXIT
+  sys_terminate 0
 
 ;; Duplicate a pair of elements.
 forth_asm PAIRDUP, '2DUP'
@@ -279,55 +366,6 @@ forth_asm NOT_, 'NOT'
   push 1
   next
 
-;; The INTERPRET word reads and interprets user input. It's behavior depends on
-;; the current STATE. It provides special handling for integers.
-forth INTERPRET, 'INTERPRET'
-  ;; Read word
-  dq READ_WORD
-  dq PAIRDUP
-  ;; Stack is (word length word length).
-  dq FIND                       ; Try to find word
-  dq DUP_
-  dq ZBRANCH, 8 * 22            ; Check if word is found
-
-  ;; - Word is found -
-
-  dq STATE, GET, ZBRANCH, 8 * 11 ; Check whether we are in compilation or immediate mode
-
-  ;; (Word found, compilation mode)
-  dq DUP_, IS_IMMEDIATE, NOT_, ZBRANCH, 8 * 6 ; If the word is immediate, continue as we would in immediate mode
-
-  ;; Otherwise, we want to compile this word
-  dq TCFA
-  dq COMMA
-  dq DROP, DROP
-  dq EXIT
-
-  ;; (Word found, immediate mode)
-  ;; Execute word
-  dq TCFA
-  ;; Stack is (word length addr)
-  dq SWAP, DROP
-  dq SWAP, DROP
-  ;; Stack is (addr)
-  dq EXEC
-  dq EXIT
-
-  ;; - No word is found, assume it is an integer literal -
-  ;; Stack is (word length addr)
-  dq DROP
-  dq PARSE_NUMBER
-
-  dq STATE, GET, ZBRANCH, 8 * 5 ; Check whether we are in compilation or immediate mode
-
-  ;; (Number, compilation mode)
-  dq LIT, LIT, COMMA
-  dq COMMA
-  dq EXIT
-
-  ;; (Number, immediate mode)
-  dq EXIT
-
 ;; .U prints the value on the stack as an unsigned integer in hexadecimal.
 forth_asm DOTU, '.U'
   mov [.length], 0
@@ -379,11 +417,9 @@ forth_asm DOTU, '.U'
   loop .flip
 
   ;; Print the buffer
-  mov rax, 1
-  mov rdi, 1
-  mov rsi, .buffer
+  mov rcx, .buffer
   mov rdx, [.printed_length]
-  syscall
+  sys_print_string
 
   ;; Restore RSI and continue execution
   pop rsi
@@ -443,45 +479,21 @@ forth_asm TIMESMOD, '/MOD'
   push rdx                      ; a % b
   next
 
-;; Get the location of the STATE variable. It can be set with '!' and read with
-;; '@'.
-forth STATE, 'STATE'
-  dq LIT, var_STATE
-  dq EXIT
-
-;; Get the location of the LATEST variable. It can be set with '!' and read with
-;; '@'.
-forth LATEST, 'LATEST'
-  dq LIT, latest_entry
-  dq EXIT
-
-;; Get the location at which compiled words are expected to be added. This
-;; pointer is usually modified automatically when calling ',', but we can also
-;; read it manually with 'HERE'.
-forth HERE, 'HERE'
-  dq LIT, here
-  dq EXIT
-
-forth COMMA, ','
-  dq HERE, GET, PUT             ; Set the memory at the address pointed to by HERE
-  dq HERE, GET, LIT, 8, PLUS    ; Calculate new address for HERE to point to
-  dq HERE, PUT                  ; Update HERE to point to the new address
-  dq EXIT
-
-;; 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 character can be read.
+;; until the next call to S" and that no more than 255 characters can be read.
 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, '"'
@@ -501,6 +513,40 @@ forth_asm READ_STRING, 'S"'
 
   next
 
+read_string_buffer:
+  push rsi
+
+  ;; We borrow READ_STRING's buffer. They won't mind.
+  mov [READ_STRING.length], 0
+
+.read_char:
+  mov rbx, [input_buffer]
+  mov al, [rbx]
+  cmp al, '"'
+  je .done
+
+  mov rdx, READ_STRING.buffer
+  add rdx, [READ_STRING.length]
+  mov [rdx], al
+  inc [READ_STRING.length]
+
+  inc [input_buffer]
+  dec [input_buffer_length]
+
+  jmp .read_char
+
+.done:
+  pop rsi
+
+  ;; Skip closing "
+  inc [input_buffer]
+  dec [input_buffer_length]
+
+  push READ_STRING.buffer
+  push [READ_STRING.length]
+
+  next
+
 ;; CREATE inserts a new header in the dictionary, and updates LATEST so that it
 ;; points to the header. To compile a word, the user can then call ',' to
 ;; continue to append data after the header.
@@ -534,30 +580,6 @@ forth_asm CREATE, 'CREATE'
 
   next
 
-;; Mark the last added word as immediate.
-forth IMMEDIATE, 'IMMEDIATE', 1
-  dq LIT, 1
-  dq LATEST, GET
-  dq LIT, 8, PLUS
-  dq PUT_BYTE
-  dq EXIT
-
-;; Given the address of a word, return 0 if the given word is not immediate.
-forth IS_IMMEDIATE, 'IMMEDIATE?'
-  dq LIT, 8, PLUS
-  dq GET_BYTE
-  dq EXIT
-
-;; Enter immediate mode, immediately
-forth INTO_IMMEDIATE, '[', 1
-  dq LIT, 0, STATE, PUT_BYTE
-  dq EXIT
-
-;; Enter compilation mode
-forth OUTOF_IMMEDIATE, ']'
-  dq LIT, 1, STATE, PUT_BYTE
-  dq EXIT
-
 forth_asm TICK, "'"
   lodsq
   push rax
@@ -592,12 +614,40 @@ forth_asm EQL, '='
   next
 
 forth MAIN, 'MAIN'
-  dq HELLO
+  dq SYSCODE
+  dq INTERPRET_STRING
   dq INTERPRET
   dq BRANCH, -8 * 2
   dq TERMINATE
 
-segment readable writable
+;; Built-in variables:
+
+forth STATE, 'STATE'
+  dq LIT, var_STATE
+  dq EXIT
+
+forth LATEST, 'LATEST'
+  dq LIT, latest_entry
+  dq EXIT
+
+forth HERE, 'HERE'
+  dq LIT, here
+  dq EXIT
+
+forth SYSCODE, 'SYSCODE'
+  dq LIT, sysf
+  dq LIT, sysf.len
+  dq EXIT
+
+forth INPUT_BUFFER, 'INPUT-BUFFER'
+  dq LIT, input_buffer
+  dq EXIT
+
+forth INPUT_LENGTH, 'INPUT-LENGTH'
+  dq LIT, input_buffer_length
+  dq EXIT
+
+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
@@ -608,6 +658,12 @@ 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 ?
@@ -623,6 +679,11 @@ 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
@@ -630,3 +691,10 @@ here_top rq $4000
 ;; Return stack
 rq $2000
 return_stack_top:
+
+;; 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.
+sysf file 'sys.f'
+sysf.len = $ - sysf
+