X-Git-Url: https://git.rrq.au/?a=blobdiff_plain;f=main.asm;h=834872cd54a756fef046f7a67c0dd1463fd8f86b;hb=be8f6fc600856043dede3a5da6aa9aded19fcb34;hp=af84a66631a0d17d5abb5922a220130f9135f8b4;hpb=3e2708b7e8434cc0678c8ee0c315166704c8f31a;p=rrq%2Fjonasforth.git diff --git a/main.asm b/main.asm index af84a66..834872c 100644 --- a/main.asm +++ b/main.asm @@ -23,6 +23,42 @@ macro popr x { add rbp, 8 } +;; The following macro generates the dictionary header. It updates the +;; initial_latest_entry variable, which is used as the initial value of the +;; latest_entry variable that is made available at runtime. +;; +;; The header contains a link to the previous entry, the length of the name of +;; the word and the word itself as a string literal. +;; +;; This macro also defines a label LABEL_entry. +initial_latest_entry = 0 +macro header label, name { + local .string_end + +label#_entry: + dq initial_latest_entry + db .string_end - ($ + 1) + db name + .string_end: +label: + +initial_latest_entry = label#_entry +} + +;; Define a Forth word that is implemented in assembly. See 'header' for details. +macro forth_asm label, name { + header label, name + dq .start +.start: +} + +;; Define a Forth word that is implemented in Forth. (The body will be a list of +;; 'dq' statements.) +macro forth label, name { + header label, name + dq docol +} + segment readable executable main: @@ -44,42 +80,77 @@ docol: ;; This word is called at the end of a Forth definition. It just needs to ;; restore the old value of RSI (saved by 'docol') and resume execution. -EXIT: - dq .start -.start: +forth_asm EXIT, 'EXIT' popr rsi next ;; LIT is a special word that reads the next "word pointer" and causes it to be ;; placed on the stack rather than executed. -LIT: - dq .start -.start: +forth_asm LIT, 'LIT' lodsq push rax next -;; 0BRANCH is the fundamental mechanism for branching. If the top of the stack -;; is zero, we jump by the given offset. 0BRANCH is given the offset as an -;; integer after the word. -ZBRANCH: - dq .start -.start: +;; 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' + mov [.rsi], rsi + pop [.search_length] + pop [.search_buffer] + + ;; RSI contains the entry we are currently looking at + mov rsi, [latest_entry] ; Start with the last added word + +.loop: + movzx rcx, byte [rsi + 8] ; Length of word being looked at + cmp rcx, [.search_length] + jne .next ; If the words don't have the same length, we have the wrong word + + ;; Otherwise, we need to compare strings + lea rdx, [rsi + 8 + 1] ; Location of character being compared in entry + mov rdi, [.search_buffer] ; Location of character being compared in search buffer +.compare_char: + mov al, [rdx] + mov ah, [rdi] + cmp al, ah + jne .next ; They don't match; try again + inc rdx ; These characters match; look at the next ones + inc rdi + loop .compare_char + + jmp .found ; They match! We are done. + +.next: + mov rsi, [rsi] ; Look at the previous entry + cmp rsi, 0 + jnz .loop ; If there is no previous word, exit and return 0 + +.found: + push rsi + + mov rsi, [.rsi] + next + +;; BRANCH is the fundamental mechanism for branching. BRANCH reads the next word +;; as a signed integer literal and jumps by that offset. +forth_asm BRANCH, 'BRANCH' + add rsi, [rsi] ; [RSI], which is the next word, contains the offset; we add this to the instruction pointer. + next ; Then, we can just continue execution as normal + +;; 0BRANCH is like BRANCH, but it jumps only if the top of the stack is zero. +forth_asm ZBRANCH, '0BRANCH' ;; Compare top of stack to see if we should branch pop rax cmp rax, 0 jnz .dont_branch .do_branch: - add rsi, [rsi] ; [RSI], which is the next word, contains the offset; we add this to the instruction pointer. - next ; Then, we can just continue execution as normal + jmp BRANCH.start .dont_branch: add rsi, 8 ; We need to skip over the next word, which contains the offset. next ;; Expects a character on the stack and prints it to standard output. -EMIT: - dq .start -.start: +forth_asm EMIT, 'EMIT' pushr rsi pushr rax mov rax, 1 @@ -93,17 +164,20 @@ EMIT: next ;; Prints a newline to standard output. -NEWLINE: - dq docol +forth NEWLINE, 'NEWLINE' dq LIT, $A dq EMIT dq EXIT +;; Prints a space to standard output. +forth SPACE, 'SPACE' + dq LIT, ' ' + dq EMIT + dq EXIT + ;; 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. -READ_WORD: ; 400170 - dq .start -.start: +forth_asm READ_WORD, 'READ-WORD' mov [.rsi], rsi mov [.rax], rax @@ -153,11 +227,60 @@ READ_WORD: ; 400170 next +;; Takes a string on the stack and replaces it with the decimal number that the +;; string represents. +forth_asm PARSE_NUMBER, 'PARSE-NUMBER' + pop [.length] ; Length + pop rdi ; String pointer + mov r8, 0 ; Result + + ;; Add (10^(rcx-1) * parse_char(rdi[length - rcx])) to the accumulated value + ;; for each rcx. + mov rcx, [.length] +.loop: + ;; First, calcuate 10^(rcx - 1) + mov rax, 1 + + mov r9, rcx + .exp_loop: + dec r9 + jz .break + mov rbx, 10 + mul rbx + jmp .exp_loop + .break: + + ;; Now, rax = 10^(rcx - 1). + + ;; We need to calulate the value of the character at rdi[length - rcx]. + mov rbx, rdi + add rbx, [.length] + sub rbx, rcx + movzx rbx, byte [rbx] + sub rbx, '0' + + ;; Multiply this value by rax to get (10^(rcx-1) * parse_char(rdi[length - rcx])), + ;; then add this to the result. + mul rbx + + ;; Add that value to r8 + add r8, rax + + dec rcx + jnz .loop + + push r8 + + 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. -TYPE: - dq .start -.start: +forth_asm TELL, 'TELL' mov rbx, rsi mov rcx, rax @@ -172,32 +295,12 @@ TYPE: next ;; Exit the program cleanly. -TERMINATE: - dq .start -.start: +forth_asm TERMINATE, 'TERMINATE' mov rax, $3C mov rdi, 0 syscall -PUSH_HELLO_CHARS: - dq docol - dq LIT, $A - dq LIT, 'o' - dq LIT, 'l' - dq LIT, 'l' - dq LIT, 'e' - dq LIT, 'H' - dq EXIT - -PUSH_YOU_TYPED: - dq .start -.start: - push you_typed_string - push you_typed_string.length - next - -HELLO: - dq docol +forth HELLO, 'HELLO' dq LIT, 'H', EMIT dq LIT, 'e', EMIT dq LIT, 'l', EMIT @@ -207,23 +310,94 @@ HELLO: dq NEWLINE dq EXIT -MAIN: - dq docol - dq HELLO - dq READ_WORD - dq LIT, you_typed_string - dq LIT, you_typed_string.length - dq TYPE - dq TYPE - dq NEWLINE +;; .U prints the value on the stack as an unsigned integer in hexadecimal. +forth_asm DOTU, '.U' + mov [.length], 0 + mov [.printed_length], 1 + pop rax ; RAX = value to print + push rsi ; Save value of RSI + + ;; We start by constructing the buffer to print in reverse + +.loop: + mov rdx, 0 + mov rbx, $10 + div rbx ; Put remainer in RDX and quotient in RAX + + ;; Place the appropriate character in the buffer + mov rsi, .chars + add rsi, rdx + mov bl, [rsi] + mov rdi, .rbuffer + add rdi, [.length] + mov [rdi], bl + inc [.length] + + ;; .printed_length is the number of characters that we ulitmately want to + ;; print. If we have printed a non-zero character, then we should update + ;; .printed_length. + cmp bl, '0' + je .skip_updating_real_length + mov rbx, [.length] + mov [.printed_length], rbx +.skip_updating_real_length: + + cmp [.length], 16 + jle .loop + + ;; Flip buffer around, since it is currently reversed + mov rcx, [.printed_length] +.flip: + mov rsi, .rbuffer + add rsi, rcx + dec rsi + mov al, [rsi] + + mov rdi, .buffer + add rdi, [.printed_length] + sub rdi, rcx + mov [rdi], al + + loop .flip + + ;; Print the buffer + mov rax, 1 + mov rdi, 1 + mov rsi, .buffer + mov rdx, [.printed_length] + syscall + + ;; Restore RSI and continue execution + pop rsi + next + +forth MAIN, 'MAIN' dq HELLO + dq READ_WORD, FIND, DOTU, NEWLINE + dq BRANCH, -8 * 5 dq TERMINATE segment readable writable +latest_entry dq initial_latest_entry + +SPACE_string db 'SPACE' +.length = $ - SPACE_string +HELLO_string db 'HELLO' +.length = $ - HELLO_string +DOTU_string db '.U' +.length = $ - DOTU_string +HELLA_string db 'HELLA' +.length = $ - HELLA_string + + you_typed_string db 'You typed: ' .length = $ - you_typed_string +FIND.search_length dq ? +FIND.search_buffer dq ? +FIND.rsi dq ? + READ_WORD.rsi dq ? READ_WORD.rax dq ? READ_WORD.max_size = $FF @@ -231,6 +405,14 @@ READ_WORD.buffer rb READ_WORD.max_size READ_WORD.length db ? READ_WORD.char_buffer db ? +DOTU.chars db '0123456789ABCDEF' +DOTU.buffer rq 16 ; 64-bit number has no more than 16 digits in hex +DOTU.rbuffer rq 16 +DOTU.length dq ? +DOTU.printed_length dq ? + +PARSE_NUMBER.length dq ? + ;; Return stack rq $2000 return_stack_top: