X-Git-Url: https://git.rrq.au/?a=blobdiff_plain;f=main.asm;h=3da2e871d8d4ccc7767f7356ebb057c815b9201b;hb=b1e9665f4639d9fe9ef0a3af7cc09c68c49b928b;hp=af84a66631a0d17d5abb5922a220130f9135f8b4;hpb=3e2708b7e8434cc0678c8ee0c315166704c8f31a;p=rrq%2Fjonasforth.git diff --git a/main.asm b/main.asm index af84a66..3da2e87 100644 --- a/main.asm +++ b/main.asm @@ -44,6 +44,10 @@ 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_entry: + dq 0 + db 4 + db 'EXIT' EXIT: dq .start .start: @@ -52,6 +56,10 @@ EXIT: ;; LIT is a special word that reads the next "word pointer" and causes it to be ;; placed on the stack rather than executed. +LIT_entry: + dq EXIT_entry + db 3 + db 'LIT' LIT: dq .start .start: @@ -59,9 +67,65 @@ LIT: 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. +;; 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. +FIND_entry: + dq LIT_entry + db 4 + db 'FIND' +FIND: + dq .start +.start: + 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. +BRANCH_entry: + dq FIND_entry + db 6 + db 'BRANCH' +BRANCH: + dq .start +.start: + 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. ZBRANCH: dq .start .start: @@ -70,8 +134,7 @@ ZBRANCH: 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 @@ -99,9 +162,20 @@ NEWLINE: dq EMIT dq EXIT +;; Prints a space to standard output. +SPACE_entry: + dq BRANCH_entry + db 5 + db 'SPACE' +SPACE: + dq docol + 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 +READ_WORD: dq .start .start: mov [.rsi], rsi @@ -153,9 +227,63 @@ READ_WORD: ; 400170 next +;; Takes a string on the stack and replaces it with the decimal number that the +;; string represents. +PARSE_NUMBER: + dq .start +.start: + 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 + +READ_NUMBER: + dq docol + 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: +TELL: dq .start .start: mov rbx, rsi @@ -196,6 +324,10 @@ PUSH_YOU_TYPED: push you_typed_string.length next +HELLO_entry: + dq SPACE_entry + db 5 + db 'HELLO' HELLO: dq docol dq LIT, 'H', EMIT @@ -207,23 +339,110 @@ HELLO: dq NEWLINE dq EXIT +;; .U prints the value on the stack as an unsigned integer in hexadecimal. +DOTU_entry: + dq HELLO_entry + db 2 + db '.U' +DOTU: + dq .start +.start: + 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 + 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 - dq HELLO + dq LIT, SPACE_entry, DOTU, NEWLINE + dq LIT, HELLO_entry, DOTU, NEWLINE + dq LIT, DOTU_entry, DOTU, NEWLINE + dq LIT, SPACE_string, LIT, SPACE_string.length, TELL, SPACE + dq LIT, SPACE_string, LIT, SPACE_string.length, FIND, DOTU, NEWLINE + dq LIT, HELLO_string, LIT, HELLO_string.length, TELL, SPACE + dq LIT, HELLO_string, LIT, HELLO_string.length, FIND, DOTU, NEWLINE + dq LIT, DOTU_string, LIT, DOTU_string.length, TELL, SPACE + dq LIT, DOTU_string, LIT, DOTU_string.length, FIND, DOTU, NEWLINE + dq LIT, HELLA_string, LIT, HELLA_string.length, TELL, SPACE + dq LIT, HELLA_string, LIT, HELLA_string.length, FIND, DOTU, NEWLINE dq TERMINATE segment readable writable +latest_entry dq DOTU_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 +450,14 @@ 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: