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9cb9566897
Merging fixes in stepA into earlier steps, and removing differences in comments and spacing
107 lines
2.5 KiB
NASM
107 lines
2.5 KiB
NASM
;;
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;; nasm -felf64 step1_read_print.asm && ld step1_read_print.o && ./a.out
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;; Calling convention: Address of input is in RSI
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;; Address of return value is in RAX
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;;
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global _start
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%include "types.asm" ; Data types, memory
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%include "system.asm" ; System calls
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%include "reader.asm" ; String -> Data structures
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%include "printer.asm" ; Data structures -> String
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%include "exceptions.asm" ; Error handling
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section .data
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;; ------------------------------------------
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;; Fixed strings for printing
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static prompt_string, db 10,"user> " ; The string to print at the prompt
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section .text
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;; Takes a string as input and processes it into a form
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read:
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jmp read_str ; In reader.asm
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;; ----------------------------------------------
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;; Evaluates a form
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;;
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;; Inputs: RSI Form to evaluate
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;;
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eval:
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mov rax, rsi ; Return the input
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ret
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;; Prints the result
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print:
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mov rdi, 1 ; print readably
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jmp pr_str
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;; Read-Eval-Print in sequence
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rep_seq:
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; -------------
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; Read
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call read
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push rax ; Save form
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; -------------
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; Eval
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mov rsi, rax ; Output of read into input of eval
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call eval
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; -------------
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; Print
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mov rsi, rax ; Output of eval into input of print
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call print ; String in RAX
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mov r8, rax ; Save output
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pop rsi ; Form returned by read
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call release_object
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mov rax, r8
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ret
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_start:
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; -----------------------------
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; Main loop
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.mainLoop:
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; print the prompt
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print_str_mac prompt_string
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call read_line
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; Check if we have a zero-length string
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cmp DWORD [rax+Array.length], 0
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je .mainLoopEnd
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push rax ; Save address of the string
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mov rsi, rax
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call rep_seq ; Read-Eval-Print
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push rax ; Save returned string
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mov rsi, rax ; Put into input of print_string
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call print_string
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; Release string from rep_seq
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pop rsi
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call release_array
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; Release the input string
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pop rsi
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call release_array
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jmp .mainLoop
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.mainLoopEnd:
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jmp quit
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