83 lines
1.6 KiB
NASM
83 lines
1.6 KiB
NASM
; string copy/compare routines
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; copy string from source pointer to destination pointer
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; if the source and destination overlap, the behavior is undefined
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; inputs:
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; r0: pointer to source
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; r1: pointer to destination
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; outputs:
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; none
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copy_string:
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push r0
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push r1
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push r2
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copy_string_loop:
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mov.8 r2, [r0]
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mov.8 [r1], r2
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inc r0
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inc r1
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cmp.8 r2, 0
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ifnz jmp copy_string_loop
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pop r2
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pop r1
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pop r0
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ret
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; compare string from source pointer with destination pointer
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; inputs:
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; r0: pointer to source
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; r1: pointer to destination
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; outputs:
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; Z flag
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compare_string:
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push r0
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push r1
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compare_string_loop:
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; check if the strings match
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cmp.8 [r0], [r1]
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ifnz jmp compare_string_not_equal
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; if this is the end of string 1, then this must also be the end of string 2
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; the cmp above already ensured that both strings have a null-terminator here
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cmp.8 [r0], 0
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ifz jmp compare_string_equal
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inc r0
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inc r1
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jmp compare_string_loop
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compare_string_not_equal:
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; Z flag is already cleared at this point
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pop r1
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pop r0
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ret
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compare_string_equal:
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; set Z flag
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mov r0, 0
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cmp r0, 0
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pop r1
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pop r0
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ret
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; get the length of a string
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; inputs:
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; r0: pointer to null-terminated string
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; outputs:
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; r0: length of the string, not including the null-terminator
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string_length:
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push r1
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mov r1, 0
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string_length_loop:
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; check if this is the end of the string
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cmp.8 [r0], 0
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ifz jmp string_length_end
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inc r0
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inc r1
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jmp string_length_loop
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string_length_end:
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mov r0, r1
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pop r1
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ret
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