60 lines
812 B
NASM
60 lines
812 B
NASM
section .text
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global strlen
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global strcpy
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global strcat
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;----- strlen(char* str) -----;
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; return value: amount of characters before EOS was found
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strlen:
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push rbp
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mov rbp, rsp
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xor rax, rax
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.findEOS:
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cmp byte [rdi+rax], 0x0
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je .quit
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inc rax
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jmp .findEOS
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.quit:
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leave
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ret
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;----- strcpy(char* dest, char* src) -----;
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; return value: pointer to dest or NULL if nothing was copied
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strcpy:
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push rbp
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mov rbp, rsp
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xor rax, rax
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xor rcx, rcx
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.loop:
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cmp byte [rsi], 0x0
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je .0f
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mov r10b, byte [rsi]
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mov byte [rdi], r10b
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inc rsi
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inc rdi
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inc rcx
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jmp .loop
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.0f:
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cmp rcx, 0
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jne .quit
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xor rax, rax
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.quit:
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leave
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ret
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;----- strcat(char* dest, char* src) -----;
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; return value: pointer to dest
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strcat:
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push rbp
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mov rbp, rsp
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call strlen
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add rdi, rax
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call strcpy
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leave
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ret
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