Kwarde
01e14d418a
Later, if buffer is full, print current buffer and reset buffer so that there is no limit.
277 lines
4.6 KiB
NASM
277 lines
4.6 KiB
NASM
extern NR_write
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extern strlen
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extern strcat
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extern itoa
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section .rodata
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NL db 0xA
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bufferLength equ 4096
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ERR_buffLen db "<!> ERROR: Failed to complete printf(), reached buffer length!",0xA,0x0
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lERR_buffLen equ $-ERR_buffLen-1
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section .bss
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printfBuff resb bufferLength
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printfNBuff resb 32
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section .text
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global print
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global puts
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global printf
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;----- print (char* string) -----;
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; return value: N/A
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print:
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push rbp
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mov rbp, rsp
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call strlen
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mov rdx, rax
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mov rax, NR_write
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mov rsi, rdi
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mov rdi, 1
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syscall
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leave
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ret
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;----- puts (char* string) -----;
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; return value: N/A
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puts:
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push rbp
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mov rbp, rsp
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mov r10, rdi
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call print
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mov rdi, r10
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mov rax, NR_write
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mov rdi, 1
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mov rsi, NL
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mov rdx, 1
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syscall
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leave
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ret
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;----- printf(const char* string, ...) -----;
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; Currently only supports specifiers: %d, %c, %s, %%
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; Return value: Amount of printed characters
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printf:
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push rbp
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mov rbp, rsp
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push rbx ; used to check if error must be sent (reached buff len)
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push r12 ; used for writing byted to printBuff
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push r13 ; (also) used for writing bytes to printBuff (why again? gotta check that out - probably not needed, just lost count of register usage at some point)
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push r14 ; count length of printBuff
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xor rbx, rbx
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xor r10, r10
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xor r14, r14
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lea r11, [rel printfBuff]
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.makeStr:
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cmp byte [rdi], 0x0
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je .finish
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cmp r14, bufferLength-1
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je .finish_L
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cmp byte [rdi], '%'
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je .replaceArg
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mov r12b, byte [rdi]
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mov byte [r11], r12b
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inc r14
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jmp .continue
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.replaceArg:
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cmp byte [rdi+1], 0x0
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je .continue
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push rdi
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cmp byte [rdi+1], 'd'
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je .rep_d
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cmp byte [rdi+1], '%'
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je .rep_pct
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cmp byte [rdi+1], 'c'
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je .rep_c
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cmp byte [rdi+1], 's'
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je .rep_s
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;--- invalid specifier ---;
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mov byte [r11], '%'
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inc r14
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inc r10 ;assuming args were passed for invalid specifiers !
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jmp .continue
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;--- %d ---;
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.rep_d:
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cmp r10, 0
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je .rep_d_rsi
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cmp r10, 1
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je .rep_d_rdx
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cmp r10, 2
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je .rep_d_rcx
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cmp r10, 3
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je .rep_d_r8
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cmp r10, 4
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je .rep_d_r9
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;get from stack
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mov rdi, qword [rbp + 16 + (r10-5)*8]
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jmp .convertInt
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.rep_d_rsi:
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mov rdi, rsi
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jmp .convertInt
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.rep_d_rdx:
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mov rdi, rdx
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jmp .convertInt
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.rep_d_rcx:
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mov rdi, rcx
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jmp .convertInt
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.rep_d_r8:
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mov rdi, r8
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jmp .convertInt
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.rep_d_r9:
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mov rdi, r9
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.convertInt:
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lea rsi, [rel printfNBuff]
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push rcx
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push rdx
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push r8
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push r10
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push rsi
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call itoa
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pop rsi
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pop r10
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pop r8
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pop rdx
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pop rcx
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mov rsi, rax
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jmp .insertLoop
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;--- %% ---;
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.rep_pct:
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mov rdi, '%'
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dec r10 ;r10 is increased at the end, but not needed because '%%' requires no arg
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jmp .charToStr
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;--- %c ---;
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.rep_c:
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cmp r10, 0
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je .rep_c_rsi
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cmp r10, 1
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je .rep_c_rdx
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cmp r10, 2
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je .rep_c_rcx
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cmp r10, 3
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je .rep_c_r8
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cmp r10, 4
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je .rep_c_r9
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;get from stack
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mov rdi, qword [rbp + 16 + (r10-5)*8]
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jmp .charToStr
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.rep_c_rsi:
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mov rdi, rsi
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jmp .charToStr
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.rep_c_rdx:
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mov rdi, rdx
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jmp .charToStr
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.rep_c_rcx:
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mov rdi, rcx
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jmp .charToStr
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.rep_c_r8:
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mov rdi, r8
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jmp .charToStr
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.rep_c_r9:
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mov rdi, r9
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jmp .charToStr
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.charToStr:
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mov [printfNBuff], dil
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inc r14
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cmp r14, bufferLength-1
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; Print error to stdout
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je .finish_L
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mov dil, 0
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mov [printfNBuff+1], dil
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inc r14
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cmp r14, bufferLength-1
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je .finish_L
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lea rsi, [rel printfNBuff]
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jmp .insertLoop
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;--- %s ---;
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.rep_s:
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cmp r10, 0
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je .insertLoop ;nothing to do, rsi already correct
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cmp r10, 1
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je .rep_s_rdx
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cmp r10, 2
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je .rep_s_rcx
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cmp r10, 3
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je .rep_s_r8
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cmp r10, 4
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je .rep_s_r9
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;get from stack
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mov rsi, qword [rbp + 16 + (r10-5)*8]
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jmp .insertLoop
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.rep_s_rdx:
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mov rsi, rdx
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jmp .insertLoop
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.rep_s_rcx:
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mov rsi, rcx
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jmp .insertLoop
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.rep_s_r8:
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mov rsi, r8
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jmp .insertLoop
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.rep_s_r9:
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mov rsi, r9
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;--- Move fetched data to buffer ---;
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.insertLoop:
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cmp r14, bufferLength-1
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je .finish_L
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cmp byte [rsi], 0x0
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je .s0f
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mov r13b, byte [rsi]
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mov byte [r11], r13b
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inc r14
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inc rsi
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inc r11
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jmp .insertLoop
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.s0f:
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inc r10
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pop rdi
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add rdi, 2
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jmp .makeStr
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.continue:
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inc rdi
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inc r11
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jmp .makeStr
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.finish_L:
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mov rbx, 1
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.finish:
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mov byte [r11], 0x0
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lea rdi, [rel printfBuff]
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call print
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lea rdi, [rel printfBuff]
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call strlen
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test rbx, rbx
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jz .final
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push r11
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mov rax, NR_write
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mov rdi, 2
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lea rsi, [rel ERR_buffLen]
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mov rdx, lERR_buffLen
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syscall
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.final:
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pop r11
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pop r14
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pop r13
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pop r12
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pop rbx
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leave
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ret
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