.text
.globl _start
_start:
cmpb $1,(rsp)
je f
push rsp
pop r13
inc r14b
movb r14b,bl
shl $62,r14
dec (r13)
call o1
push rax

mov rbx,rdi
push $04
pop rsi
mov r9,rdx
push $72
pop rax
syscall
pop rsi

scat:mov rbx,rdi #simple cat
call sf
mov rax,rsi
jmp scat

csf:inc rdi # copy via sendfile can copy as many times the file as fd_set or add a close for  infinity
call o2
mov rax,rbx
push $01101101
pop r8
call o1
push rax
bcsf:pop rdi
mov rbx,rsi
call sf
push rax
mov rbx,rdi
push $8
pop rax
mov r9,rdx
mov r12,rsi #lseek off_t switch r12 to r9 for 0 offset
syscall
jmp bcsf

rcsf:inc rdi # reverse copy '=file' is created with following args files content
push $01101101
pop r8
call o2
mov rax,rbx
mov r9,r8
call o1
brcsf:mov rbx,rdi
push rax
pop rsi
call sf
jmp brcsf

sf:push $40
pop rax
mov r14,r10
mov r12,rdx # off_t of sendfile
syscall
cmp rbp,(r13)
je f
o1:inc rbp
mov 8(r13,rbp,8),rdi
movb (rdi),cl
cmpb $'+',cl
je a4
cmpb $'^',cl
je a3
push $0777
pop rdx
cmpb $61,cl
je rcsf
cmpb $58,cl
je csf
o2:push $2
pop rax
mov r8,rsi
syscall
ret

f:mov r12,rdi # exit with '^number' the offset
push $231
pop rax
syscall

a4:inc rdi
call toi
mov rax,r14
jmp o1
a3:inc rdi
call toi
mov rax,r12
jmp o1

toi:#10d
mov r9,rax
mov r9,rcx
push $10
pop rcx
bai:mul rcx
movb (rdi),dl
sub $48,dl
add rdx,rax
inc rdi
cmpb $0,(rdi)
jne bai
ret