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/ This Source Code Form is subject to the terms of the Mozilla Public
/ License, v. 2.0. If a copy of the MPL was not distributed with this
/ file, You can obtain one at http://mozilla.org/MPL/2.0/.
/ ** ARCFOUR implementation optimized for AMD64.
/ **
/ ** The throughput achieved by this code is about 320 MBytes/sec, on
/ ** a 1.8 GHz AMD Opteron (rev C0) processor.
.text
.align 16
.globl ARCFOUR
.type ARCFOUR,@function
ARCFOUR:
pushq %rbp
pushq %rbx
movq %rdi, %rbp / key = ARG(key)
movq %rsi, %rbx / rbx = ARG(len)
movq %rdx, %rsi / in = ARG(in)
movq %rcx, %rdi / out = ARG(out)
movq (%rbp), %rcx / x = key->x
movq 8(%rbp), %rdx / y = key->y
addq $16, %rbp / d = key->data
incq %rcx / x++
andq $255, %rcx / x &= 0xff
leaq -8(%rbx,%rsi), %rbx / rbx = in+len-8
movq %rbx, %r9 / tmp = in+len-8
movq 0(%rbp,%rcx,8), %rax / tx = d[x]
cmpq %rsi, %rbx / cmp in with in+len-8
jl .Lend / jump if (in+len-8 < in)
.Lstart:
addq $8, %rsi / increment in
addq $8, %rdi / increment out
/ generate the next 8 bytes of the rc4 stream into %r8
movq $8, %r11 / byte counter
1: addb %al, %dl / y += tx
movl 0(%rbp,%rdx,8), %ebx / ty = d[y]
movl %ebx, 0(%rbp,%rcx,8) / d[x] = ty
addb %al, %bl / val = ty + tx
movl %eax, 0(%rbp,%rdx,8) / d[y] = tx
incb %cl / x++ (NEXT ROUND)
movl 0(%rbp,%rcx,8), %eax / tx = d[x] (NEXT ROUND)
movb 0(%rbp,%rbx,8), %r8b / val = d[val]
decb %r11b
rorq $8, %r8 / (ror does not change ZF)
jnz 1b
/ xor 8 bytes
xorq -8(%rsi), %r8
cmpq %r9, %rsi / cmp in+len-8 with in
movq %r8, -8(%rdi)
jle .Lstart / jump if (in <= in+len-8)
.Lend:
addq $8, %r9 / tmp = in+len
/ handle the last bytes, one by one
1: cmpq %rsi, %r9 / cmp in with in+len
jle .Lfinished / jump if (in+len <= in)
addb %al, %dl / y += tx
movl 0(%rbp,%rdx,8), %ebx / ty = d[y]
movl %ebx, 0(%rbp,%rcx,8) / d[x] = ty
addb %al, %bl / val = ty + tx
movl %eax, 0(%rbp,%rdx,8) / d[y] = tx
incb %cl / x++ (NEXT ROUND)
movl 0(%rbp,%rcx,8), %eax / tx = d[x] (NEXT ROUND)
movb 0(%rbp,%rbx,8), %r8b / val = d[val]
xorb (%rsi), %r8b / xor 1 byte
movb %r8b, (%rdi)
incq %rsi / in++
incq %rdi / out++
jmp 1b
.Lfinished:
decq %rcx / x--
movb %dl, -8(%rbp) / key->y = y
movb %cl, -16(%rbp) / key->x = x
popq %rbx
popq %rbp
ret
.L_ARCFOUR_end:
.size ARCFOUR,.L_ARCFOUR_end-ARCFOUR
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