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      1 // Copyright 2013 The Go Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style
      3 // license that can be found in the LICENSE file.
      4 
      5 // +build !nacl
      6 
      7 #include "textflag.h"
      8 
      9 // Registers
     10 #define Rdst	R0
     11 #define Rsrc	R1
     12 #define Rn	R2
     13 #define Rstate	R3
     14 #define Rpi	R4
     15 #define Rpj	R5
     16 #define Ri	R6
     17 #define Rj	R7
     18 #define Rk	R8
     19 #define Rt	R11
     20 #define Rt2	R12
     21 
     22 // func xorKeyStream(dst, src *byte, n int, state *[256]byte, i, j *uint8)
     23 TEXT xorKeyStream(SB),NOSPLIT,$0
     24 	MOVW dst+0(FP), Rdst
     25 	MOVW src+4(FP), Rsrc
     26 	MOVW n+8(FP), Rn
     27 	MOVW state+12(FP), Rstate
     28 	MOVW pi+16(FP), Rpi
     29 	MOVW pj+20(FP), Rpj
     30 	MOVBU (Rpi), Ri
     31 	MOVBU (Rpj), Rj
     32 	MOVW $0, Rk
     33 
     34 loop:
     35 	// i += 1; j += state[i]
     36 	ADD $1, Ri
     37 	AND $0xff, Ri
     38 	MOVBU Ri<<2(Rstate), Rt
     39 	ADD Rt, Rj
     40 	AND $0xff, Rj
     41 
     42 	// swap state[i] <-> state[j]
     43 	MOVBU Rj<<2(Rstate), Rt2
     44 	MOVB Rt2, Ri<<2(Rstate)
     45 	MOVB Rt, Rj<<2(Rstate)
     46 
     47 	// dst[k] = src[k] ^ state[state[i] + state[j]]
     48 	ADD Rt2, Rt
     49 	AND $0xff, Rt
     50 	MOVBU Rt<<2(Rstate), Rt
     51 	MOVBU Rk<<0(Rsrc), Rt2
     52 	EOR Rt, Rt2
     53 	MOVB Rt2, Rk<<0(Rdst)
     54 
     55 	ADD $1, Rk
     56 	CMP Rk, Rn
     57 	BNE loop
     58 
     59 done:
     60 	MOVB Ri, (Rpi)
     61 	MOVB Rj, (Rpj)
     62 	RET
     63