2007-01-18 16:18:02 +01:00
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/*
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* Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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2012-07-20 20:55:45 +02:00
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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2007-01-18 16:18:02 +01:00
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*/
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/** @file
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*
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* Optimised string operations
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*
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*/
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2009-05-01 16:41:06 +02:00
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FILE_LICENCE ( GPL2_OR_LATER );
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2007-01-18 16:18:02 +01:00
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#include <string.h>
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/**
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* Copy memory area
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*
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* @v dest Destination address
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* @v src Source address
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* @v len Length
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* @ret dest Destination address
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*/
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2012-11-04 23:43:59 +01:00
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void * __attribute__ (( noinline )) __memcpy ( void *dest, const void *src,
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size_t len ) {
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2007-01-18 16:18:02 +01:00
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void *edi = dest;
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const void *esi = src;
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int discard_ecx;
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/* We often do large dword-aligned and dword-length block
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* moves. Using movsl rather than movsb speeds these up by
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* around 32%.
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*/
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2012-06-26 13:42:24 +02:00
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__asm__ __volatile__ ( "rep movsl"
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: "=&D" ( edi ), "=&S" ( esi ),
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"=&c" ( discard_ecx )
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: "0" ( edi ), "1" ( esi ), "2" ( len >> 2 )
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: "memory" );
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__asm__ __volatile__ ( "rep movsb"
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: "=&D" ( edi ), "=&S" ( esi ),
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"=&c" ( discard_ecx )
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: "0" ( edi ), "1" ( esi ), "2" ( len & 3 )
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: "memory" );
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2007-01-18 16:18:02 +01:00
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return dest;
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}
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2012-11-04 23:43:59 +01:00
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/**
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* Copy memory area backwards
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*
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* @v dest Destination address
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* @v src Source address
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* @v len Length
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* @ret dest Destination address
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*/
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void * __attribute__ (( noinline )) __memcpy_reverse ( void *dest,
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const void *src,
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size_t len ) {
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void *edi = ( dest + len - 1 );
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const void *esi = ( src + len - 1 );
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int discard_ecx;
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/* Assume memmove() is not performance-critical, and perform a
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* bytewise copy for simplicity.
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*/
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__asm__ __volatile__ ( "std\n\t"
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"rep movsb\n\t"
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"cld\n\t"
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: "=&D" ( edi ), "=&S" ( esi ),
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"=&c" ( discard_ecx )
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: "0" ( edi ), "1" ( esi ),
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"2" ( len )
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: "memory" );
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return dest;
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}
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/**
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* Copy (possibly overlapping) memory area
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*
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* @v dest Destination address
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* @v src Source address
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* @v len Length
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* @ret dest Destination address
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*/
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void * __memmove ( void *dest, const void *src, size_t len ) {
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if ( dest <= src ) {
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return __memcpy ( dest, src, len );
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} else {
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return __memcpy_reverse ( dest, src, len );
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}
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}
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2012-11-05 00:53:59 +01:00
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/**
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* Compare strings (up to a specified length)
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*
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* @v str1 First string
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* @v str2 Second string
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* @v len Maximum length
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* @ret diff Difference
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*/
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int strncmp ( const char *str1, const char *str2, size_t len ) {
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const void *discard_S;
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const void *discard_D;
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size_t discard_c;
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int diff;
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__asm__ __volatile__ ( "\n1:\n\t"
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"dec %2\n\t"
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"js 2f\n\t"
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"lodsb\n\t"
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"scasb\n\t"
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"jne 3f\n\t"
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"testb %b3, %b3\n\t"
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"jnz 1b\n\t"
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/* Equal */
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"\n2:\n\t"
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"xor %3, %3\n\t"
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"jmp 4f\n\t"
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/* Not equal; CF indicates difference */
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"\n3:\n\t"
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"sbb %3, %3\n\t"
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"orb $1, %b3\n\t"
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"\n4:\n\t"
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: "=&S" ( discard_S ), "=&D" ( discard_D ),
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"=&c" ( discard_c ), "=&a" ( diff )
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: "0" ( str1 ), "1" ( str2 ), "2" ( len ) );
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return diff;
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}
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