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[digest] Add generic CRC32 function

Signed-off-by: Marty Connor <mdc@etherboot.org>
tags/v1.0.0-rc1
Joshua Oreman před 15 roky
rodič
revize
7eaad90976
2 změnil soubory, kde provedl 64 přidání a 0 odebrání
  1. 54
    0
      src/crypto/crc32.c
  2. 10
    0
      src/include/gpxe/crc32.h

+ 54
- 0
src/crypto/crc32.c Zobrazit soubor

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+/*
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+ * Little-endian CRC32 implementation.
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+ *
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+ * Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
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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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+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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+ */
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+
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+FILE_LICENCE ( GPL2_OR_LATER );
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+
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+#include <gpxe/crc32.h>
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+
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+#define CRCPOLY		0xedb88320
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+
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+/**
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+ * Calculate 32-bit little-endian CRC checksum
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+ *
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+ * @v seed	Initial value
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+ * @v data	Data to checksum
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+ * @v len	Length of data
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+ *
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+ * Usually @a seed is initially zero or all one bits, depending on the
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+ * protocol. To continue a CRC checksum over multiple calls, pass the
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+ * return value from one call as the @a seed parameter to the next.
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+ */
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+u32 crc32_le ( u32 seed, const void *data, size_t len )
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+{
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+	u32 crc = seed;
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+	const u8 *src = data;
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+	u32 mult;
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+	int i;
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+
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+	while ( len-- ) {
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+		crc ^= *src++;
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+		for ( i = 0; i < 8; i++ ) {
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+			mult = ( crc & 1 ) ? CRCPOLY : 0;
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+			crc = ( crc >> 1 ) ^ mult;
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+		}
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+	}
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+
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+	return crc;
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+}

+ 10
- 0
src/include/gpxe/crc32.h Zobrazit soubor

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+#ifndef _GPXE_CRC32_H
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+#define _GPXE_CRC32_H
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+
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+FILE_LICENCE ( GPL2_OR_LATER );
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+
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+#include <stdint.h>
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+
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+u32 crc32_le ( u32 seed, const void *data, size_t len );
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+
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+#endif

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