From 775dc8a9c0c83f7a2f776e97f5b90385c759535a Mon Sep 17 00:00:00 2001
From: hrydgard <hrydgard@gmail.com>
Date: Sat, 12 Jul 2008 17:40:22 +0000
Subject: Initial megacommit.

git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@4 8ced0084-cf51-0410-be5f-012b33b47a6e
---
 Source/Core/Common/Src/Hash.cpp | 138 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 138 insertions(+)
 create mode 100644 Source/Core/Common/Src/Hash.cpp

(limited to 'Source/Core/Common/Src/Hash.cpp')

diff --git a/Source/Core/Common/Src/Hash.cpp b/Source/Core/Common/Src/Hash.cpp
new file mode 100644
index 0000000000..c628f61a64
--- /dev/null
+++ b/Source/Core/Common/Src/Hash.cpp
@@ -0,0 +1,138 @@
+// Copyright (C) 2003-2008 Dolphin Project.
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, version 2.0.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License 2.0 for more details.
+
+// A copy of the GPL 2.0 should have been included with the program.
+// If not, see http://www.gnu.org/licenses/
+
+// Official SVN repository and contact information can be found at
+// http://code.google.com/p/dolphin-emu/
+
+#include "Hash.h"
+
+// uint32_t
+// WARNING - may read one more byte!
+// Implementation from Wikipedia.
+u32 HashFletcher(const u8* data_u8, size_t length)
+{
+	const u16* data = (const u16*)data_u8; /* Pointer to the data to be summed */
+	size_t len = (length + 1) / 2; /* Length in 16-bit words */
+	u32 sum1 = 0xffff, sum2 = 0xffff;
+
+	while (len)
+	{
+		size_t tlen = len > 360 ? 360 : len;
+		len -= tlen;
+
+		do {
+			sum1 += *data++;
+			sum2 += sum1;
+		}
+		while (--tlen);
+
+		sum1 = (sum1 & 0xffff) + (sum1 >> 16);
+		sum2 = (sum2 & 0xffff) + (sum2 >> 16);
+	}
+
+	/* Second reduction step to reduce sums to 16 bits */
+	sum1 = (sum1 & 0xffff) + (sum1 >> 16);
+	sum2 = (sum2 & 0xffff) + (sum2 >> 16);
+	return(sum2 << 16 | sum1);
+}
+
+
+// Implementation from Wikipedia
+// Slightly slower than Fletcher above, but slighly more reliable.
+#define MOD_ADLER 65521
+// data: Pointer to the data to be summed; len is in bytes
+u32 HashAdler32(const u8* data, size_t len)
+{
+	u32 a = 1, b = 0;
+
+	while (len)
+	{
+		size_t tlen = len > 5550 ? 5550 : len;
+		len -= tlen;
+
+		do
+		{
+			a += *data++;
+			b += a;
+		}
+		while (--tlen);
+
+		a = (a & 0xffff) + (a >> 16) * (65536 - MOD_ADLER);
+		b = (b & 0xffff) + (b >> 16) * (65536 - MOD_ADLER);
+	}
+
+	// It can be shown that a <= 0x1013a here, so a single subtract will do.
+	if (a >= MOD_ADLER)
+	{
+		a -= MOD_ADLER;
+	}
+
+	// It can be shown that b can reach 0xfff87 here.
+	b = (b & 0xffff) + (b >> 16) * (65536 - MOD_ADLER);
+
+	if (b >= MOD_ADLER)
+	{
+		b -= MOD_ADLER;
+	}
+
+	return((b << 16) | a);
+}
+
+
+// Another fast and decent hash
+u32 HashFNV(const u8* ptr, int length)
+{
+	u32 hash = 0x811c9dc5;
+
+	for (int i = 0; i < length; i++)
+	{
+		hash *= 1677761;
+		hash ^= ptr[i];
+	}
+
+	return(hash);
+}
+
+
+// Another fast and decent hash
+u32 HashFNV1(const u8* ptr, int length)
+{
+	u32 hash = 0x811c9dc5;
+
+	for (int i = 0; i < length; i++)
+	{
+		hash *= 1677761;
+		hash ^= ptr[i];
+	}
+
+	return(hash);
+}
+
+
+// Terribly stupid hash - but can't go back now :)
+// Don't use for new things. At least it's fast.
+u32 HashEctor(const u8* ptr, int length)
+{
+	u32 crc = 0;
+
+	for (int i = 0; i < length; i++)
+	{
+		crc ^= ptr[i];
+		crc = (crc << 3) | (crc >> 29);
+	}
+
+	return(crc);
+}
+
+
-- 
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