PearsonHash has been added to libbu++, I...have no way of really verifying that

our results are right, but I can at least write a unit test and make sure that
minor changes in the inputs create different results in the output.

2 files changed, 107 insertions, 0 deletions

diff --git a/src/pearsonhash.cpp b/src/pearsonhash.cpp
new file mode 100644
index 0000000..d068687
--- /dev/null
+++ b/src/pearsonhash.cpp
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2007-2011 Xagasoft, All rights reserved.
+ *
+ * This file is part of the libbu++ library and is released under the
+ * terms of the license contained in the file LICENSE.
+ */
+
+#include "bu/pearsonhash.h"
+#include "bu/stream.h"
+
+uint8_t Bu::PearsonHash::aSBox[] = {
+        251, 175, 119, 215, 81, 14, 79, 191, 103, 49, 181, 143, 186, 157, 0,
+        232, 31, 32, 55, 60, 152, 58, 17, 237, 174, 70, 160, 144, 220, 90, 57,
+        223, 59, 3, 18, 140, 111, 166, 203, 196, 134, 243, 124, 95, 222, 179,
+        197, 65, 180, 48, 36, 15, 107, 46, 233, 130, 165, 30, 123, 161, 209, 23,
+        97, 16, 40, 91, 219, 61, 100, 10, 210, 109, 250, 127, 22, 138, 29, 108,
+        244, 67, 207, 9, 178, 204, 74, 98, 126, 249, 167, 116, 34, 77, 193,
+        200, 121, 5, 20, 113, 71, 35, 128, 13, 182, 94, 25, 226, 227, 199, 75,
+        27, 41, 245, 230, 224, 43, 225, 177, 26, 155, 150, 212, 142, 218, 115,
+        241, 73, 88, 105, 39, 114, 62, 255, 192, 201, 145, 214, 168, 158, 221,
+        148, 154, 122, 12, 84, 82, 163, 44, 139, 228, 236, 205, 242, 217, 11,
+        187, 146, 159, 64, 86, 239, 195, 42, 106, 198, 118, 112, 184, 172, 87,
+        2, 173, 117, 176, 229, 247, 253, 137, 185, 99, 164, 102, 147, 45, 66,
+        231, 52, 141, 211, 194, 206, 246, 238, 56, 110, 78, 248, 63, 240, 189,
+        93, 92, 51, 53, 183, 19, 171, 72, 50, 33, 104, 101, 69, 8, 252, 83, 120,
+        76, 135, 85, 54, 202, 125, 188, 213, 96, 235, 136, 208, 162, 129, 190,
+        132, 156, 38, 47, 1, 7, 254, 24, 4, 216, 131, 89, 21, 28, 133, 37, 153,
+        149, 80, 170, 68, 6, 169, 234, 151
+};
+
+Bu::PearsonHash::PearsonHash()
+{
+        reset();
+}
+
+Bu::PearsonHash::~PearsonHash()
+{
+}
+
+void Bu::PearsonHash::reset()
+{
+        iValue = 0;
+}
+
+void Bu::PearsonHash::setSalt( const Bu::String &sSalt )
+{
+}
+
+void Bu::PearsonHash::addData( const void *sData, int iSize )
+{
+        for( int j = 0; j < iSize; j++ )
+        {
+                iValue = aSBox[ iValue^((unsigned char *)sData)[j] ];
+        }
+}
+
+Bu::String Bu::PearsonHash::getResult()
+{
+        return Bu::String((char)iValue);
+}
+
+void Bu::PearsonHash::writeResult( Stream &sOut )
+{
+        sOut.write( &iValue, 1 );
+}
+
diff --git a/src/pearsonhash.h b/src/pearsonhash.h
new file mode 100644
index 0000000..af8dfc3
--- /dev/null
+++ b/src/pearsonhash.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2007-2011 Xagasoft, All rights reserved.
+ *
+ * This file is part of the libbu++ library and is released under the
+ * terms of the license contained in the file LICENSE.
+ */
+
+#ifndef BU_PEARSON_HASH_H
+#define BU_PEARSON_HASH_H
+
+#include "bu/cryptohash.h"
+
+namespace Bu
+{
+        /**
+         * A pearson hash is a non-cryptographically secure hashing function that
+         * is very light on resources, very fast, and produces a single byte
+         * as it's output.  It is strongly dependant on every byte in the input,
+         * which means that it's a good choice for adding to short messages to
+         * ensure that the contents of the messages are unchanged.
+         */
+        class PearsonHash : public Bu::CryptoHash
+        {
+        public:
+                PearsonHash();
+                virtual ~PearsonHash();
+
+                virtual void reset();
+                virtual void setSalt( const Bu::String &sSalt );
+                virtual void addData( const void *sData, int iSize );
+                using Bu::CryptoHash::addData;
+                virtual String getResult();
+                virtual void writeResult( Stream &sOut );
+
+        private:
+                static uint8_t aSBox[256];
+                uint8_t iValue;
+        };
+};
+
+#endif