[svn-r12605] Description:

    Break out a bunch of the misc. routines that were in src/H5.c into more
specific modules.

    Add optimized fletcher32 checksum routine, for checksumming metadata as
well as raw data.

Tested On:
    Linux/32 2.6 (chicago)
    Linux/64 2.6 (chicago2)
    Will test further after checkin...

1 files changed, 145 insertions, 0 deletions

diff --git a/src/H5checksum.c b/src/H5checksum.c
new file mode 100644
index 0000000..f4d702b
--- /dev/null
+++ b/src/H5checksum.c
@@ -0,0 +1,145 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by the Board of Trustees of the University of Illinois.         *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This file is part of HDF5.  The full HDF5 copyright notice, including     *
+ * terms governing use, modification, and redistribution, is contained in    *
+ * the files COPYING and Copyright.html.  COPYING can be found at the root   *
+ * of the source code distribution tree; Copyright.html can be found at the  *
+ * root level of an installed copy of the electronic HDF5 document set and   *
+ * is linked from the top-level documents page.  It can also be found at     *
+ * http://hdf.ncsa.uiuc.edu/HDF5/doc/Copyright.html.  If you do not have     *
+ * access to either file, you may request a copy from hdfhelp@ncsa.uiuc.edu. *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*-------------------------------------------------------------------------
+ *
+ * Created:		H5checksum.c
+ *			Aug 21 2006
+ *			Quincey Koziol <koziol@hdfgroup.org>
+ *
+ * Purpose:		Internal code for computing fletcher32 checksums
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/****************/
+/* Module Setup */
+/****************/
+
+
+/***********/
+/* Headers */
+/***********/
+#include "H5private.h"		/* Generic Functions			*/
+
+
+/****************/
+/* Local Macros */
+/****************/
+
+
+/******************/
+/* Local Typedefs */
+/******************/
+
+
+/********************/
+/* Package Typedefs */
+/********************/
+
+
+/********************/
+/* Local Prototypes */
+/********************/
+
+
+/*********************/
+/* Package Variables */
+/*********************/
+
+
+/*****************************/
+/* Library Private Variables */
+/*****************************/
+
+
+/*******************/
+/* Local Variables */
+/*******************/
+
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5_fletcher32
+ *
+ * Purpose:	This routine provides a generic, fast checksum algorithm for
+ *              use in the library.
+ *
+ * Note:        See the Wikipedia page for Fletcher's checksum:
+ *                  http://en.wikipedia.org/wiki/Fletcher%27s_checksum
+ *              for more details, etc.
+ *
+ * Return:	32-bit fletcher checksum of input buffer (can't fail)
+ *
+ * Programmer:	Quincey Koziol
+ *              Monday, August 21, 2006
+ *
+ *-------------------------------------------------------------------------
+ */
+uint32_t
+H5_fletcher32(const void *_data, size_t _len)
+{
+    const uint16_t *data = (const uint16_t *)_data;  /* Pointer to the data to be summed */
+    size_t len = _len / 2;      /* Length in 16-bit words */
+    uint32_t sum1 = 0xffff, sum2 = 0xffff;
+    uint32_t ret_value;         /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5_fletcher32)
+
+    /* Sanity check */
+    HDassert(_data);
+    HDassert(_len > 0);
+
+    /* Compute checksum for pairs of bytes */
+    /* The magic "360" value is is the largest number of sums that can be
+     *  performed without numeric overflow.  See the Wikipedia page for
+     *  Fletcher's checksum: http://en.wikipedia.org/wiki/Fletcher%27s_checksum
+     *  for more details, etc.
+     */
+    while (len) {
+        unsigned tlen = len > 360 ? 360 : len;
+        len -= tlen;
+        do {
+            sum1 += *data++;
+            sum2 += sum1;
+        } while (--tlen);
+        sum1 = (sum1 & 0xffff) + (sum1 >> 16);
+        sum2 = (sum2 & 0xffff) + (sum2 >> 16);
+    }
+
+    /* Check for odd # of bytes */
+    if(_len % 2) {
+        sum1 += *(const uint8_t *)data;
+        sum2 += sum1;
+        sum1 = (sum1 & 0xffff) + (sum1 >> 16);
+        sum2 = (sum2 & 0xffff) + (sum2 >> 16);
+    } /* end if */
+
+    /* Second reduction step to reduce sums to 16 bits */
+    sum1 = (sum1 & 0xffff) + (sum1 >> 16);
+    sum2 = (sum2 & 0xffff) + (sum2 >> 16);
+
+/* Byteswap result on little-endian platforms */
+#ifdef H5_WORDS_BIGENDIAN
+    ret_value = sum2 << 16 | sum1;
+#else /* H5_WORDS_BIGENDIAN */
+    ret_value = (sum2 << 8) & 0x00ff0000;
+    ret_value |= (sum2 << 24) & 0xff000000;
+    ret_value |= (sum1 << 8) & 0x0000ff00;
+    ret_value |= (sum1 >> 8) & 0x000000ff;
+#endif /* H5_WORDS_BIGENDIAN */
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5_fletcher32() */
+