[svn-r13926] Description:

    Add small interface to "wrap" a static buffer (usually on the stack), but
still allow for buffers larger than the static buffer to be allocated.  This
can eliminate _many_ short-lived buffer allocations in situations where the
buffer is a predictable size (or at least a "very likely" size).

    Also, some minor code cleanups, particularly in the SOHM caching code.

Tested on:
    Mac OS X/32 10.4.10 (amazon)

1 files changed, 291 insertions, 0 deletions

diff --git a/src/H5WB.c b/src/H5WB.c
new file mode 100644
index 0000000..e53c70c
--- /dev/null
+++ b/src/H5WB.c
@@ -0,0 +1,291 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by The HDF Group.                                               *
+ * 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://hdfgroup.org/HDF5/doc/Copyright.html.  If you do not have          *
+ * access to either file, you may request a copy from help@hdfgroup.org.     *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*-------------------------------------------------------------------------
+ *
+ * Created:		H5WB.c
+ *			Jun 26 2007
+ *			Quincey Koziol <koziol@hdfgroup.org>
+ *
+ * Purpose:		Implements the "wrapped buffer" code for wrapping
+ *                      an existing [staticly sized] buffer, in order to
+ *                      avoid lots of memory allocation calls.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/****************/
+/* Module Setup */
+/****************/
+
+
+/***********/
+/* Headers */
+/***********/
+#include "H5private.h"		/* Generic Functions			*/
+#include "H5Eprivate.h"		/* Error handling		  	*/
+#include "H5FLprivate.h"	/* Free Lists                           */
+#include "H5WBprivate.h"        /* Wrapped Buffers                      */
+
+/****************/
+/* Local Macros */
+/****************/
+
+
+/******************/
+/* Local Typedefs */
+/******************/
+
+
+/********************/
+/* Package Typedefs */
+/********************/
+
+/* Typedef for buffer wrapper */
+struct H5WB_t {
+    void *wrapped_buf;          /* Pointer to wrapped buffer */
+    size_t wrapped_size;        /* Size of wrapped buffer */
+    void *actual_buf;           /* Pointer to actual buffer */
+    size_t actual_size;         /* Size of actual buffer used */
+    size_t alloc_size;          /* Size of actual buffer allocated */
+};
+
+
+/********************/
+/* Local Prototypes */
+/********************/
+
+
+/*********************/
+/* Package Variables */
+/*********************/
+
+
+/*****************************/
+/* Library Private Variables */
+/*****************************/
+
+
+/*******************/
+/* Local Variables */
+/*******************/
+
+/* Declare a free list to manage the H5WB_t struct */
+H5FL_DEFINE_STATIC(H5WB_t);
+
+/* Declare a free list to manage the extra buffer information */
+H5FL_BLK_DEFINE_STATIC(extra_buf);
+
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5WB_wrap
+ *
+ * Purpose:	Wraps an existing [possibly static] buffer
+ *
+ * Return:	Pointer to buffer wrapper info on success
+ *              NULL on failure
+ *
+ * Programmer:	Quincey Koziol
+ *		koziol@hdfgroup.org
+ *		Jun 26 2007
+ *
+ *-------------------------------------------------------------------------
+ */
+H5WB_t *
+H5WB_wrap(void *buf, size_t buf_size)
+{
+    H5WB_t *wb = NULL;          /* Wrapped buffer info */
+    H5WB_t *ret_value;          /* Return value */
+
+    FUNC_ENTER_NOAPI(H5WB_wrap, NULL)
+
+    /*
+     * Check arguments.
+     */
+    HDassert(buf);
+    HDassert(buf_size);
+
+    /* Create wrapped buffer info */
+    if(NULL == (wb = H5FL_MALLOC(H5WB_t)))
+        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed for wrapped buffer info")
+
+    /* Wrap buffer given */
+    wb->wrapped_buf = buf;
+    wb->wrapped_size = buf_size;
+
+    /* No actual buffer yet */
+    wb->actual_buf = NULL;
+    wb->actual_size = 0;
+    wb->alloc_size = 0;
+
+    /* Set the return value */
+    ret_value = wb;
+
+done:
+    /* Release resources on error */
+    if(!ret_value && wb)
+        (void)H5FL_FREE(H5WB_t, wb);
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5WB_wrap() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5WB_actual
+ *
+ * Purpose:	Get the pointer to an "actual" buffer, of at least a certain
+ *              size.
+ *
+ * Return:	Pointer to buffer pointer on success
+ *              NULL on failure
+ *
+ * Programmer:	Quincey Koziol
+ *		koziol@hdfgroup.org
+ *		Jun 26 2007
+ *
+ *-------------------------------------------------------------------------
+ */
+void *
+H5WB_actual(H5WB_t *wb, size_t need)
+{
+    void *ret_value;            /* Return value */
+
+    FUNC_ENTER_NOAPI(H5WB_actual, NULL)
+
+    /*
+     * Check arguments.
+     */
+    HDassert(wb);
+    HDassert(wb->wrapped_buf);
+
+    /* Check for previously allocated buffer */
+    if(wb->actual_buf && wb->actual_buf != wb->wrapped_buf) {
+        /* Sanity check */
+        HDassert(wb->actual_size > wb->wrapped_size);
+
+        /* Check if we can re-use existing buffer */
+        if(need <= wb->alloc_size)
+            HGOTO_DONE(wb->actual_buf)
+        /* Can't re-use existing buffer, free it and proceed */
+        else
+            wb->actual_buf = H5FL_BLK_FREE(extra_buf, wb->actual_buf);
+    } /* end if */
+
+    /* Check if size needed can be fulfilled with wrapped buffer */
+    if(need > wb->wrapped_size) {
+        /* Need to allocate new buffer */
+        if(NULL == (wb->actual_buf = H5FL_BLK_MALLOC(extra_buf, need)))
+            HGOTO_ERROR(H5E_ATTR, H5E_NOSPACE, NULL, "memory allocation failed")
+
+        /* Remember size of buffer allocated */
+        wb->alloc_size = need;
+    } /* end if */
+    else {
+        /* Don't have to allocate a new buffer, use the wrapped one */
+        wb->actual_buf = wb->wrapped_buf;
+        wb->alloc_size = 0;
+    } /* end else */
+
+    /* Set the return value */
+    ret_value = wb->actual_buf;
+
+done:
+    /* Remember size of buffer used, if we were successful */
+    if(ret_value)
+        wb->actual_size = need;
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5WB_actual() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5WB_actual_clear
+ *
+ * Purpose:	Get the pointer to an "actual" buffer, of at least a certain
+ *              size.  Also, clear actual buffer to zeros.
+ *
+ * Return:	Pointer to buffer pointer on success
+ *              NULL on failure
+ *
+ * Programmer:	Quincey Koziol
+ *		koziol@hdfgroup.org
+ *		Jun 26 2007
+ *
+ *-------------------------------------------------------------------------
+ */
+void *
+H5WB_actual_clear(H5WB_t *wb, size_t need)
+{
+    void *ret_value;            /* Return value */
+
+    FUNC_ENTER_NOAPI(H5WB_actual_clear, NULL)
+
+    /*
+     * Check arguments.
+     */
+    HDassert(wb);
+    HDassert(wb->wrapped_buf);
+
+    /* Get a pointer to an actual buffer */
+    if(NULL == (ret_value = H5WB_actual(wb, need)))
+        HGOTO_ERROR(H5E_ATTR, H5E_NOSPACE, NULL, "memory allocation failed")
+
+    /* Clear the buffer */
+    HDmemset(ret_value, 0, need);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5WB_actual_clear() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5WB_unwrap
+ *
+ * Purpose:	"unwrap" a wrapped buffer, releasing all resources used
+ *
+ * Return:	SUCCEED/FAIL
+ *
+ * Programmer:	Quincey Koziol
+ *		koziol@hdfgroup.org
+ *		Jun 26 2007
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5WB_unwrap(H5WB_t *wb)
+{
+    FUNC_ENTER_NOAPI_NOFUNC(H5WB_unwrap)
+
+    /*
+     * Check arguments.
+     */
+    HDassert(wb);
+    HDassert(wb->wrapped_buf);
+
+    /* Release any extra buffers allocated */
+    if(wb->actual_buf && wb->actual_buf != wb->wrapped_buf) {
+        /* Sanity check */
+        HDassert(wb->actual_size > wb->wrapped_size);
+
+        wb->actual_buf = H5FL_BLK_FREE(extra_buf, wb->actual_buf);
+    } /* end if */
+
+    /* Release the buffer wrapper info */
+    H5FL_FREE(H5WB_t, wb);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5WB_unwrap() */
+