[svn-r17690] Purpose: Code improvement

Description:
    Fixed CommonFG::getComment and CommonFG::getLinkval to provide
    default values for buffer size to improve usability.

    Added test file tlinks.cpp, which only contains test for getLinkval
    and will expand when C++ wrappers for H5L functions are implemented.

Platforms tested:
    Linux/32 2.6 (jam)
    FreeBSD/64 6.3 (liberty)
    SunOS 5.10 (linew)

2 files changed, 53 insertions, 64 deletions

diff --git a/c++/src/H5CommonFG.cpp b/c++/src/H5CommonFG.cpp
index 80efc5d..f9311c6 100644
--- a/c++/src/H5CommonFG.cpp
+++ b/c++/src/H5CommonFG.cpp
@@ -15,11 +15,6 @@
 
 #include <string>
 
-// remove when done
-#include <iostream>
-    using std::cerr;
-    using std::endl;
-
 #include "H5Include.h"
 #include "H5Exception.h"
 #include "H5IdComponent.h"
@@ -430,16 +425,37 @@ void CommonFG::getObjinfo( const H5std_string& name, H5G_stat_t& statbuf ) const
 //--------------------------------------------------------------------------
 H5std_string CommonFG::getLinkval( const char* name, size_t size ) const
 {
-   char* value_C = new char[size+1];  // temporary C-string for C API
+    H5L_info_t linkinfo;
+    char *value_C;	// value in C string
+    size_t val_size = size;
+    H5std_string value = "";
+    herr_t ret_value;
 
-   herr_t ret_value = H5Lget_val( getLocId(), name, value_C, size, H5P_DEFAULT );
-   if( ret_value < 0 )
-   {
-      throwException("getLinkval", "H5Lget_val failed");
-   }
-   H5std_string value = H5std_string( value_C );
-   delete []value_C;
-   return( value );
+    // if user doesn't provide buffer size, determine it
+    if (size == 0)
+    {
+	ret_value = H5Lget_info(getLocId(), name, &linkinfo, H5P_DEFAULT);
+	if( ret_value < 0 )
+	{
+	    throwException("getLinkval", "H5Lget_info to find buffer size failed");
+	}
+	val_size = linkinfo.u.val_size;
+    }
+
+    // if link has value, retrieve the value, otherwise, return null string
+    if (val_size > 0)
+    {
+	value_C = new char[val_size+1];  // temporary C-string for C API
+
+	ret_value = H5Lget_val(getLocId(), name, value_C, val_size, H5P_DEFAULT);
+	if( ret_value < 0 )
+	{
+	    throwException("getLinkval", "H5Lget_val failed");
+	}
+	value = H5std_string(value_C);
+	delete []value_C;
+    }
+    return(value);
 }
 
 //--------------------------------------------------------------------------
@@ -529,33 +545,38 @@ void CommonFG::removeComment(const H5std_string& name) const
 
 //--------------------------------------------------------------------------
 // Function:	CommonFG::getComment
-///\brief	Retrieves comment for the specified object.
+///\brief	Retrieves comment for the specified object and its comment's
+///		length.
 ///\param	name  - IN: Name of the object
+///\param	bufsize - IN: Length of the comment to retrieve
 ///\return	Comment string
 ///\exception	H5::FileIException or H5::GroupIException
-// Programmer	Binh-Minh Ribler - May 2005
+// Programmer	Binh-Minh Ribler - 2000
 //	2007: QAK modified to use H5O APIs; however the first parameter is
 //		no longer just file or group, this function should be moved
 //		to another class to accommodate attribute, dataset, and named
 //		datatype. - BMR
 //--------------------------------------------------------------------------
-H5std_string CommonFG::getComment (const H5std_string& name) const
+H5std_string CommonFG::getComment( const char* name, size_t bufsize ) const
 {
-   size_t bufsize = 256;        // anticipating the comment's length
+   // bufsize is default to 256
+   // temporary variable
    hid_t loc_id = getLocId();   // temporary variable
 
-   // temporary C-string for the object's comment
-   char* comment_C = new char[bufsize+1];
-   ssize_t ret_value = H5Oget_comment_by_name(loc_id, name.c_str(), comment_C, bufsize, H5P_DEFAULT);
+   // temporary C-string for the object's comment; bufsize already including
+   // null character
+   char* comment_C = new char[bufsize];
+   ssize_t ret_value = H5Oget_comment_by_name(loc_id, name, comment_C, bufsize, H5P_DEFAULT);
 
-   // if the actual length of the comment is longer than the anticipated
-   // value, then call H5Oget_comment_by_name again with the correct value
-   if ((size_t)ret_value > bufsize)
+   // if the actual length of the comment is longer than bufsize and bufsize
+   // was the default value, i.e., not given by the user, then call
+   // H5Oget_comment_by_name again with the correct value
+   if ((size_t)ret_value > bufsize && bufsize == 256)
    {
-	bufsize = ret_value;
+	size_t new_size = ret_value;
 	delete []comment_C;
-	comment_C = new char[bufsize+1];
-	ret_value = H5Oget_comment_by_name(loc_id, name.c_str(), comment_C, bufsize, H5P_DEFAULT);
+	comment_C = new char[new_size];	// new_size including null terminator
+	ret_value = H5Oget_comment_by_name(loc_id, name, comment_C, new_size, H5P_DEFAULT);
    }
 
    // if H5Oget_comment_by_name returns SUCCEED, return the string comment,
@@ -571,37 +592,6 @@ H5std_string CommonFG::getComment (const H5std_string& name) const
 
 //--------------------------------------------------------------------------
 // Function:	CommonFG::getComment
-///\brief	Retrieves comment for the specified object and its comment's
-///		length.
-///\param	name  - IN: Name of the object
-///\param	bufsize - IN: Length of the comment to retrieve
-///\return	Comment string
-///\exception	H5::FileIException or H5::GroupIException
-// Programmer	Binh-Minh Ribler - 2000
-//	2007: QAK modified to use H5O APIs; however the first parameter is
-//		no longer just file or group, this function should be moved
-//		to another class to accommodate attribute, dataset, and named
-//		datatype. - BMR
-//--------------------------------------------------------------------------
-H5std_string CommonFG::getComment( const char* name, size_t bufsize ) const
-{
-   // temporary C-string for the object's comment
-   char* comment_C = new char[bufsize+1];
-
-   herr_t ret_value = H5Oget_comment_by_name( getLocId(), name, comment_C, bufsize, H5P_DEFAULT );
-
-   // if H5Oget_comment_by_name returns SUCCEED, return the string comment
-   if( ret_value < 0 )
-   {
-      throwException("getComment", "H5Oget_comment_by_name failed");
-   }
-   H5std_string comment = H5std_string(comment_C);
-   delete []comment_C;
-   return( comment );
-}
-
-//--------------------------------------------------------------------------
-// Function:	CommonFG::getComment
 ///\brief	This is an overloaded member function, provided for convenience.
 ///		It differs from the above function in that it takes an
 ///		\c std::string for \a name.
diff --git a/c++/src/H5CommonFG.h b/c++/src/H5CommonFG.h
index 87c0615..d472d42 100644
--- a/c++/src/H5CommonFG.h
+++ b/c++/src/H5CommonFG.h
@@ -50,9 +50,8 @@ class H5_DLLCPP CommonFG {
 	DataSet openDataSet(const H5std_string& name) const;
 
 	// Retrieves comment for the HDF5 object specified by its name.
-	H5std_string getComment(const H5std_string& name) const;
-	H5std_string getComment(const char* name, size_t bufsize) const;
-	H5std_string getComment(const H5std_string& name, size_t bufsize) const;
+	H5std_string getComment(const char* name, size_t bufsize=256) const;
+	H5std_string getComment(const H5std_string& name, size_t bufsize=256) const;
 
 	// Removes the comment for the HDF5 object specified by its name.
 	void removeComment(const char* name) const;
@@ -62,9 +61,9 @@ class H5_DLLCPP CommonFG {
 	void setComment(const char* name, const char* comment) const;
 	void setComment(const H5std_string& name, const H5std_string& comment) const;
 
-	// Returns the name of the HDF5 object that the symbolic link points to.
-	H5std_string getLinkval(const char* name, size_t size) const;
-	H5std_string getLinkval(const H5std_string& name, size_t size) const;
+	// Returns the value of a symbolic link.
+	H5std_string getLinkval(const char* link_name, size_t size=0) const;
+	H5std_string getLinkval(const H5std_string& link_name, size_t size=0) const;
 
 	// Returns the number of objects in this group.
 	hsize_t getNumObjs() const;