VFD plugins (#602)

* Implement support for loading of Virtual File Drivers as plugins

Fix plugin caching for VOL connector and VFD plugins

Fix plugin iteration to skip paths that can't be opened

* Enable dynamic loading of VFDs with HDF5_DRIVER environment variable

* Temporarily disable error reporting during H5F_open double file open

* Default to using HDstat in h5_get_file_size for unknown VFDs

* Use macros for some environment variables that HDF5 interprets

* Update "null" and "ctl testing" VFDs

13 files changed, 78 insertions, 0 deletions

diff --git a/tools/testfiles/h5dump-help.txt b/tools/testfiles/h5dump-help.txt
index 5b11223..53c666b 100644
--- a/tools/testfiles/h5dump-help.txt
+++ b/tools/testfiles/h5dump-help.txt
@@ -28,6 +28,12 @@ usage: h5dump [OPTIONS] files
                           HDF5 file specified
      --vol-info           VOL-specific info to pass to the VOL connector used for
                           opening the HDF5 file specified
+     --vfd-value          Value (ID) of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-name           Name of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-info           VFD-specific info to pass to the VFL driver used for
+                          opening the HDF5 file specified
 --------------- Object Options ---------------
      -a P, --attribute=P  Print the specified attribute
                           If an attribute name contains a slash (/), escape the
diff --git a/tools/testfiles/help-1.ls b/tools/testfiles/help-1.ls
index 0926c4c..6ed1aab 100644
--- a/tools/testfiles/help-1.ls
+++ b/tools/testfiles/help-1.ls
@@ -52,6 +52,12 @@ usage: h5ls [OPTIONS] file[/OBJECT] [file[/[OBJECT]...]
                    HDF5 file specified
    --vol-info      VOL-specific info to pass to the VOL connector used for
                    opening the HDF5 file specified
+   --vfd-value     Value (ID) of the VFL driver to use for opening the
+                   HDF5 file specified
+   --vfd-name      Name of the VFL driver to use for opening the
+                   HDF5 file specified
+   --vfd-info      VFD-specific info to pass to the VFL driver used for
+                   opening the HDF5 file specified
 
   file/OBJECT
     Each object consists of an HDF5 file name optionally followed by a
diff --git a/tools/testfiles/help-2.ls b/tools/testfiles/help-2.ls
index 0926c4c..6ed1aab 100644
--- a/tools/testfiles/help-2.ls
+++ b/tools/testfiles/help-2.ls
@@ -52,6 +52,12 @@ usage: h5ls [OPTIONS] file[/OBJECT] [file[/[OBJECT]...]
                    HDF5 file specified
    --vol-info      VOL-specific info to pass to the VOL connector used for
                    opening the HDF5 file specified
+   --vfd-value     Value (ID) of the VFL driver to use for opening the
+                   HDF5 file specified
+   --vfd-name      Name of the VFL driver to use for opening the
+                   HDF5 file specified
+   --vfd-info      VFD-specific info to pass to the VFL driver used for
+                   opening the HDF5 file specified
 
   file/OBJECT
     Each object consists of an HDF5 file name optionally followed by a
diff --git a/tools/testfiles/help-3.ls b/tools/testfiles/help-3.ls
index 0926c4c..6ed1aab 100644
--- a/tools/testfiles/help-3.ls
+++ b/tools/testfiles/help-3.ls
@@ -52,6 +52,12 @@ usage: h5ls [OPTIONS] file[/OBJECT] [file[/[OBJECT]...]
                    HDF5 file specified
    --vol-info      VOL-specific info to pass to the VOL connector used for
                    opening the HDF5 file specified
+   --vfd-value     Value (ID) of the VFL driver to use for opening the
+                   HDF5 file specified
+   --vfd-name      Name of the VFL driver to use for opening the
+                   HDF5 file specified
+   --vfd-info      VFD-specific info to pass to the VFL driver used for
+                   opening the HDF5 file specified
 
   file/OBJECT
     Each object consists of an HDF5 file name optionally followed by a
diff --git a/tools/testfiles/pbits/tnofilename-with-packed-bits.ddl b/tools/testfiles/pbits/tnofilename-with-packed-bits.ddl
index 5b11223..53c666b 100644
--- a/tools/testfiles/pbits/tnofilename-with-packed-bits.ddl
+++ b/tools/testfiles/pbits/tnofilename-with-packed-bits.ddl
@@ -28,6 +28,12 @@ usage: h5dump [OPTIONS] files
                           HDF5 file specified
      --vol-info           VOL-specific info to pass to the VOL connector used for
                           opening the HDF5 file specified
+     --vfd-value          Value (ID) of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-name           Name of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-info           VFD-specific info to pass to the VFL driver used for
+                          opening the HDF5 file specified
 --------------- Object Options ---------------
      -a P, --attribute=P  Print the specified attribute
                           If an attribute name contains a slash (/), escape the
diff --git a/tools/testfiles/pbits/tpbitsIncomplete.ddl b/tools/testfiles/pbits/tpbitsIncomplete.ddl
index 5b11223..53c666b 100644
--- a/tools/testfiles/pbits/tpbitsIncomplete.ddl
+++ b/tools/testfiles/pbits/tpbitsIncomplete.ddl
@@ -28,6 +28,12 @@ usage: h5dump [OPTIONS] files
                           HDF5 file specified
      --vol-info           VOL-specific info to pass to the VOL connector used for
                           opening the HDF5 file specified
+     --vfd-value          Value (ID) of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-name           Name of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-info           VFD-specific info to pass to the VFL driver used for
+                          opening the HDF5 file specified
 --------------- Object Options ---------------
      -a P, --attribute=P  Print the specified attribute
                           If an attribute name contains a slash (/), escape the
diff --git a/tools/testfiles/pbits/tpbitsLengthExceeded.ddl b/tools/testfiles/pbits/tpbitsLengthExceeded.ddl
index 5b11223..53c666b 100644
--- a/tools/testfiles/pbits/tpbitsLengthExceeded.ddl
+++ b/tools/testfiles/pbits/tpbitsLengthExceeded.ddl
@@ -28,6 +28,12 @@ usage: h5dump [OPTIONS] files
                           HDF5 file specified
      --vol-info           VOL-specific info to pass to the VOL connector used for
                           opening the HDF5 file specified
+     --vfd-value          Value (ID) of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-name           Name of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-info           VFD-specific info to pass to the VFL driver used for
+                          opening the HDF5 file specified
 --------------- Object Options ---------------
      -a P, --attribute=P  Print the specified attribute
                           If an attribute name contains a slash (/), escape the
diff --git a/tools/testfiles/pbits/tpbitsLengthPositive.ddl b/tools/testfiles/pbits/tpbitsLengthPositive.ddl
index 5b11223..53c666b 100644
--- a/tools/testfiles/pbits/tpbitsLengthPositive.ddl
+++ b/tools/testfiles/pbits/tpbitsLengthPositive.ddl
@@ -28,6 +28,12 @@ usage: h5dump [OPTIONS] files
                           HDF5 file specified
      --vol-info           VOL-specific info to pass to the VOL connector used for
                           opening the HDF5 file specified
+     --vfd-value          Value (ID) of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-name           Name of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-info           VFD-specific info to pass to the VFL driver used for
+                          opening the HDF5 file specified
 --------------- Object Options ---------------
      -a P, --attribute=P  Print the specified attribute
                           If an attribute name contains a slash (/), escape the
diff --git a/tools/testfiles/pbits/tpbitsMaxExceeded.ddl b/tools/testfiles/pbits/tpbitsMaxExceeded.ddl
index 5b11223..53c666b 100644
--- a/tools/testfiles/pbits/tpbitsMaxExceeded.ddl
+++ b/tools/testfiles/pbits/tpbitsMaxExceeded.ddl
@@ -28,6 +28,12 @@ usage: h5dump [OPTIONS] files
                           HDF5 file specified
      --vol-info           VOL-specific info to pass to the VOL connector used for
                           opening the HDF5 file specified
+     --vfd-value          Value (ID) of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-name           Name of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-info           VFD-specific info to pass to the VFL driver used for
+                          opening the HDF5 file specified
 --------------- Object Options ---------------
      -a P, --attribute=P  Print the specified attribute
                           If an attribute name contains a slash (/), escape the
diff --git a/tools/testfiles/pbits/tpbitsOffsetExceeded.ddl b/tools/testfiles/pbits/tpbitsOffsetExceeded.ddl
index 5b11223..53c666b 100644
--- a/tools/testfiles/pbits/tpbitsOffsetExceeded.ddl
+++ b/tools/testfiles/pbits/tpbitsOffsetExceeded.ddl
@@ -28,6 +28,12 @@ usage: h5dump [OPTIONS] files
                           HDF5 file specified
      --vol-info           VOL-specific info to pass to the VOL connector used for
                           opening the HDF5 file specified
+     --vfd-value          Value (ID) of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-name           Name of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-info           VFD-specific info to pass to the VFL driver used for
+                          opening the HDF5 file specified
 --------------- Object Options ---------------
      -a P, --attribute=P  Print the specified attribute
                           If an attribute name contains a slash (/), escape the
diff --git a/tools/testfiles/pbits/tpbitsOffsetNegative.ddl b/tools/testfiles/pbits/tpbitsOffsetNegative.ddl
index 5b11223..53c666b 100644
--- a/tools/testfiles/pbits/tpbitsOffsetNegative.ddl
+++ b/tools/testfiles/pbits/tpbitsOffsetNegative.ddl
@@ -28,6 +28,12 @@ usage: h5dump [OPTIONS] files
                           HDF5 file specified
      --vol-info           VOL-specific info to pass to the VOL connector used for
                           opening the HDF5 file specified
+     --vfd-value          Value (ID) of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-name           Name of the VFL driver to use for opening the
+                          HDF5 file specified
+     --vfd-info           VFD-specific info to pass to the VFL driver used for
+                          opening the HDF5 file specified
 --------------- Object Options ---------------
      -a P, --attribute=P  Print the specified attribute
                           If an attribute name contains a slash (/), escape the
diff --git a/tools/testfiles/textlinksrc-nodangle-1.ls b/tools/testfiles/textlinksrc-nodangle-1.ls
index 0926c4c..6ed1aab 100644
--- a/tools/testfiles/textlinksrc-nodangle-1.ls
+++ b/tools/testfiles/textlinksrc-nodangle-1.ls
@@ -52,6 +52,12 @@ usage: h5ls [OPTIONS] file[/OBJECT] [file[/[OBJECT]...]
                    HDF5 file specified
    --vol-info      VOL-specific info to pass to the VOL connector used for
                    opening the HDF5 file specified
+   --vfd-value     Value (ID) of the VFL driver to use for opening the
+                   HDF5 file specified
+   --vfd-name      Name of the VFL driver to use for opening the
+                   HDF5 file specified
+   --vfd-info      VFD-specific info to pass to the VFL driver used for
+                   opening the HDF5 file specified
 
   file/OBJECT
     Each object consists of an HDF5 file name optionally followed by a
diff --git a/tools/testfiles/tgroup-1.ls b/tools/testfiles/tgroup-1.ls
index 0926c4c..6ed1aab 100644
--- a/tools/testfiles/tgroup-1.ls
+++ b/tools/testfiles/tgroup-1.ls
@@ -52,6 +52,12 @@ usage: h5ls [OPTIONS] file[/OBJECT] [file[/[OBJECT]...]
                    HDF5 file specified
    --vol-info      VOL-specific info to pass to the VOL connector used for
                    opening the HDF5 file specified
+   --vfd-value     Value (ID) of the VFL driver to use for opening the
+                   HDF5 file specified
+   --vfd-name      Name of the VFL driver to use for opening the
+                   HDF5 file specified
+   --vfd-info      VFD-specific info to pass to the VFL driver used for
+                   opening the HDF5 file specified
 
   file/OBJECT
     Each object consists of an HDF5 file name optionally followed by a