Allow read-only VFD registration (#257)

* Removes no-op callback stubs from read-only VFDs

Also changes VFD registration to allow read-only VFDs with no
write callback to be registered.

* Adds a RELEASE.txt note for HDFFV-11205

For the read-only VFD registration change

5 files changed, 33 insertions, 280 deletions

diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index f64fe74..115bbdc 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -356,6 +356,20 @@ New Features
 
     Library:
     --------
+    - H5FDregister() now allows registration of read-only VFDs
+
+      The H5FDregister() call required a VFD to have a write callback,
+      which prevented registering read-only VFDs like the read-only S3
+      (ros3) and HDFS (hdfs) VFDs from being registered unless they
+      implemented a no-op, fail-always write callback.
+
+      The registration checks no longer check for a write callback and
+      the no-op stubs have been removed from the ros3 and hdfs VFDs.
+      If a write operation is called on a VFD with no write callback, a
+      normal HDF5 error is returned.
+
+      (DER - 2021/01/12, HDFFV-11205)
+
     - Replaced H5E_ATOM with H5E_ID in H5Epubgen.h
 
       The term "atom" is archaic and not in line with current HDF5 library
diff --git a/src/H5FD.c b/src/H5FD.c
index d12bb57..5498644 100644
--- a/src/H5FD.c
+++ b/src/H5FD.c
@@ -231,9 +231,9 @@ H5FDregister(const H5FD_class_t *cls)
                     "'get_eoa' and/or 'set_eoa' methods are not defined")
     if (!cls->get_eof)
         HGOTO_ERROR(H5E_ARGS, H5E_UNINITIALIZED, H5I_INVALID_HID, "'get_eof' method is not defined")
-    if (!cls->read || !cls->write)
+    if (!cls->read)
         HGOTO_ERROR(H5E_ARGS, H5E_UNINITIALIZED, H5I_INVALID_HID,
-                    "'read' and/or 'write' method is not defined")
+                    "'read' method is not defined")
     for (type = H5FD_MEM_DEFAULT; type < H5FD_MEM_NTYPES; type++)
         if (cls->fl_map[type] < H5FD_MEM_NOLIST || cls->fl_map[type] >= H5FD_MEM_NTYPES)
             HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, H5I_INVALID_HID, "invalid free-list mapping")
@@ -277,7 +277,7 @@ H5FD_register(const void *_cls, size_t size, hbool_t app_ref)
     HDassert(cls->open && cls->close);
     HDassert(cls->get_eoa && cls->set_eoa);
     HDassert(cls->get_eof);
-    HDassert(cls->read && cls->write);
+    HDassert(cls->read);
     for (type = H5FD_MEM_DEFAULT; type < H5FD_MEM_NTYPES; type++) {
         HDassert(cls->fl_map[type] >= H5FD_MEM_NOLIST && cls->fl_map[type] < H5FD_MEM_NTYPES);
     }
@@ -1417,6 +1417,10 @@ H5FDwrite(H5FD_t *file, H5FD_mem_t type, hid_t dxpl_id, haddr_t addr, size_t siz
     if (!buf)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "result buffer parameter can't be NULL")
 
+    /* Make sure this isn't being called on a read-only VFD */
+    if (!file->cls->write)
+        HGOTO_ERROR(H5E_VFL, H5E_WRITEERROR, FAIL, "write request made to read-only VFD")
+
     /* Get the default dataset transfer property list if the user didn't provide one */
     if (H5P_DEFAULT == dxpl_id)
         dxpl_id = H5P_DATASET_XFER_DEFAULT;
diff --git a/src/H5FDhdfs.c b/src/H5FDhdfs.c
index 43ad9a1..1b28168 100644
--- a/src/H5FDhdfs.c
+++ b/src/H5FDhdfs.c
@@ -271,12 +271,6 @@ static haddr_t H5FD__hdfs_get_eof(const H5FD_t *_file, H5FD_mem_t type);
 static herr_t  H5FD__hdfs_get_handle(H5FD_t *_file, hid_t fapl, void **file_handle);
 static herr_t  H5FD__hdfs_read(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, haddr_t addr, size_t size,
                                void *buf);
-static herr_t  H5FD__hdfs_write(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, haddr_t addr, size_t size,
-                                const void *buf);
-static herr_t  H5FD__hdfs_truncate(H5FD_t *_file, hid_t dxpl_id, hbool_t closing);
-static herr_t  H5FD__hdfs_lock(H5FD_t *_file, hbool_t rw);
-static herr_t  H5FD__hdfs_unlock(H5FD_t *_file);
-
 static herr_t H5FD__hdfs_validate_config(const H5FD_hdfs_fapl_t *fa);
 
 static const H5FD_class_t H5FD_hdfs_g = {
@@ -306,11 +300,11 @@ static const H5FD_class_t H5FD_hdfs_g = {
     H5FD__hdfs_get_eof,       /* get_eof              */
     H5FD__hdfs_get_handle,    /* get_handle           */
     H5FD__hdfs_read,          /* read                 */
-    H5FD__hdfs_write,         /* write                */
+    NULL,                     /* write                */
     NULL,                     /* flush                */
-    H5FD__hdfs_truncate,      /* truncate             */
-    H5FD__hdfs_lock,          /* lock                 */
-    H5FD__hdfs_unlock,        /* unlock               */
+    NULL,                     /* truncate             */
+    NULL,                     /* lock                 */
+    NULL,                     /* unlock               */
     H5FD_FLMAP_DICHOTOMY      /* fl_map               */
 };
 
@@ -1571,132 +1565,4 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5FD__hdfs_read() */
 
-/*-------------------------------------------------------------------------
- *
- * Function: H5FD__hdfs_write()
- *
- * Purpose:
- *
- *     Write bytes to file.
- *     UNSUPPORTED IN READ-ONLY HDFS VFD.
- *
- * Return:
- *
- *     FAIL (Not possible with Read-Only S3 file.)
- *
- * Programmer: Jacob Smith
- *             2017-10-23
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5FD__hdfs_write(H5FD_t H5_ATTR_UNUSED *_file, H5FD_mem_t H5_ATTR_UNUSED type, hid_t H5_ATTR_UNUSED dxpl_id,
-                 haddr_t H5_ATTR_UNUSED addr, size_t H5_ATTR_UNUSED size, const void H5_ATTR_UNUSED *buf)
-{
-    herr_t ret_value = FAIL;
-
-    FUNC_ENTER_STATIC
-
-#if HDFS_DEBUG
-    HDfprintf(stdout, "called %s.\n", FUNC);
-#endif
-
-    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, FAIL, "cannot write to read-only file")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* H5FD__hdfs_write() */
-
-/*-------------------------------------------------------------------------
- *
- * Function: H5FD__hdfs_truncate()
- *
- * Purpose:
- *
- *     Makes sure that the true file size is the same (or larger)
- *     than the end-of-address.
- *
- *     NOT POSSIBLE ON READ-ONLY S3 FILES.
- *
- * Return:
- *
- *     FAIL (Not possible on Read-Only S3 files.)
- *
- * Programmer: Jacob Smith
- *             2017-10-23
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5FD__hdfs_truncate(H5FD_t H5_ATTR_UNUSED *_file, hid_t H5_ATTR_UNUSED dxpl_id,
-                    hbool_t H5_ATTR_UNUSED closing)
-{
-    herr_t ret_value = SUCCEED;
-
-    FUNC_ENTER_STATIC
-
-#if HDFS_DEBUG
-    HDfprintf(stdout, "called %s.\n", FUNC);
-#endif
-
-    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, FAIL, "cannot truncate read-only file")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5FD__hdfs_truncate() */
-
-/*-------------------------------------------------------------------------
- *
- * Function: H5FD__hdfs_lock()
- *
- * Purpose:
- *
- *     Place an advisory lock on a file.
- *     No effect on Read-Only S3 file.
- *
- *     Suggestion: remove lock/unlock from class
- *                 would result in error at H5FD_[un]lock() (H5FD.c)
- *
- * Return:
- *
- *     SUCCEED (No-op always succeeds)
- *
- * Programmer: Jacob Smith
- *             2017-11-03
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5FD__hdfs_lock(H5FD_t H5_ATTR_UNUSED *_file, hbool_t H5_ATTR_UNUSED rw)
-{
-    FUNC_ENTER_STATIC_NOERR
-
-    FUNC_LEAVE_NOAPI(SUCCEED)
-} /* end H5FD__hdfs_lock() */
-
-/*-------------------------------------------------------------------------
- *
- * Function: H5FD__hdfs_unlock()
- *
- * Purpose:
- *
- *     Remove the existing lock on the file.
- *     No effect on Read-Only S3 file.
- *
- * Return:
- *
- *     SUCCEED (No-op always succeeds)
- *
- * Programmer: Jacob Smith
- *             2017-11-03
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5FD__hdfs_unlock(H5FD_t H5_ATTR_UNUSED *_file)
-{
-    FUNC_ENTER_STATIC_NOERR
-
-    FUNC_LEAVE_NOAPI(SUCCEED)
-} /* end H5FD__hdfs_unlock() */
 #endif /* H5_HAVE_LIBHDFS */
diff --git a/src/H5FDint.c b/src/H5FDint.c
index b651c23..8c93f1c 100644
--- a/src/H5FDint.c
+++ b/src/H5FDint.c
@@ -215,6 +215,10 @@ H5FD_write(H5FD_t *file, H5FD_mem_t type, haddr_t addr, size_t size, const void
     HDassert(file->cls);
     HDassert(buf);
 
+    /* Make sure this isn't being called on a read-only VFD */
+    if (!file->cls->write)
+        HGOTO_ERROR(H5E_VFL, H5E_WRITEERROR, FAIL, "write request made to read-only VFD")
+
     /* Get proper DXPL for I/O */
     dxpl_id = H5CX_get_dxpl();
 
diff --git a/src/H5FDros3.c b/src/H5FDros3.c
index 83e4315..df90528 100644
--- a/src/H5FDros3.c
+++ b/src/H5FDros3.c
@@ -228,12 +228,6 @@ static haddr_t H5FD__ros3_get_eof(const H5FD_t *_file, H5FD_mem_t type);
 static herr_t  H5FD__ros3_get_handle(H5FD_t *_file, hid_t fapl, void **file_handle);
 static herr_t  H5FD__ros3_read(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, haddr_t addr, size_t size,
                                void *buf);
-static herr_t  H5FD__ros3_write(H5FD_t *_file, H5FD_mem_t type, hid_t fapl_id, haddr_t addr, size_t size,
-                                const void *buf);
-static herr_t  H5FD__ros3_truncate(H5FD_t *_file, hid_t dxpl_id, hbool_t closing);
-static herr_t  H5FD__ros3_lock(H5FD_t *_file, hbool_t rw);
-static herr_t  H5FD__ros3_unlock(H5FD_t *_file);
-
 static herr_t H5FD__ros3_validate_config(const H5FD_ros3_fapl_t *fa);
 
 static const H5FD_class_t H5FD_ros3_g = {
@@ -263,11 +257,11 @@ static const H5FD_class_t H5FD_ros3_g = {
     H5FD__ros3_get_eof,       /* get_eof              */
     H5FD__ros3_get_handle,    /* get_handle           */
     H5FD__ros3_read,          /* read                 */
-    H5FD__ros3_write,         /* write                */
+    NULL,                     /* write                */
     NULL,                     /* flush                */
-    H5FD__ros3_truncate,      /* truncate             */
-    H5FD__ros3_lock,          /* lock                 */
-    H5FD__ros3_unlock,        /* unlock               */
+    NULL,                     /* truncate             */
+    NULL,                     /* lock                 */
+    NULL,                     /* unlock               */
     H5FD_FLMAP_DICHOTOMY      /* fl_map               */
 };
 
@@ -1507,133 +1501,4 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5FD__ros3_read() */
 
-/*-------------------------------------------------------------------------
- *
- * Function: H5FD__ros3_write()
- *
- * Purpose:
- *
- *     Write bytes to file.
- *     UNSUPPORTED IN READ-ONLY ROS3 VFD.
- *
- * Return:
- *
- *     FAIL (Not possible with Read-Only S3 file.)
- *
- * Programmer: Jacob Smith
- *             2017-10-23
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5FD__ros3_write(H5FD_t H5_ATTR_UNUSED *_file, H5FD_mem_t H5_ATTR_UNUSED type, hid_t H5_ATTR_UNUSED dxpl_id,
-                 haddr_t H5_ATTR_UNUSED addr, size_t H5_ATTR_UNUSED size, const void H5_ATTR_UNUSED *buf)
-{
-    herr_t ret_value = FAIL;
-
-    FUNC_ENTER_STATIC
-
-#if ROS3_DEBUG
-    HDfprintf(stdout, "H5FD__ros3_write() called.\n");
-#endif
-
-    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, FAIL, "cannot write to read-only file.")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* H5FD__ros3_write() */
-
-/*-------------------------------------------------------------------------
- *
- * Function: H5FD__ros3_truncate()
- *
- * Purpose:
- *
- *     Makes sure that the true file size is the same (or larger)
- *     than the end-of-address.
- *
- *     NOT POSSIBLE ON READ-ONLY S3 FILES.
- *
- * Return:
- *
- *     FAIL (Not possible on Read-Only S3 files.)
- *
- * Programmer: Jacob Smith
- *             2017-10-23
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5FD__ros3_truncate(H5FD_t H5_ATTR_UNUSED *_file, hid_t H5_ATTR_UNUSED dxpl_id,
-                    hbool_t H5_ATTR_UNUSED closing)
-{
-    herr_t ret_value = SUCCEED;
-
-    FUNC_ENTER_STATIC
-
-#if ROS3_DEBUG
-    HDfprintf(stdout, "H5FD__ros3_truncate() called.\n");
-#endif
-
-    HGOTO_ERROR(H5E_VFL, H5E_UNSUPPORTED, FAIL, "cannot truncate read-only file.")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* end H5FD__ros3_truncate() */
-
-/*-------------------------------------------------------------------------
- *
- * Function: H5FD__ros3_lock()
- *
- * Purpose:
- *
- *     Place an advisory lock on a file.
- *     No effect on Read-Only S3 file.
- *
- *     Suggestion: remove lock/unlock from class
- *               > would result in error at H5FD_[un]lock() (H5FD.c)
- *
- * Return:
- *
- *     SUCCEED (No-op always succeeds)
- *
- * Programmer: Jacob Smith
- *             2017-11-03
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5FD__ros3_lock(H5FD_t H5_ATTR_UNUSED *_file, hbool_t H5_ATTR_UNUSED rw)
-{
-    FUNC_ENTER_STATIC_NOERR
-
-    FUNC_LEAVE_NOAPI(SUCCEED)
-} /* end H5FD__ros3_lock() */
-
-/*-------------------------------------------------------------------------
- *
- * Function: H5FD__ros3_unlock()
- *
- * Purpose:
- *
- *     Remove the existing lock on the file.
- *     No effect on Read-Only S3 file.
- *
- * Return:
- *
- *     SUCCEED (No-op always succeeds)
- *
- * Programmer: Jacob Smith
- *             2017-11-03
- *
- *-------------------------------------------------------------------------
- */
-static herr_t
-H5FD__ros3_unlock(H5FD_t H5_ATTR_UNUSED *_file)
-{
-    FUNC_ENTER_STATIC_NOERR
-
-    FUNC_LEAVE_NOAPI(SUCCEED)
-} /* end H5FD__ros3_unlock() */
-
 #endif /* H5_HAVE_ROS3_VFD */