libglusterfsclient: Add comments to API

Some of the functions have also been moved within
the header to reflect the order in which users will
read through and try to understand how to use the lib.

For eg. the init, mount and umount functions have been moved to
the beginning to clarify how to start by init and de-initing.

Signed-off-by: Anand V. Avati <avati@amp.gluster.com>

1 files changed, 773 insertions, 30 deletions

diff --git a/libglusterfsclient/src/libglusterfsclient.h b/libglusterfsclient/src/libglusterfsclient.h
index 87297ac132e..84881f78970 100755
--- a/libglusterfsclient/src/libglusterfsclient.h
+++ b/libglusterfsclient/src/libglusterfsclient.h
@@ -40,23 +40,6 @@ typedef struct {
         void         *dictref;
 } glusterfs_iobuf_t;
 
-typedef struct {
-        char          *logfile;
-        char          *loglevel;
-        struct {
-                char  *specfile;
-                FILE  *specfp;
-        }; 
-        char          *volume_name;
-        unsigned long  lookup_timeout;
-        unsigned long  stat_timeout;
-} glusterfs_init_params_t;
-
-typedef void * glusterfs_handle_t;
-
-/* FIXME: how is glusterfs_file_t different from glusterfs_dir_t? */
-typedef void * glusterfs_file_t;
-typedef void * glusterfs_dir_t;
 
 typedef
 int (*glusterfs_readv_cbk_t) (int op_ret, int op_errno, glusterfs_iobuf_t *buf,
@@ -69,25 +52,146 @@ typedef
 int (*glusterfs_get_cbk_t) (int op_ret, int op_errno, glusterfs_iobuf_t *buf,
 			    struct stat *stbuf, void *cbk_data);
 
-/* Used to free the glusterfs_read_buf passed to the application from
-   glusterfs_read_async_cbk
-*/
-void
-glusterfs_free (glusterfs_iobuf_t *buf);
 
-/* libglusterfsclient initialization function  */
+/* Data Interface
+ * The first section describes the data structures required for
+ * using libglusterfsclient.
+ */
+
+/* This structure needs to be filled up and
+ * passed to te glusterfs_init function which uses
+ * the params passed herein to initialize a glusterfs
+ * client context and then connect to a glusterfs server.
+ */
+typedef struct {
+        char          *logfile;         /* Path to the file which will store
+                                           the log.
+                                           */
+        char          *loglevel;        /* The log level required for
+                                           reporting various events within
+                                           libglusterfsclient.
+                                           */
+        struct {
+                char  *specfile;        /* Users can either open a volume or
+                                           specfile and assign the pointer to
+                                           specfp, or just refer to the volume
+                                           /spec file path in specfile.
+                                           */
+                FILE  *specfp;
+        };
+        char          *volume_name;     /* The volume file could describe many
+                                           volumes but the specific volume
+                                           within that file is chosen by
+                                           specifying the volume name here.
+                                           */
+        unsigned long  lookup_timeout;  /* libglusterclient provides the inode
+                                           numbers to be cached by the library.
+                                           The duration for which these are
+                                           cached are defined by lookup_timeout
+                                           . In Seconds.
+                                           */
+        unsigned long  stat_timeout;    /* The file attributes received from
+                                           a stat syscall can also be cached
+                                           for the duration specified in this
+                                           member. In Seconds.
+                                           */
+} glusterfs_init_params_t;
+
+
+
+/* This is the handle returned by glusterfs_init
+ * once the initialization is complete.
+ * Users should treat this as an opaque handle.
+ */
+typedef void * glusterfs_handle_t;
+
+
+
+/* These identifiers are used as handles for files and dirs.
+ * Users of libglusterfsclient should not in anyway try to interpret
+ * the actual structures these will point to.
+ */
+typedef void * glusterfs_file_t;
+typedef void * glusterfs_dir_t;
+
+
+/* Function Call Interface */
+/* libglusterfsclient initialization function.
+ * @ctx : the structure described above filled with required values.
+ *
+ * Returns NULL on failure and the non-NULL pointer on success.
+ * On failure, the error description might be present in the logfile
+ * depending on the log level.
+ */
 glusterfs_handle_t
 glusterfs_init (glusterfs_init_params_t *ctx);
 
+
+
+/* Used to destroy a glusterfs client context and the
+ * connection to the glusterfs server.
+ *
+ * @handle      : The glusterfs handle returned by glusterfs_init.
+ */
 int
 glusterfs_fini (glusterfs_handle_t handle);
 
-/* For smaller files, application can use just glusterfs_get/glusterfs_get_async
+
+
+/* libglusterfs client provides two interfaces.
+ * 1. handle-based interface
+ * Functions that comprise the handle-based interface accept the
+ * glusterfs_handle_t as the first argument. It specifies the
+ * glusterfs client context over which to perform the operation.
+ *
+ * 2. Virtual Mount Point based interface:
+ * Functions that do not require a handle to be given in order to
+ * identify which client context to operate on. This interface
+ * internally determines the corresponding client context for the
+ * given path. The down-side is that a virtual mount point (VMP) needs to be
+ * registered with the library. A VMP is just a string that maps to a
+ * glusterfs_handle_t. The advantage of a VMP based interface is that
+ * a user program using multiple client contexts does not need to
+ * maintain its own mapping between paths and the corresponding
+ * handles.
+ */
+
+
+
+/* glusterfs_mount is the function that allows users to register a VMP
+ * along with the parameters, which will be used to initialize a
+ * context. Applications calling glusterfs_mount do not need to
+ * initialized a context using the glusterfs_init interface.
+ *
+ * @vmp         : The virtual mount point.
+ * @ipars       : Initialization parameters populated as described
+ *              earlier.
+ *
+ * Returns 0 on success, and -1 on failure.
+ */
+int
+glusterfs_mount (char *vmp, glusterfs_init_params_t *ipars);
+
+
+
+/* glusterfs_umount is the VMP equivalent of glusterfs_fini.
+ *
+ * @vmp         : The VMP which was initialized using glusterfs_mount.
+ *
+ * Returns 0 on sucess, and -1 on failure.
+ */
+int
+glusterfs_umount (char *vmp);
+
+
+
+/* For smaller files, application can use just
+ * glusterfs_get/glusterfs_get_async
  * to read the whole content. Limit of the file-sizes to be read in
  * glusterfs_get/glusterfs_get_async is passed in the size argument
  */
 
-/* glusterfs_get:
+/* glusterfs_glh_get:
  * @handle : glusterfs handle
  * @path   : path to be looked upon
  * @size   : upper limit of file-sizes to be read in lookup
@@ -105,36 +209,147 @@ int
 glusterfs_get_async (glusterfs_handle_t handle, const char *path, size_t size,
 		     glusterfs_get_cbk_t cbk, void *cbk_data);
 
+
+
+/* Opens a file. Corresponds to the open syscall.
+ *
+ * @handle      : Handle returned from glusterfs_init
+ * @path        : Path to the file or directory on the glusterfs
+ *              export. Must be absolute to the export on the server.
+ * @flags       : flags to control open behaviour.
+ * @...         : The mode_t argument that defines the mode for a new
+ *              file, in case a new file is being created using the
+ *              O_CREAT flag in @flags.
+ *
+ * Returns a non-NULL handle on success. NULL on failure and sets
+ * errno accordingly.
+ */
 glusterfs_file_t
 glusterfs_glh_open (glusterfs_handle_t handle, const char *path, int flags,
                         ...);
 
+
+/* Opens a file without having to specify a handle.
+ *
+ * @path        : Path to the file to open in the glusterfs export.
+ *              The path to the file in glusterfs export must be
+ *              pre-fixed with the VMP string registered with
+ *              glusterfs_mount.
+ * @flags       : flags to control open behaviour.
+ * @...         : The mode_t argument that defines the mode for a new
+ *              file, in case a new file is being created using the
+ *              O_CREAT flag in @flags.
+ *
+ * Returns 0 on success, -1 on failure with errno set accordingly.
+ */
 glusterfs_file_t
 glusterfs_open (const char *path, int flags, ...);
 
+
+
+/* Creates a file. Corresponds to the creat syscall.
+ *
+ * @handle      : Handle returned from glusterfs_init
+ * @path        : Path to the file that needs to be created in the
+ *              glusterfs export.
+ * @mode        : File creation mode.
+ *
+ * Returns the file handle on success. NULL on error with errno set as
+ * required.
+ */
 glusterfs_file_t
 glusterfs_glh_creat (glusterfs_handle_t handle, const char *path, mode_t mode);
 
+
+
+/* VMP-based creat.
+ * @path        : Path to the file to be created. Must be
+ *              pre-prepended with the VMP string registered with
+ *              glusterfs_mount.
+ * @mode        : File creation mode.
+ *
+ * Returns file handle on success. NULL handle on error with errno set
+ * accordingly.
+ */
 glusterfs_file_t
 glusterfs_creat (const char *path, mode_t mode);
 
+
+
+/* Close the file identified by the handle.
+ *
+ * @fd          : Closes the file.
+ *
+ * Returns 0 on success, -1 on error with errno set accordingly.
+ */
 int
 glusterfs_close (glusterfs_file_t fd);
 
+
+
+/* Get struct stat for the file in path.
+ *
+ * @handle      : The handle that identifies a glusterfs client
+ *              context.
+ * @path        : The file for which we need to get struct stat.
+ * @stbuf       : The buffer into which the file's stat is copied.
+ *
+ * Returns 0 on success and -1 on error with errno set accordingly.
+ */
 int
 glusterfs_glh_stat (glusterfs_handle_t handle, const char *path,
                         struct stat *stbuf);
 
+
+/* Get struct stat for file in path.
+ *
+ * @path        : The file for which struct stat is required.
+ * @sbuf        : The buffer into which the stat structure is copied.
+ *
+ * Returns 0 on success and -1 on error with errno set accordingly.
+ */
 int
 glusterfs_stat (const char *path, struct stat *buf);
 
+
+
+/* Gets stat struct for the file.
+ *
+ * @handle      : The handle identifying a glusterfs client context.
+ * @path        : Path to the file for which stat structure is
+ *              required. If path is a symlink, the symlink is
+ *              interpreted and the stat structure returned for the
+ *              target of the link.
+ * @buf         : The buffer into which the stat structure is copied.
+ *
+ * Returns 0 on success and -1 on error with errno set accordingly.
+ */
 int
 glusterfs_glh_lstat (glusterfs_handle_t handle, const char *path,
                         struct stat *buf);
 
+
+
+/* Gets stat struct for a file.
+ *
+ * @path        : The file to get the struct stat for.
+ * @buf         : The receiving struct stat buffer.
+ *
+ * Returns 0 on success and -1 on error with errno set accordingly.
+ */
 int
 glusterfs_lstat (const char *path, struct stat *buf);
 
+
+
+/* Get stat structure for a file.
+ *
+ * @fd          : The file handle identifying a file on the glusterfs
+ *              server.
+ * @stbuf       : The buffer into which the stat data is copied.
+ *
+ * Returns 0 on success and -1 on error with errno set accordingly.
+ */
 int
 glusterfs_fstat (glusterfs_file_t fd, struct stat *stbuf);
 
@@ -194,9 +409,32 @@ glusterfs_lremovexattr (glusterfs_handle_t handle, const char *path,
 int
 glusterfs_fremovexattr (glusterfs_file_t fd, const char *name);
 
+
+
+/* Read data from a file.
+ * @fd          : Handle returned by glusterfs_open or
+ *              glusterfs_glh_open.
+ * @buf         : Buffer to read the data into.
+ * @nbytes      : Number of bytes to read.
+ *
+ * Returns number of bytes actually read on success or -1 on error
+ * with errno set to the appropriate error number.
+ */
 ssize_t
 glusterfs_read (glusterfs_file_t fd, void *buf, size_t nbytes);
 
+
+
+/* Read data into an array of buffers.
+ *
+ * @fd          : File handle returned by glusterfs_open or
+ *              glusterfs_glh_open.
+ * @vec         : Array of buffers into which the data is read.
+ * @count       : Number of iovecs referred to by vec.
+ *
+ * Returns number of bytes read on success or -1 on error with errno
+ * set appropriately.
+ */
 ssize_t
 glusterfs_readv (glusterfs_file_t fd, const struct iovec *vec, int count);
 
@@ -204,9 +442,33 @@ int
 glusterfs_read_async (glusterfs_file_t fd, size_t nbytes, off_t offset,
                       glusterfs_readv_cbk_t readv_cbk, void *cbk_data);
 
+
+
+/* Write data into a file.
+ *
+ * @fd          : File handle returned from glusterfs_open or
+ *              glusterfs_glh_open.
+ * @buf         : Buffer which is written to the file.
+ * @nbytes      : Number bytes of the @buf written to the file.
+ *
+ * On success, returns number of bytes written. On error, returns -1
+ * with errno set appropriately.
+ */
 ssize_t
 glusterfs_write (glusterfs_file_t fd, const void *buf, size_t nbytes);
 
+
+
+/* Writes an array of buffers into a file.
+ *
+ * @fd          : The file handle returned from glusterfs_open or
+ *              glusterfs_glh_open.
+ * @vector      : Array of buffers to be written to the file.
+ * @count       : Number of separate buffers in the @vector array.
+ *
+ * Returns number of bytes written on success or -1 on error with
+ * errno set approriately.
+ */
 ssize_t
 glusterfs_writev (glusterfs_file_t fd, const struct iovec *vector, int count);
 
@@ -220,32 +482,140 @@ glusterfs_writev_async (glusterfs_file_t fd, const struct iovec *vector,
 			int count, off_t offset,
 			glusterfs_write_cbk_t write_cbk, void *cbk_data);
 
+
+
+/* Read from a file starting at a given offset.
+ *
+ * @fd          : File handle returned from glusterfs_open or
+ *              glusterfs_glh_open.
+ * @buf         : Buffer to read the data into.
+ * @nbytes      : Number of bytes to read.
+ * @offset      : The offset to start reading @nbytes from.
+ *
+ * Returns number of bytes read on success or -1 on error with errno
+ * set appropriately.
+ */
 ssize_t
 glusterfs_pread (glusterfs_file_t fd, void *buf, size_t nbytes, off_t offset);
 
+
+
+/* Write to a file starting at a given offset.
+ *
+ * @fd          : Flie handle returned from glusterfs_open or
+ *              glusterfs_glh_open.
+ * @buf         : Buffer that will be written to the file.
+ * @nbytes      : Number of bytes to write from @buf.
+ * @offset      : The starting offset from where @nbytes will be
+ *              written.
+ *
+ * Returns number of bytes written on success and -1 on error with
+ * errno set appropriately.
+ */
 ssize_t
 glusterfs_pwrite (glusterfs_file_t fd, const void *buf, size_t nbytes,
 		  off_t offset);
 
+
+
+/* Seek to an offset in the file.
+ *
+ * @fd          : File handle in which to seek to. File handle
+ *              returned by glusterfs_open or glusterfs_glh_open.
+ * @offset      : Offset to seek to in the given file.
+ * @whence      : Determines how the offset is interpreted by this
+ *              syscall. The behaviour is similar to the options
+ *              provided by the POSIX lseek system call. See man lseek
+ *              for more details.
+ *
+ * On success, returns the resulting absolute offset in the file after the seek
+ * operation is performed. ON error, returns -1 with errno set
+ * appropriately.
+ */
 off_t
 glusterfs_lseek (glusterfs_file_t fd, off_t offset, int whence);
 
+
+
+/* Create a directory.
+ *
+ * @handle      : The handle of the glusterfs context in which the
+ *              directory needs to be created.
+ * @path        : The absolute path within the glusterfs context where
+ *              the directory needs to be created.
+ * @mode        : The mode bits for the newly created directory.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_mkdir (glusterfs_handle_t handle, const char *path, mode_t mode);
 
+
+
+/* Create a directory.
+ *
+ * @path        : Path to the directory that needs to be created. This
+ *              path must be prefixed with the VMP of the particular glusterfs
+ *              context.
+ * @mode        : Mode flags for the newly created directory.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_mkdir (const char *path, mode_t mode);
 
+
+
+/* Remove a directory.
+ *
+ * @handle      : Handle of the glusterfs context from which to remove
+ *              the directory.
+ * @path        : The path of the directory to be removed in the glusterfs
+ *              context.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_rmdir (glusterfs_handle_t handle, const char *path);
 
+
+
+/* Remove a directory.
+ *
+ * @path        : The absolute path to the directory to be removed.
+ *              This path must be pre-fixed with the VMP of the
+ *              particular glusterfs context in which this directory
+ *              resides.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_rmdir (const char *path);
-/* FIXME: implement man 3 readdir semantics */
+
+
+
+/* Read directory entries.
+ *
+ * @fd          : The handle of the directory to be read. This handle
+ *              is the one returned by opendir.
+ * @dirp        : The pointer to the array of directory entries into
+ *              which the directory data will be stored.
+ * @count       : Number of directory entries to be read.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_readdir (glusterfs_dir_t fd, struct dirent *dirp,
 		   unsigned int count);
 
+
+
+/* Close a directory handle.
+ *
+ * @fd          : The directory handle to be closed.
+ *
+ * Returns 0 on success and -1 on error with errno set to 0.
+ */
 int
 glusterfs_closedir (glusterfs_dir_t dirfd);
 /* FIXME: remove getdents */
@@ -253,123 +623,490 @@ int
 glusterfs_getdents (glusterfs_dir_t fd, struct dirent *dirp,
 		    unsigned int count);
 
+
+
+/* Create device node.
+ *
+ * @handle      : glusterfs context in which to create the device
+ *              node.
+ * @pathname    : The absolute path of the device to be created in the
+ *              given glusterfs context.
+ *
+ * @mode        : Mode flags to apply to the newly created node.
+ * @dev         : Device numbers that will apply to the node.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_mknod(glusterfs_handle_t handle, const char *pathname,
                         mode_t mode, dev_t dev);
 
+
+
+/* Create a device node.
+ *
+ * @pathname    : The full path of the node to be created. This path
+ *              should be pre-pended with the VMP of the glusterfs
+ *              context in which this node is to be created.
+ * @mode        : Mode flags that will be applied to the newly created
+ *              device file.
+ * @dev         : The device numbers that will be associated with the
+ *              device node.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_mknod(const char *pathname, mode_t mode, dev_t dev);
 
+
+
+/* Returns the real absolute path of the given path.
+ *
+ * @handle              : The glusterfs context in which the path resides in.
+ * @path                : The path to be resolved.
+ * @resolved_path       : The resolved path is stored in this buffer
+ *                      provided by the caller.
+ *
+ * Returns a pointer to resolved_path on success and NULL on error
+ * with errno set appropriately.
+ *
+ * See man realpath for details.
+ */
 char *
 glusterfs_glh_realpath (glusterfs_handle_t handle, const char *path,
                         char *resolved_path);
 
+
+/* Returns the real absolute path of the given path.
+ *
+ * @path                : The path to be resolved. This path must be
+ *                      pre-fixed with the VMP of the glusterfs
+ *                      context in which the file resides.
+ *
+ * @resolved_path       : The resolved path is stored in this user
+ *                      provided buffer.
+ *
+ * Returns a pointer to resolved_path on success, and NULL on error
+ * with errno set appropriately.
+ */
 char *
 glusterfs_realpath (const char *path, char *resolved_path);
 
-int
-glusterfs_mount (char *vmp, glusterfs_init_params_t *ipars);
 
-int
-glusterfs_umount (char *vmp);
 
+/* Change mode flags on a path.
+ *
+ * @handle      : Handle of the glusterfs instance in which the path
+ *              resides.
+ * @path        : The path whose mode bits need to be changed.
+ * @mode        : The new mode bits.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_chmod (glusterfs_handle_t handle, const char *path, mode_t mode);
 
+
+
+/* Change mode flags on a path.
+ *
+ * @path        : The path whose mode bits need to be changed. The
+ *              path should be pre-fixed with the VMP that identifies the
+ *              glusterfs context within which the path resides.
+ * @mode        : The new mode bits.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_chmod (const char *path, mode_t mode);
 
+
+
+/* Change the owner of a path.
+ *
+ * @handle      : Handle of the glusterfs context in which the path
+ *              resides.
+ * @path        : The path whose owner needs to be changed.
+ * @owner       : ID of the new owner.
+ * @group       : ID of the new group.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_chown (glusterfs_handle_t handle, const char *path, uid_t owner,
                         gid_t group);
 
+
+
+/* Change the owner of a path.
+ *
+ * @path        : The path whose owner needs to be changed. Path must
+ *              be pre-fixed with the VMP that identifies the
+ *              glusterfs context in which the path resides.
+ * @owner       : ID of the new owner.
+ * @group       : ID of the new group.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_chown (const char *path, uid_t owner, gid_t group);
 
+
+
+/* Change the owner of the file.
+ *
+ * @fd          : Handle of the file whose owner needs to be changed.
+ * @owner       : ID of the new owner.
+ * @group       : ID of the new group.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_fchown (glusterfs_file_t fd, uid_t owner, gid_t group);
 
+
+
+/* Open a directory.
+ *
+ * @handle      : Handle that identifies a glusterfs context.
+ * @path        : Path to the directory in the glusterfs context.
+ *
+ * Returns a non-NULL handle on success and NULL on failure with errno
+ * set appropriately.
+ */
 glusterfs_dir_t
 glusterfs_glh_opendir (glusterfs_handle_t handle, const char *path);
 
+
+
+/* Open a directory.
+ *
+ * @path        : Path to the directory. The path must be prepended
+ *              with the VMP in order to identify the glusterfs
+ *              context in which path resides.
+ *
+ * Returns a non-NULL handle on success and NULL on failure with errno
+ * set appropriately.
+ */
 glusterfs_dir_t
 glusterfs_opendir (const char *path);
 
+
+
+/* Change the mode bits on an open file.
+ *
+ * @fd          : The file whose mode bits need to be changed.
+ * @mode        : The new mode bits.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_fchmod (glusterfs_file_t fd, mode_t mode);
 
+
+
+/* Sync the file contents to storage.
+ *
+ * @fd          : The file whose contents need to be sync'ed to
+ *              storage.
+ *
+ * Return 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_fsync (glusterfs_file_t *fd);
 
+
+
+/* Truncate an open file.
+ *
+ * @fd          : The file to truncate.
+ * @length      : The length to truncate to.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_ftruncate (glusterfs_file_t fd, off_t length);
 
+
+
+/* Create a hard link between two paths.
+ *
+ * @handle      : glusterfs context in which both paths should reside.
+ * @oldpath     : The existing path to link to.
+ * @newpath     : The new path which will be linked to @oldpath.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_link (glusterfs_handle_t handle, const char *oldpath,
                         const char *newpath);
 
+
+
+/* Create a hard link between two paths.
+ *
+ * @oldpath     : The existing path to link to.
+ * @newpath     : The new path which will be linked to @oldpath.
+ *
+ * Both paths should exist on the same glusterfs context and should be
+ * prefixed with the same VMP.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_link (const char *oldpath, const char *newpath);
 
+
+
+/* Get stats about the underlying file system.
+ *
+ * @handle      : Identifies the glusterfs context in which resides
+ *              the given path.
+ * @path        : stats are returned for the file system on which file
+ *              is located.
+ * @buf         : The buffer into which the stats are copied.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_statfs (glusterfs_handle_t handle, const char *path,
                         struct statfs *buf);
 
+
+
+/* Get stats about the underlying file system.
+ *
+ * @path        : stats are returned for the file system on which file
+ *              is located. @path must start with the VMP of the
+ *              glusterfs context on which the file reside.
+ * @buf         : The buffer into which the stats are copied.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_statfs (const char *path, struct statfs *buf);
 
+
+
+/* Get stats about the underlying file system.
+ *
+ * @handle      : Identifies the glusterfs context in which resides
+ *              the given path.
+ * @path        : stats are returned for the file system on which file
+ *              is located.
+ * @buf         : The buffer into which the stats are copied.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_statvfs (glusterfs_handle_t handle, const char *path,
                    struct statvfs *buf);
 
+
+
+/* Get stats about the underlying file system.
+ *
+ * @path        : stats are returned for the file system on which file
+ *              is located. @path must start with the VMP of the
+ *              glusterfs context on which the file reside.
+ * @buf         : The buffer into which the stats are copied.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_statvfs (const char *path, struct statvfs *buf);
 
+
+
+/* Set the atime and mtime values for a given path.
+ *
+ * @handle      : The handle identifying the glusterfs context.
+ * @path        : The path for which the times need to be changed.
+ * @times       : The array containing new time stamps for the file.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_utimes (glusterfs_handle_t handle, const char *path,
                         const struct timeval times[2]);
 
+
+
+/* Set the atime and mtime values for a given path.
+ *
+ * @path        : The path for which the times need to be changed.
+ * @times       : The array containing new time stamps for the file.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_utimes (const char *path, const struct timeval times[2]);
 
+
+
+/* Set the atime and mtime values for a given path.
+ *
+ * @handle      : The handle identifying the glusterfs context.
+ * @path        : The path for which the times need to be changed.
+ * @buf         : The structure containing new time stamps for the file.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_utime (glusterfs_handle_t handle, const char *path,
                         const struct utimbuf *buf);
 
+
+
+/* Set the atime and mtime values for a given path.
+ *
+ * @path        : The path for which the times need to be changed.
+ * @buf         : The structure containing new time stamps for the file.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_utime (const char *path, const struct utimbuf *buf);
 
+
+
+/*  Create  FIFO at the given path.
+ *
+ *  @handle     : The glusterfs context in which to create that FIFO.
+ *  @path       : The path within the context where the FIFO is to be
+ *              created.
+ * @mode        : The mode bits for the newly create FIFO.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_mkfifo (glusterfs_handle_t handle, const char *path,
                         mode_t mode);
 
+
+
+/*  Create  FIFO at the given path.
+ *
+ *  @path       : The path within the context where the FIFO is to be
+ *              created. @path should begin with the VMP of the
+ *              glusterfs context in which the FIFO needs to be
+ *              created.
+ * @mode        : The mode bits for the newly create FIFO.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_mkfifo (const char *path, mode_t mode);
 
+
+
+/* Unlink a file.
+ *
+ * @handle      : Handle that identifies a glusterfs instance.
+ * @path        : Path in the glusterfs instance that needs to be
+ *              unlinked.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_unlink (glusterfs_handle_t handle, const char *path);
 
+
+
+/* Unlink a file.
+ *
+ * @path        : Path in the glusterfs instance that needs to be
+ *              unlinked.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_unlink (const char *path);
 
+
+
+/* Create a symbolic link.
+ *
+ * @handle      : The handle identifying the glusterfs context.
+ * @oldpath     : The existing path to which a symlink needs to be
+ *              created.
+ * @newpath     : The new path which will be symlinked to the
+ *              @oldpath.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_symlink (glusterfs_handle_t handle, const char *oldpath,
                                 const char *newpath);
 
+
+
+/* Create a symbolic link.
+ *
+ * @oldpath     : The existing path to which a symlink needs to be
+ *              created.
+ * @newpath     : The new path which will be symlinked to the
+ *              @oldpath.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_symlink (const char *oldpath, const char *newpath);
 
+
+
+/* Read a symbolic link.
+ *
+ * @handle      : Handle identifying the glusterfs context.
+ * @path        : The symlink that needs to be read.
+ * @buf         : The buffer into which the target of @path will be
+ *              stored.
+ * @bufsize     : Size of the buffer allocated to @buf.
+ *
+ * Returns number of bytes copied into @buf and -1 on error with errno
+ * set appropriately.
+ */
 ssize_t
 glusterfs_glh_readlink (glusterfs_handle_t handle, const char *path, char *buf,
                                 size_t bufsize);
 
+
+
+/* Read a symbolic link.
+ *
+ * @path        : The symlink that needs to be read.
+ * @buf         : The buffer into which the target of @path will be
+ *              stored.
+ * @bufsize     : Size of the buffer allocated to @buf.
+ *
+ * Returns number of bytes copied into @buf and -1 on error with errno
+ * set appropriately.
+ */
 ssize_t
 glusterfs_readlink (const char *path, char *buf, size_t bufsize);
 
+
+
+/* Rename a file or directory.
+ *
+ * @handle      : The identifier of a glusterfs context.
+ * @oldpath     : The path to be renamed.
+ * @newpath     : The new name for the @oldpath.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_glh_rename (glusterfs_handle_t handle, const char *oldpath,
                       const char *newpath);
 
+
+
+/* Rename a file or directory.
+ * @oldpath     : The path to be renamed.
+ * @newpath     : The new name for the @oldpath.
+ *
+ * Returns 0 on success and -1 on error with errno set appropriately.
+ */
 int
 glusterfs_rename (const char *oldpath, const char *newpath);
 /* FIXME: review the need for these apis */
@@ -382,6 +1119,12 @@ glusterfs_log_lock (void);
 
 void
 glusterfs_log_unlock (void);
+/* Used to free the glusterfs_read_buf passed to the application from
+   glusterfs_read_async_cbk
+*/
+void
+glusterfs_free (glusterfs_iobuf_t *buf);
+
 
 __END_DECLS