SWMR

CHANGELOG.md

@@ -1,11 +1,13 @@
 # Changelog
 
-## hdf5 unreleased
 ## hdf5-types unreleased
 ## hdf5-derive unreleased
 ## hdf5-sys unreleased
 ## hdf5-src unreleased
 
+## hdf5 unreleased
+- Added support for Single Writer Multiple Readers (SWMR) (breaking change, OpenMode has extra variant)
+
 ## hdf5-types v0.10.1
 Release date: Mar 19, 2025
 - Fixed deref of null ptr in `VarLenAscii`/`VarLenUnicode`

hdf5/examples/swmr.rs

@@ -0,0 +1,49 @@
+#[cfg(feature = "1.10.2")]
+use hdf5_metno as hdf5;
+
+#[cfg(feature = "1.10.2")]
+fn reader() {
+    let file = hdf5::File::open_as("swmr.h5", hdf5::OpenMode::ReadSWMR).unwrap();
+    println!("Reader: Opened file");
+    let var = file.dataset("foo").unwrap();
+
+    for _ in 0..5 {
+        var.refresh().unwrap();
+        let shape = var.shape();
+        println!("Reader: Got shape: {shape:?}");
+        // If reading one should use the shape directly without
+        // using the convenience read_2d etc. functions which
+        // might get confused if the shape is changed during reading
+        std::thread::sleep(std::time::Duration::from_secs(5));
+    }
+}
+
+fn main() {
+    #[cfg(not(feature = "1.10.2"))]
+    println!("This examples requires hdf5 >= 1.10.2 to enable SWMR and set libver_bounds");
+
+    #[cfg(feature = "1.10.2")]
+    {
+        let file = hdf5::File::with_options()
+            .with_fapl(|fapl| fapl.libver_v110())
+            .create("swmr.h5")
+            .unwrap();
+
+        let var = file.new_dataset::<u8>().shape((0.., 5)).create("foo").unwrap();
+
+        file.start_swmr().unwrap();
+        println!("Writer: Wrote file");
+
+        let thread = std::thread::spawn(|| reader());
+
+        for i in 0..5 {
+            var.resize((i + 1, 5)).unwrap();
+            var.write_slice(&[i, i, i, i, i], (i, 0..)).unwrap();
+            var.flush().unwrap();
+            println!("Writer: Wrote {i}");
+            std::thread::sleep(std::time::Duration::from_secs(5));
+        }
+
+        thread.join().unwrap();
+    }
+}

hdf5/src/hl/dataset.rs

@@ -8,6 +8,8 @@ use hdf5_sys::h5d::{
     H5Dcreate2, H5Dcreate_anon, H5Dget_access_plist, H5Dget_create_plist, H5Dget_offset,
     H5Dset_extent,
 };
+#[cfg(feature = "1.10.0")]
+use hdf5_sys::h5d::{H5Dflush, H5Drefresh};
 use hdf5_sys::h5l::H5Ldelete;
 use hdf5_sys::h5p::H5P_DEFAULT;
 use hdf5_sys::h5z::H5Z_filter_t;
@@ -154,6 +156,22 @@ impl Dataset {
     pub fn filters(&self) -> Vec<Filter> {
         self.dcpl().map_or(Vec::default(), |pl| pl.filters())
     }
+
+    /// Flush the dataset metadata from the metadata cache to the file
+    #[cfg(feature = "1.10.0")]
+    pub fn flush(&self) -> Result<()> {
+        let id = self.id();
+        h5call!(H5Dflush(id))?;
+        Ok(())
+    }
+
+    /// Refresh metadata items assosicated with the dataset
+    #[cfg(feature = "1.10.0")]
+    pub fn refresh(&self) -> Result<()> {
+        let id = self.id();
+        h5call!(H5Drefresh(id))?;
+        Ok(())
+    }
 }
 
 pub struct Maybe<T>(Option<T>);

hdf5/src/hl/file.rs

@@ -8,6 +8,8 @@ use hdf5_sys::h5f::{
     H5Fget_freespace, H5Fget_intent, H5Fget_obj_count, H5Fget_obj_ids, H5Fopen, H5F_ACC_DEFAULT,
     H5F_ACC_EXCL, H5F_ACC_RDONLY, H5F_ACC_RDWR, H5F_ACC_TRUNC, H5F_SCOPE_LOCAL,
 };
+#[cfg(feature = "1.10.0")]
+use hdf5_sys::h5f::{H5Fstart_swmr_write, H5F_ACC_SWMR_READ};
 
 use crate::hl::plist::{
     file_access::{FileAccess, FileAccessBuilder},
@@ -17,9 +19,13 @@ use crate::internal_prelude::*;
 
 /// File opening mode.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[cfg_attr(not(feature = "1.10.0"), non_exhaustive)]
 pub enum OpenMode {
     /// Open a file as read-only, file must exist.
     Read,
+    /// Open a file as read-only in SWMR mode, file must exist.
+    #[cfg(feature = "1.10.0")]
+    ReadSWMR,
     /// Open a file as read/write, file must exist.
     ReadWrite,
     /// Create a file, truncate if exists.
@@ -178,6 +184,14 @@ impl File {
     pub fn fcpl(&self) -> Result<FileCreate> {
         self.create_plist()
     }
+
+    #[cfg(feature = "1.10.0")]
+    /// Mark this file as ready for opening as SWMR
+    pub fn start_swmr(&self) -> Result<()> {
+        let id = self.id();
+        h5call!(H5Fstart_swmr_write(id))?;
+        Ok(())
+    }
 }
 
 /// File builder allowing to customize file access/creation property lists.
@@ -231,9 +245,13 @@ impl FileBuilder {
         )?;
         let flags = match mode {
             OpenMode::Read => H5F_ACC_RDONLY,
+            #[cfg(feature = "1.10.0")]
+            OpenMode::ReadSWMR => H5F_ACC_RDONLY | H5F_ACC_SWMR_READ,
             OpenMode::ReadWrite => H5F_ACC_RDWR,
             OpenMode::Create => H5F_ACC_TRUNC,
             OpenMode::CreateExcl | OpenMode::Append => H5F_ACC_EXCL,
+            #[cfg(not(feature = "1.10.0"))]
+            _ => unreachable!(),
         };
         let fname_ptr = filename.as_ptr();
         h5lock!({
@@ -242,6 +260,8 @@ impl FileBuilder {
                 OpenMode::Read | OpenMode::ReadWrite => {
                     File::from_id(h5try!(H5Fopen(fname_ptr, flags, fapl.id())))
                 }
+                #[cfg(feature = "1.10.0")]
+                OpenMode::ReadSWMR => File::from_id(h5try!(H5Fopen(fname_ptr, flags, fapl.id()))),
                 _ => {
                     let fcpl = self.fcpl.finish()?;
                     File::from_id(h5try!(H5Fcreate(fname_ptr, flags, fcpl.id(), fapl.id())))