resource: Step one of VFS support, redirect all opens

This redirects all file reading via the new resource module
which will be used to control where files come from.

Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/src/resource.rs b/src/resource.rs
new file mode 100644
index 0000000..15a239e
--- /dev/null
+++ b/src/resource.rs
@@ -0,0 +1,25 @@
+//! Resources for subplot.
+//!
+//! This module encapsulates a mechanism for subplot to find resource files.
+//! Resource files come from a number of locations, such as embedded into the
+//! binary, from template paths given on the CLI, or from paths built into the
+//! binary and present on disk.
+
+use std::io::{self, Read};
+use std::path::Path;
+
+/// Open a file for reading, honouring search paths established during
+/// startup, and falling back to potentially embedded file content
+pub fn open<P: AsRef<Path>>(subpath: P) -> io::Result<Box<impl Read>> {
+    let subpath = subpath.as_ref();
+    Ok(Box::new(std::fs::File::open(subpath)?))
+}
+
+/// Read a file, honouring search paths established during startup, and
+/// falling back to potentially embedded file content
+pub fn read_as_string<P: AsRef<Path>>(subpath: P) -> io::Result<String> {
+    let mut f = open(subpath)?;
+    let mut ret = String::new();
+    f.read_to_string(&mut ret)?;
+    Ok(ret)
+}