Create enum to hold different sources of file data

Author: jasoncouture

src/file_data_source.rs

@@ -0,0 +1,56 @@
+use std::path::{PathBuf};
+use alloc::vec::Vec;
+use core::fmt::{Debug, Formatter};
+use std::{fs, io};
+use std::fs::File;
+use std::io::Cursor;
+use anyhow::Context;
+
+#[derive(Clone)]
+pub enum FileDataSource {
+    File(PathBuf),
+    Data(Vec<u8>)
+}
+
+impl Debug for FileDataSource {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        match self {
+            FileDataSource::File(file) => f.write_fmt(format_args!("data source: File {}", file.display())),
+            FileDataSource::Data(d) => f.write_fmt(format_args!("data source: {} raw bytes ", d.len()))
+        }
+    }
+}
+
+impl FileDataSource {
+    pub fn len(&self) -> anyhow::Result<u64> {
+        Ok(match self {
+            FileDataSource::File(path) => {
+                fs::metadata(path)
+                    .with_context(|| format!("failed to read metadata of file `{}`", path.display()))?
+                    .len()
+            }
+            FileDataSource::Data(v) => v.len() as u64
+        })
+    }
+    
+    pub fn copy_to(&self, target: &mut dyn io::Write) -> anyhow::Result<()> {
+        match self {
+            FileDataSource::File(file_path) => {
+                io::copy(
+                    &mut fs::File::open(file_path)
+                        .with_context(|| format!("failed to open `{}` for copying", file_path.display()))?,
+                    target,
+                )?;
+            },
+            FileDataSource::Data(contents) => {
+                let mut cursor = Cursor::new(contents);
+                io::copy(
+                    &mut cursor,
+                    target,
+                )?;
+            }
+        };
+        
+        Ok(())
+    }
+}

src/lib.rs

@@ -4,6 +4,8 @@ An experimental x86_64 bootloader that works on both BIOS and UEFI systems.
 
 #![warn(missing_docs)]
 
+extern crate alloc;
+
 #[cfg(feature = "bios")]
 mod bios;
 #[cfg(feature = "uefi")]
@@ -20,6 +22,7 @@ pub use uefi::UefiBoot;
 pub use bios::BiosBoot;
 
 mod fat;
+mod file_data_source;
 
 use std::{
     collections::BTreeMap,