Make load_buf return Option

Author: orsinium

src/fs.rs

@@ -100,6 +100,10 @@ pub mod rom {
     /// Read the whole file with the given name from ROM.
     ///
     /// If you have a pre-allocated buffer of the right size, use [load] instead.
+    ///
+    /// If the file does not exist, the returned buffer will be empty.
+    /// This, however, should not happen in normal operation because
+    /// the contents of the ROM directory are statically known.
     #[cfg(feature = "alloc")]
     #[must_use]
     pub fn load_buf(name: &str) -> FileBuf {
@@ -111,6 +115,12 @@ pub mod rom {
 }
 
 /// Functions for accessing files in the app data dir.
+///
+/// Each app has an its own data dir. That directory is empty by default,
+/// writable by the app, and not accessible by other apps.
+/// Typically, it is used to store game save data.
+///
+/// The device owner may empty this dir if they wish to remove the app data.
 pub mod data {
     use super::*;
     use crate::bindings as b;
@@ -146,13 +156,18 @@ pub mod data {
     /// Read the whole file with the given name from the data dir.
     ///
     /// If you have a pre-allocated buffer of the right size, use [load] instead.
+    ///
+    /// `None` is returned if the file does not exist.
     #[cfg(feature = "alloc")]
     #[must_use]
-    pub fn load_buf(name: &str) -> FileBuf {
+    pub fn load_buf(name: &str) -> Option<FileBuf> {
         let size = data::get_size(name);
+        if size == 0 {
+            return None;
+        }
         let mut buf = vec![0; size];
         data::load(name, &mut buf);
-        FileBuf { raw: buf }
+        Some(FileBuf { raw: buf })
     }
 
     /// Write the buffer into the given file in the data dir.

src/sudo.rs

@@ -104,6 +104,10 @@ pub fn get_file_size(path: &str) -> usize {
     size as usize
 }
 
+/// Read a file from the filesystem into the buffer.
+///
+/// The path must be relative to the root of the FS.
+/// For example: `sys/launcher`.
 pub fn load_file<'a>(path: &str, buf: &'a mut [u8]) -> File<'a> {
     let path_ptr = path.as_ptr() as u32;
     let path_len = path.len() as u32;
@@ -115,10 +119,16 @@ pub fn load_file<'a>(path: &str, buf: &'a mut [u8]) -> File<'a> {
     File { raw: buf }
 }
 
+/// Like [`load_file`] but takes care of the buffer allocation and ownership.
+///
+/// `None` is returned if the file does not exist.
 #[cfg(feature = "alloc")]
 #[must_use]
-pub fn load_file_buf(path: &str) -> FileBuf {
+pub fn load_file_buf(path: &str) -> Option<FileBuf> {
     let size = get_file_size(path);
+    if size == 0 {
+        return None;
+    }
     let mut buf = vec![0; size];
     let path_ptr = path.as_ptr() as u32;
     let path_len = path.len() as u32;
@@ -127,7 +137,7 @@ pub fn load_file_buf(path: &str) -> FileBuf {
     unsafe {
         b::load_file(path_ptr, path_len, buf_ptr, buf_len);
     }
-    FileBuf { raw: buf }
+    Some(FileBuf { raw: buf })
 }
 
 /// Low-level bindings for host-defined "sudo" module.