Add trait Storage

src/main.rs

@@ -8,6 +8,7 @@ mod cli;
 mod error;
 mod runtime;
 mod module;
+mod storage;
 
 fn main() {
     let mut config = Config::new();

src/storage.rs

@@ -0,0 +1,69 @@
+pub use std::path::Path;
+pub use std::fs::File;
+
+pub use runtime::Runtime;
+pub use error::ImagError;
+pub use error::ImagErrorBase;
+
+pub struct StorageError {
+    base : ImagErrorBase,
+    backendname : String,
+}
+
+impl StorageError {
+
+    pub fn new<T : StorageBackend>(backend : &T, short: String, long: String) -> StorageError {
+        StorageError {
+            base: ImagErrorBase {
+                shortdesc: short,
+                longdesc: long,
+            },
+            backendname: backend.name()
+        }
+    }
+
+}
+
+impl<'a> ImagError<'a> for StorageError {
+
+    fn print(&self, rt: &Runtime) {
+        if self.base.longdesc.is_empty() {
+            let s = format!("Backend {}: {}\n\n{}\n\n",
+                            self.backendname,
+                            self.base.shortdesc,
+                            self.base.longdesc);
+            rt.print(&s)
+        } else {
+            let s = format!("Backend {}: {}\n",
+                            self.backendname,
+                            self.base.shortdesc);
+            rt.print(&s)
+        }
+    }
+
+    fn print_short(&self, rt : &Runtime) {
+        let s = format!("Backend {}: {}\n",
+                        self.backendname,
+                        self.base.shortdesc);
+        rt.print(&s)
+    }
+
+    fn print_long(&self, rt : &Runtime) {
+        let s = format!("Backend {}: {}\n\n{}\n\n",
+                        self.backendname,
+                        self.base.shortdesc,
+                        self.base.longdesc);
+        rt.print(&s)
+    }
+}
+
+pub trait StorageBackend {
+
+    fn name(&self) -> String;
+
+    fn create(&self, file : File)   -> Option<StorageError>;
+    fn read(&self, path: Path)      -> Result<File, StorageError>;
+    fn update(&self, file : File)   -> Option<StorageError>;
+    fn destroy(&self, path: Path)   -> Option<StorageError>;
+
+}