Auto merge of #115 - TheNeikos:add-lazy_file, r=matthiasbeyer

Add file creation

@matthiasbeyer, @neithernut A possible implementation of a lazy enum to have lazy loading of files.

libimagstore/Cargo.lock

@@ -3,9 +3,19 @@ name = "libimagstore"
 version = "0.1.0"
 dependencies = [
  "fs2 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tempdir 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "toml 0.1.25 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "advapi32-sys"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "winapi 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "fs2"
 version = "0.2.2"
@@ -30,11 +40,29 @@ name = "libc"
 version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "rand"
+version = "0.3.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "advapi32-sys 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "rustc-serialize"
 version = "0.3.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "tempdir"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "rand 0.3.13 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "toml"
 version = "0.1.25"

libimagstore/Cargo.toml

@@ -7,4 +7,4 @@ authors = ["Matthias Beyer <mail@beyermatthias.de>"]
 
 fs2 = "0.2.2"
 toml = "0.1.25"
-
+tempdir = "0.3.4"

libimagstore/src/error.rs

@@ -10,6 +10,8 @@ pub enum StoreErrorKind {
     IdLocked,
     IdNotFound,
     OutOfMemory,
+    FileNotFound,
+    FileNotCreated,
     // maybe more
 }
 
@@ -19,6 +21,8 @@ fn store_error_type_as_str(e: &StoreErrorKind) -> &'static str {
         &StoreErrorKind::IdLocked    => "ID locked",
         &StoreErrorKind::IdNotFound  => "ID not found",
         &StoreErrorKind::OutOfMemory => "Out of Memory",
+        &StoreErrorKind::FileNotFound => "File corresponding to ID not found",
+        &StoreErrorKind::FileNotCreated => "File corresponding to ID could not be created",
     }
 }
 

libimagstore/src/lazyfile.rs

@@ -0,0 +1,123 @@
+
+use error::{StoreError, StoreErrorKind};
+use std::io::{Seek, SeekFrom};
+use std::path::{Path, PathBuf};
+use std::fs::{File, OpenOptions};
+
+pub enum LazyFile {
+    Absent(PathBuf),
+    File(File)
+}
+
+fn open_file<A: AsRef<Path>>(p: A) -> ::std::io::Result<File> {
+    OpenOptions::new().write(true).read(true).open(p)
+}
+
+fn create_file<A: AsRef<Path>>(p: A) -> ::std::io::Result<File> {
+    OpenOptions::new().write(true).read(true).create(true).open(p)
+}
+
+impl LazyFile {
+    pub fn new(p: PathBuf) -> LazyFile {
+        LazyFile::Absent(p)
+    }
+    pub fn new_with_file(f: File) -> LazyFile {
+        LazyFile::File(f)
+    }
+
+    pub fn get_file(&mut self) -> Result<&File, StoreError> {
+        match self.get_file_mut() {
+            Ok(file) => Ok(&*file),
+            Err(e) => Err(e)
+        }
+    }
+
+    pub fn get_file_mut(&mut self) -> Result<&mut File, StoreError> {
+        let file = match *self {
+            LazyFile::File(ref mut f) => return {
+                // We seek to the beginning of the file since we expect each
+                // access to the file to be in a different context
+                f.seek(SeekFrom::Start(0)).map_err(|e|
+                    StoreError::new(
+                        StoreErrorKind::FileNotCreated, Some(Box::new(e))));
+                Ok(f)
+            },
+            LazyFile::Absent(ref p) => {
+                try!(open_file(p).map_err(|e| {
+                    StoreError::new(StoreErrorKind::FileNotFound,
+                                    Some(Box::new(e)))
+                }))
+            }
+        };
+        *self = LazyFile::File(file);
+        if let LazyFile::File(ref mut f) = *self {
+            return Ok(f);
+        }
+        unreachable!()
+    }
+
+    pub fn create_file(&mut self) -> Result<&mut File, StoreError> {
+        let file = match *self {
+            LazyFile::File(ref mut f) => return Ok(f),
+            LazyFile::Absent(ref p) => {
+                try!(create_file(p).map_err(|e| {
+                    StoreError::new(StoreErrorKind::FileNotFound,
+                                    Some(Box::new(e)))
+                }))
+            }
+        };
+        *self = LazyFile::File(file);
+        if let LazyFile::File(ref mut f) = *self {
+            return Ok(f);
+        }
+        unreachable!()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::LazyFile;
+    use std::io::{Read, Write, Seek, SeekFrom};
+    use std::path::PathBuf;
+    use std::fs::File;
+    use tempdir::TempDir;
+
+    fn get_dir() -> TempDir {
+        TempDir::new("test-image").unwrap()
+    }
+
+    #[test]
+    fn lazy_file() {
+        let dir = get_dir();
+        let mut path = PathBuf::from(dir.path());
+        path.set_file_name("test1");
+        let mut lf = LazyFile::new(path);
+
+        write!(lf.create_file().unwrap(), "Hello World").unwrap();
+        dir.close().unwrap();
+    }
+
+    #[test]
+    fn lazy_file_with_file() {
+        let dir = get_dir();
+        let mut path = PathBuf::from(dir.path());
+        path.set_file_name("test2");
+        let mut lf = LazyFile::new(path.clone());
+
+        {
+            let mut file = lf.create_file().unwrap();
+
+            file.write(b"Hello World").unwrap();
+            file.sync_all().unwrap();
+        }
+
+        {
+            let mut file = lf.get_file().unwrap();
+            let mut s = Vec::new();
+            file.read_to_end(&mut s).unwrap();
+            assert_eq!(s, "Hello World".to_string().into_bytes());
+        }
+
+        dir.close().unwrap();
+    }
+}

libimagstore/src/lib.rs

@@ -1,9 +1,11 @@
 extern crate fs2;
 extern crate toml;
+extern crate tempdir;
 
 pub mod content;
 pub mod entry;
 pub mod error;
 pub mod header;
 pub mod store;
+mod lazyfile;