Change backends to do less ser-/deserialization

This commit changes the backends to do less de/ser, as it now stores the
Entry objects in the backend and does the de/serialization there.

This means the store does only serialize things once from json to toml
in the io backend.

See the diff of the documentation for more details.

doc/src/02000-store.md

@@ -201,12 +201,6 @@ The `InMemoryFileAbstractionInstance` implementation is corrosponding to
 the `InMemoryFileAbstraction` implementation - for the in-memory
 "filesystem".
 
-The implementation of the `get_file_content()` function had to be
-changed to return a `String` rather than a `&mut Read` because of
-lifetime issues.
-This change is store-internally and the API of the store itself was not
-affected.
-
 ## The StdIo backend {#sec:thestore:backends:stdio}
 
 Sidenote: The name is "StdIo" because its main purpose is Stdin/Stdio, but it
@@ -231,42 +225,29 @@ implementation are possible.
 
 The following section assumes a JSON mapper.
 
-The backends themselves do not know "header" and "content" - they know only
+The mapper reads the JSON, parses it (thanks serde!) and translates it to
-blobs which live in pathes.
+a `Entry`, which is the in-memory representation of the files.
-Indeed, this "backend" code does not serve "content" or "header" to the `Store`
+The `Entry` contains a `Header` part and a `Content` part.
-implementation, but only a blob of bytes.
-Anyways, the JSON-protocol for passing a store around _does_ know about content
-and header (see @sec:thestore:backends:stdio:json for the JSON format).
-
-So the mapper reads the JSON, parses it (thanks serde!) and translates it to
-TOML, because TOML is the Store representation of a header.
-But because the backend does not serve header and content, but only a blob,
-this TOML is then translated (with the content of the respective file) to a
-blob.
 
 This is then made available to the store codebase.
-This is complex and probably slow, we know.
 
 To summarize what we do right now, lets have a look at the awesome ascii-art
 below:
 
 ```
-                            libimag*
+                    libimag*
-                               |
+                       |
-                               v
+                       v
- IO     Mapper        FS     Store      FS         Mapper     IO
+ IO   Mapper         Store      Mapper  IO
-+--+-------------+---------+--------+---------+--------------+--+
++--+---------+----------------+--------+--+
-|  |             |         |        |         |              |  |
+|  |         |                |        |  |
-    JSON -> TOML -> String -> Entry -> String -> TOML -> JSON
+    JSON     ->    Entry     ->  JSON
-                              + TOML
+                   + Header
-                              + Content
+                   + Content
 ```
 
 This is what gets translated where for one imag call with a stdio store backend.
 
-The rationale behind this implementation is that this is the best implementation
-we can have in a relatively short amount of time.
-
 ### The JSON Mapper {#sec:thestore:backends:stdio:json}
 
 The JSON mapper maps JSON which is read from a source into a HashMap which
@@ -278,7 +259,7 @@ The strucure is as follows:
 {
     "version": "0.3.0",
     "store": {
-        "/example": {
+        "example": {
             "header": {
                 "imag": {
                     "version": "0.3.0",
@@ -292,24 +273,14 @@ The strucure is as follows:
 
 ### TODO {#sec:thestore:backends:todo}
 
-Of course, the above is not optimal.
+If you look at the version history of this file you will see that this
-The TODO here is almost visible: Implement a proper backend where we do not need
+implementation has grown from something complex and probably slow to what we
-to translate between types all the time.
+have today.
 
-The first goal would be to reduce the above figure to:
+Still, there's one improvement we could make: abstract all the things away so
-
+the `libimag*` crates handle the header without knowing whether it is JSON or
-```
+TOML.
-           libimag*
+With this, we would not even have to translate JSON to TOML anymore.
-              |
+We should measure whether this would have actually any performance impact before
-              v
+implementing it.
- IO Mapper  Store    Mapper IO
-+--+------+--------+-------+--+
-|  |      |        |       |  |
-    JSON -> Entry -> JSON
-            + TOML
-            + Content
-```
-
-and the second step would be to abstract all the things away so the `libimag*`
-crates handle the header without knowing whether it is JSON or TOML.
 

libimagstore/src/file_abstraction/inmemory.rs

@@ -19,8 +19,6 @@
 
 use error::StoreError as SE;
 use error::StoreErrorKind as SEK;
-use std::io::Read;
-use std::io::Cursor;
 use std::path::PathBuf;
 use std::collections::HashMap;
 use std::sync::Mutex;
@@ -31,11 +29,10 @@ use libimagerror::into::IntoError;
 
 use super::FileAbstraction;
 use super::FileAbstractionInstance;
-use error::MapErrInto;
 use store::Entry;
 use storeid::StoreId;
 
-type Backend = Arc<Mutex<RefCell<HashMap<PathBuf, Cursor<Vec<u8>>>>>>;
+type Backend = Arc<Mutex<RefCell<HashMap<PathBuf, Entry>>>>;
 
 /// `FileAbstraction` type, this is the Test version!
 ///
@@ -62,22 +59,16 @@ impl FileAbstractionInstance for InMemoryFileAbstractionInstance {
     /**
      * Get the mutable file behind a InMemoryFileAbstraction object
      */
-    fn get_file_content(&mut self, id: StoreId) -> Result<Entry, SE> {
+    fn get_file_content(&mut self, _: StoreId) -> Result<Entry, SE> {
         debug!("Getting lazy file: {:?}", self);
 
         let p = self.absent_path.clone();
         match self.fs_abstraction.lock() {
             Ok(mut mtx) => {
                 mtx.get_mut()
-                    .get_mut(&p)
+                    .get(&p)
+                    .cloned()
                     .ok_or(SEK::FileNotFound.into_error())
-                    .and_then(|t| {
-                        let mut s = String::new();
-                        t.read_to_string(&mut s)
-                            .map_err_into(SEK::IoError)
-                            .map(|_| s)
-                            .and_then(|s| Entry::from_str(id, &s))
-                    })
             }
 
             Err(_) => Err(SEK::LockError.into_error())
@@ -85,20 +76,11 @@ impl FileAbstractionInstance for InMemoryFileAbstractionInstance {
     }
 
     fn write_file_content(&mut self, buf: &Entry) -> Result<(), SE> {
-        let buf = buf.to_str().into_bytes();
         match *self {
             InMemoryFileAbstractionInstance { ref absent_path, .. } => {
                 let mut mtx = self.fs_abstraction.lock().expect("Locking Mutex failed");
                 let mut backend = mtx.get_mut();
-
+                let _ = backend.insert(absent_path.clone(), buf.clone());
-                if let Some(ref mut cur) = backend.get_mut(absent_path) {
-                    let mut vec = cur.get_mut();
-                    vec.clear();
-                    vec.extend_from_slice(&buf);
-                    return Ok(());
-                }
-                let vec = Vec::from(buf);
-                backend.insert(absent_path.clone(), Cursor::new(vec));
                 return Ok(());
             },
         };

libimagstore/src/file_abstraction/stdio/mapper/json.rs

@@ -18,7 +18,6 @@
 //
 
 use std::collections::HashMap;
-use std::io::Cursor;
 use std::io::{Read, Write};
 use std::path::PathBuf;
 
@@ -29,16 +28,18 @@ use error::StoreErrorKind as SEK;
 use error::MapErrInto;
 use super::Mapper;
 use store::Result;
+use store::Entry;
+use storeid::StoreId;
 
 use libimagerror::into::IntoError;
 
 #[derive(Deserialize, Serialize)]
-struct Entry {
+struct BackendEntry {
     header: serde_json::Value,
     content: String,
 }
 
-impl Entry {
+impl BackendEntry {
 
     fn to_string(self) -> Result<String> {
         toml::to_string(&self.header)
@@ -55,7 +56,7 @@ impl Entry {
 #[derive(Deserialize, Serialize)]
 struct Document {
     version: String,
-    store: HashMap<PathBuf, Entry>,
+    store: HashMap<PathBuf, BackendEntry>,
 }
 
 pub struct JsonMapper;
@@ -69,7 +70,7 @@ impl JsonMapper {
 }
 
 impl Mapper for JsonMapper {
-    fn read_to_fs<R: Read>(&self, r: &mut R, hm: &mut HashMap<PathBuf, Cursor<Vec<u8>>>)   -> Result<()> {
+    fn read_to_fs<R: Read>(&self, r: &mut R, hm: &mut HashMap<PathBuf, Entry>)   -> Result<()> {
         let mut document = {
             let mut s = String::new();
             try!(r.read_to_string(&mut s).map_err_into(SEK::IoError));
@@ -93,7 +94,11 @@ impl Mapper for JsonMapper {
         for (key, val) in document.store.drain() {
             let res = val
                 .to_string()
-                .map(|vals| hm.insert(key, Cursor::new(vals.into_bytes())))
+                .and_then(|vals| {
+                    StoreId::new_baseless(key.clone())
+                        .and_then(|id| Entry::from_str(id, &vals))
+                        .map(|entry| hm.insert(key, entry))
+                })
                 .map(|_| ());
 
             let _ = try!(res);
@@ -102,43 +107,38 @@ impl Mapper for JsonMapper {
         Ok(())
     }
 
-    fn fs_to_write<W: Write>(&self, hm: &mut HashMap<PathBuf, Cursor<Vec<u8>>>, out: &mut W) -> Result<()> {
+    fn fs_to_write<W: Write>(&self, hm: &mut HashMap<PathBuf, Entry>, out: &mut W) -> Result<()> {
-        use util::entry_buffer_to_header_content;
+        #[derive(Serialize)]
-
+        struct BackendEntry {
-        #[derive(Serialize, Deserialize)]
-        struct Entry {
             header: ::toml::Value,
             content: String,
         }
 
+        impl BackendEntry {
+            fn construct_from(e: Entry) -> BackendEntry {
+                BackendEntry {
+                    header:  e.get_header().clone(),
+                    content: e.get_content().clone(),
+                }
+            }
+        }
+
         #[derive(Serialize)]
         struct OutDocument {
             version: String,
-            store: HashMap<PathBuf, Entry>,
+            store: HashMap<PathBuf, BackendEntry>,
         }
 
-        let mut doc = OutDocument {
+        let mut store = HashMap::new();
-            version: String::from(version!()),
-            store:   HashMap::new(),
-        };
-
         for (key, value) in hm.drain() {
-            let res = String::from_utf8(value.into_inner())
+            store.insert(key, BackendEntry::construct_from(value));
-                .map_err_into(SEK::IoError)
-                .and_then(|buf| entry_buffer_to_header_content(&buf))
-                .map(|(header, content)| {
-                    let entry = Entry {
-                        header: header,
-                        content: content
-                    };
-
-                    doc.store.insert(key, entry);
-                })
-                .map(|_| ());
-
-            let _ = try!(res);
         }
 
+        let doc = OutDocument {
+            version: String::from(version!()),
+            store:   store,
+        };
+
         serde_json::to_string(&doc)
             .map_err_into(SEK::IoError)
             .and_then(|json| out.write(&json.into_bytes()).map_err_into(SEK::IoError))
@@ -158,7 +158,7 @@ mod test {
         let json = r#"
         { "version": "0.3.0",
           "store": {
-            "/example": {
+            "example": {
                 "header": {
                     "imag": {
                         "version": "0.3.0"
@@ -191,7 +191,10 @@ mod test {
 version = "0.3.0"
 ---
 hi there!"#;
-            hm.insert(PathBuf::from("/example"), Cursor::new(String::from(content).into_bytes()));
+
+            let id = PathBuf::from("example");
+            let entry = Entry::from_str(id.clone(), content).unwrap();
+            hm.insert(id, entry);
             hm
         };
 
@@ -202,7 +205,7 @@ hi there!"#;
         {
             "version": "0.3.0",
             "store": {
-                "/example": {
+                "example": {
                     "header": {
                         "imag": {
                             "version": "0.3.0"

libimagstore/src/file_abstraction/stdio/mapper/mod.rs

@@ -18,14 +18,14 @@
 //
 
 use std::collections::HashMap;
-use std::io::Cursor;
 use std::io::{Read, Write};
 use std::path::PathBuf;
 use store::Result;
+use store::Entry;
 
 pub trait Mapper {
-    fn read_to_fs<R: Read>(&self, &mut R, &mut HashMap<PathBuf, Cursor<Vec<u8>>>)   -> Result<()>;
+    fn read_to_fs<R: Read>(&self, &mut R, &mut HashMap<PathBuf, Entry>)   -> Result<()>;
-    fn fs_to_write<W: Write>(&self, &mut HashMap<PathBuf, Cursor<Vec<u8>>>, &mut W) -> Result<()>;
+    fn fs_to_write<W: Write>(&self, &mut HashMap<PathBuf, Entry>, &mut W) -> Result<()>;
 }
 
 pub mod json;

libimagstore/src/file_abstraction/stdio/mod.rs

@@ -23,7 +23,6 @@ use std::collections::HashMap;
 use std::fmt::Debug;
 use std::fmt::Error as FmtError;
 use std::fmt::Formatter;
-use std::io::Cursor;
 use std::io::{Read, Write};
 use std::path::PathBuf;
 use std::sync::Arc;
@@ -37,12 +36,13 @@ use error::StoreError as SE;
 use super::FileAbstraction;
 use super::FileAbstractionInstance;
 use super::InMemoryFileAbstraction;
+use store::Entry;
 
 pub mod mapper;
 use self::mapper::Mapper;
 
 // Because this is not exported in super::inmemory;
-type Backend = Arc<Mutex<RefCell<HashMap<PathBuf, Cursor<Vec<u8>>>>>>;
+type Backend = Arc<Mutex<RefCell<HashMap<PathBuf, Entry>>>>;
 
 pub struct StdIoFileAbstraction<W: Write, M: Mapper> {
     mapper: M,
@@ -83,7 +83,7 @@ impl<W, M> StdIoFileAbstraction<W, M>
     }
 
     pub fn backend(&self) -> &Backend {
-        &self.mem.backend()
+        self.mem.backend()
     }
 
 }