Refactor revision IDs into RevId struct and u64 tokens

The RevId struct is a delta-compressible representation used by Engine, the
RevToken is an alias for u64 that is used by plugins as a non-colliding
identifier for a revision to base their edits on.

The RevToken is currently just a DefaultHasher hashed version of RevId,
which since DefaultHasher is cryptographically-pseudorandom should never
really collide. The collision set is just concurrent revisions since it
searches for the corresponding revision from newest to oldest.

This refactor paves the way for different Fuchsia devices to have separate
device IDs on their Engine, allowing them to generate non-conflicting
revisions that can be merged using the Ledger syncing mechanics.

rust/core-lib/src/editor.rs

@@ -24,7 +24,7 @@ use serde_json::Value;
 use xi_rope::rope::{LinesMetric, Rope, RopeInfo};
 use xi_rope::interval::Interval;
 use xi_rope::delta::{self, Delta, Transformer};
-use xi_rope::engine::Engine;
+use xi_rope::engine::{Engine, RevId, RevToken};
 use xi_rope::spans::SpansBuilder;
 use view::View;
 use word_boundaries::WordCursor;
@@ -68,8 +68,8 @@ pub struct Editor<W: Write> {
     /// different views arrive.
     view: View,
     engine: Engine,
-    last_rev_id: usize,
-    pristine_rev_id: usize,
+    last_rev_id: RevId,
+    pristine_rev_id: RevId,
     undo_group_id: usize,
     live_undos: Vec<usize>, //  undo groups that may still be toggled
     cur_undo: usize, // index to live_undos, ones after this are undone
@@ -89,7 +89,7 @@ pub struct Editor<W: Write> {
     #[allow(dead_code)]
     sync_store: Option<SyncStore>,
     #[allow(dead_code)]
-    last_synced_rev: usize,
+    last_synced_rev: RevId,
 }
 
 #[derive(PartialEq, Eq, Clone, Copy)]
@@ -239,7 +239,7 @@ impl<W: Write + Send + 'static> Editor<W> {
         }
 
         PluginBufferInfo::new(self.buffer_id, &views,
-                              self.engine.get_head_rev_id(), self.text.len(),
+                              self.engine.get_head_rev_id().token(), self.text.len(),
                               nb_lines, self.path.clone(), self.syntax.clone())
     }
 
@@ -307,7 +307,7 @@ impl<W: Write + Send + 'static> Editor<W> {
         }
         self.last_edit_type = self.this_edit_type;
         let priority = 0x10000;
-        self.engine.edit_rev(priority, undo_group, head_rev_id, delta);
+        self.engine.edit_rev(priority, undo_group, head_rev_id.token(), delta);
         self.text = self.engine.get_head().clone();
     }
 
@@ -322,10 +322,10 @@ impl<W: Write + Send + 'static> Editor<W> {
     pub fn apply_plugin_edit(&mut self, edit: PluginEdit, undo_group: usize) {
         let interval = Interval::new_closed_open(edit.start as usize, edit.end as usize);
         let text = Rope::from(&edit.text);
-        let rev_len = self.engine.get_rev(edit.rev as usize).unwrap().len();
+        let rev_len = self.engine.get_rev(edit.rev).unwrap().len();
         let delta = Delta::simple_edit(interval, text, rev_len);
         //let prev_head_rev_id = self.engine.get_head_rev_id();
-        self.engine.edit_rev(edit.priority as usize, undo_group, edit.rev as usize, delta);
+        self.engine.edit_rev(edit.priority as usize, undo_group, edit.rev, delta);
         self.text = self.engine.get_head().clone();
 
         // TODO: actually implement priority, which makes the need for the following
@@ -349,7 +349,7 @@ impl<W: Write + Send + 'static> Editor<W> {
     }
 
     fn update_after_revision(&mut self, author: Option<&str>) {
-        let delta = self.engine.delta_rev_head(self.last_rev_id);
+        let delta = self.engine.delta_rev_head(self.last_rev_id.token());
         let is_pristine = self.is_pristine();
         self.scroll_to = self.view.after_edit(&self.text, &delta, is_pristine);
         let (iv, new_len) = delta.summary();
@@ -375,7 +375,7 @@ impl<W: Write + Send + 'static> Editor<W> {
             let update = PluginUpdate::new(
                 self.view.view_id.clone(),
                 iv.start(), iv.end(), new_len,
-                self.engine.get_head_rev_id(), text,
+                self.engine.get_head_rev_id().token(), text,
                 self.this_edit_type.json_string().to_owned(),
                 author.to_owned());
 
@@ -1004,7 +1004,7 @@ impl<W: Write + Send + 'static> Editor<W> {
     }
 
     pub fn plugin_update_spans(&mut self, plugin: PluginPid, start: usize, len: usize,
-                               spans: Vec<ScopeSpan>, rev: usize) {
+                               spans: Vec<ScopeSpan>, rev: RevToken) {
         // TODO: more protection against invalid input
         let mut start = start;
         let mut end_offset = start + len;
@@ -1013,7 +1013,7 @@ impl<W: Write + Send + 'static> Editor<W> {
             sb.add_span(Interval::new_open_open(span.start, span.end), span.scope_id);
         }
         let mut spans = sb.build();
-        if rev != self.engine.get_head_rev_id() {
+        if rev != self.engine.get_head_rev_id().token() {
             let delta = self.engine.delta_rev_head(rev);
             let mut transformer = Transformer::new(&delta);
             let new_start = transformer.transform(start, false);
@@ -1030,8 +1030,8 @@ impl<W: Write + Send + 'static> Editor<W> {
         self.render();
     }
 
-    pub fn plugin_get_data(&self, offset: usize, max_size: usize, rev: usize) -> Option<String> {
-        let text_cow = if rev == self.engine.get_head_rev_id() {
+    pub fn plugin_get_data(&self, offset: usize, max_size: usize, rev: RevToken) -> Option<String> {
+        let text_cow = if rev == self.engine.get_head_rev_id().token() {
             Cow::Borrowed(&self.text)
         } else {
             match self.engine.get_rev(rev) {

rust/core-lib/src/plugins/rpc_types.rs

@@ -34,7 +34,7 @@ pub struct PluginBufferInfo {
     pub buffer_id: BufferIdentifier,
     /// The buffer's current views.
     pub views: Vec<ViewIdentifier>,
-    pub rev: usize,
+    pub rev: u64,
     pub buf_size: usize,
     pub nb_lines: usize,
     #[serde(skip_serializing_if = "Option::is_none")]
@@ -60,7 +60,7 @@ pub struct PluginUpdate {
     new_len: usize,
     #[serde(skip_serializing_if = "Option::is_none")]
     text: Option<String>,
-    rev: usize,
+    rev: u64,
     edit_type: String,
     author: String,
 }
@@ -108,15 +108,15 @@ pub struct ScopeSpan {
 /// RPC commands sent from plugins.
 pub enum PluginCommand {
     AddScopes { view_id: ViewIdentifier, scopes: Vec<Vec<String>> },
-    UpdateSpans { view_id: ViewIdentifier, start: usize, len: usize, spans: Vec<ScopeSpan>, rev: usize },
-    GetData { view_id: ViewIdentifier, offset: usize, max_size: usize, rev: usize },
+    UpdateSpans { view_id: ViewIdentifier, start: usize, len: usize, spans: Vec<ScopeSpan>, rev: u64 },
+    GetData { view_id: ViewIdentifier, offset: usize, max_size: usize, rev: u64 },
     Alert { view_id: ViewIdentifier, msg: String },
     LineCount { view_id: ViewIdentifier },
 }
 
 impl PluginBufferInfo {
     pub fn new(buffer_id: BufferIdentifier, views: &[ViewIdentifier],
-               rev: usize, buf_size: usize, nb_lines: usize,
+               rev: u64, buf_size: usize, nb_lines: usize,
                path: Option<PathBuf>, syntax: SyntaxDefinition) -> Self {
         //TODO: do make any current assertions about paths being valid utf-8? do we want to?
         let path = path.map(|p| p.to_str().unwrap().to_owned());
@@ -127,9 +127,8 @@ impl PluginBufferInfo {
 
 impl PluginUpdate {
     pub fn new(view_id: ViewIdentifier, start: usize, end: usize,
-               new_len: usize, rev: usize, text: Option<String>,
+               new_len: usize, rev: u64, text: Option<String>,
                edit_type: String, author: String) -> Self {
-        PluginUpdate {
             view_id: view_id,
             start: start,
             end: end,

rust/plugin-lib/src/caching_plugin.rs

@@ -38,7 +38,7 @@ pub trait Handler {
 struct State {
     buf_size: usize,
     view_id: String,
-    rev: usize,
+    rev: u64,
     cache: Option<String>,
     cache_offset: usize,
 

rust/plugin-lib/src/plugin_base.rs

@@ -68,7 +68,7 @@ pub struct PluginCtx<'a>(RpcCtx<'a, io::Stdout>);
 
 impl<'a> PluginCtx<'a> {
     pub fn get_data(&self, view_id: &str, offset: usize,
-                    max_size: usize, rev: usize) -> Result<String, Error> {
+                    max_size: usize, rev: u64) -> Result<String, Error> {
         let params = json!({
             "view_id": view_id,
             "offset": offset,
@@ -91,7 +91,7 @@ impl<'a> PluginCtx<'a> {
         self.send_rpc_notification("add_scopes", &params);
     }
 
-    pub fn update_spans(&self, view_id: &str, start: usize, len: usize, rev: usize, spans: &[ScopeSpan]) {
+    pub fn update_spans(&self, view_id: &str, start: usize, len: usize, rev: u64, spans: &[ScopeSpan]) {
         let params = json!({
             "view_id": view_id,
             "start": start,
@@ -150,7 +150,7 @@ pub enum PluginRequest<'a> {
         start: usize,
         end: usize,
         new_len: usize,
-        rev: usize,
+        rev: u64,
         edit_type: EditType,
         author: &'a str,
         text: Option<&'a str>,
@@ -168,7 +168,7 @@ pub enum PluginRequest<'a> {
 pub struct PluginBufferInfo {
     pub buffer_id: usize,
     pub views: Vec<String>,
-    pub rev: usize,
+    pub rev: u64,
     pub buf_size: usize,
     pub nb_lines: usize,
     #[serde(skip_serializing_if = "Option::is_none")]
@@ -235,7 +235,7 @@ fn parse_plugin_request<'a>(method: &str, params: &'a Value) ->
                             start: start as usize,
                             end: end as usize,
                             new_len: new_len as usize,
-                            rev: rev as usize,
+                            rev: rev,
                             edit_type: EditType::from_str(edit_type),
                             author: author,
                             text: dict_get_string(dict, "text"),