1 files changed, 126 insertions, 0 deletions
diff --git a/cli/lsp/memory_cache.rs b/cli/lsp/memory_cache.rs
new file mode 100644
index 000000000..75c5bdb25
--- /dev/null
+++ b/cli/lsp/memory_cache.rs
@@ -0,0 +1,126 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+use deno_core::error::AnyError;
+use deno_core::ModuleSpecifier;
+use std::collections::HashMap;
+use std::fmt;
+use std::mem;
+
+#[derive(Copy, Clone, Debug, Ord, PartialOrd, Eq, PartialEq, Hash)]
+pub struct FileId(pub u32);
+
+#[derive(Eq, PartialEq, Copy, Clone, Debug)]
+pub enum ChangeKind {
+  Create,
+  Modify,
+  Delete,
+}
+
+pub struct ChangedFile {
+  pub change_kind: ChangeKind,
+  pub file_id: FileId,
+}
+
+#[derive(Default)]
+struct SpecifierInterner {
+  map: HashMap<ModuleSpecifier, FileId>,
+  vec: Vec<ModuleSpecifier>,
+}
+
+impl SpecifierInterner {
+  pub fn get(&self, specifier: &ModuleSpecifier) -> Option<FileId> {
+    self.map.get(specifier).copied()
+  }
+
+  pub fn intern(&mut self, specifier: ModuleSpecifier) -> FileId {
+    if let Some(id) = self.get(&specifier) {
+      return id;
+    }
+    let id = FileId(self.vec.len() as u32);
+    self.map.insert(specifier.clone(), id);
+    self.vec.push(specifier);
+    id
+  }
+
+  pub fn lookup(&self, id: FileId) -> &ModuleSpecifier {
+    &self.vec[id.0 as usize]
+  }
+}
+
+#[derive(Default)]
+pub struct MemoryCache {
+  data: Vec<Option<Vec<u8>>>,
+  interner: SpecifierInterner,
+  changes: Vec<ChangedFile>,
+}
+
+impl MemoryCache {
+  fn alloc_file_id(&mut self, specifier: ModuleSpecifier) -> FileId {
+    let file_id = self.interner.intern(specifier);
+    let idx = file_id.0 as usize;
+    let len = self.data.len().max(idx + 1);
+    self.data.resize_with(len, || None);
+    file_id
+  }
+
+  fn get(&self, file_id: FileId) -> &Option<Vec<u8>> {
+    &self.data[file_id.0 as usize]
+  }
+
+  pub fn get_contents(&self, file_id: FileId) -> Result<String, AnyError> {
+    String::from_utf8(self.get(file_id).as_deref().unwrap().to_vec())
+      .map_err(|err| err.into())
+  }
+
+  fn get_mut(&mut self, file_id: FileId) -> &mut Option<Vec<u8>> {
+    &mut self.data[file_id.0 as usize]
+  }
+
+  pub fn get_specifier(&self, file_id: FileId) -> &ModuleSpecifier {
+    self.interner.lookup(file_id)
+  }
+
+  pub fn len(&self) -> usize {
+    self.data.len()
+  }
+
+  pub fn lookup(&self, specifier: &ModuleSpecifier) -> Option<FileId> {
+    self
+      .interner
+      .get(specifier)
+      .filter(|&it| self.get(it).is_some())
+  }
+
+  pub fn set_contents(
+    &mut self,
+    specifier: ModuleSpecifier,
+    contents: Option<Vec<u8>>,
+  ) {
+    let file_id = self.alloc_file_id(specifier);
+    let change_kind = match (self.get(file_id), &contents) {
+      (None, None) => return,
+      (None, Some(_)) => ChangeKind::Create,
+      (Some(_), None) => ChangeKind::Delete,
+      (Some(old), Some(new)) if old == new => return,
+      (Some(_), Some(_)) => ChangeKind::Modify,
+    };
+
+    *self.get_mut(file_id) = contents;
+    self.changes.push(ChangedFile {
+      file_id,
+      change_kind,
+    })
+  }
+
+  pub fn take_changes(&mut self) -> Vec<ChangedFile> {
+    mem::take(&mut self.changes)
+  }
+}
+
+impl fmt::Debug for MemoryCache {
+  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    f.debug_struct("MemoryCache")
+      .field("no_files", &self.data.len())
+      .finish()
+  }
+}