Add a Cursor trait and use it

We need an abstract cursor trait to implement a sorter, for example.

bindings/wasm/lib.rs

@@ -18,8 +18,7 @@ impl Database {
     }
 
     #[wasm_bindgen]
-    pub fn exec(&self, _sql: &str) {
-    }
+    pub fn exec(&self, _sql: &str) {}
 }
 
 pub struct IO {}

core/btree.rs

@@ -1,6 +1,6 @@
 use crate::pager::Pager;
 use crate::sqlite3_ondisk::{BTreeCell, TableInteriorCell, TableLeafCell};
-use crate::types::OwnedRecord;
+use crate::types::{Cursor, CursorResult, OwnedRecord};
 
 use anyhow::Result;
 
@@ -32,12 +32,7 @@ impl MemPage {
     }
 }
 
-pub enum CursorResult<T> {
-    Ok(T),
-    IO,
-}
-
-pub struct Cursor {
+pub struct BTreeCursor {
     pager: Rc<Pager>,
     root_page: usize,
     page: RefCell<Option<Rc<MemPage>>>,
@@ -45,7 +40,7 @@ pub struct Cursor {
     record: RefCell<Option<OwnedRecord>>,
 }
 
-impl Cursor {
+impl BTreeCursor {
     pub fn new(pager: Rc<Pager>, root_page: usize) -> Self {
         Self {
             pager,
@@ -56,51 +51,6 @@ impl Cursor {
         }
     }
 
-    pub fn is_empty(&self) -> bool {
-        self.page.borrow().is_none()
-    }
-
-    pub fn rewind(&mut self) -> Result<CursorResult<()>> {
-        let mem_page = MemPage::new(None, self.root_page, 0);
-        self.page.replace(Some(Rc::new(mem_page)));
-        match self.get_next_record()? {
-            CursorResult::Ok((rowid, next)) => {
-                self.rowid.replace(rowid);
-                self.record.replace(next);
-                Ok(CursorResult::Ok(()))
-            }
-            CursorResult::IO => Ok(CursorResult::IO),
-        }
-    }
-
-    pub fn next(&mut self) -> Result<CursorResult<()>> {
-        match self.get_next_record()? {
-            CursorResult::Ok((rowid, next)) => {
-                self.rowid.replace(rowid);
-                self.record.replace(next);
-                Ok(CursorResult::Ok(()))
-            }
-            CursorResult::IO => Ok(CursorResult::IO),
-        }
-    }
-
-    pub fn wait_for_completion(&mut self) -> Result<()> {
-        // TODO: Wait for pager I/O to complete
-        Ok(())
-    }
-
-    pub fn rowid(&self) -> Result<Ref<Option<u64>>> {
-        Ok(self.rowid.borrow())
-    }
-
-    pub fn record(&self) -> Result<Ref<Option<OwnedRecord>>> {
-        Ok(self.record.borrow())
-    }
-
-    pub fn has_record(&self) -> bool {
-        self.record.borrow().is_some()
-    }
-
     fn get_next_record(&mut self) -> Result<CursorResult<(Option<u64>, Option<OwnedRecord>)>> {
         loop {
             let mem_page = {
@@ -155,3 +105,50 @@ impl Cursor {
         }
     }
 }
+
+impl Cursor for BTreeCursor {
+    fn is_empty(&self) -> bool {
+        self.page.borrow().is_none()
+    }
+
+    fn rewind(&mut self) -> Result<CursorResult<()>> {
+        let mem_page = MemPage::new(None, self.root_page, 0);
+        self.page.replace(Some(Rc::new(mem_page)));
+        match self.get_next_record()? {
+            CursorResult::Ok((rowid, next)) => {
+                self.rowid.replace(rowid);
+                self.record.replace(next);
+                Ok(CursorResult::Ok(()))
+            }
+            CursorResult::IO => Ok(CursorResult::IO),
+        }
+    }
+
+    fn next(&mut self) -> Result<CursorResult<()>> {
+        match self.get_next_record()? {
+            CursorResult::Ok((rowid, next)) => {
+                self.rowid.replace(rowid);
+                self.record.replace(next);
+                Ok(CursorResult::Ok(()))
+            }
+            CursorResult::IO => Ok(CursorResult::IO),
+        }
+    }
+
+    fn wait_for_completion(&mut self) -> Result<()> {
+        // TODO: Wait for pager I/O to complete
+        Ok(())
+    }
+
+    fn rowid(&self) -> Result<Ref<Option<u64>>> {
+        Ok(self.rowid.borrow())
+    }
+
+    fn record(&self) -> Result<Ref<Option<OwnedRecord>>> {
+        Ok(self.record.borrow())
+    }
+
+    fn has_record(&self) -> bool {
+        self.record.borrow().is_some()
+    }
+}

core/schema.rs

@@ -95,9 +95,7 @@ fn create_table(tbl_name: QualifiedName, body: CreateTableBody, root_page: usize
                             || type_name.contains("TEXT")
                         {
                             Type::Text
-                        } else if type_name.contains("BLOB")
-                            || type_name.is_empty()
-                        {
+                        } else if type_name.contains("BLOB") || type_name.is_empty() {
                             Type::Blob
                         } else if type_name.contains("REAL")
                             || type_name.contains("FLOA")

core/types.rs

@@ -1,4 +1,4 @@
-use std::rc::Rc;
+use std::{cell::Ref, rc::Rc};
 
 use anyhow::Result;
 
@@ -74,3 +74,18 @@ impl OwnedRecord {
         Self { values }
     }
 }
+
+pub enum CursorResult<T> {
+    Ok(T),
+    IO,
+}
+
+pub trait Cursor {
+    fn is_empty(&self) -> bool;
+    fn rewind(&mut self) -> Result<CursorResult<()>>;
+    fn next(&mut self) -> Result<CursorResult<()>>;
+    fn wait_for_completion(&mut self) -> Result<()>;
+    fn rowid(&self) -> Result<Ref<Option<u64>>>;
+    fn record(&self) -> Result<Ref<Option<OwnedRecord>>>;
+    fn has_record(&self) -> bool;
+}

core/vdbe.rs

@@ -1,6 +1,6 @@
-use crate::btree::{Cursor, CursorResult};
+use crate::btree::BTreeCursor;
 use crate::pager::Pager;
-use crate::types::{OwnedValue, Record};
+use crate::types::{Cursor, CursorResult, OwnedValue, Record};
 
 use anyhow::Result;
 use std::cell::RefCell;
@@ -153,7 +153,7 @@ pub enum StepResult<'a> {
 /// The program state describes the environment in which the program executes.
 pub struct ProgramState {
     pub pc: usize,
-    cursors: RefCell<BTreeMap<usize, Cursor>>,
+    cursors: RefCell<BTreeMap<usize, Box<dyn Cursor>>>,
     registers: Vec<OwnedValue>,
 }
 
@@ -209,7 +209,7 @@ impl Program {
                     cursor_id,
                     root_page,
                 } => {
-                    let cursor = Cursor::new(pager.clone(), *root_page);
+                    let cursor = Box::new(BTreeCursor::new(pager.clone(), *root_page));
                     cursors.insert(*cursor_id, cursor);
                     state.pc += 1;
                 }