dvas0004 · April 1, 2024 12:57 · Apr 1, 2024 · Apr 1, 2024
diff --git a/vtab_1.rs b/vtab_1.rs
@@ -0,0 +1,94 @@
+use std::{ffi::c_int, marker::PhantomData};
+use rusqlite::ffi;
+use rusqlite::{ffi::{sqlite3_vtab, sqlite3_vtab_cursor}, vtab::{Context, IndexInfo, VTab, VTabConnection, VTabCursor, Values}, Connection};
+use std::os::raw::c_char;
+
+use rusqlite::{to_sqlite_error,  Result};
+
+#[repr(C)]
+struct Test {
+    /// Base class. Must be first
+    base: sqlite3_vtab,
+}
+
+#[derive(Default)]
+#[repr(C)]
+struct TestCursor<'vtab> {
+    /// Base class. Must be first
+    base: sqlite3_vtab_cursor,
+    /// The rowid
+    row_id: i64,
+    phantom: PhantomData<&'vtab Test>,
+    data: Vec<String>, // this is where we load and store our "external" data - see `open`
+}
+
+// Write implementation of VTab trait.
+// Step 1(a) from https://docs.rs/rusqlite/latest/rusqlite/vtab/index.html
+unsafe impl<'vtab> VTab<'vtab> for Test {
+    type Aux = ();
+    type Cursor = TestCursor<'vtab>;
+
+    fn connect(
+        _: &mut VTabConnection,
+        _aux: Option<&()>,
+        _args: &[&[u8]],
+    ) -> Result<(String, Test), rusqlite::Error> {
+        let vtab = Test {
+            base: sqlite3_vtab::default()  
+        };
+      	// our vtab schema is defined here
+        Ok(("CREATE TABLE test(id INT, name TEXT)".to_owned(), vtab))
+    }
+
+    fn best_index(&self, info: &mut IndexInfo) -> Result<(), rusqlite::Error> {
+        info.set_estimated_cost(1.);
+        Ok(())
+    }
+
+  	// this is where we do external calls (e.g. APIs, files) 
+    // to populate our external data
+    fn open(&'vtab mut self) -> Result<TestCursor<'vtab>, rusqlite::Error> {
+        let mut test_cursor = TestCursor::default();
+        test_cursor.data = vec!["a".to_owned(), "b".to_owned(), "c".to_owned()];
+        Ok(test_cursor)
+    }
+}
+
+// Write implementation of VTabCursor trait.
+// Step 1(b) from https://docs.rs/rusqlite/latest/rusqlite/vtab/index.html
+unsafe impl VTabCursor for TestCursor<'_> {
+    fn filter(
+        &mut self,
+        _idx_num: c_int,
+        _idx_str: Option<&str>,
+        _args: &Values<'_>,
+    ) -> Result<(), rusqlite::Error> {                
+        Ok(())        
+    }
+
+    // next - how do we get the next record?
+    fn next(&mut self) -> Result<(), rusqlite::Error> {
+        self.row_id += 1;
+        Ok(())
+    }
+
+    // EOF - when should we stop calling `next`?
+    fn eof(&self) -> bool {        
+        self.row_id >= self.data.len().try_into().unwrap()
+    }
+
+    // descibe the mappings between columns (expressed as numbers) and our data 
+    // stored in the cursor
+    fn column(&self, ctx: &mut Context, col_number: c_int) -> Result<(), rusqlite::Error> {
+        match col_number {
+            0 => ctx.set_result(&self.row_id),
+            1 => ctx.set_result(&self.data[self.row_id as usize]),
+            _ => Err(rusqlite::Error::InvalidColumnName("n/a".to_owned())),
+        }
+
+    }
+
+    fn rowid(&self) -> Result<i64, rusqlite::Error> {
+        Ok(self.row_id)
+    }
+}
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