Port vtablog as an example of a writable VTab

src/vtab/array.rs

@@ -117,7 +117,7 @@ unsafe impl<'vtab> VTab<'vtab> for ArrayTab {
         Ok(())
     }
 
-    fn open(&self) -> Result<ArrayTabCursor<'_>> {
+    fn open(&mut self) -> Result<ArrayTabCursor<'_>> {
         Ok(ArrayTabCursor::new())
     }
 }

src/vtab/csvtab.rs

@@ -30,8 +30,8 @@ use std::str;
 use crate::ffi;
 use crate::types::Null;
 use crate::vtab::{
-    dequote, escape_double_quote, parse_boolean, read_only_module, Context, CreateVTab, IndexInfo,
-    VTab, VTabConfig, VTabConnection, VTabCursor, VTabKind, Values,
+    escape_double_quote, parse_boolean, read_only_module, Context, CreateVTab, IndexInfo, VTab,
+    VTabConfig, VTabConnection, VTabCursor, VTabKind, Values,
 };
 use crate::{Connection, Error, Result};
 
@@ -74,19 +74,6 @@ impl CsvTab {
             .from_path(&self.filename)
     }
 
-    fn parameter(c_slice: &[u8]) -> Result<(&str, &str)> {
-        let arg = str::from_utf8(c_slice)?.trim();
-        let mut split = arg.split('=');
-        if let Some(key) = split.next() {
-            if let Some(value) = split.next() {
-                let param = key.trim();
-                let value = dequote(value);
-                return Ok((param, value));
-            }
-        }
-        Err(Error::ModuleError(format!("illegal argument: '{}'", arg)))
-    }
-
     fn parse_byte(arg: &str) -> Option<u8> {
         if arg.len() == 1 {
             arg.bytes().next()
@@ -122,7 +109,7 @@ unsafe impl<'vtab> VTab<'vtab> for CsvTab {
 
         let args = &args[3..];
         for c_slice in args {
-            let (param, value) = CsvTab::parameter(c_slice)?;
+            let (param, value) = super::parameter(c_slice)?;
             match param {
                 "filename" => {
                     if !Path::new(value).exists() {
@@ -259,7 +246,7 @@ unsafe impl<'vtab> VTab<'vtab> for CsvTab {
         Ok(())
     }
 
-    fn open(&self) -> Result<CsvTabCursor<'_>> {
+    fn open(&mut self) -> Result<CsvTabCursor<'_>> {
         Ok(CsvTabCursor::new(self.reader()?))
     }
 }

src/vtab/mod.rs

@@ -263,7 +263,7 @@ pub unsafe trait VTab<'vtab>: Sized {
 
     /// Create a new cursor used for accessing a virtual table.
     /// (See [SQLite doc](https://sqlite.org/vtab.html#the_xopen_method))
-    fn open(&'vtab self) -> Result<Self::Cursor>;
+    fn open(&'vtab mut self) -> Result<Self::Cursor>;
 }
 
 /// Read-only virtual table instance trait.
@@ -882,7 +882,7 @@ pub fn dequote(s: &str) -> &str {
     }
     match s.bytes().next() {
         Some(b) if b == b'"' || b == b'\'' => match s.bytes().rev().next() {
-            Some(e) if e == b => &s[1..s.len() - 1],
+            Some(e) if e == b => &s[1..s.len() - 1], // FIXME handle inner escaped quote(s)
             _ => s,
         },
         _ => s,
@@ -912,6 +912,20 @@ pub fn parse_boolean(s: &str) -> Option<bool> {
     }
 }
 
+/// `<param_name>=['"]?<param_value>['"]?` => `(<param_name>, <param_value>)`
+pub fn parameter(c_slice: &[u8]) -> Result<(&str, &str)> {
+    let arg = std::str::from_utf8(c_slice)?.trim();
+    let mut split = arg.split('=');
+    if let Some(key) = split.next() {
+        if let Some(value) = split.next() {
+            let param = key.trim();
+            let value = dequote(value);
+            return Ok((param, value));
+        }
+    }
+    Err(Error::ModuleError(format!("illegal argument: '{}'", arg)))
+}
+
 // FIXME copy/paste from function.rs
 unsafe extern "C" fn free_boxed_value<T>(p: *mut c_void) {
     drop(Box::from_raw(p.cast::<T>()));
@@ -1309,6 +1323,8 @@ pub mod csvtab;
 #[cfg(feature = "series")]
 #[cfg_attr(docsrs, doc(cfg(feature = "series")))]
 pub mod series; // SQLite >= 3.9.0
+#[cfg(test)]
+mod vtablog;
 
 #[cfg(test)]
 mod test {

src/vtab/series.rs

@@ -153,7 +153,7 @@ unsafe impl<'vtab> VTab<'vtab> for SeriesTab {
         Ok(())
     }
 
-    fn open(&self) -> Result<SeriesTabCursor<'_>> {
+    fn open(&mut self) -> Result<SeriesTabCursor<'_>> {
         Ok(SeriesTabCursor::new())
     }
 }

src/vtab/vtablog.rs

@@ -0,0 +1,291 @@
+///! Port of C [vtablog](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/vtablog.c)
+use std::default::Default;
+use std::marker::PhantomData;
+use std::os::raw::c_int;
+use std::str::FromStr;
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+use crate::vtab::{
+    update_module, Context, CreateVTab, IndexInfo, UpdateVTab, VTab, VTabConnection, VTabCursor,
+    VTabKind, Values,
+};
+use crate::{ffi, ValueRef};
+use crate::{Connection, Error, Result};
+
+/// Register the "vtablog" module.
+pub fn load_module(conn: &Connection) -> Result<()> {
+    let aux: Option<()> = None;
+    conn.create_module("vtablog", update_module::<VTabLog>(), aux)
+}
+
+/// An instance of the vtablog virtual table
+#[repr(C)]
+struct VTabLog {
+    /// Base class. Must be first
+    base: ffi::sqlite3_vtab,
+    /// Number of rows in the table
+    n_row: i64,
+    /// Instance number for this vtablog table
+    i_inst: usize,
+    /// Number of cursors created
+    n_cursor: usize,
+}
+
+impl VTabLog {
+    fn connect_create(
+        _: &mut VTabConnection,
+        _: Option<&()>,
+        args: &[&[u8]],
+        is_create: bool,
+    ) -> Result<(String, VTabLog)> {
+        static N_INST: AtomicUsize = AtomicUsize::new(1);
+        let i_inst = N_INST.fetch_add(1, Ordering::SeqCst);
+        println!(
+            "VTabLog::{}(tab={}, args={:?}):",
+            if is_create { "create" } else { "connect" },
+            i_inst,
+            args,
+        );
+        let mut schema = None;
+        let mut n_row = None;
+
+        let args = &args[3..];
+        for c_slice in args {
+            let (param, value) = super::parameter(c_slice)?;
+            match param {
+                "schema" => {
+                    if schema.is_some() {
+                        return Err(Error::ModuleError(format!(
+                            "more than one '{}' parameter",
+                            param
+                        )));
+                    }
+                    schema = Some(value.to_owned())
+                }
+                "rows" => {
+                    if n_row.is_some() {
+                        return Err(Error::ModuleError(format!(
+                            "more than one '{}' parameter",
+                            param
+                        )));
+                    }
+                    if let Ok(n) = i64::from_str(value) {
+                        n_row = Some(n)
+                    }
+                }
+                _ => {
+                    return Err(Error::ModuleError(format!(
+                        "unrecognized parameter '{}'",
+                        param
+                    )));
+                }
+            }
+        }
+        if schema.is_none() {
+            return Err(Error::ModuleError("no schema defined".to_owned()));
+        }
+        let vtab = VTabLog {
+            base: ffi::sqlite3_vtab::default(),
+            n_row: n_row.unwrap_or(10),
+            i_inst,
+            n_cursor: 0,
+        };
+        Ok((schema.unwrap(), vtab))
+    }
+}
+
+impl Drop for VTabLog {
+    fn drop(&mut self) {
+        println!("VTabLog::drop({})", self.i_inst);
+    }
+}
+
+unsafe impl<'vtab> VTab<'vtab> for VTabLog {
+    type Aux = ();
+    type Cursor = VTabLogCursor<'vtab>;
+
+    fn connect(
+        db: &mut VTabConnection,
+        aux: Option<&Self::Aux>,
+        args: &[&[u8]],
+    ) -> Result<(String, Self)> {
+        VTabLog::connect_create(db, aux, args, false)
+    }
+
+    fn best_index(&self, info: &mut IndexInfo) -> Result<()> {
+        println!("VTabLog::best_index({})", self.i_inst);
+        info.set_estimated_cost(500.);
+        info.set_estimated_rows(500);
+        Ok(())
+    }
+
+    fn open(&'vtab mut self) -> Result<Self::Cursor> {
+        self.n_cursor += 1;
+        println!(
+            "VTabLog::open(tab={}, cursor={})",
+            self.i_inst, self.n_cursor
+        );
+        Ok(VTabLogCursor {
+            base: ffi::sqlite3_vtab_cursor::default(),
+            i_cursor: self.n_cursor,
+            row_id: 0,
+            phantom: PhantomData,
+        })
+    }
+}
+
+impl<'vtab> CreateVTab<'vtab> for VTabLog {
+    const KIND: VTabKind = VTabKind::Default;
+
+    fn create(
+        db: &mut VTabConnection,
+        aux: Option<&Self::Aux>,
+        args: &[&[u8]],
+    ) -> Result<(String, Self)> {
+        VTabLog::connect_create(db, aux, args, true)
+    }
+
+    fn destroy(&self) -> Result<()> {
+        println!("VTabLog::destroy({})", self.i_inst);
+        Ok(())
+    }
+}
+
+impl<'vtab> UpdateVTab<'vtab> for VTabLog {
+    fn delete(&mut self, arg: ValueRef<'_>) -> Result<()> {
+        println!("VTabLog::delete({}, {:?})", self.i_inst, arg);
+        Ok(())
+    }
+
+    fn insert(&mut self, args: &Values<'_>) -> Result<i64> {
+        println!(
+            "VTabLog::insert({}, {:?})",
+            self.i_inst,
+            args.iter().collect::<Vec<ValueRef<'_>>>()
+        );
+        Ok(self.n_row as i64)
+    }
+
+    fn update(&mut self, args: &Values<'_>) -> Result<()> {
+        println!(
+            "VTabLog::update({}, {:?})",
+            self.i_inst,
+            args.iter().collect::<Vec<ValueRef<'_>>>()
+        );
+        Ok(())
+    }
+}
+
+/// A cursor for the Series virtual table
+#[repr(C)]
+struct VTabLogCursor<'vtab> {
+    /// Base class. Must be first
+    base: ffi::sqlite3_vtab_cursor,
+    /// Cursor number
+    i_cursor: usize,
+    /// The rowid
+    row_id: i64,
+    phantom: PhantomData<&'vtab VTabLog>,
+}
+
+impl VTabLogCursor<'_> {
+    fn vtab(&self) -> &VTabLog {
+        unsafe { &*(self.base.pVtab as *const VTabLog) }
+    }
+}
+
+impl Drop for VTabLogCursor<'_> {
+    fn drop(&mut self) {
+        println!(
+            "VTabLogCursor::drop(tab={}, cursor={})",
+            self.vtab().i_inst,
+            self.i_cursor
+        );
+    }
+}
+
+unsafe impl VTabCursor for VTabLogCursor<'_> {
+    fn filter(&mut self, _: c_int, _: Option<&str>, _: &Values<'_>) -> Result<()> {
+        println!(
+            "VTabLogCursor::filter(tab={}, cursor={})",
+            self.vtab().i_inst,
+            self.i_cursor
+        );
+        self.row_id = 0;
+        Ok(())
+    }
+
+    fn next(&mut self) -> Result<()> {
+        println!(
+            "VTabLogCursor::next(tab={}, cursor={}): rowid {} -> {}",
+            self.vtab().i_inst,
+            self.i_cursor,
+            self.row_id,
+            self.row_id + 1
+        );
+        self.row_id += 1;
+        Ok(())
+    }
+
+    fn eof(&self) -> bool {
+        let eof = self.row_id >= self.vtab().n_row;
+        println!(
+            "VTabLogCursor::eof(tab={}, cursor={}): {}",
+            self.vtab().i_inst,
+            self.i_cursor,
+            eof,
+        );
+        eof
+    }
+
+    fn column(&self, ctx: &mut Context, i: c_int) -> Result<()> {
+        let value = if i < 26 {
+            format!(
+                "{}{}",
+                "abcdefghijklmnopqrstuvwyz".chars().nth(i as usize).unwrap(),
+                self.row_id
+            )
+        } else {
+            format!("{}{}", i, self.row_id)
+        };
+        println!(
+            "VTabLogCursor::column(tab={}, cursor={}, i={}): {}",
+            self.vtab().i_inst,
+            self.i_cursor,
+            i,
+            value,
+        );
+        ctx.set_result(&value)
+    }
+
+    fn rowid(&self) -> Result<i64> {
+        println!(
+            "VTabLogCursor::rowid(tab={}, cursor={}): {}",
+            self.vtab().i_inst,
+            self.i_cursor,
+            self.row_id,
+        );
+        Ok(self.row_id)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{Connection, Result};
+    #[test]
+    fn test_module() -> Result<()> {
+        let db = Connection::open_in_memory()?;
+        super::load_module(&db)?;
+
+        db.execute_batch(
+            "CREATE VIRTUAL TABLE temp.log USING vtablog(
+                    schema='CREATE TABLE x(a,b,c)',
+                    rows=25
+                );",
+        )?;
+        let mut stmt = db.prepare("SELECT * FROM log;")?;
+        let mut rows = stmt.query([])?;
+        while let Some(_) = rows.next()? {}
+        Ok(())
+    }
+}