Draft for carray module in Rust

Incomplete support for sqlite3_bind_pointer.
Make Context::set_result return a Result.
Add Values::get_array.

src/vtab/array.rs

@@ -0,0 +1,179 @@
+//! Array Virtual Table
+//! Port of [carray](http://www.sqlite.org/cgi/src/finfo?name=ext/misc/carray.c) C extension.
+use std::default::Default;
+use std::os::raw::{c_char, c_int, c_void};
+use std::rc::Rc;
+
+use ffi;
+use types::{ToSql, ToSqlOutput, Value};
+use vtab::{self, declare_vtab, Context, IndexInfo, VTab, VTabCursor, Values};
+use {Connection, Error, Result};
+
+// http://sqlite.org/bindptr.html
+
+pub(crate) const ARRAY_TYPE: *const c_char = b"rarray\0" as *const u8 as *const c_char;
+
+pub(crate) unsafe extern "C" fn free_array(p: *mut c_void) {
+    let _: Array = Rc::from_raw(p as *const Vec<Value>);
+}
+
+pub type Array = Rc<Vec<Value>>;
+
+impl ToSql for Array {
+    fn to_sql(&self) -> Result<ToSqlOutput> {
+        Ok(ToSqlOutput::Array(self.clone()))
+    }
+}
+
+/// Register the "rarray" module.
+pub fn load_module(conn: &Connection) -> Result<()> {
+    let aux: Option<()> = None;
+    conn.create_module("rarray", &ARRAY_MODULE, aux)
+}
+
+eponymous_module!(
+    ARRAY_MODULE,
+    ArrayTab,
+    (),
+    ArrayTabCursor,
+    None,
+    array_connect,
+    array_best_index,
+    array_disconnect,
+    None,
+    array_open,
+    array_close,
+    array_filter,
+    array_next,
+    array_eof,
+    array_column,
+    array_rowid
+);
+
+// Column numbers
+// const CARRAY_COLUMN_VALUE : c_int = 0;
+const CARRAY_COLUMN_POINTER: c_int = 1;
+
+/// An instance of the Array virtual table
+#[repr(C)]
+struct ArrayTab {
+    /// Base class. Must be first
+    base: ffi::sqlite3_vtab,
+}
+
+impl VTab for ArrayTab {
+    type Aux = ();
+    type Cursor = ArrayTabCursor;
+
+    unsafe fn connect(db: *mut ffi::sqlite3, _aux: *mut (), _args: &[&[u8]]) -> Result<ArrayTab> {
+        let vtab = ArrayTab {
+            base: Default::default(),
+        };
+        try!(declare_vtab(db, "CREATE TABLE x(value,pointer hidden)"));
+        Ok(vtab)
+    }
+
+    fn best_index(&self, info: &mut IndexInfo) -> Result<()> {
+        // Index of the pointer= constraint
+        let mut ptr_idx = None;
+        for (i, constraint) in info.constraints().enumerate() {
+            if !constraint.is_usable() {
+                continue;
+            }
+            if constraint.operator() != vtab::IndexConstraintOp::SQLITE_INDEX_CONSTRAINT_EQ {
+                continue;
+            }
+            match constraint.column() {
+                CARRAY_COLUMN_POINTER => {
+                    ptr_idx = Some(i);
+                }
+                _ => {}
+            }
+        }
+        if let Some(ptr_idx) = ptr_idx {
+            {
+                let mut constraint_usage = info.constraint_usage(ptr_idx);
+                constraint_usage.set_argv_index(1);
+                constraint_usage.set_omit(true);
+            }
+            info.set_estimated_cost(1f64);
+            info.set_estimated_rows(100);
+            info.set_idx_num(1);
+        } else {
+            info.set_estimated_cost(2_147_483_647f64);
+            info.set_estimated_rows(2_147_483_647);
+            info.set_idx_num(0);
+        }
+        Ok(())
+    }
+
+    fn open(&self) -> Result<ArrayTabCursor> {
+        Ok(ArrayTabCursor::new())
+    }
+}
+
+/// A cursor for the Array virtual table
+#[repr(C)]
+struct ArrayTabCursor {
+    /// Base class. Must be first
+    base: ffi::sqlite3_vtab_cursor,
+    /// The rowid
+    row_id: i64,
+    /// Pointer to the array of values ("pointer")
+    ptr: Option<Array>,
+}
+
+impl ArrayTabCursor {
+    fn new() -> ArrayTabCursor {
+        ArrayTabCursor {
+            base: Default::default(),
+            row_id: 0,
+            ptr: None,
+        }
+    }
+    fn len(&self) -> i64 {
+        match self.ptr {
+            Some(ref a) => a.len() as i64,
+            _ => 0,
+        }
+    }
+}
+impl VTabCursor for ArrayTabCursor {
+    type Table = ArrayTab;
+
+    fn vtab(&self) -> &ArrayTab {
+        unsafe { &*(self.base.pVtab as *const ArrayTab) }
+    }
+    fn filter(&mut self, idx_num: c_int, _idx_str: Option<&str>, args: &Values) -> Result<()> {
+        if idx_num > 0 {
+            self.ptr = try!(args.get_array(0));
+        } else {
+            self.ptr = None;
+        }
+        self.row_id = 1;
+        Ok(())
+    }
+    fn next(&mut self) -> Result<()> {
+        self.row_id += 1;
+        Ok(())
+    }
+    fn eof(&self) -> bool {
+        self.row_id > self.len()
+    }
+    fn column(&self, ctx: &mut Context, i: c_int) -> Result<()> {
+        match i {
+            CARRAY_COLUMN_POINTER => Ok(()),
+            _ => {
+                if let Some(ref array) = self.ptr {
+                    let value = &array[i as usize];
+                    ctx.set_result(&value)
+                } else {
+                    Ok(())
+                }
+            }
+        }
+    }
+    fn rowid(&self) -> Result<i64> {
+        Ok(self.row_id)
+    }
+}

src/vtab/csvtab.rs

@@ -327,12 +327,10 @@ impl VTabCursor for CSVTabCursor {
             )));
         }
         if self.cols.is_empty() {
-            ctx.set_result(&Null);
-            return Ok(());
+            return ctx.set_result(&Null);
         }
         // TODO Affinity
-        ctx.set_result(&self.cols[col as usize].to_owned());
-        Ok(())
+        ctx.set_result(&self.cols[col as usize].to_owned())
     }
     fn rowid(&self) -> Result<i64> {
         Ok(self.row_number as i64)
@@ -365,7 +363,8 @@ mod test {
                 assert_eq!(vec!["rowid", "colA", "colB", "colC"], headers);
             }
 
-            let ids: Result<Vec<i32>> = s.query_map(&[], |row| row.get::<i32, i32>(0))
+            let ids: Result<Vec<i32>> = s
+                .query_map(&[], |row| row.get::<i32, i32>(0))
                 .unwrap()
                 .collect();
             let sum = ids.unwrap().iter().fold(0, |acc, &id| acc + id);
@@ -382,10 +381,11 @@ mod test {
             .unwrap();
 
         {
-            let mut s = db.prepare(
-                "SELECT v1.rowid, v1.* FROM vtab v1 NATURAL JOIN vtab v2 WHERE \
-                 v1.rowid < v2.rowid",
-            ).unwrap();
+            let mut s =
+                db.prepare(
+                    "SELECT v1.rowid, v1.* FROM vtab v1 NATURAL JOIN vtab v2 WHERE \
+                     v1.rowid < v2.rowid",
+                ).unwrap();
 
             let mut rows = s.query(&[]).unwrap();
             let row = rows.next().unwrap().unwrap();

src/vtab/int_array.rs

@@ -139,9 +139,8 @@ impl VTabCursor for IntArrayVTabCursor {
         let vtab = self.vtab();
         unsafe {
             let array = (*vtab.array).borrow();
-            ctx.set_result(&array[self.i]);
+            ctx.set_result(&array[self.i])
         }
-        Ok(())
     }
     fn rowid(&self) -> Result<i64> {
         Ok(self.i as i64)

src/vtab/mod.rs

@@ -6,7 +6,7 @@ use std::os::raw::{c_char, c_int, c_void};
 use std::ptr;
 use std::slice;
 
-use context::{report_error, set_result};
+use context::set_result;
 use error::error_from_sqlite_code;
 use ffi;
 use types::{FromSql, FromSqlError, ToSql, ValueRef};
@@ -207,12 +207,10 @@ pub trait VTabCursor: Sized {
 pub struct Context(*mut ffi::sqlite3_context);
 
 impl Context {
-    pub fn set_result<T: ToSql>(&mut self, value: &T) {
-        let t = value.to_sql();
-        match t {
-            Ok(ref value) => unsafe { set_result(self.0, value) },
-            Err(err) => unsafe { report_error(self.0, &err) },
-        }
+    pub fn set_result<T: ToSql>(&mut self, value: &T) -> Result<()> {
+        let t = value.to_sql()?;
+        unsafe { set_result(self.0, &t) };
+        Ok(())
     }
 }
 
@@ -241,6 +239,22 @@ impl<'a> Values<'a> {
         })
     }
 
+    // `sqlite3_value_type` returns `SQLITE_NULL` for pointer.
+    // So it seems not possible to enhance `ValueRef::from_value`.
+    #[cfg(feature = "array")]
+    pub fn get_array(&self, idx: usize) -> Result<Option<array::Array>> {
+        use types::Value;
+        let arg = self.args[idx];
+        let ptr = unsafe { ffi::sqlite3_value_pointer(arg, array::ARRAY_TYPE) };
+        if ptr.is_null() {
+            Ok(None)
+        } else {
+            Ok(Some(unsafe {
+                array::Array::from_raw(ptr as *const Vec<Value>)
+            }))
+        }
+    }
+
     pub fn iter(&self) -> ValueIter {
         ValueIter {
             iter: self.args.iter(),
@@ -361,12 +375,16 @@ pub fn dequote(s: &str) -> &str {
 /// 0 no false off
 /// ```
 pub fn parse_boolean(s: &str) -> Option<bool> {
-    if s.eq_ignore_ascii_case("yes") || s.eq_ignore_ascii_case("on")
-        || s.eq_ignore_ascii_case("true") || s.eq("1")
+    if s.eq_ignore_ascii_case("yes")
+        || s.eq_ignore_ascii_case("on")
+        || s.eq_ignore_ascii_case("true")
+        || s.eq("1")
     {
         Some(true)
-    } else if s.eq_ignore_ascii_case("no") || s.eq_ignore_ascii_case("off")
-        || s.eq_ignore_ascii_case("false") || s.eq("0")
+    } else if s.eq_ignore_ascii_case("no")
+        || s.eq_ignore_ascii_case("off")
+        || s.eq_ignore_ascii_case("false")
+        || s.eq("0")
     {
         Some(false)
     } else {
@@ -530,7 +548,8 @@ macro_rules! create_or_connect {
 
             let aux = aux as *mut $aux;
             let args = slice::from_raw_parts(argv, argc as usize);
-            let vec = args.iter()
+            let vec = args
+                .iter()
                 .map(|&cs| CStr::from_ptr(cs).to_bytes())
                 .collect::<Vec<_>>();
             match $vtab::$vtab_func(db, aux, &vec[..]) {
@@ -756,6 +775,8 @@ pub fn mprintf(err_msg: &str) -> *mut c_char {
     unsafe { ffi::sqlite3_mprintf(c_format.as_ptr(), c_err.as_ptr()) }
 }
 
+#[cfg(feature = "array")]
+pub mod array;
 #[cfg(feature = "csvtab")]
 pub mod csvtab;
 pub mod int_array;

src/vtab/series.rs

@@ -255,8 +255,7 @@ impl VTabCursor for SeriesTabCursor {
             SERIES_COLUMN_STEP => self.step,
             _ => self.value,
         };
-        ctx.set_result(&x);
-        Ok(())
+        ctx.set_result(&x)
     }
     fn rowid(&self) -> Result<i64> {
         Ok(self.row_id)