diff --git a/src/functions.rs b/src/functions.rs
index 47bfe3e..bf32399 100644
--- a/src/functions.rs
+++ b/src/functions.rs
@@ -177,7 +177,7 @@ impl ToResult for TooBig {
 }
 
 impl<'a> ValueRef<'a> {
-    unsafe fn from_value(value: *mut sqlite3_value) -> ValueRef<'a> {
+    pub unsafe fn from_value(value: *mut sqlite3_value) -> ValueRef<'a> {
         use std::slice::from_raw_parts;
 
         match ffi::sqlite3_value_type(value) {
diff --git a/src/vtab/csvtab.rs b/src/vtab/csvtab.rs
index be7e1a3..e49048f 100644
--- a/src/vtab/csvtab.rs
+++ b/src/vtab/csvtab.rs
@@ -9,7 +9,7 @@ use libc;
 use {Connection, Error, Result};
 use ffi;
 use types::Null;
-use vtab::{declare_vtab, escape_double_quote, Context, IndexInfo, VTab, VTabCursor};
+use vtab::{declare_vtab, escape_double_quote, Context, IndexInfo, Values, VTab, VTabCursor};
 
 /// Register the "csv" module.
 pub fn load_module(conn: &Connection) -> Result<()> {
@@ -171,7 +171,7 @@ impl VTabCursor<CSVTab> for CSVTabCursor {
     fn filter(&mut self,
               _idx_num: libc::c_int,
               _idx_str: Option<&str>,
-              _args: &mut [*mut ffi::sqlite3_value])
+              _args: &Values)
               -> Result<()> {
         {
             let offset_first_row = self.vtab().offset_first_row;
diff --git a/src/vtab/int_array.rs b/src/vtab/int_array.rs
index 2bdb8e3..a298324 100644
--- a/src/vtab/int_array.rs
+++ b/src/vtab/int_array.rs
@@ -7,7 +7,7 @@ use libc;
 
 use {Connection, Error, Result};
 use ffi;
-use vtab::{declare_vtab, escape_double_quote, Context, IndexInfo, VTab, VTabCursor};
+use vtab::{declare_vtab, escape_double_quote, Context, IndexInfo, Values, VTab, VTabCursor};
 
 /// Create a specific instance of an intarray object.
 /// The new intarray object is returned.
@@ -103,7 +103,7 @@ impl VTabCursor<IntArrayVTab> for IntArrayVTabCursor {
     fn filter(&mut self,
               _idx_num: libc::c_int,
               _idx_str: Option<&str>,
-              _args: &mut [*mut ffi::sqlite3_value])
+              _args: &Values)
               -> Result<()> {
         self.i = 0;
         Ok(())
diff --git a/src/vtab/mod.rs b/src/vtab/mod.rs
index 46e684e..1662ac4 100644
--- a/src/vtab/mod.rs
+++ b/src/vtab/mod.rs
@@ -10,6 +10,7 @@ use {Connection, Error, Result, InnerConnection, str_to_cstring};
 use error::error_from_sqlite_code;
 use ffi;
 use functions::ToResult;
+use types::FromSql;
 
 // let conn: Connection = ...;
 // let mod: Module = ...; // VTab builder
@@ -61,11 +62,7 @@ pub trait VTabCursor<V: VTab<Self>>: Sized {
     /// Accessor to the associated virtual table.
     fn vtab(&self) -> &mut V;
     /// Begin a search of a virtual table.
-    fn filter(&mut self,
-              idx_num: libc::c_int,
-              idx_str: Option<&str>,
-              args: &mut [*mut ffi::sqlite3_value])
-              -> Result<()>;
+    fn filter(&mut self, idx_num: libc::c_int, idx_str: Option<&str>, args: &Values) -> Result<()>;
     /// Advance cursor to the next row of a result set initiated by `filter`.
     fn next(&mut self) -> Result<()>;
     /// Must return `false` if the cursor currently points to a valid row of data, or `true` otherwise.
@@ -88,6 +85,30 @@ impl Context {
     }
 }
 
+pub struct Values<'a> {
+    args: &'a [*mut ffi::sqlite3_value],
+}
+
+impl<'a> Values<'a> {
+    pub fn len(&self) -> usize {
+        self.args.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.args.is_empty()
+    }
+
+    pub fn get<T: FromSql>(&self, idx: usize) -> Result<T> {
+        use types::ValueRef;
+        let arg = self.args[idx];
+        let value = unsafe { ValueRef::from_value(arg) };
+        FromSql::column_result(value).map_err(|err| match err {
+            Error::InvalidColumnType => Error::InvalidFunctionParameterType,
+            _ => err,
+        })
+    }
+}
+
 impl Connection {
     /// Register a virtual table implementation.
     pub fn create_module<A>(&self,
@@ -277,16 +298,17 @@ unsafe extern "C" fn $filter(cursor: *mut ffi::sqlite3_vtab_cursor,
     use std::ffi::CStr;
     use std::slice;
     use std::str;
-    use vtab::cursor_error;
+    use vtab::{cursor_error, Values};
     let idx_name = if idx_str.is_null() {
         None
     } else {
         let c_slice = CStr::from_ptr(idx_str).to_bytes();
         Some(str::from_utf8_unchecked(c_slice))
     };
-    let mut args = slice::from_raw_parts_mut(argv, argc as usize);
+    let args = slice::from_raw_parts_mut(argv, argc as usize);
+    let values = Values { args: args };
     let cr = cursor as *mut $cursor;
-    cursor_error(cursor, (*cr).filter(idx_num, idx_name, &mut args))
+    cursor_error(cursor, (*cr).filter(idx_num, idx_name, &values))
 }
 unsafe extern "C" fn $next(cursor: *mut ffi::sqlite3_vtab_cursor) -> libc::c_int {
     use vtab::cursor_error;