Add get to function::Context.

This allows user-defined functions to now only accept a `Context`, as it
embeds the arguments inside itself.

src/functions.rs

@@ -1,6 +1,7 @@
 //! Create or redefine SQL functions
 use std::ffi::CStr;
 use std::mem;
+use std::slice;
 use std::str;
 use libc::{c_int, c_double, c_char, c_void};
 
@@ -228,11 +229,30 @@ unsafe extern "C" fn free_boxed_value<T>(p: *mut c_void) {
     let _: Box<T> = Box::from_raw(mem::transmute(p));
 }
 
-pub struct Context {
+pub struct Context<'a> {
     pub ctx: *mut sqlite3_context,
+    args: &'a [*mut sqlite3_value],
 }
 
-impl Context {
+impl<'a> Context<'a> {
+    pub fn len(&self) -> usize {
+        self.args.len()
+    }
+
+    pub fn get<T: FromValue>(&self, idx: usize) -> SqliteResult<T> {
+        let arg = self.args[idx];
+        unsafe {
+            if T::parameter_has_valid_sqlite_type(arg) {
+                T::parameter_value(arg)
+            } else {
+                Err(SqliteError {
+                    code: ffi::SQLITE_MISMATCH,
+                    message: "Invalid value type".to_string(),
+                })
+            }
+        }
+    }
+
     pub fn set_aux<T>(&self, arg: c_int, value: T) {
         let boxed = Box::into_raw(Box::new(value));
         unsafe {
@@ -253,9 +273,6 @@ impl Context {
     }
 }
 
-pub trait ScalarFunction: FnMut(&Context, c_int, *mut *mut sqlite3_value) {}
-impl<F: FnMut(&Context, c_int, *mut *mut sqlite3_value)> ScalarFunction for F {}
-
 impl SqliteConnection {
     pub fn create_scalar_function<F>(&self,
                                      fn_name: &str,
@@ -263,31 +280,34 @@ impl SqliteConnection {
                                      deterministic: bool,
                                      x_func: F)
                                      -> SqliteResult<()>
-        where F: ScalarFunction
+        where F: FnMut(&Context)
     {
         self.db.borrow_mut().create_scalar_function(fn_name, n_arg, deterministic, x_func)
     }
 }
 
 impl InnerSqliteConnection {
-    pub fn create_scalar_function<F>(&mut self,
-                                     fn_name: &str,
-                                     n_arg: c_int,
-                                     deterministic: bool,
-                                     x_func: F)
-                                     -> SqliteResult<()>
-        where F: ScalarFunction
+    fn create_scalar_function<F>(&mut self,
+                                 fn_name: &str,
+                                 n_arg: c_int,
+                                 deterministic: bool,
+                                 x_func: F)
+                                 -> SqliteResult<()>
+        where F: FnMut(&Context)
     {
         extern "C" fn call_boxed_closure<F>(ctx: *mut sqlite3_context,
                                             argc: c_int,
                                             argv: *mut *mut sqlite3_value)
-            where F: ScalarFunction
+            where F: FnMut(&Context)
         {
-            let ctx = Context { ctx: ctx };
             unsafe {
+                let ctx = Context {
+                    ctx: ctx,
+                    args: slice::from_raw_parts(argv, argc as usize),
+                };
                 let boxed_f: *mut F = mem::transmute(ffi::sqlite3_user_data(ctx.ctx));
                 assert!(!boxed_f.is_null(), "Internal error - null function pointer");
-                (*boxed_f)(&ctx, argc, argv);
+                (*boxed_f)(&ctx);
             }
         }
 
@@ -317,23 +337,18 @@ mod test {
     extern crate regex;
 
     use std::ffi::CString;
-    use libc::{c_int, c_double};
+    use libc::c_double;
     use self::regex::Regex;
 
     use SqliteConnection;
     use ffi;
-    use ffi::sqlite3_value;
-    use functions::{Context, FromValue, ToResult};
+    use functions::{Context, ToResult};
 
-    fn half(ctx: &Context, _: c_int, argv: *mut *mut sqlite3_value) {
-        unsafe {
-            let arg = *argv.offset(0);
-            if c_double::parameter_has_valid_sqlite_type(arg) {
-                let value = c_double::parameter_value(arg).unwrap() / 2f64;
-                value.set_result(ctx.ctx);
-            } else {
-                ffi::sqlite3_result_error_code(ctx.ctx, ffi::SQLITE_MISMATCH);
-            }
+    fn half(ctx: &Context) {
+        assert!(ctx.len() == 1, "called with unexpected number of arguments");
+        match ctx.get::<c_double>(0) {
+            Ok(value) => unsafe { (value / 2f64).set_result(ctx.ctx) },
+            Err(err) => unsafe { ffi::sqlite3_result_error_code(ctx.ctx, err.code) },
         }
     }
 
@@ -346,11 +361,13 @@ mod test {
         assert_eq!(3f64, result.unwrap());
     }
 
-    fn regexp(ctx: &Context, _: c_int, argv: *mut *mut sqlite3_value) {
+    fn regexp(ctx: &Context) {
+        assert!(ctx.len() == 2, "called with unexpected number of arguments");
+
         let saved_re: Option<&Regex> = unsafe { ctx.get_aux(0) };
         let new_re = match saved_re {
             None => unsafe {
-                let raw = String::parameter_value(*argv.offset(0));
+                let raw = ctx.get::<String>(0);
                 if raw.is_err() {
                     let msg = CString::new(format!("{}", raw.unwrap_err())).unwrap();
                     ffi::sqlite3_result_error(ctx.ctx, msg.as_ptr(), -1);
@@ -370,7 +387,7 @@ mod test {
         {
             let re = saved_re.unwrap_or_else(|| new_re.as_ref().unwrap());
 
-            let text = unsafe { String::parameter_value(*argv.offset(1)) };
+            let text = ctx.get::<String>(1);
             if text.is_ok() {
                 let text = text.unwrap();
                 unsafe {
@@ -391,13 +408,27 @@ mod test {
     }
 
     #[test]
+    #[cfg_attr(rustfmt, rustfmt_skip)]
     fn test_function_regexp() {
         let db = SqliteConnection::open_in_memory().unwrap();
+        db.execute_batch("BEGIN;
+                         CREATE TABLE foo (x string);
+                         INSERT INTO foo VALUES ('lisa');
+                         INSERT INTO foo VALUES ('lXsi');
+                         INSERT INTO foo VALUES ('lisX');
+                         END;").unwrap();
         db.create_scalar_function("regexp", 2, true, regexp).unwrap();
+
         let result = db.query_row("SELECT regexp('l.s[aeiouy]', 'lisa')",
                                   &[],
                                   |r| r.get::<bool>(0));
 
         assert_eq!(true, result.unwrap());
+
+        let result = db.query_row("SELECT COUNT(*) FROM foo WHERE regexp('l.s[aeiouy]', x) == 1",
+                                  &[],
+                                  |r| r.get::<i64>(0));
+
+        assert_eq!(2, result.unwrap());
     }
 }