Introduce Context wrapper for user-defined functions.

This commit adds get/set auxilliary data for arguments; more to come.

src/functions.rs

@@ -224,8 +224,37 @@ impl<T: FromValue> FromValue for Option<T> {
 // sqlite3_get_auxdata
 // sqlite3_set_auxdata
 
-pub trait ScalarFunction: FnMut(*mut sqlite3_context, c_int, *mut *mut sqlite3_value) {}
-impl<F: FnMut(*mut sqlite3_context, c_int, *mut *mut sqlite3_value)> ScalarFunction for F {}
+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 ctx: *mut sqlite3_context,
+}
+
+impl Context {
+    pub fn set_aux<T>(&self, arg: c_int, value: T) {
+        let boxed = Box::into_raw(Box::new(value));
+        unsafe {
+            ffi::sqlite3_set_auxdata(self.ctx,
+                                     arg,
+                                     mem::transmute(boxed),
+                                     Some(mem::transmute(free_boxed_value::<T>)))
+        };
+    }
+
+    pub unsafe fn get_aux<T>(&self, arg: c_int) -> Option<&T> {
+        let p = ffi::sqlite3_get_auxdata(self.ctx, arg) as *mut T;
+        if p.is_null() {
+            None
+        } else {
+            Some(&*p)
+        }
+    }
+}
+
+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,
@@ -249,21 +278,16 @@ impl InnerSqliteConnection {
                                      -> SqliteResult<()>
         where F: ScalarFunction
     {
-        extern "C" fn free_boxed_closure<F>(p: *mut c_void)
-            where F: ScalarFunction
-        {
-            let _: Box<F> = unsafe { Box::from_raw(mem::transmute(p)) };
-        }
-
         extern "C" fn call_boxed_closure<F>(ctx: *mut sqlite3_context,
                                             argc: c_int,
                                             argv: *mut *mut sqlite3_value)
             where F: ScalarFunction
         {
+            let ctx = Context { ctx: ctx };
             unsafe {
-                let boxed_f: *mut F = mem::transmute(ffi::sqlite3_user_data(ctx));
+                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, argc, argv);
             }
         }
 
@@ -282,7 +306,7 @@ impl InnerSqliteConnection {
                                             Some(call_boxed_closure::<F>),
                                             None,
                                             None,
-                                            Some(free_boxed_closure::<F>))
+                                            Some(mem::transmute(free_boxed_value::<F>)))
         };
         self.decode_result(r)
     }
@@ -292,26 +316,23 @@ impl InnerSqliteConnection {
 mod test {
     extern crate regex;
 
-    use std::boxed::Box;
     use std::ffi::CString;
-    use std::mem;
-    use libc::{c_int, c_double, c_void};
+    use libc::{c_int, c_double};
     use self::regex::Regex;
 
     use SqliteConnection;
     use ffi;
-    use ffi::sqlite3_context;
     use ffi::sqlite3_value;
-    use functions::{FromValue, ToResult};
+    use functions::{Context, FromValue, ToResult};
 
-    fn half(ctx: *mut sqlite3_context, _: c_int, argv: *mut *mut sqlite3_value) {
+    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);
+                value.set_result(ctx.ctx);
             } else {
-                ffi::sqlite3_result_error_code(ctx, ffi::SQLITE_MISMATCH);
+                ffi::sqlite3_result_error_code(ctx.ctx, ffi::SQLITE_MISMATCH);
             }
         }
     }
@@ -325,40 +346,47 @@ mod test {
         assert_eq!(3f64, result.unwrap());
     }
 
-    extern "C" fn regexp_free(raw: *mut c_void) {
-        let _: Box<Regex> = unsafe { Box::from_raw(mem::transmute(raw)) };
-    }
-
-    fn regexp(ctx: *mut sqlite3_context, _: c_int, argv: *mut *mut sqlite3_value) {
-        unsafe {
-            let mut re_ptr = ffi::sqlite3_get_auxdata(ctx, 0) as *const Regex;
-            let need_re = re_ptr.is_null();
-            if need_re {
+    fn regexp(ctx: &Context, _: c_int, argv: *mut *mut sqlite3_value) {
+        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));
                 if raw.is_err() {
                     let msg = CString::new(format!("{}", raw.unwrap_err())).unwrap();
-                    ffi::sqlite3_result_error(ctx, msg.as_ptr(), -1);
+                    ffi::sqlite3_result_error(ctx.ctx, msg.as_ptr(), -1);
                     return;
                 }
                 let comp = Regex::new(raw.unwrap().as_ref());
                 if comp.is_err() {
                     let msg = CString::new(format!("{}", comp.unwrap_err())).unwrap();
-                    ffi::sqlite3_result_error(ctx, msg.as_ptr(), -1);
+                    ffi::sqlite3_result_error(ctx.ctx, msg.as_ptr(), -1);
                     return;
                 }
-                let re = Box::new(comp.unwrap());
-                re_ptr = Box::into_raw(re);
-            }
+                Some(comp.unwrap())
+            },
+            Some(_) => None,
+        };
 
-            let text = String::parameter_value(*argv.offset(1));
+        {
+            let re = saved_re.unwrap_or_else(|| new_re.as_ref().unwrap());
+
+            let text = unsafe { String::parameter_value(*argv.offset(1)) };
             if text.is_ok() {
                 let text = text.unwrap();
-                (*re_ptr).is_match(text.as_ref()).set_result(ctx);
+                unsafe {
+                    re.is_match(text.as_ref()).set_result(ctx.ctx);
+                }
+            } else {
+                let msg = CString::new(format!("{}", text.unwrap_err())).unwrap();
+                unsafe {
+                    ffi::sqlite3_result_error(ctx.ctx, msg.as_ptr(), -1);
+                }
+                return;
+            }
         }
 
-            if need_re {
-                ffi::sqlite3_set_auxdata(ctx, 0, mem::transmute(re_ptr), Some(regexp_free));
-            }
+        if let Some(re) = new_re {
+            ctx.set_aux(0, re);
         }
     }