Allow getting a ValueRef out of Row and Context, fixes #259

src/functions.rs

@@ -139,6 +139,16 @@ impl<'a> Context<'a> {
         })
     }
 
+    /// Returns the `idx`th argument as a `ValueRef`.
+    ///
+    /// # Failure
+    ///
+    /// Will panic if `idx` is greater than or equal to `self.len()`.
+    pub fn get_raw(&self, idx: usize) -> ValueRef<'a> {
+        let arg = self.args[idx];
+        unsafe { ValueRef::from_value(arg) }
+    }
+
     /// Sets the auxilliary data associated with a particular parameter. See
     /// https://www.sqlite.org/c3ref/get_auxdata.html for a discussion of
     /// this feature, or the unit tests of this module for an example.
@@ -530,8 +540,10 @@ mod test {
         let is_match = {
             let re = saved_re.unwrap_or_else(|| new_re.as_ref().unwrap());
 
-            let text = try!(ctx.get::<String>(1));
-            re.is_match(&text)
+            let text = ctx.get_raw(1).as_str().map_err(|e|
+                Error::UserFunctionError(e.into()))?;
+
+            re.is_match(text)
         };
 
         if let Some(re) = new_re {

src/lib.rs

@@ -1592,6 +1592,29 @@ mod test {
         // degree of reliability.
     }
 
+    #[test]
+    fn test_get_raw() {
+        let db = checked_memory_handle();
+        db.execute_batch("CREATE TABLE foo(i, x);").unwrap();
+        let vals = ["foobar", "1234", "qwerty"];
+        let mut insert_stmt = db.prepare("INSERT INTO foo(i, x) VALUES(?, ?)").unwrap();
+        for (i, v) in vals.iter().enumerate() {
+            let i_to_insert = i as i64;
+            assert_eq!(insert_stmt.execute(&[&i_to_insert as &dyn ToSql, &v]).unwrap(), 1);
+        }
+
+        let mut query = db.prepare("SELECT i, x FROM foo").unwrap();
+        let mut rows = query.query(NO_PARAMS).unwrap();
+
+        while let Some(res) = rows.next() {
+            let row = res.unwrap();
+            let i = row.get_raw(0).as_i64().unwrap();
+            let expect = vals[i as usize];
+            let x = row.get_raw("x").as_str().unwrap();
+            assert_eq!(x, expect);
+        }
+    }
+
     mod query_and_then_tests {
         extern crate libsqlite3_sys as ffi;
         use super::*;

src/row.rs

@@ -2,7 +2,7 @@ use std::marker::PhantomData;
 use std::{convert, result};
 
 use super::{Error, Result, Statement};
-use types::{FromSql, FromSqlError};
+use types::{FromSql, FromSqlError, ValueRef};
 
 /// An handle for the resulting rows of a query.
 pub struct Rows<'stmt> {
@@ -126,7 +126,7 @@ where
 }
 
 /// A single result row of a query.
-pub struct Row<'a, 'stmt> {
+pub struct Row<'a, 'stmt: 'a> {
     stmt: &'stmt Statement<'stmt>,
     phantom: PhantomData<&'a ()>,
 }
@@ -173,6 +173,49 @@ impl<'a, 'stmt> Row<'a, 'stmt> {
         })
     }
 
+    /// Get the value of a particular column of the result row as a `ValueRef`,
+    /// allowing data to be read out of a row without copying.
+    ///
+    /// This `ValueRef` is valid only as long as this Row, which is enforced by
+    /// it's lifetime. This means that while this method is completely safe,
+    /// it can be somewhat difficult to use, and most callers will be better
+    /// served by `get` or `get_checked`.
+    ///
+    /// ## Failure
+    ///
+    /// Returns an `Error::InvalidColumnIndex` if `idx` is outside the valid
+    /// column range for this row.
+    ///
+    /// Returns an `Error::InvalidColumnName` if `idx` is not a valid column
+    /// name for this row.
+    pub fn get_raw_checked<I: RowIndex>(&self, idx: I) -> Result<ValueRef<'a>> {
+        let idx = idx.idx(self.stmt)?;
+        // Narrowing from `ValueRef<'stmt>` (which `self.stmt.value_ref(idx)`
+        // returns) to `ValueRef<'a>` is needed because it's only valid until
+        // the next call to sqlite3_step.
+        let val_ref = self.stmt.value_ref(idx);
+        Ok(val_ref)
+    }
+
+    /// Get the value of a particular column of the result row as a `ValueRef`,
+    /// allowing data to be read out of a row without copying.
+    ///
+    /// This `ValueRef` is valid only as long as this Row, which is enforced by
+    /// it's lifetime. This means that while this method is completely safe,
+    /// it can be difficult to use, and most callers will be better served by
+    /// `get` or `get_checked`.
+    ///
+    /// ## Failure
+    ///
+    /// Panics if calling `row.get_raw_checked(idx)` would return an error,
+    /// including:
+    ///
+    ///    * If `idx` is outside the range of columns in the returned query.
+    ///    * If `idx` is not a valid column name for this row.
+    pub fn get_raw<I: RowIndex>(&self, idx: I) -> ValueRef<'a> {
+        self.get_raw_checked(idx).unwrap()
+    }
+
     /// Return the number of columns in the current row.
     pub fn column_count(&self) -> usize {
         self.stmt.column_count()

src/types/value_ref.rs

@@ -52,7 +52,7 @@ impl<'a> ValueRef<'a> {
 
     /// If `self` is case `Text`, returns the string value. Otherwise, returns
     /// `Err(Error::InvalidColumnType)`.
-    pub fn as_str(&self) -> FromSqlResult<&str> {
+    pub fn as_str(&self) -> FromSqlResult<&'a str> {
         match *self {
             ValueRef::Text(t) => Ok(t),
             _ => Err(FromSqlError::InvalidType),
@@ -61,7 +61,7 @@ impl<'a> ValueRef<'a> {
 
     /// If `self` is case `Blob`, returns the byte slice. Otherwise, returns
     /// `Err(Error::InvalidColumnType)`.
-    pub fn as_blob(&self) -> FromSqlResult<&[u8]> {
+    pub fn as_blob(&self) -> FromSqlResult<&'a [u8]> {
         match *self {
             ValueRef::Blob(b) => Ok(b),
             _ => Err(FromSqlError::InvalidType),