Merge pull request #161 from jgallagher/safe-fromsql

Redesign FromSql

Changelog.md

@@ -1,3 +1,9 @@
+# Version UPCOMING (...)
+
+* BREAKING CHANGE: The `FromSql` trait has been redesigned. It now requires a single, safe
+  method instead of the previous definition which required implementing one or two unsafe
+  methods.
+
 # Version 0.7.2 (2016-05-19)
 
 * BREAKING CHANGE: `Rows` no longer implements `Iterator`. It still has a `next()` method, but

src/functions.rs

@@ -54,7 +54,6 @@ use std::ffi::CStr;
 use std::mem;
 use std::ptr;
 use std::slice;
-use std::str;
 use libc::{c_int, c_double, c_char, c_void};
 
 use ffi;
@@ -63,7 +62,7 @@ pub use ffi::sqlite3_value;
 pub use ffi::sqlite3_value_type;
 pub use ffi::sqlite3_value_numeric_type;
 
-use types::Null;
+use types::{Null, FromSql, ValueRef};
 
 use {Result, Error, Connection, str_to_cstring, InnerConnection};
 
@@ -157,108 +156,35 @@ impl ToResult for Null {
     }
 }
 
-/// A trait for types that can be created from a SQLite function parameter value.
+impl<'a> ValueRef<'a> {
-pub trait FromValue: Sized {
+    unsafe fn from_value(value: *mut sqlite3_value) -> ValueRef<'a> {
-    unsafe fn parameter_value(v: *mut sqlite3_value) -> Result<Self>;
-
-    /// FromValue types can implement this method and use sqlite3_value_type to check that
-    /// the type reported by SQLite matches a type suitable for Self. This method is used
-    /// by `Context::get` to confirm that the parameter contains a valid type before
-    /// attempting to retrieve the value.
-    unsafe fn parameter_has_valid_sqlite_type(_: *mut sqlite3_value) -> bool {
-        true
-    }
-}
-
-
-macro_rules! raw_from_impl(
-    ($t:ty, $f:ident, $c:expr) => (
-        impl FromValue for $t {
-            unsafe fn parameter_value(v: *mut sqlite3_value) -> Result<$t> {
-                Ok(ffi::$f(v))
-            }
-
-            unsafe fn parameter_has_valid_sqlite_type(v: *mut sqlite3_value) -> bool {
-                sqlite3_value_numeric_type(v) == $c
-            }
-        }
-    )
-);
-
-raw_from_impl!(c_int, sqlite3_value_int, ffi::SQLITE_INTEGER);
-raw_from_impl!(i64, sqlite3_value_int64, ffi::SQLITE_INTEGER);
-
-impl FromValue for bool {
-    unsafe fn parameter_value(v: *mut sqlite3_value) -> Result<bool> {
-        match ffi::sqlite3_value_int(v) {
-            0 => Ok(false),
-            _ => Ok(true),
-        }
-    }
-
-    unsafe fn parameter_has_valid_sqlite_type(v: *mut sqlite3_value) -> bool {
-        sqlite3_value_numeric_type(v) == ffi::SQLITE_INTEGER
-    }
-}
-
-impl FromValue for c_double {
-    unsafe fn parameter_value(v: *mut sqlite3_value) -> Result<c_double> {
-        Ok(ffi::sqlite3_value_double(v))
-    }
-
-    unsafe fn parameter_has_valid_sqlite_type(v: *mut sqlite3_value) -> bool {
-        sqlite3_value_numeric_type(v) == ffi::SQLITE_FLOAT ||
-        sqlite3_value_numeric_type(v) == ffi::SQLITE_INTEGER
-    }
-}
-
-impl FromValue for String {
-    unsafe fn parameter_value(v: *mut sqlite3_value) -> Result<String> {
-        let c_text = ffi::sqlite3_value_text(v);
-        if c_text.is_null() {
-            Ok("".to_owned())
-        } else {
-            let c_slice = CStr::from_ptr(c_text as *const c_char).to_bytes();
-            let utf8_str = try!(str::from_utf8(c_slice));
-            Ok(utf8_str.into())
-        }
-    }
-
-    unsafe fn parameter_has_valid_sqlite_type(v: *mut sqlite3_value) -> bool {
-        sqlite3_value_type(v) == ffi::SQLITE_TEXT
-    }
-}
-
-impl FromValue for Vec<u8> {
-    unsafe fn parameter_value(v: *mut sqlite3_value) -> Result<Vec<u8>> {
         use std::slice::from_raw_parts;
-        let c_blob = ffi::sqlite3_value_blob(v);
-        let len = ffi::sqlite3_value_bytes(v);
 
-        assert!(len >= 0,
+        match ffi::sqlite3_value_type(value) {
-                "unexpected negative return from sqlite3_value_bytes");
+            ffi::SQLITE_NULL => ValueRef::Null,
-        let len = len as usize;
+            ffi::SQLITE_INTEGER => ValueRef::Integer(ffi::sqlite3_value_int64(value)),
+            ffi::SQLITE_FLOAT => ValueRef::Real(ffi::sqlite3_value_double(value)),
+            ffi::SQLITE_TEXT => {
+                let text = ffi::sqlite3_value_text(value);
+                assert!(!text.is_null(), "unexpected SQLITE_TEXT value type with NULL data");
+                let s = CStr::from_ptr(text as *const c_char);
 
-        Ok(from_raw_parts(mem::transmute(c_blob), len).to_vec())
+                // sqlite3_value_text returns UTF8 data, so our unwrap here should be fine.
-    }
+                let s = s.to_str().expect("sqlite3_value_text returned invalid UTF-8");
+                ValueRef::Text(s)
+            }
+            ffi::SQLITE_BLOB => {
+                let blob = ffi::sqlite3_value_blob(value);
+                assert!(!blob.is_null(), "unexpected SQLITE_BLOB value type with NULL data");
 
-    unsafe fn parameter_has_valid_sqlite_type(v: *mut sqlite3_value) -> bool {
+                let len = ffi::sqlite3_value_bytes(value);
-        sqlite3_value_type(v) == ffi::SQLITE_BLOB
+                assert!(len >= 0, "unexpected negative return from sqlite3_value_bytes");
-    }
-}
 
-impl<T: FromValue> FromValue for Option<T> {
+                ValueRef::Blob(from_raw_parts(blob as *const u8, len as usize))
-    unsafe fn parameter_value(v: *mut sqlite3_value) -> Result<Option<T>> {
+            }
-        if sqlite3_value_type(v) == ffi::SQLITE_NULL {
+            _ => unreachable!("sqlite3_value_type returned invalid value")
-            Ok(None)
-        } else {
-            FromValue::parameter_value(v).map(Some)
         }
     }
-
-    unsafe fn parameter_has_valid_sqlite_type(v: *mut sqlite3_value) -> bool {
-        sqlite3_value_type(v) == ffi::SQLITE_NULL || T::parameter_has_valid_sqlite_type(v)
-    }
 }
 
 unsafe extern "C" fn free_boxed_value<T>(p: *mut c_void) {
@@ -288,15 +214,13 @@ impl<'a> Context<'a> {
     /// Will panic if `idx` is greater than or equal to `self.len()`.
     ///
     /// Will return Err if the underlying SQLite type cannot be converted to a `T`.
-    pub fn get<T: FromValue>(&self, idx: usize) -> Result<T> {
+    pub fn get<T: FromSql>(&self, idx: usize) -> Result<T> {
         let arg = self.args[idx];
-        unsafe {
+        let value = unsafe { ValueRef::from_value(arg) };
-            if T::parameter_has_valid_sqlite_type(arg) {
+        FromSql::column_result(value).map_err(|err| match err {
-                T::parameter_value(arg)
+            Error::InvalidColumnType => Error::InvalidFunctionParameterType,
-            } else {
+            _ => err
-                Err(Error::InvalidFunctionParameterType)
+        })
-            }
-        }
     }
 
     /// Sets the auxilliary data associated with a particular parameter. See

src/lib.rs

@@ -75,7 +75,7 @@ use std::result;
 use std::str;
 use libc::{c_int, c_char};
 
-use types::{ToSql, FromSql};
+use types::{ToSql, FromSql, ValueRef};
 use error::{error_from_sqlite_code, error_from_handle};
 use raw_statement::RawStatement;
 use cache::StatementCache;
@@ -1064,15 +1064,9 @@ impl<'a, 'stmt> Row<'a, 'stmt> {
     /// Returns an `Error::InvalidColumnName` if `idx` is not a valid column name
     /// for this row.
     pub fn get_checked<I: RowIndex, T: FromSql>(&self, idx: I) -> Result<T> {
-        unsafe {
+        let idx = try!(idx.idx(self.stmt));
-            let idx = try!(idx.idx(self.stmt));
+        let value = unsafe { ValueRef::new(&self.stmt.stmt, idx) };
-
+        FromSql::column_result(value)
-            if T::column_has_valid_sqlite_type(self.stmt.stmt.ptr(), idx) {
-                FromSql::column_result(self.stmt.stmt.ptr(), idx)
-            } else {
-                Err(Error::InvalidColumnType)
-            }
-        }
     }
 
     /// Return the number of columns in the current row.
@@ -1106,6 +1100,39 @@ impl<'a> RowIndex for &'a str {
     }
 }
 
+impl<'a> ValueRef<'a> {
+    unsafe fn new(stmt: &RawStatement, col: c_int) -> ValueRef {
+        use std::slice::from_raw_parts;
+
+        let raw = stmt.ptr();
+
+        match stmt.column_type(col) {
+            ffi::SQLITE_NULL => ValueRef::Null,
+            ffi::SQLITE_INTEGER => ValueRef::Integer(ffi::sqlite3_column_int64(raw, col)),
+            ffi::SQLITE_FLOAT => ValueRef::Real(ffi::sqlite3_column_double(raw, col)),
+            ffi::SQLITE_TEXT => {
+                let text = ffi::sqlite3_column_text(raw, col);
+                assert!(!text.is_null(), "unexpected SQLITE_TEXT column type with NULL data");
+                let s = CStr::from_ptr(text as *const c_char);
+
+                // sqlite3_column_text returns UTF8 data, so our unwrap here should be fine.
+                let s = s.to_str().expect("sqlite3_column_text returned invalid UTF-8");
+                ValueRef::Text(s)
+            }
+            ffi::SQLITE_BLOB => {
+                let blob = ffi::sqlite3_column_blob(raw, col);
+                assert!(!blob.is_null(), "unexpected SQLITE_BLOB column type with NULL data");
+
+                let len = ffi::sqlite3_column_bytes(raw, col);
+                assert!(len >= 0, "unexpected negative return from sqlite3_column_bytes");
+
+                ValueRef::Blob(from_raw_parts(blob as *const u8, len as usize))
+            }
+            _ => unreachable!("sqlite3_column_type returned invalid value")
+        }
+    }
+}
+
 #[cfg(test)]
 mod test {
     extern crate tempdir;

src/raw_statement.rs

@@ -20,6 +20,10 @@ impl RawStatement {
         unsafe { ffi::sqlite3_column_count(self.0) }
     }
 
+    pub fn column_type(&self, idx: c_int) -> c_int {
+        unsafe { ffi::sqlite3_column_type(self.0, idx) }
+    }
+
     pub fn column_name(&self, idx: c_int) -> &CStr {
         unsafe { CStr::from_ptr(ffi::sqlite3_column_name(self.0, idx)) }
     }

src/types/chrono.rs

@@ -1,11 +1,13 @@
 //! Convert most of the [Time Strings](http://sqlite.org/lang_datefunc.html) to chrono types.
 extern crate chrono;
 
+use std::borrow::Cow;
+
 use self::chrono::{NaiveDate, NaiveTime, NaiveDateTime, DateTime, TimeZone, UTC, Local};
 use libc::c_int;
 
 use {Error, Result};
-use types::{FromSql, ToSql};
+use types::{FromSql, ToSql, ValueRef};
 
 use ffi::sqlite3_stmt;
 
@@ -19,16 +21,11 @@ impl ToSql for NaiveDate {
 
 /// "YYYY-MM-DD" => ISO 8601 calendar date without timezone.
 impl FromSql for NaiveDate {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<NaiveDate> {
+    fn column_result(value: ValueRef) -> Result<Self> {
-        let s = try!(String::column_result(stmt, col));
+        value.as_str().and_then(|s| match NaiveDate::parse_from_str(s, "%Y-%m-%d") {
-        match NaiveDate::parse_from_str(&s, "%Y-%m-%d") {
             Ok(dt) => Ok(dt),
             Err(err) => Err(Error::FromSqlConversionFailure(Box::new(err))),
-        }
+        })
-    }
-
-    unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
-        String::column_has_valid_sqlite_type(stmt, col)
     }
 }
 
@@ -42,21 +39,18 @@ impl ToSql for NaiveTime {
 
 /// "HH:MM"/"HH:MM:SS"/"HH:MM:SS.SSS" => ISO 8601 time without timezone.
 impl FromSql for NaiveTime {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<NaiveTime> {
+    fn column_result(value: ValueRef) -> Result<Self> {
-        let s = try!(String::column_result(stmt, col));
+        value.as_str().and_then(|s| {
-        let fmt = match s.len() {
+            let fmt = match s.len() {
-            5 => "%H:%M",
+                5 => "%H:%M",
-            8 => "%H:%M:%S",
+                8 => "%H:%M:%S",
-            _ => "%H:%M:%S%.f",
+                _ => "%H:%M:%S%.f",
-        };
+            };
-        match NaiveTime::parse_from_str(&s, fmt) {
+            match NaiveTime::parse_from_str(s, fmt) {
-            Ok(dt) => Ok(dt),
+                Ok(dt) => Ok(dt),
-            Err(err) => Err(Error::FromSqlConversionFailure(Box::new(err))),
+                Err(err) => Err(Error::FromSqlConversionFailure(Box::new(err))),
-        }
+            }
-    }
+        })
-
-    unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
-        String::column_has_valid_sqlite_type(stmt, col)
     }
 }
 
@@ -71,23 +65,19 @@ impl ToSql for NaiveDateTime {
 /// "YYYY-MM-DD HH:MM:SS"/"YYYY-MM-DD HH:MM:SS.SSS" => ISO 8601 combined date and time
 /// without timezone. ("YYYY-MM-DDTHH:MM:SS"/"YYYY-MM-DDTHH:MM:SS.SSS" also supported)
 impl FromSql for NaiveDateTime {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<NaiveDateTime> {
+    fn column_result(value: ValueRef) -> Result<Self> {
-        let s = try!(String::column_result(stmt, col));
+        value.as_str().and_then(|s| {
+            let fmt = if s.len() >= 11 && s.as_bytes()[10] == b'T' {
+                "%Y-%m-%dT%H:%M:%S%.f"
+            } else {
+                "%Y-%m-%d %H:%M:%S%.f"
+            };
 
-        let fmt = if s.len() >= 11 && s.as_bytes()[10] == b'T' {
+            match NaiveDateTime::parse_from_str(s, fmt) {
-            "%Y-%m-%dT%H:%M:%S%.f"
+                Ok(dt) => Ok(dt),
-        } else {
+                Err(err) => Err(Error::FromSqlConversionFailure(Box::new(err))),
-            "%Y-%m-%d %H:%M:%S%.f"
+            }
-        };
+        })
-
-        match NaiveDateTime::parse_from_str(&s, fmt) {
-            Ok(dt) => Ok(dt),
-            Err(err) => Err(Error::FromSqlConversionFailure(Box::new(err))),
-        }
-    }
-
-    unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
-        String::column_has_valid_sqlite_type(stmt, col)
     }
 }
 
@@ -101,38 +91,40 @@ impl<Tz: TimeZone> ToSql for DateTime<Tz> {
 
 /// RFC3339 ("YYYY-MM-DDTHH:MM:SS.SSS[+-]HH:MM") into DateTime<UTC>.
 impl FromSql for DateTime<UTC> {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<DateTime<UTC>> {
+    fn column_result(value: ValueRef) -> Result<Self> {
-        let s = {
+        {
-            let mut s = try!(String::column_result(stmt, col));
+            // Try to parse value as rfc3339 first.
-            if s.len() >= 11 {
+            let s = try!(value.as_str());
-                let sbytes = s.as_mut_vec();
+
-                if sbytes[10] == b' ' {
+            // If timestamp looks space-separated, make a copy and replace it with 'T'.
+            let s = if s.len() >= 11 && s.as_bytes()[10] == b' ' {
+                let mut s = s.to_string();
+                unsafe {
+                    let sbytes = s.as_mut_vec();
                     sbytes[10] = b'T';
                 }
-            }
+                Cow::Owned(s)
-            s
+            } else {
-        };
+                Cow::Borrowed(s)
-        match DateTime::parse_from_rfc3339(&s) {
+            };
-            Ok(dt) => Ok(dt.with_timezone(&UTC)),
-            Err(_) => NaiveDateTime::column_result(stmt, col).map(|dt| UTC.from_utc_datetime(&dt)),
-        }
-    }
 
-    unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
+            match DateTime::parse_from_rfc3339(&s) {
-        String::column_has_valid_sqlite_type(stmt, col)
+                Ok(dt) => return Ok(dt.with_timezone(&UTC)),
+                Err(_) => (),
+            }
+        }
+
+        // Couldn't parse as rfc3339 - fall back to NaiveDateTime.
+        NaiveDateTime::column_result(value).map(|dt| UTC.from_utc_datetime(&dt))
     }
 }
 
 /// RFC3339 ("YYYY-MM-DDTHH:MM:SS.SSS[+-]HH:MM") into DateTime<Local>.
 impl FromSql for DateTime<Local> {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<DateTime<Local>> {
+    fn column_result(value: ValueRef) -> Result<Self> {
-        let utc_dt = try!(DateTime::<UTC>::column_result(stmt, col));
+        let utc_dt = try!(DateTime::<UTC>::column_result(value));
         Ok(utc_dt.with_timezone(&Local))
     }
-
-    unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
-        DateTime::<UTC>::column_has_valid_sqlite_type(stmt, col)
-    }
 }
 
 #[cfg(test)]

src/types/from_sql.rs

@@ -1,119 +1,66 @@
-use std::ffi::CStr;
+use super::{ValueRef, Value};
-use std::mem;
+use ::Result;
-use std::str;
-
-use libc::{c_char, c_double, c_int};
-
-use super::Value;
-use ffi::{sqlite3_stmt, sqlite3_column_type};
-use ::{ffi, Result};
 use ::error::Error;
 
 /// A trait for types that can be created from a SQLite value.
 pub trait FromSql: Sized {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<Self>;
+    fn column_result(value: ValueRef) -> Result<Self>;
+}
 
-    /// FromSql types can implement this method and use sqlite3_column_type to check that
+impl FromSql for i32 {
-    /// the type reported by SQLite matches a type suitable for Self. This method is used
+    fn column_result(value: ValueRef) -> Result<Self> {
-    /// by `Row::get_checked` to confirm that the column contains a valid type before
+        i64::column_result(value).map(|i| i as i32)
-    /// attempting to retrieve the value.
-    unsafe fn column_has_valid_sqlite_type(_: *mut sqlite3_stmt, _: c_int) -> bool {
-        true
     }
 }
 
-macro_rules! raw_from_impl(
+impl FromSql for i64 {
-    ($t:ty, $f:ident, $c:expr) => (
+    fn column_result(value: ValueRef) -> Result<Self> {
-        impl FromSql for $t {
+        value.as_i64()
-            unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<$t> {
-                Ok(ffi::$f(stmt, col))
-            }
-
-            unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
-                sqlite3_column_type(stmt, col) == $c
-            }
-        }
-    )
-);
-
-raw_from_impl!(c_int, sqlite3_column_int, ffi::SQLITE_INTEGER); // i32
-raw_from_impl!(i64, sqlite3_column_int64, ffi::SQLITE_INTEGER);
-raw_from_impl!(c_double, sqlite3_column_double, ffi::SQLITE_FLOAT); // f64
-
-impl FromSql for bool {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<bool> {
-        match ffi::sqlite3_column_int(stmt, col) {
-            0 => Ok(false),
-            _ => Ok(true),
-        }
-    }
-
-    unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
-        sqlite3_column_type(stmt, col) == ffi::SQLITE_INTEGER
     }
 }
 
-impl FromSql for String {
+impl FromSql for f64 {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<String> {
+    fn column_result(value: ValueRef) -> Result<Self> {
-        let c_text = ffi::sqlite3_column_text(stmt, col);
+        match value {
-        if c_text.is_null() {
+            ValueRef::Integer(i) => Ok(i as f64),
-            Ok("".to_owned())
+            ValueRef::Real(f) => Ok(f),
-        } else {
-            let c_slice = CStr::from_ptr(c_text as *const c_char).to_bytes();
-            let utf8_str = try!(str::from_utf8(c_slice));
-            Ok(utf8_str.into())
-        }
-    }
-
-    unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
-        sqlite3_column_type(stmt, col) == ffi::SQLITE_TEXT
-    }
-}
-
-impl FromSql for Vec<u8> {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<Vec<u8>> {
-        use std::slice::from_raw_parts;
-        let c_blob = ffi::sqlite3_column_blob(stmt, col);
-        let len = ffi::sqlite3_column_bytes(stmt, col);
-
-        // The documentation for sqlite3_column_bytes indicates it is always non-negative,
-        // but we should assert here just to be sure.
-        assert!(len >= 0,
-                "unexpected negative return from sqlite3_column_bytes");
-        let len = len as usize;
-
-        Ok(from_raw_parts(mem::transmute(c_blob), len).to_vec())
-    }
-
-    unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
-        sqlite3_column_type(stmt, col) == ffi::SQLITE_BLOB
-    }
-}
-
-impl<T: FromSql> FromSql for Option<T> {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<Option<T>> {
-        if sqlite3_column_type(stmt, col) == ffi::SQLITE_NULL {
-            Ok(None)
-        } else {
-            FromSql::column_result(stmt, col).map(Some)
-        }
-    }
-
-    unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
-        sqlite3_column_type(stmt, col) == ffi::SQLITE_NULL ||
-        T::column_has_valid_sqlite_type(stmt, col)
-    }
-}
-
-impl FromSql for Value {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<Value> {
-        match sqlite3_column_type(stmt, col) {
-            ffi::SQLITE_TEXT => FromSql::column_result(stmt, col).map(Value::Text),
-            ffi::SQLITE_INTEGER => Ok(Value::Integer(ffi::sqlite3_column_int64(stmt, col))),
-            ffi::SQLITE_FLOAT => Ok(Value::Real(ffi::sqlite3_column_double(stmt, col))),
-            ffi::SQLITE_NULL => Ok(Value::Null),
-            ffi::SQLITE_BLOB => FromSql::column_result(stmt, col).map(Value::Blob),
             _ => Err(Error::InvalidColumnType),
         }
     }
 }
+
+impl FromSql for bool {
+    fn column_result(value: ValueRef) -> Result<Self> {
+        i64::column_result(value).map(|i| match i {
+            0 => false,
+            _ => true,
+        })
+    }
+}
+
+impl FromSql for String {
+    fn column_result(value: ValueRef) -> Result<Self> {
+        value.as_str().map(|s| s.to_string())
+    }
+}
+
+impl FromSql for Vec<u8> {
+    fn column_result(value: ValueRef) -> Result<Self> {
+        value.as_blob().map(|b| b.to_vec())
+    }
+}
+
+impl<T: FromSql> FromSql for Option<T> {
+    fn column_result(value: ValueRef) -> Result<Self> {
+        match value {
+            ValueRef::Null => Ok(None),
+            _ => FromSql::column_result(value).map(Some),
+        }
+    }
+}
+
+impl FromSql for Value {
+    fn column_result(value: ValueRef) -> Result<Self> {
+        Ok(value.into())
+    }
+}

src/types/mod.rs

@@ -4,7 +4,9 @@
 //! the `ToSql` and `FromSql` traits are provided for the basic types that SQLite provides methods
 //! for:
 //!
-//! * C integers and doubles (`c_int` and `c_double`)
+//! * Integers (`i32` and `i64`; SQLite uses `i64` internally, so getting an `i32` will truncate
+//!   if the value is too large or too small).
+//! * Reals (`f64`)
 //! * Strings (`String` and `&str`)
 //! * Blobs (`Vec<u8>` and `&[u8]`)
 //!
@@ -13,13 +15,7 @@
 //! `"%Y-%m-%d %H:%M:%S"`, as SQLite's builtin
 //! [datetime](https://www.sqlite.org/lang_datefunc.html) function.  Note that this storage
 //! truncates timespecs to the nearest second. If you want different storage for timespecs, you can
-//! use a newtype. For example, to store timespecs as doubles:
+//! use a newtype. For example, to store timespecs as `f64`s:
-//!
-//! `ToSql` and `FromSql` are also implemented for `Option<T>` where `T` implements `ToSql` or
-//! `FromSql` for the cases where you want to know if a value was NULL (which gets translated to
-//! `None`). If you get a value that was NULL in SQLite but you store it into a non-`Option` value
-//! in Rust, you will get a "sensible" zero value - 0 for numeric types (including timespecs), an
-//! empty string, or an empty vector of bytes.
 //!
 //! ```rust,ignore
 //! extern crate rusqlite;
@@ -33,10 +29,8 @@
 //! pub struct TimespecSql(pub time::Timespec);
 //!
 //! impl FromSql for TimespecSql {
-//!     unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int)
+//!     fn column_result(value: ValueRef) -> Result<Self> {
-//!             -> Result<TimespecSql> {
+//!         f64::column_result(value).map(|as_f64| {
-//!         let as_f64_result = FromSql::column_result(stmt, col);
-//!         as_f64_result.map(|as_f64: f64| {
 //!             TimespecSql(time::Timespec{ sec: as_f64.trunc() as i64,
 //!                                         nsec: (as_f64.fract() * 1.0e9) as i32 })
 //!         })
@@ -51,14 +45,18 @@
 //!     }
 //! }
 //! ```
+//!
+//! `ToSql` and `FromSql` are also implemented for `Option<T>` where `T` implements `ToSql` or
+//! `FromSql` for the cases where you want to know if a value was NULL (which gets translated to
+//! `None`).
 
 pub use ffi::sqlite3_stmt;
-pub use ffi::sqlite3_column_type;
-pub use ffi::{SQLITE_INTEGER, SQLITE_FLOAT, SQLITE_TEXT, SQLITE_BLOB, SQLITE_NULL};
 
 pub use self::from_sql::FromSql;
 pub use self::to_sql::ToSql;
+pub use self::value_ref::ValueRef;
 
+mod value_ref;
 mod from_sql;
 mod to_sql;
 mod time;
@@ -86,8 +84,10 @@ mod serde_json;
 #[derive(Copy,Clone)]
 pub struct Null;
 
-/// Dynamic type value (http://sqlite.org/datatype3.html)
+/// Owning [dynamic type value](http://sqlite.org/datatype3.html). Value's type is typically
-/// Value's type is dictated by SQLite (not by the caller).
+/// dictated by SQLite (not by the caller).
+///
+/// See [`ValueRef`](enum.ValueRef.html) for a non-owning dynamic type value.
 #[derive(Clone,Debug,PartialEq)]
 pub enum Value {
     /// The value is a `NULL` value.
@@ -219,10 +219,9 @@ mod test {
         assert!(is_invalid_column_type(row.get_checked::<i32, Option<c_int>>(1).err().unwrap()));
 
         // 2 is actually an integer
-        assert!(is_invalid_column_type(row.get_checked::<i32, c_double>(2).err().unwrap()));
         assert!(is_invalid_column_type(row.get_checked::<i32, String>(2).err().unwrap()));
         assert!(is_invalid_column_type(row.get_checked::<i32, Vec<u8>>(2).err().unwrap()));
-        assert!(is_invalid_column_type(row.get_checked::<i32, Option<c_double>>(2).err().unwrap()));
+        assert!(is_invalid_column_type(row.get_checked::<i32, Option<String>>(2).err().unwrap()));
 
         // 3 is actually a float (c_double)
         assert!(is_invalid_column_type(row.get_checked::<i32, c_int>(3).err().unwrap()));

src/types/serde_json.rs

@@ -5,11 +5,9 @@ use libc::c_int;
 use self::serde_json::Value;
 
 use {Error, Result};
-use types::{FromSql, ToSql};
+use types::{FromSql, ToSql, ValueRef};
 
-use ffi;
 use ffi::sqlite3_stmt;
-use ffi::sqlite3_column_type;
 
 /// Serialize JSON `Value` to text.
 impl ToSql for Value {
@@ -21,19 +19,12 @@ impl ToSql for Value {
 
 /// Deserialize text/blob to JSON `Value`.
 impl FromSql for Value {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<Value> {
+    fn column_result(value: ValueRef) -> Result<Self> {
-        let value_result = match sqlite3_column_type(stmt, col) {
+        match value {
-            ffi::SQLITE_TEXT => {
+            ValueRef::Text(ref s) => serde_json::from_str(s),
-                let s = try!(String::column_result(stmt, col));
+            ValueRef::Blob(ref b) => serde_json::from_slice(b),
-                serde_json::from_str(&s)
-            }
-            ffi::SQLITE_BLOB => {
-                let blob = try!(Vec::<u8>::column_result(stmt, col));
-                serde_json::from_slice(&blob)
-            }
             _ => return Err(Error::InvalidColumnType),
-        };
+        }.map_err(|err| Error::FromSqlConversionFailure(Box::new(err)))
-        value_result.map_err(|err| Error::FromSqlConversionFailure(Box::new(err)))
     }
 }
 

src/types/time.rs

@@ -2,7 +2,7 @@ extern crate time;
 
 use libc::c_int;
 use {Error, Result};
-use types::{FromSql, ToSql};
+use types::{FromSql, ToSql, ValueRef};
 
 use ffi::sqlite3_stmt;
 
@@ -16,16 +16,11 @@ impl ToSql for time::Timespec {
 }
 
 impl FromSql for time::Timespec {
-    unsafe fn column_result(stmt: *mut sqlite3_stmt, col: c_int) -> Result<time::Timespec> {
+    fn column_result(value: ValueRef) -> Result<Self> {
-        let s = try!(String::column_result(stmt, col));
+        value.as_str().and_then(|s| match time::strptime(s, SQLITE_DATETIME_FMT) {
-        match time::strptime(&s, SQLITE_DATETIME_FMT) {
             Ok(tm) => Ok(tm.to_timespec()),
             Err(err) => Err(Error::FromSqlConversionFailure(Box::new(err))),
-        }
+        })
-    }
-
-    unsafe fn column_has_valid_sqlite_type(stmt: *mut sqlite3_stmt, col: c_int) -> bool {
-        String::column_has_valid_sqlite_type(stmt, col)
     }
 }
 

src/types/value_ref.rs

@@ -0,0 +1,83 @@
+use ::Result;
+use ::error::Error;
+use super::Value;
+
+/// A non-owning [dynamic type value](http://sqlite.org/datatype3.html). Typically the
+/// memory backing this value is owned by SQLite.
+///
+/// See [`Value`](enum.Value.html) for an owning dynamic type value.
+#[derive(Copy,Clone,Debug,PartialEq)]
+pub enum ValueRef<'a> {
+    /// The value is a `NULL` value.
+    Null,
+    /// The value is a signed integer.
+    Integer(i64),
+    /// The value is a floating point number.
+    Real(f64),
+    /// The value is a text string.
+    Text(&'a str),
+    /// The value is a blob of data
+    Blob(&'a [u8]),
+}
+
+impl<'a> ValueRef<'a> {
+    /// If `self` is case `Integer`, returns the integral value. Otherwise, returns
+    /// `Err(Error::InvalidColumnType)`.
+    pub fn as_i64(&self) -> Result<i64> {
+        match *self {
+            ValueRef::Integer(i) => Ok(i),
+            _ => Err(Error::InvalidColumnType),
+        }
+    }
+
+    /// If `self` is case `Real`, returns the floating point value. Otherwise, returns
+    /// `Err(Error::InvalidColumnType)`.
+    pub fn as_f64(&self) -> Result<f64> {
+        match *self {
+            ValueRef::Real(f) => Ok(f),
+            _ => Err(Error::InvalidColumnType),
+        }
+    }
+
+    /// If `self` is case `Text`, returns the string value. Otherwise, returns
+    /// `Err(Error::InvalidColumnType)`.
+    pub fn as_str(&self) -> Result<&str> {
+        match *self {
+            ValueRef::Text(ref t) => Ok(t),
+            _ => Err(Error::InvalidColumnType),
+        }
+    }
+
+    /// If `self` is case `Blob`, returns the byte slice. Otherwise, returns
+    /// `Err(Error::InvalidColumnType)`.
+    pub fn as_blob(&self) -> Result<&[u8]> {
+        match *self {
+            ValueRef::Blob(ref b) => Ok(b),
+            _ => Err(Error::InvalidColumnType),
+        }
+    }
+}
+
+impl<'a> From<ValueRef<'a>> for Value {
+    fn from(borrowed: ValueRef) -> Value {
+        match borrowed {
+            ValueRef::Null => Value::Null,
+            ValueRef::Integer(i) => Value::Integer(i),
+            ValueRef::Real(r) => Value::Real(r),
+            ValueRef::Text(s) => Value::Text(s.to_string()),
+            ValueRef::Blob(b) => Value::Blob(b.to_vec()),
+        }
+    }
+}
+
+impl<'a> From<&'a Value> for ValueRef<'a> {
+    fn from(value: &'a Value) -> ValueRef<'a> {
+        match *value {
+            Value::Null => ValueRef::Null,
+            Value::Integer(i) => ValueRef::Integer(i),
+            Value::Real(r) => ValueRef::Real(r),
+            Value::Text(ref s) => ValueRef::Text(s),
+            Value::Blob(ref b) => ValueRef::Blob(b),
+        }
+    }
+}