diff --git a/src/context.rs b/src/context.rs
new file mode 100644
index 0000000..33a7c15
--- /dev/null
+++ b/src/context.rs
@@ -0,0 +1,141 @@
+//! Code related to `sqlite3_context` common to `functions` and `vtab` modules.
+
+use std::error::Error as StdError;
+use std::ffi::CStr;
+use std::os::raw::{c_char, c_int, c_void};
+
+use ffi;
+use ffi::sqlite3_context;
+use ffi::sqlite3_value;
+
+use types::{ToSqlOutput, ValueRef};
+use {str_to_cstring, Error};
+
+impl<'a> 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) {
+            ffi::SQLITE_NULL => ValueRef::Null,
+            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);
+
+                // 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, len) = (
+                    ffi::sqlite3_value_blob(value),
+                    ffi::sqlite3_value_bytes(value),
+                );
+
+                assert!(
+                    len >= 0,
+                    "unexpected negative return from sqlite3_value_bytes"
+                );
+                if len > 0 {
+                    assert!(
+                        !blob.is_null(),
+                        "unexpected SQLITE_BLOB value type with NULL data"
+                    );
+                    ValueRef::Blob(from_raw_parts(blob as *const u8, len as usize))
+                } else {
+                    // The return value from sqlite3_value_blob() for a zero-length BLOB
+                    // is a NULL pointer.
+                    ValueRef::Blob(&[])
+                }
+            }
+            _ => unreachable!("sqlite3_value_type returned invalid value"),
+        }
+    }
+}
+
+pub unsafe fn set_result<'a>(ctx: *mut sqlite3_context, result: &ToSqlOutput<'a>) {
+    let value = match *result {
+        ToSqlOutput::Borrowed(v) => v,
+        ToSqlOutput::Owned(ref v) => ValueRef::from(v),
+
+        #[cfg(feature = "blob")]
+        ToSqlOutput::ZeroBlob(len) => {
+            return ffi::sqlite3_result_zeroblob(ctx, len);
+        }
+    };
+
+    match value {
+        ValueRef::Null => ffi::sqlite3_result_null(ctx),
+        ValueRef::Integer(i) => ffi::sqlite3_result_int64(ctx, i),
+        ValueRef::Real(r) => ffi::sqlite3_result_double(ctx, r),
+        ValueRef::Text(s) => {
+            let length = s.len();
+            if length > ::std::i32::MAX as usize {
+                ffi::sqlite3_result_error_toobig(ctx);
+            } else {
+                let c_str = match str_to_cstring(s) {
+                    Ok(c_str) => c_str,
+                    // TODO sqlite3_result_error
+                    Err(_) => return ffi::sqlite3_result_error_code(ctx, ffi::SQLITE_MISUSE),
+                };
+                let destructor = if length > 0 {
+                    ffi::SQLITE_TRANSIENT()
+                } else {
+                    ffi::SQLITE_STATIC()
+                };
+                ffi::sqlite3_result_text(ctx, c_str.as_ptr(), length as c_int, destructor);
+            }
+        }
+        ValueRef::Blob(b) => {
+            let length = b.len();
+            if length > ::std::i32::MAX as usize {
+                ffi::sqlite3_result_error_toobig(ctx);
+            } else if length == 0 {
+                ffi::sqlite3_result_zeroblob(ctx, 0)
+            } else {
+                ffi::sqlite3_result_blob(
+                    ctx,
+                    b.as_ptr() as *const c_void,
+                    length as c_int,
+                    ffi::SQLITE_TRANSIENT(),
+                );
+            }
+        }
+    }
+}
+
+pub unsafe fn report_error(ctx: *mut sqlite3_context, err: &Error) {
+    // Extended constraint error codes were added in SQLite 3.7.16. We don't have an explicit
+    // feature check for that, and this doesn't really warrant one. We'll use the extended code
+    // if we're on the bundled version (since it's at least 3.17.0) and the normal constraint
+    // error code if not.
+    #[cfg(feature = "bundled")]
+    fn constraint_error_code() -> i32 {
+        ffi::SQLITE_CONSTRAINT_FUNCTION
+    }
+    #[cfg(not(feature = "bundled"))]
+    fn constraint_error_code() -> i32 {
+        ffi::SQLITE_CONSTRAINT
+    }
+
+    match *err {
+        Error::SqliteFailure(ref err, ref s) => {
+            ffi::sqlite3_result_error_code(ctx, err.extended_code);
+            if let Some(Ok(cstr)) = s.as_ref().map(|s| str_to_cstring(s)) {
+                ffi::sqlite3_result_error(ctx, cstr.as_ptr(), -1);
+            }
+        }
+        _ => {
+            ffi::sqlite3_result_error_code(ctx, constraint_error_code());
+            if let Ok(cstr) = str_to_cstring(err.description()) {
+                ffi::sqlite3_result_error(ctx, cstr.as_ptr(), -1);
+            }
+        }
+    }
+}