Introduce ZeoBlob struct.

src/blob.rs

@@ -17,6 +17,7 @@
 //! extern crate rusqlite;
 //!
 //! use rusqlite::{Connection, DatabaseName};
+//! use rusqlite::types::ZeroBlob;
 //! use std::io::{Read, Write, Seek, SeekFrom};
 //!
 //! fn main() {
@@ -38,7 +39,7 @@
 //!     let bytes_read = blob.read(&mut buf[..]).unwrap();
 //!     assert_eq!(bytes_read, 10); // note we read 10 bytes because the blob has size 10
 //!
-//!     db.execute("INSERT INTO test (content) VALUES (ZEROBLOB(64))", &[]).unwrap();
+//!     db.execute("INSERT INTO test (content) VALUES (?)", &[&ZeroBlob(64)]).unwrap();
 //!
 //!     // given a new row ID, we can reopen the blob on that row
 //!     let rowid = db.last_insert_rowid();

src/types.rs

@@ -194,6 +194,21 @@ impl ToSql for Null {
     }
 }
 
+/// BLOB of length N that is filled with zeroes.
+/// Zeroblobs are intended to serve as placeholders for BLOBs whose content is later written using incremental BLOB I/O routines.
+/// A negative value for the zeroblob results in a zero-length BLOB.
+#[cfg(feature = "blob")]
+#[derive(Copy,Clone)]
+pub struct ZeroBlob(pub i32);
+
+#[cfg(feature = "blob")]
+impl ToSql for ZeroBlob {
+    unsafe fn bind_parameter(&self, stmt: *mut sqlite3_stmt, col: c_int) -> c_int {
+        let ZeroBlob(length) = *self;
+        ffi::sqlite3_bind_zeroblob(stmt, col, length)
+    }
+}
+
 macro_rules! raw_from_impl(
     ($t:ty, $f:ident, $c:expr) => (
         impl FromSql for $t {