handle non-existent keys in db.Get(key, buffer, ...), fixing #44

Author: warrenfalk

RocksDbSharp/RocksDb.cs

@@ -119,16 +119,42 @@ public byte[] Get(byte[] key, long keyLength, ColumnFamilyHandle cf = null, Read
             return Native.Instance.rocksdb_get(Handle, (readOptions ?? DefaultReadOptions).Handle, key, keyLength, cf);
         }
 
+        /// <summary>
+        /// Reads the contents of the database value associated with <paramref name="key"/>, if present, into the supplied
+        /// <paramref name="buffer"/> at <paramref name="offset"/> up to <paramref name="length"/> bytes, returning the
+        /// length of the value in the database, or -1 if the key is not present.
+        /// </summary>
+        /// <param name="key"></param>
+        /// <param name="buffer"></param>
+        /// <param name="offset"></param>
+        /// <param name="length"></param>
+        /// <param name="cf"></param>
+        /// <param name="readOptions"></param>
+        /// <returns>The actual length of the database field if it exists, otherwise -1</returns>
         public long Get(byte[] key, byte[] buffer, long offset, long length, ColumnFamilyHandle cf = null, ReadOptions readOptions = null)
         {
             return Get(key, key.GetLongLength(0), buffer, offset, length, cf, readOptions);
         }
 
+        /// <summary>
+        /// Reads the contents of the database value associated with <paramref name="key"/>, if present, into the supplied
+        /// <paramref name="buffer"/> at <paramref name="offset"/> up to <paramref name="length"/> bytes, returning the
+        /// length of the value in the database, or -1 if the key is not present.
+        /// </summary>
+        /// <param name="key"></param>
+        /// <param name="buffer"></param>
+        /// <param name="offset"></param>
+        /// <param name="length"></param>
+        /// <param name="cf"></param>
+        /// <param name="readOptions"></param>
+        /// <returns>The actual length of the database field if it exists, otherwise -1</returns>
         public long Get(byte[] key, long keyLength, byte[] buffer, long offset, long length, ColumnFamilyHandle cf = null, ReadOptions readOptions = null)
         {
             unsafe
             {
                 var ptr = Native.Instance.rocksdb_get(Handle, (readOptions ?? DefaultReadOptions).Handle, key, keyLength, out long valLength, cf);
+                if (ptr == IntPtr.Zero)
+                    return -1;
                 var copyLength = Math.Min(length, valLength);
                 Marshal.Copy(ptr, buffer, (int)offset, (int)copyLength);
                 Native.Instance.rocksdb_free(ptr);

tests/RocksDbSharpTest/FunctionalTests.cs

@@ -61,6 +61,9 @@ public void FunctionalTest()
                 Assert.Equal(8, length);
                 Assert.Equal(new byte[] { 0, 1, 2, 3, 4 }, buffer.Take((int)Math.Min(buffer.Length, length)));
 
+                length = db.Get(Encoding.UTF8.GetBytes("bogus"), buffer, 0, buffer.Length);
+                Assert.Equal(-1, length);
+
                 // Write batches
                 // With strings
                 using (WriteBatch batch = new WriteBatch()