add some code

managed_components/espressif__esp-dsp/modules/windows/blackman/float/dsps_wind_blackman_f32.c

@@ -0,0 +1,29 @@
+// Copyright 2018-2019 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#define _USE_MATH_DEFINES
+#include "dsps_wind_blackman.h"
+#include <math.h>
+
+void dsps_wind_blackman_f32(float *window, int len)
+{
+    const float a0 = 0.42;
+    const float a1 = 0.5;
+    const float a2 = 0.08;
+
+    float len_mult = 1 / (float)(len - 1);
+    for (int i = 0; i < len; i++) {
+        window[i] = a0 - a1 * cosf(i * 2 * M_PI * len_mult) + a2 * cosf(i * 4 * M_PI * len_mult);
+    }
+}