| /* |
| * Copyright (c) 2015 The WebM project authors. All Rights Reserved. |
| * |
| * Use of this source code is governed by a BSD-style license |
| * that can be found in the LICENSE file in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| |
| #ifndef VP10_COMMON_DIVIDE_H_ |
| #define VP10_COMMON_DIVIDE_H_ |
| // An implemntation of the divide by multiply alogrithm |
| // https://gmplib.org/~tege/divcnst-pldi94.pdf |
| |
| #include <limits.h> |
| |
| #include "./vpx_config.h" |
| #include "vpx/vpx_integer.h" |
| |
| #ifdef __cplusplus |
| extern "C" { |
| #endif // __cplusplus |
| |
| struct fastdiv_elem { |
| unsigned mult; |
| unsigned shift; |
| }; |
| |
| extern const struct fastdiv_elem vp10_fastdiv_tab[256]; |
| |
| static INLINE unsigned fastdiv(unsigned x, int y) { |
| unsigned t = |
| ((uint64_t)x * vp10_fastdiv_tab[y].mult) >> (sizeof(x) * CHAR_BIT); |
| return (t + x) >> vp10_fastdiv_tab[y].shift; |
| } |
| #ifdef __cplusplus |
| } // extern "C" |
| #endif // __cplusplus |
| #endif // VP10_COMMON_DIVIDE_H_ |