68 lines
2.4 KiB
C
68 lines
2.4 KiB
C
/*
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* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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// This header file includes the inline functions in
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// the fix point signal processing library.
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#ifndef COMMON_AUDIO_SIGNAL_PROCESSING_INCLUDE_SPL_INL_H_
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#define COMMON_AUDIO_SIGNAL_PROCESSING_INCLUDE_SPL_INL_H_
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#include "common.h"
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extern const int8_t kWebRtcSpl_CountLeadingZeros32_Table[64];
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// Don't call this directly except in tests!
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static __inline int WebRtcSpl_CountLeadingZeros32_NotBuiltin(uint32_t n) {
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// Normalize n by rounding up to the nearest number that is a sequence of 0
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// bits followed by a sequence of 1 bits. This number has the same number of
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// leading zeros as the original n. There are exactly 33 such values.
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n |= n >> 1;
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n |= n >> 2;
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n |= n >> 4;
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n |= n >> 8;
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n |= n >> 16;
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// Multiply the modified n with a constant selected (by exhaustive search)
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// such that each of the 33 possible values of n give a product whose 6 most
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// significant bits are unique. Then look up the answer in the table.
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return kWebRtcSpl_CountLeadingZeros32_Table[(n * 0x8c0b2891) >> 26];
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}
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// Returns the number of leading zero bits in the argument.
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static __inline int WebRtcSpl_CountLeadingZeros32(uint32_t n) {
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#ifdef __GNUC__
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// RTC_COMPILE_ASSERT(sizeof(unsigned int) == sizeof(uint32_t));
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return n == 0 ? 32 : __builtin_clz(n);
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#else
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return WebRtcSpl_CountLeadingZeros32_NotBuiltin(n);
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#endif
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}
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static __inline int16_t WebRtcSpl_GetSizeInBits(uint32_t n) {
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return 32 - WebRtcSpl_CountLeadingZeros32(n);
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}
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// Return the number of steps a can be left-shifted without overflow,
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// or 0 if a == 0.
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static __inline int16_t WebRtcSpl_NormW32(int32_t a) {
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return a == 0 ? 0 : WebRtcSpl_CountLeadingZeros32(a < 0 ? ~a : a) - 1;
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}
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// Return the number of steps a can be left-shifted without overflow,
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// or 0 if a == 0.
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static __inline int16_t WebRtcSpl_NormU32(uint32_t a) {
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return a == 0 ? 0 : WebRtcSpl_CountLeadingZeros32(a);
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}
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#endif // COMMON_AUDIO_SIGNAL_PROCESSING_INCLUDE_SPL_INL_H_
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