From d7fc2c3ca207b294cb1594081d8aacb3315594ac Mon Sep 17 00:00:00 2001 From: Steve Cossette Date: Thu, 15 Oct 2026 10:11:59 -0400 Subject: [PATCH 1/3] Fixing licenses, adding used ones from source files --- LICENSES/BSD-3-Clause.txt | 35 +++++++++++ LICENSES/CC0-1.0.txt | 121 ++++++++++++++++++++++++++++++++++++++ LICENSES/MIT.txt | 18 ++++++ LICENSES/Unlicense.txt | 30 ++++++++++ 4 files changed, 204 insertions(+) create mode 100644 LICENSES/BSD-3-Clause.txt create mode 100644 LICENSES/CC0-1.0.txt create mode 100644 LICENSES/MIT.txt create mode 100644 LICENSES/Unlicense.txt diff --git a/LICENSES/BSD-3-Clause.txt b/LICENSES/BSD-3-Clause.txt new file mode 100644 index 0000000..b8d5681 --- /dev/null +++ b/LICENSES/BSD-3-Clause.txt @@ -0,0 +1,35 @@ +Valid-License-Identifier: BSD-3-Clause +SPDX-URL: https://spdx.org/licenses/BSD-3-Clause.html +Usage-Guide: + To use the BSD 3-clause "New" or "Revised" License put the following SPDX + tag/value pair into a comment according to the placement guidelines in + the licensing rules documentation: + SPDX-License-Identifier: BSD-3-Clause +License-Text: + +Copyright (c) . 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IN NO +EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER +IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE +USE OR OTHER DEALINGS IN THE SOFTWARE. diff --git a/LICENSES/Unlicense.txt b/LICENSES/Unlicense.txt new file mode 100644 index 0000000..95e1b74 --- /dev/null +++ b/LICENSES/Unlicense.txt @@ -0,0 +1,30 @@ +Valid-License-Identifier: Unlicense +SPDX-URL: https://spdx.org/licenses/Unlicense.html +Usage-Guide: + To use the Unlicense put the following SPDX tag/value pair into a + comment according to the placement guidelines in the licensing rules + documentation: + SPDX-License-Identifier: Unlicense +License-Text: + +This is free and unencumbered software released into the public domain. + +Anyone is free to copy, modify, publish, use, compile, sell, or distribute +this software, either in source code form or as a compiled binary, for any +purpose, commercial or non-commercial, and by any means. + +In jurisdictions that recognize copyright laws, the author or authors of this +software dedicate any and all copyright interest in the software to the public +domain. We make this dedication for the benefit of the public at large and +to the detriment of our heirs and successors. We intend this dedication to be +an overt act of relinquishment in perpetuity of all present and future rights +to this software under copyright law. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS +FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS +BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION +OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH +THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. + +For more information, please refer to From d3a85a9e01ed550088aa8a8b2ed87823c7c2fe0b Mon Sep 17 00:00:00 2001 From: AC Date: Mon, 19 Oct 2026 11:51:48 +0800 Subject: [PATCH 2/3] docs: explain forward and inverse normalization --- README.md | 23 +++++++++++++++++++++++ kiss_fft.h | 4 ++++ kiss_fftr.h | 3 +++ 3 files changed, 30 insertions(+) diff --git a/README.md b/README.md index f4c1602..9980815 100644 --- a/README.md +++ b/README.md @@ -44,6 +44,29 @@ You can do other cool stuff with the extras you'll find in tools/ The core fft and most tools/ code can be compiled to use float, double, Q15 short or Q31 samples. The default is float. +### Forward and inverse scaling + +For floating-point builds (`float` or `double`), neither direction is +normalized. A forward transform followed by an inverse transform returns +`nfft` times the original input. Divide each inverse output sample by +`nfft` to recover the input: + +```c + /* After kiss_fft(inverse_cfg, spectrum, recovered): */ + for (int k = 0; k < nfft; ++k) { + recovered[k].r /= nfft; + recovered[k].i /= nfft; + } +``` + +The same convention applies to `kiss_fft_stride()` and the real transform +pair `kiss_fftr()` / `kiss_fftri()`. For the real pair, divide the `nfft` +real output samples by the original real transform length, not by the +number of complex frequency bins (`nfft / 2 + 1`). + +Fixed-point builds scale internally in both directions to prevent overflow; +do not apply the floating-point normalization recipe to them. + ## BUILDING: There are two functionally-equivalent build systems supported by kissfft: diff --git a/kiss_fft.h b/kiss_fft.h index 51b6306..e6906d5 100644 --- a/kiss_fft.h +++ b/kiss_fft.h @@ -147,6 +147,10 @@ kiss_fft_cfg KISS_FFT_API kiss_fft_alloc(int nfft,int inverse_fft,void * mem,siz * for a forward FFT, * fin should be f[0] , f[1] , ... ,f[nfft-1] * fout will be F[0] , F[1] , ... ,F[nfft-1] + * Floating-point transforms are unnormalized in both directions: a forward + * transform followed by an inverse yields nfft times the original input. + * Divide the inverse output by nfft to recover the input. Fixed-point builds + * instead scale internally in both directions to prevent overflow. * Note that each element is complex and can be accessed like f[k].r and f[k].i * */ diff --git a/kiss_fftr.h b/kiss_fftr.h index 7fd73d2..9061a5d 100644 --- a/kiss_fftr.h +++ b/kiss_fftr.h @@ -44,6 +44,9 @@ void KISS_FFT_API kiss_fftri(kiss_fftr_cfg cfg,const kiss_fft_cpx *freqdata,kiss /* input freqdata has nfft/2+1 complex points output timedata has nfft scalar points + For floating-point builds, a kiss_fftr / kiss_fftri round trip returns + nfft times the input; divide timedata by nfft to recover the input. + Fixed-point builds scale internally and use a different convention. */ #define kiss_fftr_free KISS_FFT_FREE From 80aec22623a86e2d726c0f9d01eb3acd694c7662 Mon Sep 17 00:00:00 2001 From: zhouyunding Date: Wed, 21 Oct 2026 19:25:11 +0800 Subject: [PATCH 3/3] Fix infinite loop in kiss_fft_next_fast_size for n<=0 (issue #121) kiss_fft_next_fast_size(0) never terminated because the factorization loop divides m by 2/3/5 forever when m stays 0. Per maintainer decision, return 1 for n<=0. Add regression test next_fast_size covering n=0, n<0 and positive inputs. --- kiss_fft.c | 2 ++ test/CMakeLists.txt | 2 ++ test/next_fast_size.c | 39 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 43 insertions(+) create mode 100644 test/next_fast_size.c diff --git a/kiss_fft.c b/kiss_fft.c index aba63e0..c97515f 100644 --- a/kiss_fft.c +++ b/kiss_fft.c @@ -411,6 +411,8 @@ void kiss_fft_cleanup(void) int kiss_fft_next_fast_size(int n) { + if (n <= 0) /* nothing to factor; avoid infinite loop for n<=0 */ + return 1; while(1) { int m=n; while ( (m%2) == 0 ) m/=2; diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt index 0bd0938..505a748 100644 --- a/test/CMakeLists.txt +++ b/test/CMakeLists.txt @@ -49,6 +49,8 @@ target_compile_definitions(tkfc PRIVATE KFC_TEST) add_kissfft_test_executable(ffr twotonetest.c) add_kissfft_test_executable(tr test_real.c) +add_kissfft_test_executable(next_fast_size next_fast_size.c) + add_kissfft_test_executable(testcpp testcpp.cc) if(KISSFFT_DATATYPE MATCHES "^simd$") diff --git a/test/next_fast_size.c b/test/next_fast_size.c new file mode 100644 index 0000000..3d29109 --- /dev/null +++ b/test/next_fast_size.c @@ -0,0 +1,39 @@ +/* + * Copyright (c) 2003-2010, Mark Borgerding. All rights reserved. + * This file is part of KISS FFT - https://github.com/mborgerding/kissfft + * + * SPDX-License-Identifier: BSD-3-Clause + * See COPYING file for more information. + * + * Regression test for github issue #121: kiss_fft_next_fast_size(0) + * used to hang forever in the factorization loop. + */ +#include "kiss_fft.h" +#include + +int main(void) +{ + int n; + /* n<=0 must return 1 per maintainer decision, not hang */ + if (kiss_fft_next_fast_size(0) != 1) { + fprintf(stderr, "FAIL: kiss_fft_next_fast_size(0) != 1\n"); + return 1; + } + if (kiss_fft_next_fast_size(-3) != 1) { + fprintf(stderr, "FAIL: kiss_fft_next_fast_size(-3) != 1\n"); + return 1; + } + /* positive inputs keep their pre-fix behavior */ + { + int expected[9] = { 0, 1, 2, 3, 4, 5, 6, 8, 8 }; + for (n = 1; n <= 8; ++n) { + if (kiss_fft_next_fast_size(n) != expected[n]) { + fprintf(stderr, "FAIL: kiss_fft_next_fast_size(%d) = %d, expected %d\n", + n, kiss_fft_next_fast_size(n), expected[n]); + return 1; + } + } + } + printf("kiss_fft_next_fast_size: all checks passed\n"); + return 0; +}