C API reference¶

Include the main C API with:

#include <bfft/bfft.h>

Types¶

Type	Description
`bfft_plan`	Opaque reusable real FFT plan.
`bfft_workspace`	Opaque aligned scratch workspace.
`bfft_complex`	Double-precision complex value with `re` and `im`.
`bfft_complex_f32`	Single-precision complex value with `re` and `im`.
`bfft_status`	Return status enum.
`bfft_layout`	Descriptive layout enum.

Version and diagnostics¶

bfft_version_string() returns the library version string.
bfft_backend_name() returns the selected SIMD backend name.
bfft_status_string(status) returns a readable status string.

Plan lifecycle¶

bfft_plan_create(n, &plan) creates a real FFT plan for power-of-two n >= 4.
bfft_plan_destroy(plan) destroys a plan. Passing NULL is allowed.

Plan queries¶

bfft_plan_size(plan) returns N.
bfft_plan_bins(plan) returns N / 2 + 1.
bfft_plan_work_size(plan) returns double work buffer length.
bfft_plan_work_size_f32(plan) returns float work buffer length.
bfft_plan_native_scratch_size(plan) returns standard transform scratch size.
bfft_plan_standard_policy(plan) returns the standard-output packing policy.

Forward transforms¶

bfft_forward computes standard FFT-order double-precision output.
bfft_forward_native computes native-order double-precision output.
bfft_forward_native_workspace computes native-order output with workspace storage.
bfft_forward_f32 computes standard FFT-order single-precision output.
bfft_forward_native_f32 computes native-order single-precision output.

Magnitude transforms¶

bfft_forward_magnitude writes standard-order double magnitudes.
bfft_forward_magnitude_f32 writes standard-order float magnitudes.

Inverse transforms¶

bfft_inverse inverts standard FFT-order double-precision input.
bfft_inverse_f32 inverts standard FFT-order single-precision input.
bfft_inverse_native inverts native-order double-precision input.
bfft_inverse_native_f32 inverts native-order single-precision input.

Layout conversion¶

bfft_native_to_standard converts double native output to standard output.
bfft_standard_to_native converts double standard input to native input.
bfft_native_to_standard_f32 converts float native output to standard output.
bfft_standard_to_native_f32 converts float standard input to native input.

Residue transforms and filters¶

bfft_forward_residues transforms real input to residue coordinates.
bfft_inverse_residues transforms residue coordinates back in place.
bfft_filter_size returns the residue filter length.
bfft_residue_filter_from_standard converts a complex response to a residue filter.
bfft_residue_filter_from_real converts a real zero-phase response to a residue filter.
bfft_apply_residue_filter applies a residue filter in place.
bfft_filter_signal transforms, filters, and inverts a signal.

All valid BFFT real FFT plans are power-of-two plans, so residue transforms and residue filters are available for every valid plan.

STFT C ABI¶

<bfft/stft.h> exposes bfft_stft_plan, a reusable short-time transform plan. Create it with bfft_stft_plan_create, run bfft_stft_forward, and run bfft_stft_inverse for streaming overlap-add inversion. The inverse overlap buffer is owned by the plan; call bfft_stft_reset_buffer before a fresh stream. Spectrograms are row-major as output[bin * segments + segment]. Pass NULL as the window pointer to use the default Hann window, or pass n_fft finite doubles.