File hbdecim_core.h

#ifndef HBDECIM_CORE_H
#define HBDECIM_CORE_H

#include "clib_common.h"

#ifdef __cplusplus
extern "C" {
#endif

typedef struct {
    size_t num_taps;    /* FIR branch length                         */
    size_t centre;      /* = num_taps / 2                            */
    int    fir_on_even; /* 1 if N even, 0 if N odd                   */
    float *h;           /* FIR coeffs × 0.5 (polyphase normalisation) */

    /* Even delay line: stores x[2m], x[2m-2], ...
     * Dual-write ring: 2 × even_cap elements.                       */
    float _Complex *even_buf;
    size_t          even_cap;
    size_t          even_mask;
    size_t          even_head;

    /* Odd delay line: stores x[2m+1], x[2m-1], ...
     * Shares even_cap and even_mask with even_buf.                  */
    float _Complex *odd_buf;
    size_t          odd_head;

    int            has_pending; /* 1 when a trailing even sample is held */
    float _Complex pending;     /* the held even sample                  */
} hbdecim_state_t;

hbdecim_state_t *hbdecim_create(size_t num_taps, const float *h);

void hbdecim_destroy(hbdecim_state_t *r);

void hbdecim_reset(hbdecim_state_t *r);

size_t hbdecim_execute(hbdecim_state_t      *r,
                       const float _Complex *in,
                       size_t                num_in,
                       float _Complex       *out,
                       size_t                max_out);

double hbdecim_get_rate(const hbdecim_state_t *r);

size_t hbdecim_get_num_taps(const hbdecim_state_t *r);

#ifdef __cplusplus
}
#endif

#endif /* HBDECIM_CORE_H */