hpf.h

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#ifndef LIBA_HPF_H
#define LIBA_HPF_H
 
#include "math.h"


typedef struct a_hpf
{
    a_real alpha; 
    a_real output; 
    a_real input; 
#if defined(__cplusplus)
    A_INLINE void gen(a_real fc, a_real ts)
    {
        alpha = 1 / (A_REAL_TAU * fc * ts + 1);
    }
    A_INLINE a_real operator()(a_real x)
    {
        output = alpha * (output + x - input);
        return (void)(input = x), output;
    }
    A_INLINE void zero()
    {
        output = 0;
        input = 0;
    }
#endif /* __cplusplus */
} a_hpf;
#if defined(__cplusplus)
namespace a
{
typedef struct a_hpf hpf;
} /* namespace a */
#endif /* __cplusplus */
/* clang-format off */
#define A_HPF_1(alpha) {a_real_c(alpha), 0, 0}
#define A_HPF_2(fc, ts) {A_HPF_GEN(fc, ts), 0, 0}
/* clang-format on */
#define A_HPF_GEN(fc, ts) (1 / (A_REAL_TAU * a_real_c(fc) * a_real_c(ts) + 1))

A_INTERN a_real a_hpf_gen(a_real fc, a_real ts)
{
    return 1 / (A_REAL_TAU * fc * ts + 1);
}

A_INTERN void a_hpf_init(a_hpf *ctx, a_real alpha)
{
    ctx->alpha = alpha;
    ctx->output = 0;
    ctx->input = 0;
}

A_INTERN a_real a_hpf_iter(a_hpf *ctx, a_real x)
{
    ctx->output = ctx->alpha * (ctx->output + x - ctx->input);
    return (void)(ctx->input = x), ctx->output;
}

A_INTERN void a_hpf_zero(a_hpf *ctx)
{
    ctx->output = 0;
    ctx->input = 0;
}

 
#endif /* a/hpf.h */