hpf.h

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#ifndef LIBA_HPF_H
#define LIBA_HPF_H
 
#include "math.h"
 
typedef struct a_hpf
{
    a_float alpha; 
    a_float output; 
    a_float input; 
#if defined(__cplusplus)
    A_INLINE void gen(a_float fc, a_float ts)
    {
        alpha = 1 / (A_FLOAT_TAU * fc * ts + 1);
    }
    A_INLINE a_float operator()(a_float 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
#if defined(__cplusplus)
#define A_HPF_INIT(alpha) {a_float_c(alpha), 0, 0}
#define A_HPF_INIT2(fc, ts) {A_HPF_GEN(fc, ts), 0, 0}
#else /* !__cplusplus */
#define A_HPF_INIT(alpha) (a_hpf){a_float_c(alpha), 0, 0}
#define A_HPF_INIT2(fc, ts) (a_hpf){A_HPF_GEN(fc, ts), 0, 0}
#endif /* __cplusplus */
// clang-format on
#define A_HPF_GEN(fc, ts) (1 / (A_FLOAT_TAU * a_float_c(fc) * a_float_c(ts) + 1))
 
A_INTERN a_float a_hpf_gen(a_float fc, a_float ts)
{
    return 1 / (A_FLOAT_TAU * fc * ts + 1);
}
 
A_INTERN void a_hpf_init(a_hpf *ctx, a_float alpha)
{
    ctx->alpha = alpha;
    ctx->output = 0;
    ctx->input = 0;
}
 
A_INTERN a_float a_hpf_iter(a_hpf *ctx, a_float 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 */