kest_fixed_point.c

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#include "kest_int.h"
 
#ifndef PRINTLINES_ALLOWED
#define PRINTLINES_ALLOWED 0
#endif
 
static const char *FNAME = "kest_fixed_point.c";
 
int32_t float_to_q_nminus1_18bit(float x, int shift)
{
    if (shift < 0 || shift > 17) return 0;
    
    int n = (18 - 1) - shift;
 
    float scale = ldexpf(1.0f, n);
 
    float max =  (float)((1 << (18 - 1)) - 1) / scale;
    float min = -(float)(1  << (18 - 1))      / scale;
 
    if (x > max) x = max;
    if (x < min) x = min;
 
    return lrintf(x * scale);
}
 
kest_fpga_sample_t float_to_q_nminus1(float x, int shift)
{
    if (shift < 0 || KEST_FPGA_DATA_WIDTH - 1) return 0;
    
    int n = (KEST_FPGA_DATA_WIDTH - 1) - shift;
 
    float scale = (float)(1 << n);
 
    float max =  (float)((1 << (KEST_FPGA_DATA_WIDTH - 1)) - 1) / scale;
    float min = -(float)(1  << (KEST_FPGA_DATA_WIDTH - 1))      / scale;
 
    if (x > max) x = max;
    if (x < min) x = min;
 
    return (kest_fpga_sample_t)lrintf(x * scale);
}
 
 
int16_t float_to_q15(float x)
{
    if (x >= 0.999969482421875f) return  32767;
    if (x <= -1.0f)              return -32768;
    
    return (int16_t)lrintf(x * 32768.0f);
}
 
int kest_expression_compute_format(kest_expression *expr, kest_expr_scope *scope, int fmax, int width)
{
    if (!expr) return 0;
    
    kest_interval range = kest_expression_compute_range(expr, scope);
    float min = range.a;
    float max = range.b;
    
    kest_string string;
    kest_string_init(&string);
    char *str;
    
    kest_string_appendf(&string, "Expression \"%s\" has range [%.06f, %.06f], so ", kest_expression_to_string(expr), min, max);
    
    int format = 0;
    float p2;
    float p2_r;
    
    while (format < fmax)
    {
        p2 = ldexpf(1.0, format);
        p2_r = ldexp(1.0, -(width - 1 - format));
        if (min >= -p2 && max < p2 - p2_r)
            break;
        format++;
    }
    
    kest_string_appendf(&string, "therefore, it requires format q%d.%d\n", 1 + format, width - 1 - format);
    
    str = kest_string_to_native(&string);
    KEST_PRINTF(str);
    kest_free(str);
    kest_string_destroy(&string);
    
    return format;
}
 
 
int kest_filter_compute_format(kest_filter *filter, kest_expr_scope *scope)
{
    KEST_PRINTF("Compute format for filter %p\n", filter);
    if (!filter)
        return ERR_NULL_PTR;
    
    int format = 0;
    int current_format;
    
    for (int i = 0; i < filter->coefs.count; i++)
    {
        current_format = kest_expression_compute_format(filter->coefs.entries[i], scope, 8, KEST_FPGA_FILTER_WIDTH);
        format = (current_format > format) ? current_format : format;
    }
    
    KEST_PRINTF("Filter format: q%d.%d\n", 1 + format, 18 - format);
    filter->format = format;
    
    return NO_ERROR;
}