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analog: improve output readability by using SI prefix

This commit is contained in:
Aurelien Jacobs 2016-08-28 22:11:20 +02:00 committed by Uwe Hermann
parent 6c1c13cdcd
commit 962172e495
4 changed files with 104 additions and 2 deletions
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1
include/libsigrok/proto.h
View File

@ -30,6 +30,7 @@
SR_API int sr_analog_to_float(const struct sr_datafeed_analog *analog,
float *buf);
SR_API const char *sr_analog_si_prefix(float *value, int *digits);
SR_API int sr_analog_unit_to_string(const struct sr_datafeed_analog *analog,
char **result);
SR_API void sr_rational_set(struct sr_rational *r, int64_t p, uint64_t q);

32
src/analog.c
View File

@ -22,6 +22,7 @@
#include <stdint.h>
#include <string.h>
#include <ctype.h>
#include <math.h>
#include <libsigrok/libsigrok.h>
#include "libsigrok-internal.h"
@ -292,6 +293,37 @@ SR_API int sr_analog_to_float(const struct sr_datafeed_analog *analog,
return SR_OK;
}
/**
* Scale a float value to the appropriate SI prefix.
*
* @param[in,out] value The float value to convert to appropriate SI prefix.
* @param[in,out] digits The number of significant decimal digits in value.
*
* @return The SI prefix to which value was scaled, as a printable string.
*
* @since 0.5.0
*/
SR_API const char *sr_analog_si_prefix(float *value, int *digits)
{
#define NEG_PREFIX_COUNT 5 /* number of prefixes below unity */
#define POS_PREFIX_COUNT (int)(ARRAY_SIZE(prefixes) - NEG_PREFIX_COUNT - 1)
static const char *prefixes[] = { "f","p","n","µ","m","","k","M","G","T" };
if (value == NULL || digits == NULL || isnan(*value))
return prefixes[NEG_PREFIX_COUNT];
float logval = log10f(fabsf(*value));
int prefix = (logval / 3) - (logval < 1);
if (prefix < -NEG_PREFIX_COUNT) prefix = -NEG_PREFIX_COUNT;
if (3 * prefix < -*digits) prefix = (-*digits + 2 * (*digits < 0)) / 3;
if (prefix > POS_PREFIX_COUNT) prefix = POS_PREFIX_COUNT;
*value *= powf(10, -3 * prefix);
*digits += 3 * prefix;
return prefixes[prefix + NEG_PREFIX_COUNT];
}
/**
* Convert the unit/MQ/MQ flags in the analog struct to a string.
*

6
src/output/analog.c
View File

@ -116,13 +116,15 @@ static int receive(const struct sr_output *o, const struct sr_datafeed_packet *p
sr_analog_unit_to_string(analog, &suffix);
for (i = 0; i < analog->num_samples; i++) {
for (l = analog->meaning->channels, c = 0; l; l = l->next, c++) {
float value = fdata[i * num_channels + c];
const char *prefix = sr_analog_si_prefix(&value, &digits);
ch = l->data;
g_string_append_printf(*out, "%s: ", ch->name);
number = g_strdup_printf("%.*f", MAX(digits, 0),
fdata[i * num_channels + c]);
number = g_strdup_printf("%.*f", MAX(digits, 0), value);
g_string_append(*out, number);
g_free(number);
g_string_append(*out, " ");
g_string_append(*out, prefix);
g_string_append(*out, suffix);
g_string_append(*out, "\n");
}

67
tests/analog.c
View File

@ -124,6 +124,71 @@ START_TEST(test_analog_to_float_null)
}
END_TEST
START_TEST(test_analog_si_prefix)
{
struct {
float input_value;
int input_digits;
float output_value;
int output_digits;
const char *output_si_prefix;
} v[] = {
{ 12.0 , 0, 12.0 , 0, "" },
{ 12.0 , 1, 12.0 , 1, "" },
{ 12.0 , -1, 0.012, 2, "k" },
{ 1024.0 , 0, 1.024, 3, "k" },
{ 1024.0 , -1, 1.024, 2, "k" },
{ 1024.0 , -3, 1.024, 0, "k" },
{ 12.0e5 , 0, 1.2, 6, "M" },
{ 0.123456, 0, 0.123456, 0, "" },
{ 0.123456, 1, 0.123456, 1, "" },
{ 0.123456, 2, 0.123456, 2, "" },
{ 0.123456, 3, 123.456, 0, "m" },
{ 0.123456, 4, 123.456, 1, "m" },
{ 0.123456, 5, 123.456, 2, "m" },
{ 0.123456, 6, 123.456, 3, "m" },
{ 0.123456, 7, 123.456, 4, "m" },
{ 0.0123 , 4, 12.3, 1, "m" },
{ 0.00123 , 5, 1.23, 2, "m" },
{ 0.000123, 4, 0.123, 1, "m" },
{ 0.000123, 5, 0.123, 2, "m" },
{ 0.000123, 6, 123.0, 0, "µ" },
{ 0.000123, 7, 123.0, 1, "µ" },
};
for (unsigned int i = 0; i < ARRAY_SIZE(v); i++) {
float value = v[i].input_value;
int digits = v[i].input_digits;
const char *si_prefix = sr_analog_si_prefix(&value, &digits);
fail_unless(fabs(value - v[i].output_value) <= 0.00001,
"sr_analog_si_prefix() unexpected output value %f (i=%d).",
value , i);
fail_unless(digits == v[i].output_digits,
"sr_analog_si_prefix() unexpected output digits %d (i=%d).",
digits, i);
fail_unless(!strcmp(si_prefix, v[i].output_si_prefix),
"sr_analog_si_prefix() unexpected output prefix \"%s\" (i=%d).",
si_prefix, i);
}
}
END_TEST
START_TEST(test_analog_si_prefix_null)
{
float value = 1.23;
int digits = 1;
const char *si_prefix;
si_prefix = sr_analog_si_prefix(NULL, &digits);
fail_unless(!strcmp(si_prefix, ""));
si_prefix = sr_analog_si_prefix(&value, NULL);
fail_unless(!strcmp(si_prefix, ""));
si_prefix = sr_analog_si_prefix(NULL, NULL);
fail_unless(!strcmp(si_prefix, ""));
}
END_TEST
START_TEST(test_analog_unit_to_string)
{
int ret;
@ -320,6 +385,8 @@ Suite *suite_analog(void)
tc = tcase_create("analog_to_float");
tcase_add_test(tc, test_analog_to_float);
tcase_add_test(tc, test_analog_to_float_null);
tcase_add_test(tc, test_analog_si_prefix);
tcase_add_test(tc, test_analog_si_prefix_null);
tcase_add_test(tc, test_analog_unit_to_string);
tcase_add_test(tc, test_analog_unit_to_string_null);
tcase_add_test(tc, test_set_rational);