From: Aurelien Jacobs Date: Sun, 28 Aug 2016 20:11:20 +0000 (+0200) Subject: analog: improve output readability by using SI prefix X-Git-Tag: libsigrok-0.5.0~236 X-Git-Url: https://sigrok.org/gitweb/?p=libsigrok.git;a=commitdiff_plain;h=962172e4950f3fbc42d5a79cdf63dc179d7513be analog: improve output readability by using SI prefix --- diff --git a/include/libsigrok/proto.h b/include/libsigrok/proto.h index 1a3fba8c..c799919e 100644 --- a/include/libsigrok/proto.h +++ b/include/libsigrok/proto.h @@ -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); diff --git a/src/analog.c b/src/analog.c index 7343b481..634e9a67 100644 --- a/src/analog.c +++ b/src/analog.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #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. * diff --git a/src/output/analog.c b/src/output/analog.c index 5f77a59c..5e2b7cd5 100644 --- a/src/output/analog.c +++ b/src/output/analog.c @@ -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"); } diff --git a/tests/analog.c b/tests/analog.c index 3e8fd494..6dd82999 100644 --- a/tests/analog.c +++ b/tests/analog.c @@ -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);