]> sigrok.org Git - libsigrok.git/blobdiff - src/analog.c
analog.c: sr_analog_to_float(): Support for receiving double values.
[libsigrok.git] / src / analog.c
index 9e01566f8799b1e572d2e188e324391696b00569..4ec724cfde488a0ae4a37a5c2ab0f0b414264da8 100644 (file)
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <config.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
 #include <ctype.h>
-#include "libsigrok.h"
+#include <math.h>
+#include <libsigrok/libsigrok.h>
 #include "libsigrok-internal.h"
 
+/** @cond PRIVATE */
 #define LOG_PREFIX "analog"
+/** @endcond */
+
+/**
+ * @file
+ *
+ * Handling and converting analog data.
+ */
+
+/**
+ * @defgroup grp_analog Analog data handling
+ *
+ * Handling and converting analog data.
+ *
+ * @{
+ */
 
 struct unit_mq_string {
        uint64_t value;
-       char *str;
+       const char *str;
 };
 
+/* Please use the same order as in enum sr_unit (libsigrok.h). */
 static struct unit_mq_string unit_strings[] = {
        { SR_UNIT_VOLT, "V" },
        { SR_UNIT_AMPERE, "A" },
        { SR_UNIT_OHM, "\xe2\x84\xa6" },
        { SR_UNIT_FARAD, "F" },
-       { SR_UNIT_HENRY, "H" },
        { SR_UNIT_KELVIN, "K" },
        { SR_UNIT_CELSIUS, "\xc2\xb0""C" },
        { SR_UNIT_FAHRENHEIT, "\xc2\xb0""F" },
        { SR_UNIT_HERTZ, "Hz" },
        { SR_UNIT_PERCENTAGE, "%" },
+       { SR_UNIT_BOOLEAN, "" },
        { SR_UNIT_SECOND, "s" },
        { SR_UNIT_SIEMENS, "S" },
-       { SR_UNIT_DECIBEL_MW, "dBu" },
-       { SR_UNIT_DECIBEL_VOLT, "dBv" },
+       { SR_UNIT_DECIBEL_MW, "dBm" },
+       { SR_UNIT_DECIBEL_VOLT, "dBV" },
+       { SR_UNIT_UNITLESS, "" },
        { SR_UNIT_DECIBEL_SPL, "dB" },
        { SR_UNIT_CONCENTRATION, "ppm" },
        { SR_UNIT_REVOLUTIONS_PER_MINUTE, "RPM" },
@@ -56,19 +76,26 @@ static struct unit_mq_string unit_strings[] = {
        { SR_UNIT_HECTOPASCAL, "hPa" },
        { SR_UNIT_HUMIDITY_293K, "%rF" },
        { SR_UNIT_DEGREE, "\xc2\xb0" },
+       { SR_UNIT_HENRY, "H" },
+       { SR_UNIT_GRAM, "g" },
+       { SR_UNIT_CARAT, "ct" },
+       { SR_UNIT_OUNCE, "oz" },
+       { SR_UNIT_TROY_OUNCE, "oz t" },
+       { SR_UNIT_POUND, "lb" },
+       { SR_UNIT_PENNYWEIGHT, "dwt" },
+       { SR_UNIT_GRAIN, "gr" },
+       { SR_UNIT_TAEL, "tael" },
+       { SR_UNIT_MOMME, "momme" },
+       { SR_UNIT_TOLA, "tola" },
+       { SR_UNIT_PIECE, "pcs" },
+       { SR_UNIT_JOULE, "J" },
+       { SR_UNIT_COULOMB, "C" },
+       { SR_UNIT_AMPERE_HOUR, "Ah" },
        ALL_ZERO
 };
 
+/* Please use the same order as in enum sr_mqflag (libsigrok.h). */
 static struct unit_mq_string mq_strings[] = {
-       { SR_MQFLAG_SPL_FREQ_WEIGHT_A, "(A)" },
-       { SR_MQFLAG_SPL_FREQ_WEIGHT_C, "(C)" },
-       { SR_MQFLAG_SPL_FREQ_WEIGHT_Z, "(Z)" },
-       { SR_MQFLAG_SPL_FREQ_WEIGHT_FLAT, "(SPL)" },
-       { SR_MQFLAG_SPL_TIME_WEIGHT_S, " S" },
-       { SR_MQFLAG_SPL_TIME_WEIGHT_F, " F" },
-       { SR_MQFLAG_SPL_LAT, " LAT" },
-       /* Not a standard function for SLMs, so this is a made-up notation. */
-       { SR_MQFLAG_SPL_PCT_OVER_ALARM, "%oA" },
        { SR_MQFLAG_AC, " AC" },
        { SR_MQFLAG_DC, " DC" },
        { SR_MQFLAG_RMS, " RMS" },
@@ -78,12 +105,25 @@ static struct unit_mq_string mq_strings[] = {
        { SR_MQFLAG_MIN, " MIN" },
        { SR_MQFLAG_AUTORANGE, " AUTO" },
        { SR_MQFLAG_RELATIVE, " REL" },
+       { SR_MQFLAG_SPL_FREQ_WEIGHT_A, "(A)" },
+       { SR_MQFLAG_SPL_FREQ_WEIGHT_C, "(C)" },
+       { SR_MQFLAG_SPL_FREQ_WEIGHT_Z, "(Z)" },
+       { SR_MQFLAG_SPL_FREQ_WEIGHT_FLAT, "(SPL)" },
+       { SR_MQFLAG_SPL_TIME_WEIGHT_S, " S" },
+       { SR_MQFLAG_SPL_TIME_WEIGHT_F, " F" },
+       { SR_MQFLAG_SPL_LAT, " LAT" },
+       /* Not a standard function for SLMs, so this is a made-up notation. */
+       { SR_MQFLAG_SPL_PCT_OVER_ALARM, "%oA" },
+       { SR_MQFLAG_DURATION, " DURATION" },
        { SR_MQFLAG_AVG, " AVG" },
        { SR_MQFLAG_REFERENCE, " REF" },
+       { SR_MQFLAG_UNSTABLE, " UNSTABLE" },
+       { SR_MQFLAG_FOUR_WIRE, " 4-WIRE" },
        ALL_ZERO
 };
 
-SR_PRIV int sr_analog_init(struct sr_datafeed_analog2 *analog,
+/** @private */
+SR_PRIV int sr_analog_init(struct sr_datafeed_analog *analog,
                struct sr_analog_encoding *encoding,
                struct sr_analog_meaning *meaning,
                struct sr_analog_spec *spec,
@@ -117,99 +157,269 @@ SR_PRIV int sr_analog_init(struct sr_datafeed_analog2 *analog,
        return SR_OK;
 }
 
-SR_API int sr_analog_to_float(const struct sr_datafeed_analog2 *analog,
+/**
+ * Convert an analog datafeed payload to an array of floats.
+ *
+ * Sufficient memory for outbuf must have been pre-allocated by the caller,
+ * who is also responsible for freeing it when no longer needed.
+ *
+ * @param[in] analog The analog payload to convert. Must not be NULL.
+ *                   analog->data, analog->meaning, and analog->encoding
+ *                   must not be NULL.
+ * @param[out] outbuf Memory where to store the result. Must not be NULL.
+ *
+ * @retval SR_OK Success.
+ * @retval SR_ERR Unsupported encoding.
+ * @retval SR_ERR_ARG Invalid argument.
+ *
+ * @since 0.4.0
+ */
+SR_API int sr_analog_to_float(const struct sr_datafeed_analog *analog,
                float *outbuf)
 {
-       float offset;
-       unsigned int b, i;
+       unsigned int b, count;
        gboolean bigendian;
+       uint8_t conv_buf[sizeof(double)];
+       float *conv_f = (float*)conv_buf;
+       double *conv_d = (double*)conv_buf;
+
+       if (!analog || !(analog->data) || !(analog->meaning)
+                       || !(analog->encoding) || !outbuf)
+               return SR_ERR_ARG;
+
+       count = analog->num_samples * g_slist_length(analog->meaning->channels);
 
 #ifdef WORDS_BIGENDIAN
        bigendian = TRUE;
 #else
        bigendian = FALSE;
 #endif
+
        if (!analog->encoding->is_float) {
-               /* TODO */
-               sr_err("Only floating-point encoding supported so far.");
-               return SR_ERR;
+               float offset = analog->encoding->offset.p / (float)analog->encoding->offset.q;
+               float scale = analog->encoding->scale.p / (float)analog->encoding->scale.q;
+               gboolean is_signed = analog->encoding->is_signed;
+               gboolean is_bigendian = analog->encoding->is_bigendian;
+               int8_t *data8 = (int8_t *)(analog->data);
+               int16_t *data16 = (int16_t *)(analog->data);
+               int32_t *data32 = (int32_t *)(analog->data);
+
+               switch (analog->encoding->unitsize) {
+               case 1:
+                       if (is_signed) {
+                               for (unsigned int i = 0; i < count; i++) {
+                                       outbuf[i] = scale * data8[i];
+                                       outbuf[i] += offset;
+                               }
+                       } else {
+                               for (unsigned int i = 0; i < count; i++) {
+                                       outbuf[i] = scale * R8(data8 + i);
+                                       outbuf[i] += offset;
+                               }
+                       }
+                       break;
+               case 2:
+                       if (is_signed && is_bigendian) {
+                               for (unsigned int i = 0; i < count; i++) {
+                                       outbuf[i] = scale * RB16S(&data16[i]);
+                                       outbuf[i] += offset;
+                               }
+                       } else if (is_bigendian) {
+                               for (unsigned int i = 0; i < count; i++) {
+                                       outbuf[i] = scale * RB16(&data16[i]);
+                                       outbuf[i] += offset;
+                               }
+                       } else if (is_signed) {
+                               for (unsigned int i = 0; i < count; i++) {
+                                       outbuf[i] = scale * RL16S(&data16[i]);
+                                       outbuf[i] += offset;
+                               }
+                       } else {
+                               for (unsigned int i = 0; i < count; i++) {
+                                       outbuf[i] = scale * RL16(&data16[i]);
+                                       outbuf[i] += offset;
+                               }
+                       }
+                       break;
+               case 4:
+                       if (is_signed && is_bigendian) {
+                               for (unsigned int i = 0; i < count; i++) {
+                                       outbuf[i] = scale * RB32S(&data32[i]);
+                                       outbuf[i] += offset;
+                               }
+                       } else if (is_bigendian) {
+                               for (unsigned int i = 0; i < count; i++) {
+                                       outbuf[i] = scale * RB32(&data32[i]);
+                                       outbuf[i] += offset;
+                               }
+                       } else if (is_signed) {
+                               for (unsigned int i = 0; i < count; i++) {
+                                       outbuf[i] = scale * RL32S(&data32[i]);
+                                       outbuf[i] += offset;
+                               }
+                       } else {
+                               for (unsigned int i = 0; i < count; i++) {
+                                       outbuf[i] = scale * RL32(&data32[i]);
+                                       outbuf[i] += offset;
+                               }
+                       }
+                       break;
+               default:
+                       sr_err("Unsupported unit size '%d' for analog-to-float"
+                              " conversion.", analog->encoding->unitsize);
+                       return SR_ERR;
+               }
+               return SR_OK;
        }
 
        if (analog->encoding->unitsize == sizeof(float)
                        && analog->encoding->is_bigendian == bigendian
-                       && (analog->encoding->scale.p == analog->encoding->scale.q)
+                       && analog->encoding->scale.p == 1
+                       && analog->encoding->scale.q == 1
                        && analog->encoding->offset.p / (float)analog->encoding->offset.q == 0) {
                /* The data is already in the right format. */
-               memcpy(outbuf, analog->data, analog->num_samples * sizeof(float));
+               memcpy(outbuf, analog->data, count * sizeof(float));
        } else {
-               for (i = 0; i < analog->num_samples; i += analog->encoding->unitsize) {
+               for (unsigned int i = 0; i < count; i++) {
                        for (b = 0; b < analog->encoding->unitsize; b++) {
                                if (analog->encoding->is_bigendian == bigendian)
-                                       outbuf[i + b] = ((float *)analog->data)[i * analog->encoding->unitsize + b];
+                                       conv_buf[b] =
+                                               ((uint8_t *)analog->data)[i * analog->encoding->unitsize + b];
                                else
-                                       outbuf[i + (analog->encoding->unitsize - b)] = ((float *)analog->data)[i * analog->encoding->unitsize + b];
+                                       conv_buf[analog->encoding->unitsize - b - 1] =
+                                               ((uint8_t *)analog->data)[i * analog->encoding->unitsize + b];
+                       }
+
+                       if (analog->encoding->unitsize == sizeof(float)) {
+                               if (analog->encoding->scale.p != 1
+                                   || analog->encoding->scale.q != 1)
+                                       *conv_f = (*conv_f * analog->encoding->scale.p) / analog->encoding->scale.q;
+                               float offset = ((float)analog->encoding->offset.p / (float)analog->encoding->offset.q);
+                               *conv_f += offset;
+
+                               outbuf[i] = *conv_f;
+                       }
+                       else if (analog->encoding->unitsize == sizeof(double)) {
+                               if (analog->encoding->scale.p != 1
+                                   || analog->encoding->scale.q != 1)
+                                       *conv_d = (*conv_d * analog->encoding->scale.p) / analog->encoding->scale.q;
+                               double offset = ((double)analog->encoding->offset.p / (double)analog->encoding->offset.q);
+                               *conv_d += offset;
+
+                               outbuf[i] = *conv_d;
+                       }
+                       else {
+                               sr_err("Unsupported floating-point unit size '%d' for analog-to-float"
+                                      " conversion.", analog->encoding->unitsize);
+                               return SR_ERR;
                        }
-                       if (analog->encoding->scale.p != analog->encoding->scale.q)
-                               outbuf[i] = (outbuf[i] * analog->encoding->scale.p) / analog->encoding->scale.q;
-                       offset = ((float)analog->encoding->offset.p / (float)analog->encoding->offset.q);
-                       outbuf[i] += offset;
                }
        }
 
        return SR_OK;
 }
 
-/*
- * Convert a floating point value to a string, limited to the given
- * number of decimal digits.
+/**
+ * Scale a float value to the appropriate SI prefix.
  *
- * @param value The value to convert.
- * @param digits Number of digits after the decimal point to print.
- * @param result Pointer to store result.
+ * @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.
  *
- * The string is allocated by the function and must be freed by the caller
- * after use by calling g_free().
+ * @return The SI prefix to which value was scaled, as a printable string.
  *
- * @retval SR_OK
+ * @since 0.5.0
+ */
+SR_API const char *sr_analog_si_prefix(float *value, int *digits)
+{
+/** @cond PRIVATE */
+#define NEG_PREFIX_COUNT 5 /* number of prefixes below unity */
+#define POS_PREFIX_COUNT (int)(ARRAY_SIZE(prefixes) - NEG_PREFIX_COUNT - 1)
+/** @endcond */
+       static const char *prefixes[] = { "f", "p", "n", "ยต", "m", "", "k", "M", "G", "T" };
+
+       if (!value || !digits || 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];
+}
+
+/**
+ * Check if a unit "accepts" an SI prefix.
  *
- * @since 0.4.0
+ * E.g. SR_UNIT_VOLT is SI prefix friendly while SR_UNIT_DECIBEL_MW or
+ * SR_UNIT_PERCENTAGE are not.
+ *
+ * @param[in] unit The unit to check for SI prefix "friendliness".
+ *
+ * @return TRUE if the unit "accept" an SI prefix.
+ *
+ * @since 0.5.0
  */
-SR_API int sr_analog_float_to_string(float value, int digits, char **result)
+SR_API gboolean sr_analog_si_prefix_friendly(enum sr_unit unit)
 {
-       int cnt, i;
-
-       /* This produces at least one too many digits */
-       *result = g_strdup_printf("%.*f", digits, value);
-       for (i = 0, cnt = 0; (*result)[i]; i++) {
-               if (isdigit((*result)[i++]))
-                       cnt++;
-               if (cnt == digits) {
-                       (*result)[i] = 0;
-                       break;
-               }
-       }
+       static const enum sr_unit prefix_friendly_units[] = {
+               SR_UNIT_VOLT,
+               SR_UNIT_AMPERE,
+               SR_UNIT_OHM,
+               SR_UNIT_FARAD,
+               SR_UNIT_KELVIN,
+               SR_UNIT_HERTZ,
+               SR_UNIT_SECOND,
+               SR_UNIT_SIEMENS,
+               SR_UNIT_VOLT_AMPERE,
+               SR_UNIT_WATT,
+               SR_UNIT_WATT_HOUR,
+               SR_UNIT_METER_SECOND,
+               SR_UNIT_HENRY,
+               SR_UNIT_GRAM
+       };
+       unsigned int i;
 
-       return SR_OK;
+       for (i = 0; i < ARRAY_SIZE(prefix_friendly_units); i++)
+               if (unit == prefix_friendly_units[i])
+                       return TRUE;
+
+       return FALSE;
 }
 
-/*
+/**
  * Convert the unit/MQ/MQ flags in the analog struct to a string.
  *
- * @param analog Struct containing the unit, MQ and MQ flags.
- * @param result Pointer to store result.
- *
  * The string is allocated by the function and must be freed by the caller
  * after use by calling g_free().
  *
- * @retval SR_OK
+ * @param[in] analog Struct containing the unit, MQ and MQ flags.
+ *                   Must not be NULL. analog->meaning must not be NULL.
+ * @param[out] result Pointer to store result. Must not be NULL.
+ *
+ * @retval SR_OK Success.
+ * @retval SR_ERR_ARG Invalid argument.
  *
  * @since 0.4.0
  */
-SR_API int sr_analog_unit_to_string(const struct sr_datafeed_analog2 *analog,
+SR_API int sr_analog_unit_to_string(const struct sr_datafeed_analog *analog,
                char **result)
 {
        int i;
-       GString *buf = g_string_new(NULL);
+       GString *buf;
+
+       if (!analog || !(analog->meaning) || !result)
+               return SR_ERR_ARG;
+
+       buf = g_string_new(NULL);
 
        for (i = 0; unit_strings[i].value; i++) {
                if (analog->meaning->unit == unit_strings[i].value) {
@@ -229,3 +439,218 @@ SR_API int sr_analog_unit_to_string(const struct sr_datafeed_analog2 *analog,
        return SR_OK;
 }
 
+/**
+ * Set sr_rational r to the given value.
+ *
+ * @param[out] r Rational number struct to set. Must not be NULL.
+ * @param[in] p Numerator.
+ * @param[in] q Denominator.
+ *
+ * @since 0.4.0
+ */
+SR_API void sr_rational_set(struct sr_rational *r, int64_t p, uint64_t q)
+{
+       if (!r)
+               return;
+
+       r->p = p;
+       r->q = q;
+}
+
+#ifndef HAVE___INT128_T
+struct sr_int128_t {
+       int64_t high;
+       uint64_t low;
+};
+
+struct sr_uint128_t {
+       uint64_t high;
+       uint64_t low;
+};
+
+static void mult_int64(struct sr_int128_t *res, const int64_t a,
+       const int64_t b)
+{
+       uint64_t t1, t2, t3, t4;
+
+       t1 = (UINT32_MAX & a) * (UINT32_MAX & b);
+       t2 = (UINT32_MAX & a) * (b >> 32);
+       t3 = (a >> 32) * (UINT32_MAX & b);
+       t4 = (a >> 32) * (b >> 32);
+
+       res->low = t1 + (t2 << 32) + (t3 << 32);
+       res->high = (t1 >> 32) + (uint64_t)((uint32_t)(t2)) + (uint64_t)((uint32_t)(t3));
+       res->high >>= 32;
+       res->high += ((int64_t)t2 >> 32) + ((int64_t)t3 >> 32) + t4;
+}
+
+static void mult_uint64(struct sr_uint128_t *res, const uint64_t a,
+       const uint64_t b)
+{
+       uint64_t t1, t2, t3, t4;
+
+       // (x1 + x2) * (y1 + y2) = x1*y1 + x1*y2 + x2*y1 + x2*y2
+       t1 = (UINT32_MAX & a) * (UINT32_MAX & b);
+       t2 = (UINT32_MAX & a) * (b >> 32);
+       t3 = (a >> 32) * (UINT32_MAX & b);
+       t4 = (a >> 32) * (b >> 32);
+
+       res->low = t1 + (t2 << 32) + (t3 << 32);
+       res->high = (t1 >> 32) + (uint64_t)((uint32_t)(t2)) + (uint64_t)((uint32_t)(t3));
+       res->high >>= 32;
+       res->high += ((int64_t)t2 >> 32) + ((int64_t)t3 >> 32) + t4;
+}
+#endif
+
+/**
+ * Compare two sr_rational for equality.
+ *
+ * The values are compared for numerical equality, i.e. 2/10 == 1/5.
+ *
+ * @param[in] a First value.
+ * @param[in] b Second value.
+ *
+ * @retval 1 if both values are equal.
+ * @retval 0 Otherwise.
+ *
+ * @since 0.5.0
+ */
+SR_API int sr_rational_eq(const struct sr_rational *a, const struct sr_rational *b)
+{
+#ifdef HAVE___INT128_T
+       __int128_t m1, m2;
+
+       /* p1/q1 = p2/q2  <=>  p1*q2 = p2*q1 */
+       m1 = ((__int128_t)(b->p)) * ((__uint128_t)a->q);
+       m2 = ((__int128_t)(a->p)) * ((__uint128_t)b->q);
+
+       return (m1 == m2);
+
+#else
+       struct sr_int128_t m1, m2;
+
+       mult_int64(&m1, a->q, b->p);
+       mult_int64(&m2, a->p, b->q);
+
+       return (m1.high == m2.high) && (m1.low == m2.low);
+#endif
+}
+
+/**
+ * Multiply two sr_rational.
+ *
+ * The resulting nominator/denominator are reduced if the result would not fit
+ * otherwise. If the resulting nominator/denominator are relatively prime,
+ * this may not be possible.
+ *
+ * It is safe to use the same variable for result and input values.
+ *
+ * @param[in] a First value.
+ * @param[in] b Second value.
+ * @param[out] res Result.
+ *
+ * @retval SR_OK Success.
+ * @retval SR_ERR_ARG Resulting value too large.
+ *
+ * @since 0.5.0
+ */
+SR_API int sr_rational_mult(struct sr_rational *res, const struct sr_rational *a,
+       const struct sr_rational *b)
+{
+#ifdef HAVE___INT128_T
+       __int128_t p;
+       __uint128_t q;
+
+       p = (__int128_t)(a->p) * (__int128_t)(b->p);
+       q = (__uint128_t)(a->q) * (__uint128_t)(b->q);
+
+       if ((p > INT64_MAX) || (p < INT64_MIN) || (q > UINT64_MAX)) {
+               while (!((p & 1) || (q & 1))) {
+                       p /= 2;
+                       q /= 2;
+               }
+       }
+
+       if ((p > INT64_MAX) || (p < INT64_MIN) || (q > UINT64_MAX)) {
+               // TODO: determine gcd to do further reduction
+               return SR_ERR_ARG;
+       }
+
+       res->p = (int64_t)p;
+       res->q = (uint64_t)q;
+
+       return SR_OK;
+
+#else
+       struct sr_int128_t p;
+       struct sr_uint128_t q;
+
+       mult_int64(&p, a->p, b->p);
+       mult_uint64(&q, a->q, b->q);
+
+       while (!(p.low & 1) && !(q.low & 1)) {
+               p.low /= 2;
+               if (p.high & 1)
+                       p.low |= (1ll << 63);
+               p.high >>= 1;
+               q.low /= 2;
+               if (q.high & 1)
+                       q.low |= (1ll << 63);
+               q.high >>= 1;
+       }
+
+       if (q.high)
+               return SR_ERR_ARG;
+       if ((p.high >= 0) && (p.low > INT64_MAX))
+               return SR_ERR_ARG;
+       if (p.high < -1)
+               return SR_ERR_ARG;
+
+       res->p = (int64_t)p.low;
+       res->q = q.low;
+
+       return SR_OK;
+#endif
+}
+
+/**
+ * Divide rational a by rational b.
+ *
+ * The resulting nominator/denominator are reduced if the result would not fit
+ * otherwise. If the resulting nominator/denominator are relatively prime,
+ * this may not be possible.
+ *
+ * It is safe to use the same variable for result and input values.
+ *
+ * @param[in] num Numerator.
+ * @param[in] div Divisor.
+ * @param[out] res Result.
+ *
+ * @retval SR_OK Success.
+ * @retval SR_ERR_ARG Division by zero, denominator of divisor too large,
+ *                    or resulting value too large.
+ *
+ * @since 0.5.0
+ */
+SR_API int sr_rational_div(struct sr_rational *res, const struct sr_rational *num,
+       const struct sr_rational *div)
+{
+       struct sr_rational t;
+
+       if (div->q > INT64_MAX)
+               return SR_ERR_ARG;
+       if (div->p == 0)
+               return SR_ERR_ARG;
+
+       if (div->p > 0) {
+               t.p = div->q;
+               t.q = div->p;
+       } else {
+               t.p = -div->q;
+               t.q = -div->p;
+       }
+
+       return sr_rational_mult(res, num, &t);
+}
+
+/** @} */