Diff: libscpi/src/units.c

Revision:

0:be95bfb06686

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libscpi/src/units.c	Mon Jan 17 13:20:09 2022 +0000
@@ -0,0 +1,513 @@
+/*-
+ * BSD 2-Clause License
+ *
+ * Copyright (c) 2012-2018, Jan Breuer
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * @file   scpi_units.c
+ * @date   Thu Nov 15 10:58:45 UTC 2012
+ *
+ * @brief  SCPI units
+ *
+ *
+ */
+
+#include <string.h>
+#include "scpi/parser.h"
+#include "scpi/units.h"
+#include "utils_private.h"
+#include "scpi/utils.h"
+#include "scpi/error.h"
+#include "lexer_private.h"
+
+
+/*
+ * multipliers IEEE 488.2-1992 tab 7-2
+ * 1E18         EX
+ * 1E15         PE
+ * 1E12         T
+ * 1E9          G
+ * 1E6          MA (use M for OHM and HZ)
+ * 1E3          K
+ * 1E-3         M (disaalowed for OHM and HZ)
+ * 1E-6         U
+ * 1E-9         N
+ * 1E-12        P
+ * 1E-15        F
+ * 1E-18        A
+ */
+
+/*
+ * units definition IEEE 488.2-1992 tab 7-1
+ */
+const scpi_unit_def_t scpi_units_def[] = {
+#if USE_UNITS_PARTICLES
+    /* Absorbet dose */
+    {/* name */ "GY", /* unit */ SCPI_UNIT_GRAY, /* mult */ 1},
+
+    /* Activity of radionuclide */
+    {/* name */ "BQ", /* unit */ SCPI_UNIT_BECQUEREL, /* mult */ 1},
+
+    /* Amount of substance */
+    {/* name */ "MOL", /* unit */ SCPI_UNIT_MOLE, /* mult */ 1},
+
+    /* Dose equivalent */
+    {/* name */ "NSV", /* unit */ SCPI_UNIT_SIEVERT, /* mult */ 1e-9},
+    {/* name */ "USV", /* unit */ SCPI_UNIT_SIEVERT, /* mult */ 1e-6},
+    {/* name */ "MSV", /* unit */ SCPI_UNIT_SIEVERT, /* mult */ 1e-3},
+    {/* name */ "SV", /* unit */ SCPI_UNIT_SIEVERT, /* mult */ 1},
+    {/* name */ "KSV", /* unit */ SCPI_UNIT_SIEVERT, /* mult */ 1e3},
+    {/* name */ "MASV", /* unit */ SCPI_UNIT_SIEVERT, /* mult */ 1e6},
+
+    /* Energy */
+    {/* name */ "EV", /* unit */ SCPI_UNIT_ELECTRONVOLT, /* mult */ 1},
+    {/* name */ "KEV", /* unit */ SCPI_UNIT_ELECTRONVOLT, /* mult */ 1e3},
+    {/* name */ "MAEV", /* unit */ SCPI_UNIT_ELECTRONVOLT, /* mult */ 1e6},
+    {/* name */ "GEV", /* unit */ SCPI_UNIT_ELECTRONVOLT, /* mult */ 1e9},
+    {/* name */ "TEV", /* unit */ SCPI_UNIT_ELECTRONVOLT, /* mult */ 1e12},
+
+    /* Mass */
+    {/* name */ "U", /* unit */ SCPI_UNIT_ATOMIC_MASS, /* mult */ 1},
+#endif /* USE_UNITS_PARTICLES */
+
+#if USE_UNITS_ANGLE
+    /* Angle */
+    {/* name */ "DEG", /* unit */ SCPI_UNIT_DEGREE, /* mult */ 1},
+    {/* name */ "GON", /* unit */ SCPI_UNIT_GRADE, /* mult */ 1},
+    {/* name */ "MNT", /* unit */ SCPI_UNIT_DEGREE, /* mult */ 1. / 60.},
+    {/* name */ "RAD", /* unit */ SCPI_UNIT_RADIAN, /* mult */ 1},
+    {/* name */ "SEC", /* unit */ SCPI_UNIT_DEGREE, /* mult */ 1. / 3600.},
+    {/* name */ "REV", /* unit */ SCPI_UNIT_REVOLUTION, /* mult */ 1},
+    {/* name */ "RS", /* unit */ SCPI_UNIT_STERADIAN, /* mult */ 1},
+#endif /* USE_UNITS_ANGLE */
+
+#if USE_UNITS_ELECTRIC
+    /* Electric - capacitance */
+    {/* name */ "PF", /* unit */ SCPI_UNIT_FARAD, /* mult */ 1e-12},
+    {/* name */ "NF", /* unit */ SCPI_UNIT_FARAD, /* mult */ 1e-9},
+    {/* name */ "UF", /* unit */ SCPI_UNIT_FARAD, /* mult */ 1e-6},
+    {/* name */ "MF", /* unit */ SCPI_UNIT_FARAD, /* mult */ 1e-3},
+    {/* name */ "F", /* unit */ SCPI_UNIT_FARAD, /* mult */ 1},
+
+    /* Electric - current */
+    {/* name */ "UA", /* unit */ SCPI_UNIT_AMPER, /* mult */ 1e-6},
+    {/* name */ "MA", /* unit */ SCPI_UNIT_AMPER, /* mult */ 1e-3},
+    {/* name */ "A", /* unit */ SCPI_UNIT_AMPER, /* mult */ 1},
+    {/* name */ "KA", /* unit */ SCPI_UNIT_AMPER, /* mult */ 1e3},
+
+    /* Electric - potential */
+    {/* name */ "UV", /* unit */ SCPI_UNIT_VOLT, /* mult */ 1e-6},
+    {/* name */ "MV", /* unit */ SCPI_UNIT_VOLT, /* mult */ 1e-3},
+    {/* name */ "V", /* unit */ SCPI_UNIT_VOLT, /* mult */ 1},
+    {/* name */ "KV", /* unit */ SCPI_UNIT_VOLT, /* mult */ 1e3},
+
+    /* Electric - resistance */
+    {/* name */ "OHM", /* unit */ SCPI_UNIT_OHM, /* mult */ 1},
+    {/* name */ "KOHM", /* unit */ SCPI_UNIT_OHM, /* mult */ 1e3},
+    {/* name */ "MOHM", /* unit */ SCPI_UNIT_OHM, /* mult */ 1e6},
+
+    /* Inductance */
+    {/* name */ "UH", /* unit */ SCPI_UNIT_HENRY, /* mult */ 1e-6},
+    {/* name */ "MH", /* unit */ SCPI_UNIT_HENRY, /* mult */ 1e-3},
+    {/* name */ "H", /* unit */ SCPI_UNIT_HENRY, /* mult */ 1},
+#endif /* USE_UNITS_ELECTRIC */
+
+#if USE_UNITS_ELECTRIC_CHARGE_CONDUCTANCE
+    /* Electric - charge */
+    {/* name */ "C", /* unit */ SCPI_UNIT_COULOMB, /* mult */ 1},
+
+    /* Electric - conductance */
+    {/* name */ "USIE", /* unit */ SCPI_UNIT_SIEMENS, /* mult */ 1e-6},
+    {/* name */ "MSIE", /* unit */ SCPI_UNIT_SIEMENS, /* mult */ 1e-3},
+    {/* name */ "SIE", /* unit */ SCPI_UNIT_SIEMENS, /* mult */ 1},
+#endif /* USE_UNITS_ELECTRIC_CHARGE_CONDUCTANCE */
+
+#if USE_UNITS_ENERGY_FORCE_MASS
+    /* Energy */
+    {/* name */ "J", /* unit */ SCPI_UNIT_JOULE, /* mult */ 1},
+    {/* name */ "KJ", /* unit */ SCPI_UNIT_JOULE, /* mult */ 1e3},
+    {/* name */ "MAJ", /* unit */ SCPI_UNIT_JOULE, /* mult */ 1e6},
+
+    /* Force */
+    {/* name */ "N", /* unit */ SCPI_UNIT_NEWTON, /* mult */ 1},
+    {/* name */ "KN", /* unit */ SCPI_UNIT_NEWTON, /* mult */ 1e3},
+
+    /* Pressure */
+    {/* name */ "ATM", /* unit */ SCPI_UNIT_ATMOSPHERE, /* mult */ 1},
+    {/* name */ "INHG", /* unit */ SCPI_UNIT_INCH_OF_MERCURY, /* mult */ 1},
+    {/* name */ "MMHG", /* unit */ SCPI_UNIT_MM_OF_MERCURY, /* mult */ 1},
+
+    {/* name */ "TORR", /* unit */ SCPI_UNIT_TORT, /* mult */ 1},
+    {/* name */ "BAR", /* unit */ SCPI_UNIT_BAR, /* mult */ 1},
+
+    {/* name */ "PAL", /* unit */ SCPI_UNIT_PASCAL, /* mult */ 1},
+    {/* name */ "KPAL", /* unit */ SCPI_UNIT_PASCAL, /* mult */ 1e3},
+    {/* name */ "MAPAL", /* unit */ SCPI_UNIT_PASCAL, /* mult */ 1e6},
+
+    /* Viscosity kinematic */
+    {/* name */ "ST", /* unit */ SCPI_UNIT_STROKES, /* mult */ 1},
+
+    /* Viscosity dynamic */
+    {/* name */ "P", /* unit */ SCPI_UNIT_POISE, /* mult */ 1},
+
+    /* Viscosity dynamic */
+    {/* name */ "L", /* unit */ SCPI_UNIT_LITER, /* mult */ 1},
+
+    /* Mass */
+    {/* name */ "MG", /* unit */ SCPI_UNIT_KILOGRAM, /* mult */ 1e-6},
+    {/* name */ "G", /* unit */ SCPI_UNIT_KILOGRAM, /* mult */ 1e-3},
+    {/* name */ "KG", /* unit */ SCPI_UNIT_KILOGRAM, /* mult */ 1},
+    {/* name */ "TNE", /* unit */ SCPI_UNIT_KILOGRAM, /* mult */ 1000},
+#endif /* USE_UNITS_ENERGY_FORCE_MASS */
+
+#if USE_UNITS_FREQUENCY
+    /* Frequency */
+    {/* name */ "HZ", /* unit */ SCPI_UNIT_HERTZ, /* mult */ 1},
+    {/* name */ "KHZ", /* unit */ SCPI_UNIT_HERTZ, /* mult */ 1e3},
+    {/* name */ "MHZ", /* unit */ SCPI_UNIT_HERTZ, /* mult */ 1e6},
+    {/* name */ "GHZ", /* unit */ SCPI_UNIT_HERTZ, /* mult */ 1e9},
+#endif /* USE_UNITS_FREQUENCY */
+
+#if USE_UNITS_DISTANCE
+    /* Length */
+    {/* name */ "ASU", /* unit */ SCPI_UNIT_ASTRONOMIC_UNIT, /* mult */ 1},
+    {/* name */ "PRS", /* unit */ SCPI_UNIT_PARSEC, /* mult */ 1},
+#if USE_UNITS_IMPERIAL
+    {/* name */ "IN", /* unit */ SCPI_UNIT_INCH, /* mult */ 1},
+    {/* name */ "FT", /* unit */ SCPI_UNIT_FOOT, /* mult */ 1},
+    {/* name */ "MI", /* unit */ SCPI_UNIT_MILE, /* mult */ 1},
+    {/* name */ "NAMI", /* unit */ SCPI_UNIT_NAUTICAL_MILE, /* mult */ 1},
+#endif /* USE_UNITS_IMPERIAL */
+
+    {/* name */ "NM", /* unit */ SCPI_UNIT_METER, /* mult */ 1e-9},
+    {/* name */ "UM", /* unit */ SCPI_UNIT_METER, /* mult */ 1e-6},
+    {/* name */ "MM", /* unit */ SCPI_UNIT_METER, /* mult */ 1e-3},
+    {/* name */ "M", /* unit */ SCPI_UNIT_METER, /* mult */ 1},
+    {/* name */ "KM", /* unit */ SCPI_UNIT_METER, /* mult */ 1e3},
+#endif /* USE_UNITS_DISTANCE */
+
+#if USE_UNITS_LIGHT
+    /* Illuminance */
+    {/* name */ "LX", /* unit */ SCPI_UNIT_LUX, /* mult */ 1},
+
+    /* Luminous flux */
+    {/* name */ "LM", /* unit */ SCPI_UNIT_LUMEN, /* mult */ 1},
+
+    /* Luminous intensity */
+    {/* name */ "CD", /* unit */ SCPI_UNIT_CANDELA, /* mult */ 1},
+#endif /* USE_UNITS_LIGHT */
+
+#if USE_UNITS_MAGNETIC
+    /* Magnetic flux */
+    {/* name */ "WB", /* unit */ SCPI_UNIT_WEBER, /* mult */ 1},
+
+    /* Magnetic induction */
+    {/* name */ "NT", /* unit */ SCPI_UNIT_TESLA, /* mult */ 1e-9},
+    {/* name */ "UT", /* unit */ SCPI_UNIT_TESLA, /* mult */ 1e-6},
+    {/* name */ "MT", /* unit */ SCPI_UNIT_TESLA, /* mult */ 1e-3},
+    {/* name */ "T", /* unit */ SCPI_UNIT_TESLA, /* mult */ 1},
+#endif /* USE_UNITS_MAGNETIC */
+
+#if USE_UNITS_POWER
+    /* Power */
+    {/* name */ "W", /* unit */ SCPI_UNIT_WATT, /* mult */ 1},
+    {/* name */ "DBM", /* unit */ SCPI_UNIT_DBM, /* mult */ 1},
+    {/* name */ "DBMW", /* unit */ SCPI_UNIT_DBM, /* mult */ 1},
+#endif /* USE_UNITS_POWER  */
+
+#if USE_UNITS_RATIO
+    /* Ratio */
+    {/* name */ "DB", /* unit */ SCPI_UNIT_DECIBEL, /* mult */ 1},
+    {/* name */ "PCT", /* unit */ SCPI_UNIT_UNITLESS, /* mult */ 1e-2},
+    {/* name */ "PPM", /* unit */ SCPI_UNIT_UNITLESS, /* mult */ 1e-6},
+#endif /* USE_UNITS_RATIO */
+
+#if USE_UNITS_TEMPERATURE
+    /* Temperature */
+    {/* name */ "CEL", /* unit */ SCPI_UNIT_CELSIUS, /* mult */ 1},
+#if USE_UNITS_IMPERIAL
+    {/* name */ "FAR", /* unit */ SCPI_UNIT_FAHRENHEIT, /* mult */ 1},
+#endif /* USE_UNITS_IMPERIAL */
+    {/* name */ "K", /* unit */ SCPI_UNIT_KELVIN, /* mult */ 1},
+#endif /* USE_UNITS_TEMPERATURE */
+
+#if USE_UNITS_TIME
+    /* Time */
+    {/* name */ "PS", /* unit */ SCPI_UNIT_SECOND, /* mult */ 1e-12},
+    {/* name */ "NS", /* unit */ SCPI_UNIT_SECOND, /* mult */ 1e-9},
+    {/* name */ "US", /* unit */ SCPI_UNIT_SECOND, /* mult */ 1e-6},
+    {/* name */ "MS", /* unit */ SCPI_UNIT_SECOND, /* mult */ 1e-3},
+    {/* name */ "S", /* unit */ SCPI_UNIT_SECOND, /* mult */ 1},
+    {/* name */ "MIN", /* unit */ SCPI_UNIT_SECOND, /* mult */ 60},
+    {/* name */ "HR", /* unit */ SCPI_UNIT_SECOND, /* mult */ 3600},
+    {/* name */ "D", /* unit */ SCPI_UNIT_DAY, /* mult */ 1},
+    {/* name */ "ANN", /* unit */ SCPI_UNIT_YEAR, /* mult */ 1},
+#endif /* USE_UNITS_TIME */
+
+    SCPI_UNITS_LIST_END,
+};
+
+/*
+ * Special number values definition
+ */
+const scpi_choice_def_t scpi_special_numbers_def[] = {
+    {/* name */ "MINimum", /* type */ SCPI_NUM_MIN},
+    {/* name */ "MAXimum", /* type */ SCPI_NUM_MAX},
+    {/* name */ "DEFault", /* type */ SCPI_NUM_DEF},
+    {/* name */ "UP", /* type */ SCPI_NUM_UP},
+    {/* name */ "DOWN", /* type */ SCPI_NUM_DOWN},
+    {/* name */ "NAN", /* type */ SCPI_NUM_NAN},
+    {/* name */ "INFinity", /* type */ SCPI_NUM_INF},
+    {/* name */ "NINF", /* type */ SCPI_NUM_NINF},
+    {/* name */ "AUTO", /* type */ SCPI_NUM_AUTO},
+    SCPI_CHOICE_LIST_END,
+};
+
+/**
+ * Convert string describing unit to its representation
+ * @param units units patterns
+ * @param unit text representation of unknown unit
+ * @param len length of text representation
+ * @return pointer of related unit definition or NULL
+ */
+static const scpi_unit_def_t * translateUnit(const scpi_unit_def_t * units, const char * unit, size_t len) {
+    int i;
+
+    if (units == NULL) {
+        return NULL;
+    }
+
+    for (i = 0; units[i].name != NULL; i++) {
+        if (compareStr(unit, len, units[i].name, strlen(units[i].name))) {
+            return &units[i];
+        }
+    }
+
+    return NULL;
+}
+
+/**
+ * Convert unit definition to string
+ * @param units units definitions (patterns)
+ * @param unit type of unit
+ * @return string representation of unit
+ */
+static const char * translateUnitInverse(const scpi_unit_def_t * units, const scpi_unit_t unit) {
+    int i;
+
+    if (units == NULL) {
+        return NULL;
+    }
+
+    for (i = 0; units[i].name != NULL; i++) {
+        if ((units[i].unit == unit) && (units[i].mult == 1)) {
+            return units[i].name;
+        }
+    }
+
+    return NULL;
+}
+
+/**
+ * Transform number to base units
+ * @param context
+ * @param unit text representation of unit
+ * @param len length of text representation
+ * @param value preparsed numeric value
+ * @return TRUE if value parameter was converted to base units
+ */
+static scpi_bool_t transformNumber(scpi_t * context, const char * unit, size_t len, scpi_number_t * value) {
+    size_t s;
+    const scpi_unit_def_t * unitDef;
+    s = skipWhitespace(unit, len);
+
+    if (s == len) {
+        value->unit = SCPI_UNIT_NONE;
+        return TRUE;
+    }
+
+    unitDef = translateUnit(context->units, unit + s, len - s);
+
+    if (unitDef == NULL) {
+        SCPI_ErrorPush(context, SCPI_ERROR_INVALID_SUFFIX);
+        return FALSE;
+    }
+
+    value->content.value *= unitDef->mult;
+    value->unit = unitDef->unit;
+
+    return TRUE;
+}
+
+/**
+ * Parse parameter as number, number with unit or special value (min, max, default, ...)
+ * @param context
+ * @param value return value
+ * @param mandatory if the parameter is mandatory
+ * @return
+ */
+scpi_bool_t SCPI_ParamNumber(scpi_t * context, const scpi_choice_def_t * special, scpi_number_t * value, scpi_bool_t mandatory) {
+    scpi_token_t token;
+    lex_state_t state;
+    scpi_parameter_t param;
+    scpi_bool_t result;
+    int32_t tag;
+
+    if (!value) {
+        SCPI_ErrorPush(context, SCPI_ERROR_SYSTEM_ERROR);
+        return FALSE;
+    }
+
+    result = SCPI_Parameter(context, &param, mandatory);
+
+    if (!result) {
+        return result;
+    }
+
+    state.buffer = param.ptr;
+    state.pos = state.buffer;
+    state.len = param.len;
+
+    switch (param.type) {
+        case SCPI_TOKEN_DECIMAL_NUMERIC_PROGRAM_DATA:
+        case SCPI_TOKEN_HEXNUM:
+        case SCPI_TOKEN_OCTNUM:
+        case SCPI_TOKEN_BINNUM:
+        case SCPI_TOKEN_DECIMAL_NUMERIC_PROGRAM_DATA_WITH_SUFFIX:
+        case SCPI_TOKEN_PROGRAM_MNEMONIC:
+            value->unit = SCPI_UNIT_NONE;
+            value->special = FALSE;
+            result = TRUE;
+            break;
+        default:
+            break;
+    }
+
+    switch (param.type) {
+        case SCPI_TOKEN_DECIMAL_NUMERIC_PROGRAM_DATA:
+        case SCPI_TOKEN_DECIMAL_NUMERIC_PROGRAM_DATA_WITH_SUFFIX:
+        case SCPI_TOKEN_PROGRAM_MNEMONIC:
+            value->base = 10;
+            break;
+        case SCPI_TOKEN_BINNUM:
+            value->base = 2;
+            break;
+        case SCPI_TOKEN_HEXNUM:
+            value->base = 16;
+            break;
+        case SCPI_TOKEN_OCTNUM:
+            value->base = 8;
+            break;
+        default:
+            break;
+    }
+
+    switch (param.type) {
+        case SCPI_TOKEN_DECIMAL_NUMERIC_PROGRAM_DATA:
+            SCPI_ParamToDouble(context, &param, &(value->content.value));
+            break;
+        case SCPI_TOKEN_HEXNUM:
+            SCPI_ParamToDouble(context, &param, &(value->content.value));
+            break;
+        case SCPI_TOKEN_OCTNUM:
+            SCPI_ParamToDouble(context, &param, &(value->content.value));
+            break;
+        case SCPI_TOKEN_BINNUM:
+            SCPI_ParamToDouble(context, &param, &(value->content.value));
+            break;
+        case SCPI_TOKEN_DECIMAL_NUMERIC_PROGRAM_DATA_WITH_SUFFIX:
+            scpiLex_DecimalNumericProgramData(&state, &token);
+            scpiLex_WhiteSpace(&state, &token);
+            scpiLex_SuffixProgramData(&state, &token);
+
+            SCPI_ParamToDouble(context, &param, &(value->content.value));
+
+            result = transformNumber(context, token.ptr, token.len, value);
+            break;
+        case SCPI_TOKEN_PROGRAM_MNEMONIC:
+            scpiLex_WhiteSpace(&state, &token);
+            scpiLex_CharacterProgramData(&state, &token);
+
+            /* convert string to special number type */
+            result = SCPI_ParamToChoice(context, &token, special, &tag);
+
+            value->special = TRUE;
+            value->content.tag = tag;
+
+            break;
+        default:
+            result = FALSE;
+    }
+
+    return result;
+}
+
+/**
+ * Convert scpi_number_t to string
+ * @param context
+ * @param value number value
+ * @param str target string
+ * @param len max length of string including null-character termination
+ * @return number of chars written to string
+ */
+size_t SCPI_NumberToStr(scpi_t * context, const scpi_choice_def_t * special, scpi_number_t * value, char * str, size_t len) {
+    const char * type;
+    const char * unit;
+    size_t result;
+
+    if (!value || !str || len==0) {
+        return 0;
+    }
+
+    if (value->special) {
+        if (SCPI_ChoiceToName(special, value->content.tag, &type)) {
+            strncpy(str, type, len);
+            result = SCPIDEFINE_strnlen(str, len - 1);
+            str[result] = '\0';
+            return result;
+        } else {
+            str[0] = '\0';
+            return 0;
+        }
+    }
+
+    result = SCPI_DoubleToStr(value->content.value, str, len);
+
+    if (result + 1 < len) {
+        unit = translateUnitInverse(context->units, value->unit);
+
+        if (unit) {
+            strncat(str, " ", len - result);
+            if (result + 2 < len) {
+                strncat(str, unit, len - result - 1);
+            }
+            result = strlen(str);
+        }
+    }
+
+    return result;
+}
+