WIP: Units plugin

doc/news/_preparation_next_release.md

@@ -205,6 +205,10 @@ The following section lists news about the [modules](https://www.libelektra.org/
 - Fixed missing Metadata in README and METADATA.ini. _(Michael Zronek)_
 
 ### Specload
+### units
+
+- The [units](https://www.libelektra.org/plugins/units) plugin provides the capability to enter values with additional SI units. The unit will be checked if it as a valid SI base-unit,  additional SI prefixes will be validated and the value re-calculated to it's base-unit in respect to the prefix.  _(Josef Wechselauer)_
+- Work in Progress _(Josef Wechselauer)_
 
 - The [specload](https://www.libelektra.org/plugins/specload) plugin is a special storage plugin. Instead of using a storage file
   it calls an external application to request its specification. For the transfer it relies on the
@@ -235,6 +239,11 @@ The following section lists news about the [modules](https://www.libelektra.org/
 
 - [cache](https://www.libelektra.org/plugins/cache) is a new global caching plugin. It uses [mmapstorage](https://www.libelektra.org/plugins/mmapstorage) as its storage backend and lazily stores keysets from previous ´kdbGet()´ calls. We added initial support for the default resolver and multifile resolver. _(Mihael Pranjić)_
 
+### units
+
+- The [units](https://www.libelektra.org/plugins/units) plugin provides the capability to enter values with additional SI units. The unit will be checked if it as a valid SI base-unit,  additional SI prefixes will be validated and the value re-calculated to it's base-unit in respect to the prefix.  _(Josef Wechselauer)_
+- Work in Progress _(Josef Wechselauer)_
+
 ## Libraries
 
 The text below summarizes updates to the [C (and C++)-based libraries](https://www.libelektra.org/libraries/readme) of Elektra.

src/error/specification

@@ -1345,3 +1345,9 @@ description:the contract was malformed
 severity:error
 ingroup:kdb
 macro:MALFORMED_CONTRACT
+
+number:214
+description:value of key is not a valid SI-unit
+severity:error
+ingroup:plugin
+module:units

src/plugins/units/CMakeLists.txt

@@ -0,0 +1,6 @@
+include (LibAddMacros)
+
+add_plugin (units
+	    SOURCES units.h
+		    units.c
+	    TEST_README)

src/plugins/units/README.md

@@ -0,0 +1,56 @@
+- infos = Information about the units plugin is in keys below
+- infos/author = Josef Wechselauer <e1326671@student.tuwien.ac.at>
+- infos/licence = BSD
+- infos/needs =
+- infos/provides = check/transformation
+- infos/recommends =
+- infos/placements = presetstorage 
+- infos/status = unfinished
+- infos/metadata = check/units
+- infos/description = validates and transforms values entered as units
+
+## Introduction
+
+This plugin provides the capability to enter values with additional SI units. The unit will be checked if it as a valid SI base-unit,  additional SI prefixes will be validated and the value re-calculated to it's base-unit in respect to the prefix. 
+
+E.g. If the value **1 km** is entered, it will be checked if **m** is a valid SI unit and **k** is a valid SI prefix. If both are valid, the prefix will be used to calculate the correct value with the base unit, which would be 1000 m in this example. The value is stored without the SI unit (in this case without the **m**). 
+
+This plugin is written in C.
+
+## Usage
+
+## Dependencies
+
+None.
+
+## Examples
+
+```sh
+sudo kdb mount /tests/units.ini /tests/units ini units
+#> Mount a config file with the units plugin
+
+sudo kdb setmeta /tests/units check/units any
+#> Check the /tests/units key for validity
+
+kdb set /tests/units "1m"
+#> Suceeds, since the value is a valid decimal with SI-unit representation.
+
+kdb set /tests/units "35453.327468 µH"
+#> Suceeds, since the value is a valid decimal with SI-unit representation.
+
+kdb set /tests/units "32"
+#> Throws an error: value of key is not a representation for a value with a SI-unit
+
+kdb set /tests/units "12 n"
+#> Throws an error: value of key is not a representation for a value with a SI-unit
+#> This could be changed in a further step (see issue #1398) to be valid, as for example the user wants to enter 1k to represent 1000 without an SI-Unit. 
+#> For now, this is ignored as the entered units should be checked for correctness
+
+kdb set /tests/units 432 km
+#> Throws an error: quotes are expected.
+```
+
+
+## Limitations
+
+None.

src/plugins/units/units.c

@@ -0,0 +1,88 @@
+/**
+ * @file
+ *
+ * @brief Source file for the units plugin
+ *
+ * @copyright BSD License (see LICENSE.md or https://www.libelektra.org)
+ *
+ */
+
+#include <kdberrors.h>
+#include "units.h"
+#include <regex.h>
+#include <kdbhelper.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+int is_valid_key(Key * key, Key * parentKey)
+{
+	const Key * meta = keyGetMeta(key, "check/units");
+	if (!meta) return 1;
+	const char* value = keyString(key);
+	const char * prefix = "(Y|Z|E|P|T|G|M|k|h|da|d|c|m|µ|n|p|f|a|z|y)";
+    const char * unit = "?(m|g|s|A|K|mol|cd|rad|sr|Hz|N|Pa|J|W|C|V|F|Ω|Ohm|S|Wb|T|H|C|lm|lx|Bq|Gy|Sv|kat|l|L)";
+    char regexString[256];
+    snprintf(regexString, sizeof regexString, "%s%s%s%s%s", "^([0-9]+)\\.?([0-9]*)\\s*", prefix, "?", unit, "$");
+
+	regex_t regex;
+	regmatch_t offsets;
+	int compile_failure = regcomp (&regex, regexString, REG_NOSUB | REG_EXTENDED | REG_NEWLINE);
+	if (compile_failure) return -1;
+	// regexec returns 0 on a successful match
+	int match = !(regexec (&regex, value, 0, &offsets, 0));
+	regfree (&regex);
+
+	if(!match) {
+		ELEKTRA_SET_ERRORF (214, parentKey, "Validation of key %s with value %s failed.", keyName (key), keyString (key));
+	}
+
+	return match;
+
+}
+
+int elektraUnitsGet (Plugin * handle ELEKTRA_UNUSED, KeySet * returned, Key * parentKey)
+{
+	if (!elektraStrCmp (keyName (parentKey), "system/elektra/modules/units"))
+	{
+		KeySet * contract =
+			ksNew (30, keyNew ("system/elektra/modules/units", KEY_VALUE, "units plugin waits for your orders", KEY_END),
+			       keyNew ("system/elektra/modules/units/exports", KEY_END),
+			       keyNew ("system/elektra/modules/units/exports/get", KEY_FUNC, elektraUnitsGet, KEY_END),
+			       keyNew ("system/elektra/modules/units/exports/set", KEY_FUNC, elektraUnitsSet, KEY_END),
+#include ELEKTRA_README
+			       keyNew ("system/elektra/modules/units/infos/version", KEY_VALUE, PLUGINVERSION, KEY_END), KS_END);
+		ksAppend (returned, contract);
+		ksDel (contract);
+
+		return ELEKTRA_PLUGIN_STATUS_SUCCESS;
+	}
+	// get all keys
+
+	return ELEKTRA_PLUGIN_STATUS_NO_UPDATE;
+}
+
+int elektraUnitsSet (Plugin * handle ELEKTRA_UNUSED, KeySet * returned ELEKTRA_UNUSED, Key * parentKey ELEKTRA_UNUSED)
+{
+	// set all keys
+	// this function is optional
+	Key * cur;
+	ksRewind (returned);
+	while ((cur = ksNext (returned)) != NULL)
+	{
+		const Key * meta = keyGetMeta (cur, "check/units");
+		if (!meta) continue;
+		int is_valid = is_valid_key (cur, parentKey);
+		if (!is_valid) return ELEKTRA_PLUGIN_STATUS_ERROR;
+	}
+	return ELEKTRA_PLUGIN_STATUS_SUCCESS;
+}
+
+Plugin * ELEKTRA_PLUGIN_EXPORT
+{
+	// clang-format off
+	return elektraPluginExport ("units",
+		ELEKTRA_PLUGIN_GET,	&elektraUnitsGet,
+		ELEKTRA_PLUGIN_SET,	&elektraUnitsSet,
+		ELEKTRA_PLUGIN_END);
+}

src/plugins/units/units.h

@@ -0,0 +1,21 @@
+/**
+ * @file
+ *
+ * @brief Header file for the units plugin
+ *
+ * @copyright BSD License (see LICENSE.md or https://www.libelektra.org)
+ *
+ */
+
+#ifndef ELEKTRA_PLUGIN_UNITS_H
+#define ELEKTRA_PLUGIN_UNITS_H
+
+#include <kdbplugin.h>
+
+
+int elektraUnitsGet (Plugin * handle, KeySet * ks, Key * parentKey);
+int elektraUnitsSet (Plugin * handle, KeySet * ks, Key * parentKey);
+
+Plugin * ELEKTRA_PLUGIN_EXPORT;
+
+#endif