From 78603c50f61f74624218459ad6d8e212d36e681f Mon Sep 17 00:00:00 2001
From: Gregor Kleen <kleen@cip.ifi.lmu.de>
Date: Thu, 3 Nov 2016 13:05:49 +0100
Subject: temperaturUmrechner

---
 .gitignore            |   1 +
 Makefile              |  15 ++++++
 default.nix           |  10 ++++
 temperaturUmrechner.c | 139 ++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 165 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 default.nix
 create mode 100644 temperaturUmrechner.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..41fbeb0
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+**/result
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..ae2159d
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,15 @@
+CC = gcc
+CCFLAGS = -owall
+INCLUDES = 
+PREFIX = /usr/local
+
+.PHONY: all install
+
+all: temperaturUmrechner
+
+install:
+	mkdir -p $(PREFIX)/bin
+	install -m 0755 -t $(PREFIX)/bin temperaturUmrechner
+
+temperaterUmrechner:
+	$(CC) $(INCLUDES) $(CCFLAGS) -o temperaturUmrechner temperaturUmrechner.c
diff --git a/default.nix b/default.nix
new file mode 100644
index 0000000..665253c
--- /dev/null
+++ b/default.nix
@@ -0,0 +1,10 @@
+{ stdenv
+}:
+
+stdenv.mkDerivation {
+  name = "sysprak.exc";
+  src = ./.;
+  preInstall = ''
+    sed -i s,/usr/local,$out, Makefile
+  '';
+}
diff --git a/temperaturUmrechner.c b/temperaturUmrechner.c
new file mode 100644
index 0000000..25ecc31
--- /dev/null
+++ b/temperaturUmrechner.c
@@ -0,0 +1,139 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <getopt.h>
+
+/* Supported units and string conversion */
+typedef enum TemperatureUnit { CELSIUS, DELISLE, FARENHEIT, KELVIN, RANKINE } TemperatureUnit;
+const TemperatureUnit temperatureUnits[] = { CELSIUS, DELISLE, FARENHEIT, KELVIN, RANKINE };
+const char* temperatureUnitNames[] = { "Celsius", "Delisle", "Farenheit", "Kelvin", "Rankine" };
+
+/* Conversion table to kelvin */
+const double kelvinMult[] = {1., -2. / 3., 5. / 9., 1, 5. / 9.};
+const double kelvinAdd[] = {273.15, 373.15, 255.37, 0, 0};
+
+static int const maxUnitLength = 31; // Maximum Length of members of temperatureUnitNames (not counting trailing \0)
+static int const unknownUnit = -1; // Ugh.
+
+void printUsage()
+{
+  printf("usage: temperaturUmrechner {-f|--from} <UNIT> {-t|--to} <UNIT> [<VALUE> [...]]\n"
+         );
+}
+
+TemperatureUnit parseUnit(char str[])
+{
+  char lowerUnit[maxUnitLength + 1];
+  
+  char lowerStr[maxUnitLength + 1];
+  memset(lowerStr, '\0', maxUnitLength + 1);
+  strncpy(lowerStr, str, maxUnitLength);
+
+  for (int i = 0; i < maxUnitLength; i++)
+    {
+      if (lowerStr[i] == '\0')
+        break;
+
+      lowerStr[i] = tolower(lowerStr[i]);
+    }
+
+
+  for (int unit = 0; unit < (int)( sizeof(temperatureUnits) / sizeof(TemperatureUnit) ); unit++)
+    {
+      memset(lowerUnit, '\0', maxUnitLength + 1);
+      for (int i = 0; i < maxUnitLength; i++)
+        {
+          if (temperatureUnitNames[unit][i] == '\0')
+            break;
+
+          lowerUnit[i] = tolower(temperatureUnitNames[unit][i]);
+        }
+
+      if (strcmp(lowerUnit, lowerStr) == 0)
+        return temperatureUnits[unit];
+    }
+
+  return unknownUnit;
+}
+
+double convert(double value, TemperatureUnit fromUnit, TemperatureUnit toUnit)
+{
+  int fromUnitIndex = -1;
+  int toUnitIndex = -1;
+
+  for (int unit = 0; unit < (int)( sizeof(temperatureUnits) / sizeof(TemperatureUnit) ); unit++)
+    {
+      if (temperatureUnits[unit] == fromUnit)
+        fromUnitIndex = unit;
+
+      if (temperatureUnits[unit] == toUnit)
+        toUnitIndex = unit;
+
+      if (fromUnitIndex != -1 && toUnitIndex != -1)
+        break;
+    }
+
+  if (fromUnitIndex == -1 || toUnitIndex == -1)
+    abort();
+
+  return (value * kelvinMult[fromUnitIndex] + kelvinAdd[fromUnitIndex]) / kelvinMult[toUnitIndex] - kelvinAdd[toUnitIndex];
+}
+
+void main(int argc, char* argv[])
+{
+  TemperatureUnit fromUnit = unknownUnit;
+  TemperatureUnit toUnit = unknownUnit;
+
+  while (1) {
+    int c;
+    int optionIndex = 0;
+
+    static struct option longOptions[] = {
+      {"from", required_argument, 0, 'f'},
+      {"to", required_argument, 0, 't'},
+      {"help", no_argument, 0, 'h'},
+      {0, 0, 0, 0}
+    };
+
+    c = getopt_long(argc, argv, "f:t:h", longOptions, &optionIndex);
+
+    if (c == -1)
+      break;
+
+    switch (c)
+      {
+      case 'f':
+        fromUnit = parseUnit(optarg);
+        break;
+      case 't':
+        toUnit = parseUnit(optarg);
+        break;
+      case 'h':
+        printUsage();
+        exit(0);
+        break;
+      default:
+        printUsage();
+      }
+  }
+
+  if (fromUnit == unknownUnit)
+    fprintf(stderr, "Unknown (or unset) unit to convert from\n");
+  if (toUnit == unknownUnit)
+    fprintf(stderr, "Unknown (or unset) unit to convert to\n");
+
+  if (toUnit == unknownUnit || fromUnit == unknownUnit)
+    {
+      printUsage();
+      exit(2);
+    }
+
+  for (double value;optind < argc;optind++)
+    {
+      sscanf(argv[optind], "%lf", &value);
+      printf("%.3g\n", convert(value, fromUnit, toUnit));
+    }
+
+  exit(0);
+}
-- 
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