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[rtl-433.git] / src / util.c

diff --git a/src/util.c b/src/util.c
new file mode 100644 (file)
index 0000000..4684bb7
--- /dev/null
+++ b/src/util.c
@@ -0,0 +1,166 @@
+/**
+ * Various utility functions for use by device drivers
+ * 
+ * Copyright (C) 2015 Tommy Vestermark
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include "util.h"
+#include <stdio.h>
+
+uint8_t reverse8(uint8_t x) {
+    x = (x & 0xF0) >> 4 | (x & 0x0F) << 4;
+    x = (x & 0xCC) >> 2 | (x & 0x33) << 2;
+    x = (x & 0xAA) >> 1 | (x & 0x55) << 1;
+    return x;
+}
+
+
+uint8_t crc8(uint8_t const message[], unsigned nBytes, uint8_t polynomial, uint8_t init) {
+    uint8_t remainder = init;  
+    unsigned byte, bit;
+
+    for (byte = 0; byte < nBytes; ++byte) {
+        remainder ^= message[byte];
+        for (bit = 0; bit < 8; ++bit) {
+            if (remainder & 0x80) {
+                remainder = (remainder << 1) ^ polynomial;
+            }
+            else {
+                remainder = (remainder << 1);
+            }
+        }
+    }
+    return remainder;
+}
+
+
+uint8_t crc8le(uint8_t const message[], unsigned nBytes, uint8_t polynomial, uint8_t init) {
+    uint8_t crc = init, i;     
+    unsigned byte;
+    uint8_t bit;
+
+
+    for (byte = 0; byte < nBytes; ++byte) {
+       for (i = 0x01; i & 0xff; i <<= 1) {
+           bit = (crc & 0x80) == 0x80;     
+           if (message[byte] & i) {
+               bit = !bit;
+           }
+           crc <<= 1;
+           if (bit) {
+               crc ^= polynomial;
+           }
+       }
+       crc &= 0xff;
+    }
+
+    return reverse8(crc);
+}
+
+uint16_t crc16(uint8_t const message[], unsigned nBytes, uint16_t polynomial, uint16_t init) {
+    uint16_t remainder = init;
+    unsigned byte, bit;
+
+    for (byte = 0; byte < nBytes; ++byte) {
+        remainder ^= message[byte];
+        for (bit = 0; bit < 8; ++bit) {
+            if (remainder & 1) {
+                remainder = (remainder >> 1) ^ polynomial;
+            }
+            else {
+                remainder = (remainder >> 1);
+            }
+        }
+    }
+    return remainder;
+}
+
+uint16_t crc16_ccitt(uint8_t const message[], unsigned nBytes, uint16_t polynomial, uint16_t init) {
+    uint16_t remainder = init;
+    unsigned byte, bit;
+
+    for (byte = 0; byte < nBytes; ++byte) {
+        remainder ^= message[byte] << 8;
+        for (bit = 0; bit < 8; ++bit) {
+            if (remainder & 0x8000) {
+                remainder = (remainder << 1) ^ polynomial;
+            }
+            else {
+                remainder = (remainder << 1);
+            }
+        }
+    }
+    return remainder;
+}
+
+
+
+int byteParity(uint8_t inByte){
+    inByte ^= inByte >> 4;
+    inByte &= 0xf;
+    return (0x6996 >> inByte) & 1;
+}
+
+
+char* local_time_str(time_t time_secs, char *buf) {
+       time_t etime;
+       struct tm *tm_info;
+
+       if (time_secs == 0) {
+               extern float sample_file_pos;
+               if (sample_file_pos != -1.0) {
+                       snprintf(buf, LOCAL_TIME_BUFLEN, "@%fs", sample_file_pos);
+                       return buf;
+               }
+               time(&etime);
+       } else {
+               etime = time_secs;
+       }
+
+       tm_info = localtime(&etime);
+
+       strftime(buf, LOCAL_TIME_BUFLEN, "%Y-%m-%d %H:%M:%S", tm_info);
+       return buf;
+}
+
+float celsius2fahrenheit(float celsius)
+{
+  return celsius * 9 / 5 + 32;
+}
+
+
+float fahrenheit2celsius(float fahrenheit)
+{
+    return (fahrenheit - 32) / 1.8;
+}
+
+
+float kmph2mph(float kmph)
+{
+    return kmph / 1.609344;
+}
+
+float mph2kmph(float mph)
+{
+    return mph * 1.609344;
+}
+
+
+// Test code
+// gcc -I include/ -std=gnu99 -D _TEST src/util.c
+#ifdef _TEST
+int main(int argc, char **argv) {
+       fprintf(stderr, "util:: test\n");
+
+       uint8_t msg[] = {0x08, 0x0a, 0xe8, 0x80};
+
+       fprintf(stderr, "util::crc8(): odd parity:  %02X\n", crc8(msg, 3, 0x80));
+       fprintf(stderr, "util::crc8(): even parity: %02X\n", crc8(msg, 4, 0x80));
+
+       return 0;
+}
+#endif /* _TEST */