Use Huffman compression for blackbox data transfer

Conflicts:
	src/test/Makefile

src/main/common/huffman.c

@@ -0,0 +1,59 @@
+/*
+ * This file is part of Cleanflight.
+ *
+ * Cleanflight 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Cleanflight is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Cleanflight.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "huffman.h"
+
+
+int huffmanEncodeBuf(uint8_t *outBuf, int outBufLen, const uint8_t *inBuf, int inLen, const huffmanTable_t *huffmanTable)
+{
+    int ret = 0;
+
+    uint8_t *outByte = outBuf;
+    *outByte = 0;
+    uint8_t outBit = 0x80;
+    for (int ii = 0; ii< inLen; ++ii) {
+        const int huffCodeLen = huffmanTable[*inBuf].codeLen;
+        const uint16_t huffCode = huffmanTable[*inBuf].code;
+        ++inBuf;
+        uint16_t testBit = 0x8000;
+        for (int jj = 0; jj < huffCodeLen; ++jj) {
+            if (huffCode & testBit) {
+                *outByte |= outBit;
+            }
+            testBit >>= 1;
+            outBit >>= 1;
+            if (outBit == 0) {
+                outBit = 0x80;
+                ++outByte;
+                *outByte = 0;
+                ++ret;
+            }
+            if (ret >= outBufLen) {
+                return -1;
+            }
+        }
+    }
+    if (outBit != 0x80) {
+        // ensure last character in output buffer is counted
+        ++ret;
+    }
+    return ret;
+}
+