correct CRC-32 implementation; remove old code;

edac/CRC.cpp

@@ -368,19 +368,23 @@ bool CRC::checkCRC32(const uint8_t *in, uint32_t length)
         uint8_t  crc8[4U];
     };
 
-    crc32 = 0xFFFFFFFFU;
+    uint32_t i = 0;
+    crc32 = 0x00000000U;
 
-    for (uint32_t i = 0U; i < (length - 4U); i++)
+    for (uint32_t j = (length - 4U); j-- > 0; i++) {
-        crc32 = (crc32 << 8) ^ CRC32_TABLE[((crc32 >> 24) ^ in[i]) & 0xFF];
+        uint32_t idx = ((crc32 >> 24) ^ in[i]) & 0xFFU;
+        crc32 = (CRC32_TABLE[idx] ^ (crc32 << 8)) & 0xFFFFFFFFU;
+    }
 
     crc32 = ~crc32;
+    crc32 &= 0xFFFFFFFFU;
 
 #if DEBUG_CRC
     uint32_t inCrc = (in[length - 4U] << 24) | (in[length - 3U] << 16) | (in[length - 2U] << 8) | (in[length - 1U] << 0);
     LogDebug(LOG_HOST, "CRC:checkCRC32(), crc = $%08X, in = $%08X, len = %u", crc32, inCrc, length);
 #endif
 
-    return crc8[0U] == in[length - 4U] && crc8[1U] == in[length - 3U] && crc8[2U] == in[length - 2U] && crc8[3U] == in[length - 1U];
+    return crc8[0U] == in[length - 1U] && crc8[1U] == in[length - 2U] && crc8[2U] == in[length - 3U] && crc8[3U] == in[length - 4U];
 }
 
 /// <summary>
@@ -398,21 +402,25 @@ void CRC::addCRC32(uint8_t* in, uint32_t length)
         uint8_t  crc8[4U];
     };
 
-    crc32 = 0xFFFFFFFFU;
+    uint32_t i = 0;
+    crc32 = 0x00000000U;
 
-    for (uint32_t i = 0U; i < (length - 4U); i++)
+    for (uint32_t j = (length - 4U); j-- > 0; i++) {
-        crc32 = (crc32 << 8) ^ CRC32_TABLE[((crc32 >> 24) ^ in[i]) & 0xFF];
+        uint32_t idx = ((crc32 >> 24) ^ in[i]) & 0xFFU;
+        crc32 = (CRC32_TABLE[idx] ^ (crc32 << 8)) & 0xFFFFFFFFU;
+    }
 
     crc32 = ~crc32;
+    crc32 &= 0xFFFFFFFFU;
 
 #if DEBUG_CRC
     LogDebug(LOG_HOST, "CRC:addCRC32(), crc = $%08X, len = %u", crc32, length);
 #endif
 
-    in[length - 4U] = crc8[0U];
+    in[length - 1U] = crc8[0U];
-    in[length - 3U] = crc8[1U];
+    in[length - 2U] = crc8[1U];
-    in[length - 2U] = crc8[2U];
+    in[length - 3U] = crc8[2U];
-    in[length - 1U] = crc8[3U];
+    in[length - 4U] = crc8[3U];
 }
 
 /// <summary>

edac/CRC.h

@@ -62,6 +62,9 @@ namespace edac
         /// <summary>Encode 32-bit CRC.</summary>
         static void addCRC32(uint8_t* in, uint32_t length);
 
+        /// <summary>Generate 32-bit CRC.</summary>
+        static uint32_t crc32(const uint8_t *in, uint32_t length);
+
         /// <summary>Generate 8-bit CRC.</summary>
         static uint8_t crc8(const uint8_t* in, uint32_t length);
 

p25/data/DataBlock.cpp

@@ -96,7 +96,6 @@ bool DataBlock::decode(const uint8_t* data, const DataHeader header)
             uint32_t count = P25_PDU_CONFIRMED_DATA_LENGTH_BYTES;
             if ((m_serialNo == (header.getBlocksToFollow() - 1) && header.getBlocksToFollow() > 1) ||
                 (m_headerSap == PDU_SAP_EXT_ADDR && m_serialNo == 0U)) {
-                count = P25_PDU_CONFIRMED_DATA_LENGTH_BYTES - 4U;
                 m_lastBlock = true;
             } else {
                 if (header.getBlocksToFollow() <= 1) {
@@ -115,6 +114,8 @@ bool DataBlock::decode(const uint8_t* data, const DataHeader header)
 
             // if this is extended addressing and the first block decode the SAP and LLId
             if (m_headerSap == PDU_SAP_EXT_ADDR && m_serialNo == 0U) {
+                count = P25_PDU_CONFIRMED_DATA_LENGTH_BYTES - 4U;                
+
                 m_sap = buffer[5U] & 0x3FU;                                              // Service Access Point
                 m_llId = (buffer[2U] << 16) + (buffer[3U] << 8) + buffer[4U];            // Logical Link ID
 
@@ -295,34 +296,3 @@ uint32_t DataBlock::getData(uint8_t* buffer) const
         return 0U;
     }
 }
-
-// ---------------------------------------------------------------------------
-//  Private Class Members
-// ---------------------------------------------------------------------------
-/// <summary>
-///
-/// </summary>
-/// <param name="buffer"></param>
-uint16_t DataBlock::crc9()
-{
-    assert(m_data != NULL);
-
-    uint16_t crc = 0x00U;
-/*
-    edac::CRC::tmp_bit_cnt = 135U;
-    edac::CRC::crc9(&crc, m_serialNo, 7U);
-    for (uint8_t i = 0; i < P25_PDU_CONFIRMED_DATA_LENGTH_BYTES; i++) {
-        edac::CRC::crc9(&crc, m_data[i], 8U);
-    }
-    edac::CRC::crc9Finish(&crc, 8U);
-
-    crc = ~crc;
-    crc &= 0x01FFU;
-    crc ^= 0x01FFU;
-
-#if DEBUG_P25_PDU_DATA
-    LogDebug(LOG_P25, "DataBlock::crc9(), crc = $%03X", crc);
-#endif
-*/
-    return crc;
-}

p25/data/DataBlock.h

@@ -86,9 +86,6 @@ namespace p25
             uint8_t m_headerSap;
 
             uint8_t* m_data;
-
-            /// <summary></summary>
-            uint16_t crc9();
         };
     } // namespace data
 } // namespace p25