diff --git a/include/rde_common.h b/include/rde_common.h
new file mode 100644
index 0000000..bb55a37
--- /dev/null
+++ b/include/rde_common.h
@@ -0,0 +1,218 @@
+#pragma once
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * @brief If expr is non zero, return with that value.
+ */
+#ifndef RETURN_IF_IERROR
+#define RETURN_IF_IERROR(expr)                                                 \
+    do                                                                         \
+    {                                                                          \
+        int __status = (expr);                                                 \
+        if (__status != 0)                                                     \
+        {                                                                      \
+            return __status;                                                   \
+        }                                                                      \
+    } while (0)
+#endif
+
+    /**
+     * @brief RDE BEJ decoding errors.
+     */
+    enum BejError
+    {
+        BejErrorNoError = 0,
+        BejErrorUnknown,
+        BejErrorInvalidSize,
+        BejErrorNotSuppoted,
+        BejErrorUnknownProperty,
+        BejErrorInvalidSchemaType,
+        BejErrorInvalidPropertyOffset,
+    };
+
+    /**
+     * @brief BEJ schema classes.
+     */
+    enum BejSchemaClass
+    {
+        BejMajorSchemaClass = 0,
+        BejEventSchemaClass = 1,
+        BejAnnotationSchemaClass = 2,
+        BejCollectionMemberTypeSchemaClass = 3,
+        BejErrorSchemaClass = 4,
+    };
+
+    /**
+     * @brief BEJ data types supported in BEJ version 0xF1F0F000.
+     */
+    enum BejPrincipalDataType
+    {
+        BejSet = 0,
+        BejArray = 1,
+        BejNull = 2,
+        BejInteger = 3,
+        BejEnum = 4,
+        BejString = 5,
+        BejReal = 6,
+        BejBoolean = 7,
+        BejBytestring = 8,
+        BejChoice = 9,
+        BejPropertyAnnotation = 10,
+        Reserved1 = 11,
+        Reserved2 = 12,
+        Reserved3 = 13,
+        BejResourceLink = 14,
+        BejResourceLinkExpansion = 15,
+    };
+
+    /**
+     * @brief Format BEJ tuple.
+     */
+    struct BejTupleF
+    {
+        uint8_t deferredBinding : 1;
+        uint8_t readOnlyProperty : 1;
+        uint8_t nullableProperty : 1;
+        uint8_t reserved : 1;
+        enum BejPrincipalDataType principalDataType : 4;
+    } __attribute__((__packed__));
+
+    /**
+     * @brief Sequence Number BEJ tuple.
+     */
+    struct BejTupleS
+    {
+        uint8_t schema;
+        // Dictionaries contain 16bit sequence numbers. So allocating 16bits for
+        // the sequence number here.
+        uint16_t sequenceNumber;
+    };
+
+    /**
+     * @brief Represent offsets of Format, Value Length and Value of a SFLV
+     * tuple.
+     */
+    struct BejSFLVOffset
+    {
+        uint32_t formatOffset;
+        uint32_t valueLenNnintOffset;
+        uint32_t valueOffset;
+    };
+
+    /**
+     * @brief Fields in Bej Real data type.
+     */
+    struct BejReal
+    {
+        // Number bytes in exp.
+        uint8_t expLen;
+        int64_t whole;
+        uint64_t zeroCount;
+        uint64_t fract;
+        int64_t exp;
+    };
+
+    /**
+     * @brief SFLV BEJ tuple infomation.
+     */
+    struct BejSFLV
+    {
+        struct BejTupleS tupleS;
+        struct BejTupleF format;
+        // Value portion size in bytes.
+        uint32_t valueLength;
+        // Value end-offset with respect to the begining of the encoded stream.
+        uint32_t valueEndOffset;
+        // Pointer to the value.
+        const uint8_t* value;
+    };
+
+    /**
+     * @brief bejEncoding PLDM data type header.
+     */
+    struct BejPldmBlockHeader
+    {
+        uint32_t bejVersion;
+        uint16_t reserved;
+        uint8_t schemaClass;
+    } __attribute__((__packed__));
+
+    enum RdeOperationInitType
+    {
+        RdeOpInitOperationHead = 0,
+        RdeOpInitOperationRead = 1,
+        RdeOpInitOperationCreate = 2,
+        RdeOpInitOperationDelete = 3,
+        RdeOpInitOperationUpdate = 4,
+        RdeOpInitOperationReplace = 5,
+        RdeOpInitOperationAction = 6,
+    };
+
+    enum RdeMultiReceiveTransferFlag
+    {
+        RdeMRecFlagStart = 0,
+        RdeMRecFlagMiddle = 1,
+        RdeMRecFlagEnd = 2,
+        RdeMRecFlagStartAndEnd = 3,
+    };
+
+    struct RdeOperationInitReqHeader
+    {
+        uint32_t resourceID;
+        uint16_t operationID;
+        uint8_t operationType;
+
+        // OperationFlags bits
+        uint8_t locatorValid : 1;
+        uint8_t containsRequestPayload : 1;
+        uint8_t containsCustomRequestParameters : 1;
+
+        uint8_t reserved : 5;
+        uint32_t sendDataTransferHandle;
+        uint8_t operationLocatorLength;
+        uint32_t requestPayloadLength;
+    } __attribute__((__packed__));
+
+    struct MultipartReceiveResHeader
+    {
+        uint8_t completionCode;
+        uint8_t transferFlag;
+        uint32_t nextDataTransferHandle;
+        uint32_t dataLengthBytes;
+    } __attribute__((__packed__));
+
+    /**
+     * @brief Get the unsigned integer value from provided bytes.
+     *
+     * @param bytes - valid pointer to a byte stream in little-endian format.
+     * @param numOfBytes - number of bytes belongs to the value. Maximum number
+     * of bytes supported is 8. If numOfBytes > 8, the result is undefined.
+     * @return unsigend 64bit representation of the value.
+     */
+    uint64_t rdeGetUnsignedInteger(const uint8_t* bytes, uint8_t numOfBytes);
+
+    /**
+     * @brief Get the value from nnint type.
+     *
+     * @param  nnint - nnint should be pointing to a valid nnint.
+     * @return unsigend 64bit representation of the value.
+     */
+    uint64_t rdeGetNnint(const uint8_t* nnint);
+
+    /**
+     * @brief Get the size of the complete nnint.
+     *
+     * @param nnint - pointer to a valid nnint.
+     * @return size of the complete nnint.
+     */
+    uint8_t rdeGetNnintSize(const uint8_t* nnint);
+
+#ifdef __cplusplus
+}
+#endif