diff --git a/src/base.c b/src/base.c
new file mode 100644
index 0000000..9a5ae09
--- /dev/null
+++ b/src/base.c
@@ -0,0 +1,488 @@
+#include <endian.h>
+#include <string.h>
+
+#include "base.h"
+
+uint8_t pack_pldm_header(const struct pldm_header_info *hdr,
+			 struct pldm_msg_hdr *msg)
+{
+	if (msg == NULL || hdr == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	if (hdr->msg_type != PLDM_RESPONSE && hdr->msg_type != PLDM_REQUEST &&
+	    hdr->msg_type != PLDM_ASYNC_REQUEST_NOTIFY) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	if (hdr->instance > PLDM_INSTANCE_MAX) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	if (hdr->pldm_type > (PLDM_MAX_TYPES - 1)) {
+		return PLDM_ERROR_INVALID_PLDM_TYPE;
+	}
+
+	uint8_t datagram = (hdr->msg_type == PLDM_ASYNC_REQUEST_NOTIFY) ? 1 : 0;
+
+	if (hdr->msg_type == PLDM_RESPONSE) {
+		msg->request = PLDM_RESPONSE;
+	} else if (hdr->msg_type == PLDM_REQUEST ||
+		   hdr->msg_type == PLDM_ASYNC_REQUEST_NOTIFY) {
+		msg->request = PLDM_REQUEST;
+	}
+	msg->datagram = datagram;
+	msg->reserved = 0;
+	msg->instance_id = hdr->instance;
+	msg->header_ver = PLDM_CURRENT_VERSION;
+	msg->type = hdr->pldm_type;
+	msg->command = hdr->command;
+
+	return PLDM_SUCCESS;
+}
+
+uint8_t unpack_pldm_header(const struct pldm_msg_hdr *msg,
+			   struct pldm_header_info *hdr)
+{
+	if (msg == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	if (msg->request == PLDM_RESPONSE) {
+		hdr->msg_type = PLDM_RESPONSE;
+	} else {
+		hdr->msg_type =
+		    msg->datagram ? PLDM_ASYNC_REQUEST_NOTIFY : PLDM_REQUEST;
+	}
+
+	hdr->instance = msg->instance_id;
+	hdr->pldm_type = msg->type;
+	hdr->command = msg->command;
+
+	return PLDM_SUCCESS;
+}
+
+int encode_get_types_req(uint8_t instance_id, struct pldm_msg *msg)
+{
+	if (msg == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	struct pldm_header_info header = {0};
+	header.instance = instance_id;
+	header.msg_type = PLDM_REQUEST;
+	header.command = PLDM_GET_PLDM_TYPES;
+
+	return pack_pldm_header(&header, &(msg->hdr));
+}
+
+int encode_get_commands_req(uint8_t instance_id, uint8_t type, ver32_t version,
+			    struct pldm_msg *msg)
+{
+	if (msg == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	struct pldm_header_info header = {0};
+	header.instance = instance_id;
+	header.msg_type = PLDM_REQUEST;
+	header.command = PLDM_GET_PLDM_COMMANDS;
+
+	uint8_t rc = pack_pldm_header(&header, &(msg->hdr));
+	if (rc != PLDM_SUCCESS) {
+		return rc;
+	}
+
+	struct pldm_get_commands_req *request =
+	    (struct pldm_get_commands_req *)msg->payload;
+
+	request->type = type;
+	request->version = version;
+
+	return PLDM_SUCCESS;
+}
+
+int encode_get_types_resp(uint8_t instance_id, uint8_t completion_code,
+			  const bitfield8_t *types, struct pldm_msg *msg)
+{
+	if (msg == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	struct pldm_header_info header = {0};
+	header.instance = instance_id;
+	header.msg_type = PLDM_RESPONSE;
+	header.command = PLDM_GET_PLDM_TYPES;
+
+	uint8_t rc = pack_pldm_header(&header, &(msg->hdr));
+	if (rc != PLDM_SUCCESS) {
+		return rc;
+	}
+
+	struct pldm_get_types_resp *response =
+	    (struct pldm_get_types_resp *)msg->payload;
+	response->completion_code = completion_code;
+	if (response->completion_code == PLDM_SUCCESS) {
+		if (types == NULL) {
+			return PLDM_ERROR_INVALID_DATA;
+		}
+		memcpy(response->types, &(types->byte), PLDM_MAX_TYPES / 8);
+	}
+
+	return PLDM_SUCCESS;
+}
+
+int decode_get_commands_req(const struct pldm_msg *msg, size_t payload_length,
+			    uint8_t *type, ver32_t *version)
+{
+	if (msg == NULL || type == NULL || version == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	if (payload_length != PLDM_GET_COMMANDS_REQ_BYTES) {
+		return PLDM_ERROR_INVALID_LENGTH;
+	}
+
+	struct pldm_get_commands_req *request =
+	    (struct pldm_get_commands_req *)msg->payload;
+	*type = request->type;
+	*version = request->version;
+	return PLDM_SUCCESS;
+}
+
+int encode_get_commands_resp(uint8_t instance_id, uint8_t completion_code,
+			     const bitfield8_t *commands, struct pldm_msg *msg)
+{
+	if (msg == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	struct pldm_header_info header = {0};
+	header.instance = instance_id;
+	header.msg_type = PLDM_RESPONSE;
+	header.command = PLDM_GET_PLDM_COMMANDS;
+	uint8_t rc = pack_pldm_header(&header, &(msg->hdr));
+	if (rc != PLDM_SUCCESS) {
+		return rc;
+	}
+
+	struct pldm_get_commands_resp *response =
+	    (struct pldm_get_commands_resp *)msg->payload;
+	response->completion_code = completion_code;
+	if (response->completion_code == PLDM_SUCCESS) {
+		if (commands == NULL) {
+			return PLDM_ERROR_INVALID_DATA;
+		}
+		memcpy(response->commands, &(commands->byte),
+		       PLDM_MAX_CMDS_PER_TYPE / 8);
+	}
+
+	return PLDM_SUCCESS;
+}
+
+int decode_get_types_resp(const struct pldm_msg *msg, size_t payload_length,
+			  uint8_t *completion_code, bitfield8_t *types)
+{
+	if (msg == NULL || types == NULL || completion_code == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	*completion_code = msg->payload[0];
+	if (PLDM_SUCCESS != *completion_code) {
+		return PLDM_SUCCESS;
+	}
+
+	if (payload_length != PLDM_GET_TYPES_RESP_BYTES) {
+		return PLDM_ERROR_INVALID_LENGTH;
+	}
+
+	struct pldm_get_types_resp *response =
+	    (struct pldm_get_types_resp *)msg->payload;
+
+	memcpy(&(types->byte), response->types, PLDM_MAX_TYPES / 8);
+
+	return PLDM_SUCCESS;
+}
+
+int decode_get_commands_resp(const struct pldm_msg *msg, size_t payload_length,
+			     uint8_t *completion_code, bitfield8_t *commands)
+{
+	if (msg == NULL || commands == NULL || completion_code == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	*completion_code = msg->payload[0];
+	if (PLDM_SUCCESS != *completion_code) {
+		return PLDM_SUCCESS;
+	}
+
+	if (payload_length != PLDM_GET_COMMANDS_RESP_BYTES) {
+		return PLDM_ERROR_INVALID_LENGTH;
+	}
+
+	struct pldm_get_commands_resp *response =
+	    (struct pldm_get_commands_resp *)msg->payload;
+
+	memcpy(&(commands->byte), response->commands,
+	       PLDM_MAX_CMDS_PER_TYPE / 8);
+
+	return PLDM_SUCCESS;
+}
+
+int encode_get_version_req(uint8_t instance_id, uint32_t transfer_handle,
+			   uint8_t transfer_opflag, uint8_t type,
+			   struct pldm_msg *msg)
+{
+	if (NULL == msg) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	struct pldm_header_info header = {0};
+	header.msg_type = PLDM_REQUEST;
+	header.instance = instance_id;
+	header.pldm_type = PLDM_BASE;
+	header.command = PLDM_GET_PLDM_VERSION;
+
+	uint8_t rc = pack_pldm_header(&header, &(msg->hdr));
+	if (rc != PLDM_SUCCESS) {
+		return rc;
+	}
+
+	struct pldm_get_version_req *request =
+	    (struct pldm_get_version_req *)msg->payload;
+	transfer_handle = htole32(transfer_handle);
+	request->transfer_handle = transfer_handle;
+	request->transfer_opflag = transfer_opflag;
+	request->type = type;
+
+	return PLDM_SUCCESS;
+}
+
+int encode_get_version_resp(uint8_t instance_id, uint8_t completion_code,
+			    uint32_t next_transfer_handle,
+			    uint8_t transfer_flag, const ver32_t *version_data,
+			    size_t version_size, struct pldm_msg *msg)
+{
+	if (NULL == msg) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	struct pldm_header_info header = {0};
+	header.msg_type = PLDM_RESPONSE;
+	header.instance = instance_id;
+	header.pldm_type = PLDM_BASE;
+	header.command = PLDM_GET_PLDM_VERSION;
+
+	uint8_t rc = pack_pldm_header(&header, &(msg->hdr));
+	if (rc != PLDM_SUCCESS) {
+		return rc;
+	}
+
+	struct pldm_get_version_resp *response =
+	    (struct pldm_get_version_resp *)msg->payload;
+	response->completion_code = completion_code;
+	if (response->completion_code == PLDM_SUCCESS) {
+		response->next_transfer_handle = htole32(next_transfer_handle);
+		response->transfer_flag = transfer_flag;
+		memcpy(response->version_data, (uint8_t *)version_data,
+		       version_size);
+	}
+	return PLDM_SUCCESS;
+}
+
+int decode_get_version_req(const struct pldm_msg *msg, size_t payload_length,
+			   uint32_t *transfer_handle, uint8_t *transfer_opflag,
+			   uint8_t *type)
+{
+
+	if (payload_length != PLDM_GET_VERSION_REQ_BYTES) {
+		return PLDM_ERROR_INVALID_LENGTH;
+	}
+
+	struct pldm_get_version_req *request =
+	    (struct pldm_get_version_req *)msg->payload;
+	*transfer_handle = le32toh(request->transfer_handle);
+	*transfer_opflag = request->transfer_opflag;
+	*type = request->type;
+	return PLDM_SUCCESS;
+}
+
+int decode_get_version_resp(const struct pldm_msg *msg, size_t payload_length,
+			    uint8_t *completion_code,
+			    uint32_t *next_transfer_handle,
+			    uint8_t *transfer_flag, ver32_t *version)
+{
+	if (msg == NULL || next_transfer_handle == NULL ||
+	    transfer_flag == NULL || completion_code == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	*completion_code = msg->payload[0];
+	if (PLDM_SUCCESS != *completion_code) {
+		return PLDM_SUCCESS;
+	}
+
+	if (payload_length < PLDM_GET_VERSION_RESP_BYTES) {
+		return PLDM_ERROR_INVALID_LENGTH;
+	}
+
+	struct pldm_get_version_resp *response =
+	    (struct pldm_get_version_resp *)msg->payload;
+
+	*next_transfer_handle = le32toh(response->next_transfer_handle);
+	*transfer_flag = response->transfer_flag;
+	memcpy(version, (uint8_t *)response->version_data, sizeof(ver32_t));
+
+	return PLDM_SUCCESS;
+}
+
+int encode_get_tid_req(uint8_t instance_id, struct pldm_msg *msg)
+{
+	if (msg == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	struct pldm_header_info header = {0};
+	header.instance = instance_id;
+	header.msg_type = PLDM_REQUEST;
+	header.command = PLDM_GET_TID;
+
+	return pack_pldm_header(&header, &(msg->hdr));
+}
+int encode_get_tid_resp(uint8_t instance_id, uint8_t completion_code,
+			uint8_t tid, struct pldm_msg *msg)
+{
+	if (msg == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	struct pldm_header_info header = {0};
+	header.instance = instance_id;
+	header.msg_type = PLDM_RESPONSE;
+	header.command = PLDM_GET_TID;
+
+	uint8_t rc = pack_pldm_header(&header, &(msg->hdr));
+	if (rc != PLDM_SUCCESS) {
+		return rc;
+	}
+
+	struct pldm_get_tid_resp *response =
+	    (struct pldm_get_tid_resp *)msg->payload;
+	response->completion_code = completion_code;
+	response->tid = tid;
+
+	return PLDM_SUCCESS;
+}
+
+int decode_get_tid_resp(const struct pldm_msg *msg, size_t payload_length,
+			uint8_t *completion_code, uint8_t *tid)
+{
+	if (msg == NULL || tid == NULL || completion_code == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	*completion_code = msg->payload[0];
+	if (PLDM_SUCCESS != *completion_code) {
+		return PLDM_SUCCESS;
+	}
+
+	if (payload_length != PLDM_GET_TID_RESP_BYTES) {
+		return PLDM_ERROR_INVALID_LENGTH;
+	}
+
+	struct pldm_get_tid_resp *response =
+	    (struct pldm_get_tid_resp *)msg->payload;
+
+	*tid = response->tid;
+
+	return PLDM_SUCCESS;
+}
+
+int decode_multipart_receive_req(
+    const struct pldm_msg *msg, size_t payload_length, uint8_t *pldm_type,
+    uint8_t *transfer_opflag, uint32_t *transfer_ctx, uint32_t *transfer_handle,
+    uint32_t *section_offset, uint32_t *section_length)
+{
+	if (msg == NULL || pldm_type == NULL || transfer_opflag == NULL ||
+	    transfer_ctx == NULL || transfer_handle == NULL ||
+	    section_offset == NULL || section_length == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	if (payload_length != PLDM_MULTIPART_RECEIVE_REQ_BYTES) {
+		return PLDM_ERROR_INVALID_LENGTH;
+	}
+
+	struct pldm_multipart_receive_req *request =
+	    (struct pldm_multipart_receive_req *)msg->payload;
+
+	if (request->pldm_type != PLDM_BASE) {
+		return PLDM_ERROR_INVALID_PLDM_TYPE;
+	}
+
+	// Any enum value above PLDM_XFER_CURRENT_PART is invalid.
+	if (request->transfer_opflag > PLDM_XFER_CURRENT_PART) {
+		return PLDM_INVALID_TRANSFER_OPERATION_FLAG;
+	}
+
+	// A section offset of 0 is only valid on FIRST_PART or COMPLETE Xfers.
+	uint32_t sec_offset = le32toh(request->section_offset);
+	if (sec_offset == 0 &&
+	    (request->transfer_opflag != PLDM_XFER_FIRST_PART &&
+	     request->transfer_opflag != PLDM_XFER_COMPLETE)) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	uint32_t handle = le32toh(request->transfer_handle);
+	if (handle == 0 && request->transfer_opflag != PLDM_XFER_COMPLETE) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	*pldm_type = request->pldm_type;
+	*transfer_opflag = request->transfer_opflag;
+	*transfer_ctx = request->transfer_ctx;
+	*transfer_handle = handle;
+	*section_offset = sec_offset;
+	*section_length = le32toh(request->section_length);
+
+	return PLDM_SUCCESS;
+}
+
+int encode_cc_only_resp(uint8_t instance_id, uint8_t type, uint8_t command,
+			uint8_t cc, struct pldm_msg *msg)
+{
+	if (msg == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	struct pldm_header_info header = {0};
+	header.instance = instance_id;
+	header.msg_type = PLDM_RESPONSE;
+	header.pldm_type = type;
+	header.command = command;
+
+	uint8_t rc = pack_pldm_header(&header, &msg->hdr);
+	if (rc != PLDM_SUCCESS) {
+		return rc;
+	}
+
+	msg->payload[0] = cc;
+
+	return PLDM_SUCCESS;
+}
+
+int encode_pldm_header_only(uint8_t msg_type, uint8_t instance_id,
+			    uint8_t pldm_type, uint8_t command,
+			    struct pldm_msg *msg)
+{
+	if (msg == NULL) {
+		return PLDM_ERROR_INVALID_DATA;
+	}
+
+	struct pldm_header_info header = {0};
+	header.msg_type = msg_type;
+	header.instance = instance_id;
+	header.pldm_type = pldm_type;
+	header.command = command;
+	return pack_pldm_header(&header, &(msg->hdr));
+}