C Binary Packet Serializer

A simple, efficient system for packing multiple C structures into a single contiguous memory buffer. This pattern is commonly used in network programming, binary file formats, and embedded systems to minimize overhead and ensure data integrity during transmission.

🚀 Features

• Magic Number Validation: Uses a unique identifier (0xCAFEBABE) to verify packet integrity.
• Version Control: Includes a version field to ensure compatibility between sender and receiver.
• Dynamic Payload: Supports a variable number of Order entries in a single packet.
• Zero-Copy Logic: Uses pointer arithmetic and casting to navigate memory efficiently without unnecessary data duplication.

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📦 Packet Structure

The data is organized in memory as a single contiguous block. The header tells the parser how to interpret the bytes that follow.

Offset	Field	Type	Description
0	magic	uint32_t	Identifies the protocol (0xCAFEBABE).
4	version	uint16_t	Protocol version number.
6	count	uint16_t	Number of Order entries in the payload.
8+	Payload	Order[]	Array of Order structs (ID, Price, Quantity).

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🛠️ How It Works

1. Serialization (serialize_orders)

This function acts as the "Encoder." It calculates the total memory required for the header and the orders. It then performs a pointer cast on the raw buffer:

• It writes the PacketHeader at the very beginning.
• It offsets the pointer by sizeof(PacketHeader) to find the starting address for the data.
• It loops through the input array and copies each Order into the buffer.

2. Parsing (parse_packet)

This function acts as the "Decoder." It treats the incoming char* buffer as a structured object:

• It first reads the header to validate the Magic Number. If the magic number doesn't match, it rejects the packet as corrupted or invalid.
• It reads the count field to determine how many times it needs to iterate over the remaining memory to extract the Order data.

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💻 Getting Started

Prerequisites

• A C compiler (GCC, Clang, or MSVC).
• Standard C libraries.

Compilation

Use the following command to compile the source code:

gcc -o order_entry order_entry.c

Running the Demo

./order_entry

The program will:

1. Generate a random number of orders.
2. Serialize them into a byte buffer.
3. Print the total bytes written.
4. Parse the buffer and display the extracted trade information to the console.

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⚠️ Important Considerations

• Memory Alignment: This code assumes that the compiler's padding for PacketHeader and Order is consistent. In a production environment, you should use #pragma pack(push, 1) to ensure there is no hidden padding between fields.
• Endianness: This implementation assumes both the sender and receiver use the same byte order (Little Endian or Big Endian). For cross-platform networking, you should use functions like htonl() and ntohl().
• Buffer Safety: The serialize_orders function includes a basic size check, but always ensure the destination buffer is correctly allocated before calling.