writeLong

writeLong is a common name for a function or method in many programming environments that serializes a 64-bit signed integer (often called long or int64) to a binary destination such as a stream or buffer. The primary purpose is to produce an eight-byte representation of the value that can be stored or transmitted and later reconstructed.

The exact byte order and encoding of the eight bytes are defined by the API. Some APIs write in a fixed, network-friendly big-endian order, while others follow the platform’s native endianness (which is usually little-endian on modern desktop and mobile platforms). Some libraries provide explicit options to select endianness.

Common language implementations include:

- In Java and other JVM-based I/O interfaces, writeLong(long v) writes eight bytes to the underlying stream in big-endian order.

- In .NET, BinaryWriter.Write(long value) writes a 64-bit integer to the stream in the platform’s endianness (typically little-endian on common runtimes).

Other languages or libraries may offer similar functionality under different names or with explicit endianness parameters. When using writeLong, developers should consult the specific API documentation to confirm the endianness, signedness, and exact error behavior.

Usage considerations include ensuring the destination is ready for binary data, handling I/O exceptions, and ensuring that the same write/read order is used in paired serialization and deserialization. It is also important to distinguish between signed 64-bit values and unsigned representations, depending on the protocol or file format.