formatsize

Formatsize is a term used in data encoding and storage to denote the amount of space a piece of data occupies when encoded in a given format, typically measured in bytes. It can refer to the actual encoded size of a specific value, or to the maximum size permitted by the format or schema.

In fixed-length formats, formatsize is constant for a given type. For example, a 16-bit integer encoded in a fixed binary form occupies 2 bytes, so its formatsize is 2. In variable-length formats, formatsize depends on content; schemes often store a length prefix (for example, a string with a length field followed by that many bytes) to determine the total formatsize.

Formatsize is important for memory allocation, streaming, network transport, and validation. Systems may enforce maximum formatsize to avoid resource exhaustion and to guarantee compatibility with storage devices, protocols, or interfaces. Accurate formatsize calculations enable efficient buffer management and help enforce protocol constraints.

Examples of formatsize considerations appear across serialization, file, and media formats. In serialization formats such as Protocol Buffers, fields have encoded lengths that contribute to the total formatsize. In image and audio formats, headers, frame sizes, or chunk lengths influence formatsize calculations. Archive and compression formats track both compressed and uncompressed sizes, which relate to formatsize in different contexts.

Computing formatsize can be done by a serializer that writes data to a buffer, or by inspecting the format’s schema and summing fixed fields and encoded lengths. See also data encoding, serialization, and length-prefix encoding.

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