Книга: Practical Common Lisp

Binary Files

Binary Files

At a sufficiently low level of abstraction, all files are "binary" in the sense that they just contain a bunch of numbers encoded in binary form. However, it's customary to distinguish between text files, where all the numbers can be interpreted as characters representing human-readable text, and binary files, which contain data that, if interpreted as characters, yields nonprintable characters.[260]

Binary file formats are usually designed to be both compact and efficient to parse—that's their main advantage over text-based formats. To meet both those criteria, they're usually composed of on-disk structures that are easily mapped to data structures that a program might use to represent the same data in memory.[261]

The library will give you an easy way to define the mapping between the on-disk structures defined by a binary file format and in-memory Lisp objects. Using the library, it should be easy to write a program that can read a binary file, translating it into Lisp objects that you can manipulate, and then write back out to another properly formatted binary file.

Оглавление книги