readbytes

Readbytes is a generic operation used in programming to read a specified number of bytes from a byte-oriented input source, such as a file, socket, or in-memory buffer. The term is not tied to a single standardized function, but appears as either a method name or a conceptual operation in many libraries. The goal is to retrieve an exact block of bytes for processing.

Behavior: The function typically accepts either a target size in bytes and optionally a destination buffer. It returns the number of bytes actually read and may fill a buffer. If the end of the stream is reached before the requested amount is read, the function may return fewer bytes and signal EOF; some interfaces guarantee exact length by looping until the requested amount is read or EOF occurs. Blocking vs non-blocking and buffering influence performance.

Language observations: In Python, file-like objects implement read(n) and may return fewer than n bytes if EOF; in asynchronous contexts there is readexactly in asyncio streams. In Java, InputStream.read(byte[], int, int) returns the number of bytes read; exact-length reads require repeated calls. In POSIX C, read(fd, buf, n) returns bytes read and can return less than requested. In Rust, Read trait's read returns bytes read, while read_exact guarantees exactly n bytes unless EOF occurs.

Usage considerations: Always handle partial reads, differentiate between 0 and EOF, consider buffering, handle encoding separately, choose between synchronous and asynchronous variants based on I/O pattern.

See also: read, readinto, readexactly, buffering, streams, I/O.