Byte input/output

6.13 | Byte input/output

These built-in predicates enable a single byte to be input from and output to a binary stream. `-1` is returned to indicate the end-of-file.

6.13.1 | `get_byte/2`, `get_byte/1`

Templates

  `get_byte(+stream_or_alias, ?in_byte)
  get_byte(?in_byte)`

Description
`get_byte(SorA, Byte)` succeeds if `Byte` unifies with the next byte read from the stream associated with the stream-term or alias `SorA`.
`get_byte/1` applies to the current input stream.
Errors

`SorA` is a variable |  | `instantiation_error`
`Byte` is neither a variable nor an in-byte |  | `type_error(in_byte, Byte)`
`SorA` is neither a variable nor a stream-term or alias |  | `domain_error(stream_or_alias, SorA)`
`SorA` is not associated with an open stream |  | `existence_error(stream, SorA)`
`SorA` is an output stream |  | `permission_error(input, stream, SorA)`
`SorA` is associated with a text stream |  | `permission_error(input, text_stream, SorA)`
`SorA` has stream properties `end_of_stream(past)` and `eof_action(error)` |  | `permission_error(input, past_end_of_stream, SorA)`

Portability
ISO predicates.

6.13.2 | `peek_byte/2`, `peek_byte/1`

Templates

  `peek_byte(+stream_or_alias, ?in_byte)
  peek_byte(?in_byte)`

Description
`peek_byte(SorA, Byte)` succeeds if `Byte` unifies with the next byte that will be read from the stream associated with the stream-term or alias `SorA`. The byte is not read.
`peek_byte/1` applies to the current input stream.
Errors

`SorA` is a variable |  | `instantiation_error`
`Byte` is neither a variable nor an in-byte |  | `type_error(in_byte, Byte)`
`SorA` is neither a variable nor a stream-term or alias |  | `domain_error(stream_or_alias, SorA)`
`SorA` is not associated with an open stream |  | `existence_error(stream, SorA)`
`SorA` is an output stream |  | `permission_error(input, stream, SorA)`
`SorA` is associated with a text stream |  | `permission_error(input, text_stream, SorA)`
`SorA` has stream properties `end_of_stream(past)` and `eof_action(error)` |  | `permission_error(input, past_end_of_stream, SorA)`

Portability
ISO predicates.

6.13.3 | `unget_byte/2`, `unget_byte/1`

Templates

  `unget_byte(+stream_or_alias, +byte)
  unget_byte(+byte)`

Description
`unget_byte(SorA, Byte)` pushes back `Byte` onto the stream associated with the stream-term or alias `SorA`. `Byte` will be the next byte read by `get_byte/2`. The maximum number of bytes that can be successively pushed back is given by the `max_unget` Prolog flag (section 6.22.1).
`unget_byte/1` applies to the current input stream.
Errors

`SorA` is a variable |  | `instantiation_error`
`Byte` is a variable |  | `instantiation_error`
`Byte` is neither a variable nor a byte |  | `type_error(byte, Byte)`
`SorA` is neither a variable nor a stream-term or alias |  | `domain_error(stream_or_alias, SorA)`
`SorA` is not associated with an open stream |  | `existence_error(stream, SorA)`
`SorA` is an output stream |  | `permission_error(input, stream, SorA)`
`SorA` is associated with a text stream |  | `permission_error(input, text_stream, SorA)`

Portability
GNU Prolog predicates.

6.13.4 | `put_byte/2`, `put_byte/1`

Templates

  `put_byte(+stream_or_alias, +byte)
  put_byte(+byte)`

Description
`put_byte(SorA, Byte)` writes `Byte` onto the stream associated with the stream-term or alias `SorA`.
`put_byte/1` applies to the current output stream.
Errors

`SorA` is a variable |  | `instantiation_error`
`Byte` is a variable |  | `instantiation_error`
`Byte` is neither a variable nor a byte |  | `type_error(byte, Byte)`
`SorA` is neither a variable nor a stream-term or alias |  | `domain_error(stream_or_alias, SorA)`
`SorA` is not associated with an open stream |  | `existence_error(stream, SorA)`
`SorA` is an output stream |  | `permission_error(output, stream, SorA)`
`SorA` is associated with a text stream |  | `permission_error(output, text_stream, SorA)`

Portability
GNU Prolog predicates.

Copyright (C) 1999,2000 Daniel Diaz
Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved.
More about the copyright