This is a WG2 proposal for a (scheme files advanced) library providing R6RS-equivalent file I/O operations in an upward compatible way, with the following exceptions:
The procedures open-input-file, open-binary-input-file, open-output-file, open-binary-output-file, with-input-from-file, with-output-from-file, call-with-input-file, and call-with-output-file are the same as in the (scheme files) library, except that they accept settings lists as well as filenames. Settings lists allow various features of the port to be set when it is opened; see SettingsListsCowan for details.
The procedures file-exists? and delete-file are the same as in the (scheme files) library.
(native-encoding)
Returns a symbol suitable for use in a settings list to represent the native encoding used by the implementation.
(native-newline)
Returns a symbol suitable for use in a settings list to represent the native newline translation used by the implementation.
(port-position port)
Returns the current position of port. For a binary port, returns the index of the position at which the next byte would be read from or written to the port as an non-negative exact integer. For a textual port, returns a value of some implementation-dependent type representing the port’s position; this value may be useful only as the position argument to set-port-position!, if the latter is supported on the port.
(can-get-port-position? port)
Returns #t if the port supports the port-position operation, and #f otherwise.
(set-port-position port position)
Changes the current position of port. If port is a binary port, and position is a non-negative exact integer object, it is used as the index of the position at which the next byte will be read from or written to the port. If port is a textual port, and position is the return value of a preceding call to port-position on port, then the next character will be read or written from that position. If port is a binary output port and the position is beyond the current end of the data, set-port-position! will succeed, but the contents of any intervening positions are unspecified.
Calling this procedure on port resets the buffer state, allowing a binary operation to follow even if the previous operation was textual, an input operation to follow even if the previous operation was output, or an output operation to follow even if the previous operation of input.
(can-set-port-position? port)
Returns #t if the port supports the set-port-position! operation, and #f otherwise.
(binary-port-eof? port)
Returns #t if the next attempt to read a byte from port would return an eof-object, and #f otherwise.
(textual-port-eof? port)
Returns #t if the next attempt to read a character from port would return an eof-object, and #f otherwise.
(read-string n [ port ])
Reads at most n characters from port and returns them as a newly allocated string. If fewer characters can be read, they are returned. If no characters can be read, an eof-object is returned. The default port is the value of (current-input-port).
(write-string string start end [port])
Reads characters from string beginning at start (inclusive) and ending at end (exclusive) to port. The default port is the value of (current-output-port).
(read-maximal-bytevector [port])
Returns a bytevector consisting of all the bytes that can be read from port before an eof-object is returned, or an eof-object if there are none. The default port is the value of (current-input-port).
(read-maximal-string [ port ])
Returns a string consisting of all the characters that can be read from port before an eof-object is returned, or an eof-object if there are none. The default port is the value of (current-input-port).
(port-settings port)
Returns an approximation to the settings list used to create port. The order of keys may not be the same, some keys may be omitted if they have no effect on the implementation or if they explicitly specify the implementation default, and some values may be different if they have the same effect on the implementation. If no settings list was used, the list (path filename) is returned.
(string->bytevector string [ settings-list ])
Converts string to a bytevector using the keys encoding, newline, encoding-error, and possibly other implementation-specific keys in settings-list, and returns the string.
(bytevector->string bytevector [ settings-list ])
Converts bytevector to a string using the keys encoding, newline, encoding-error, and possibly other implementation-specific keys in settings-list, and returns the bytevector.