144 lines
6.1 KiB
Modula-2
144 lines
6.1 KiB
Modula-2
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DEFINITION MODULE Streams;
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(*
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* This module provides sequential IO through streams.
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* A stream is either a text stream or a binary stream, and is either in
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* reading, writing or appending mode.
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* By default, there are three open text streams, connected to standard input,
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* standard output, and standard error respectively.
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* These are text streams.
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* When connected to a terminal, the standard output and standard error
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* streams are linebuffered.
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* The user can create more streams with the OpenStream call, and
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* delete streams with the CloseStream call.
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* Streams are automatically closed at program termination.
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*)
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FROM SYSTEM IMPORT BYTE;
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TYPE StreamKind = (text, binary, none);
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StreamMode = (reading, writing, appending);
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StreamResult = (succeeded, illegaloperation,
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nomemory, openfailed, nostream, endoffile);
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StreamBuffering = (unbuffered, linebuffered, blockbuffered);
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TYPE Stream;
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VAR InputStream, OutputStream, ErrorStream: Stream;
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PROCEDURE OpenStream(VAR stream: Stream;
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filename: ARRAY OF CHAR;
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kind: StreamKind;
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mode: StreamMode;
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VAR result: StreamResult);
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(* Associates a stream with the file named filename.
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If kind = none, result is set to illegaloperation.
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mode has one of the follwing values:
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reading: the file is opened for reading
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writing: the file is truncated or created for writing
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appending: the file is opened for writing at end of file,
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or created for writing.
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On failure, result is set to openfailed.
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On success, result is set to succeeded.
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*)
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PROCEDURE SetStreamBuffering( stream: Stream;
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b: StreamBuffering;
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VAR result: StreamResult);
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(* This procedure is only allowed for output streams.
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The three types of buffering available are unbuffered, linebuffered,
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and blockbuffered. When an output stream is unbuffered, the output
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appears as soon as written; when it is blockbuffered, output is saved
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up and written as a block; When it is linebufferded (only possible for
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text output streams), output is saved up until a newline is encountered
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or input is read from standard input.
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*)
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PROCEDURE CloseStream(VAR stream: Stream; VAR result: StreamResult);
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(* Closes the stream.
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result is set to nostream if "stream" was not associated with a stream.
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*)
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PROCEDURE FlushStream(stream: Stream; VAR result: StreamResult);
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(* Flushes the stream.
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result is set to nostream if "stream" was not associated with a stream.
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It is set to illegaloperation if "stream" is not an output or
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appending stream.
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*)
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PROCEDURE EndOfStream(stream: Stream; VAR result: StreamResult): BOOLEAN;
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(* Returns true if the stream is an input stream, and the end of the file
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has been reached.
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result is set to nostream if "stream" was not associated with a stream.
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It is set to illegaloperation if the stream is not an input stream.
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*)
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PROCEDURE Read(stream: Stream; VAR ch: CHAR; VAR result: StreamResult);
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(* reads a character from the stream. Certain character translations may
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occur, such as the mapping of the end-of-line sequence to the
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character 12C.
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result is set to nostream if "stream" was not associated with a stream.
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It is set to endoffile if EndOfStream would have returned TRUE before the
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call to Read. In this case, "ch" is set to 0C.
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It is set to illegaloperation if the stream is not a text input stream.
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*)
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PROCEDURE ReadByte(stream: Stream; VAR byte: BYTE; VAR result: StreamResult);
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(* reads a byte from the stream. No character translations occur.
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result is set to nostream if "stream" was not associated with a stream.
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It is set to endoffile if EndOfStream would have returned TRUE before the
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call to ReadByte. In this case, "byte" is set to 0C.
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It is set to illegaloperation if the stream is not a binary input stream.
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*)
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PROCEDURE ReadBytes(stream: Stream;
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VAR bytes: ARRAY OF BYTE;
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VAR result: StreamResult);
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(* reads bytes from the stream. No character translations occur.
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The number of bytes is determined by the size of the parameter.
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result is set to nostream if "stream" was not associated with a stream.
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It is set to endoffile if there are not enough bytes left on the stream.
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In this case, the rest of the bytes are set to 0C.
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It is set to illegaloperation if the stream is not a binary input stream.
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*)
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PROCEDURE Write(stream: Stream; ch: CHAR; VAR result: StreamResult);
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(* writes a character to the stream. Certain character translations may
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occur, such as the mapping of a line-feed or carriage return (12C or 15C)
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to the end-of-line sequence of the system.
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result is set to nostream if "stream" was not associated with a stream.
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It is set to illegaloperation if the stream is not a text output stream.
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*)
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PROCEDURE WriteByte(stream: Stream; byte: BYTE; VAR result: StreamResult);
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(* writes a byte to the stream. No character translations occur.
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result is set to nostream if "stream" was not associated with a stream.
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It is set to illegaloperation if the stream is not a binary output stream.
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*)
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PROCEDURE WriteBytes(stream: Stream;
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VAR bytes: ARRAY OF BYTE;
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VAR result: StreamResult);
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(* writes bytes to the stream. No character translations occur.
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The number of bytes written is equal to the size of the parameter.
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result is set to nostream if "stream" was not associated with a stream.
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It is set to illegaloperation if the stream is not a binary output stream.
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*)
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PROCEDURE GetPosition(stream: Stream;
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VAR position: LONGINT;
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VAR result: StreamResult);
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(* gives the actual read/write position in "position".
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"result" is set to illegaloperation if "stream" is not a stream.
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*)
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PROCEDURE SetPosition(stream: Stream;
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position: LONGINT;
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VAR result: StreamResult);
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(* sets the actual read/write position to "position".
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"result" is set to illegaloperation if "stream" is not a stream or
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the stream was opened for appending and the position is in front of
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the current position, or it failed for some other
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reason (f.i. when the stream is connected to a terminal).
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*)
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END Streams.
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