Input- and OutputStreams.
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README.md

stubbles/streams

Input- and OutputStreams.

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Installation

stubbles/streams is distributed as Composer package. To install it as a dependency of your package use the following command:

composer require "stubbles/streams": "^8.0"

Requirements

stubbles/streams requires at least PHP 7.0. For PHP 5.6 please use release 7.0.

For using encoding and decoding decorated streams the PHP extension iconv is required.

For the stubbles\streams\linesOf() and stubbles\streams\nonEmptyLinesOf() functions the package stubbles/sequence is required.

Interfaces and methods

stubbles/streams provides input and output streams for different kind of sources. All input streams implement the stubbles\streams\InputStream interface, all output streams the stubbles\streams\OutputStream interface. While input streams can be used to read data from a source, output streams can be used to write data to a certain source.

Interfaces and their methods

Input stream methods

The input stream interface provides the following methods:

  • read($length = 8192) - returns given amount of bytes
  • readLine($length = 8192) - returns all characters up to given length until next line break
  • bytesLeft() - returns the amount of bytes left to be read
  • eof() - checks whether end of input was reached
  • close() - closes the stream

Output stream methods

The output stream interface provides the following methods:

  • write($bytes) - writes given bytes and returns amount of written bytes
  • writeLine($bytes) - same as write(), but adds a line break at end of bytes
  • close() - closes the stream

Seekable streams

Some streams are seekable which means you can go from one position in the stream to another. Input streams which are seekable implement the stubbles\streams\Seekable interface. It provides the following methods:

  • seek($offset, $whence = Seekable::SET) - sets internal stream pointer to given position
  • tell() - returns the current position of the internal stream pointer

Copy from input to output stream

Available since release 8.1.0

The shortcut function stubbles\streams\copy() provides a simple way to copy everything what's in an input stream to an output stream:

copy($in)->to($out);

Please note that copying starts at the offset where the input stream currently is located, and changes the offset of the input stream to the end of the stream. In case a non-seekable input stream is copied it can not return to its initial offset.

Decorating streams

Encoding-related streams

Sometimes it is necessary to decode input stream data into the internal encoding of the application. While Stubbles' internal encoding is UTF-8, all data read from input streams should be UTF-8 itself or at least converted to UTF-8 before returned from the input stream. To ease this, the stubbles\streams\DecodingInputStream class decorates another input stream given as first parameter on construction, and tries to decode the data read from the decorated input stream from the stream encoding to UTF-8 using iconv(). However you need to specify the charset of the decorated input stream as second parameter to the constructor:

$decodingInputStream = new DecodingInputStream($encodedInputStream, 'iso-8859-1');

Of course there must be a possibility to write back into the correct encoding. For this, the stubbles\streams\EncodingOutputStream class can be used. It tries to convert from internal UTF-8 into the encoding of the decorated output stream using iconv().

$encodingOutputStream = new EncodingOutputStream($encodedOutputStream, 'iso-8859-1');

File related streams

To read data from a file one may use the stubbles\streams\file\FileInputStream class. Its constructor expects either a name of a file, or an already opened file pointer resource. If it is the name of the file the second parameter of the constructor sets the mode in which the file is opened, it defaults to rb (binary reading). The file input stream is a seekable stream.

To write data to a file one may use the stubbles\streams\file\FileOutputStream class. Similarly to the file input stream class its constructor expects either a name of a file, or an already opened file pointer resource. If it is the name of the file the second parameter of the constructor sets the mode in which the file is opened, it defaults to wb (binary writing).

Warning: the mode parameter accepts modes which might not make any sense with the stream class - e.g. the input stream allows wb as value for the mode parameter, but then you can not read from the given file, and vice versa for the output stream.

Memory streams

Sometimes it is helpful if one can read or write data into memory. For such purposes the stubbles\streams\memory\MemoryInputStream and stubbles\streams\memory\MemoryOutputStream exist. While the memory input stream class expects the content to be read from as string parameter for its constructor, the memory output stream does not expect a value on construction, but offers an additional method buffer() which returns all data written to this stream so far. Additionally, casting the stubbles\streams\memory\MemoryOutputStream to string will return the buffer (available since release 4.0.0).

The memory input stream is a seekable stream.

Filter streams

When reading from or writing data to a stream sometimes it may happen that not all data to read or not all data to be written is relevant for what you want to achieve. For example, a file you read may contain comment lines, and you don't want to ignore those comment lines. Normally, you would have the logic on what to ignore in your reading class:

while (!$inputStream->eof()) {
    $line = $inputStream->readLine();
    if (substr(0, 1, $line) !== '#') {
        $this->processLine($line);
    }
}

In this small example it may not be much work, but what if comment lines may also start with // or there may even be comments stretching over more than one line as we have in PHP with /* comment over several lines ... */. Now the logic might get a bit to complicated at this point. Stream filters to the rescue:

$filterStream = new FilteredInputStream(
        $inputStream,
        function($line) { return substr($line, 0, 1) !== '#'; }
);
while (!$filterStream->eof()) {
    $this->processLine($inputStream->readLine());
}

The second argument for stubbles\streams\filter\FilteredInputStream can be any callable which accepts a string as argument and returns true when this string should be passed through, and false when this string should be filtered. Please note that you can't filter single characters from the passed string, only characters as a whole.

The same applies to the stubbles\streams\filter\FilteredOutputStream, just that the filter is applied to the data that is written.

Input stream sequences

Because iterating over input streams with while can be quite cumbersome, stubbles/streams provides an input stream implementation which is also an instance of \Iterator.

$lines = new InputStreamIterator(new FileInputStream('somefile.txt'));
foreach ($lines as $line {
    processLine($line);
}

Each iteration step is a call to readLine() of the decorated input stream.

Please note: when the decorated stream is not an instance of stubbles\streams\Seekable it can be iterated only once, trying to rewind will do nothing.

Integration with stubbles/sequence

Optionally iteration can be even more enhanced when the package stubbles/sequence is available.

This allows to use two functions which return an instance of stubbles\sequence\Sequence that allow all sequence operation on an input stream:

stubbles\streams\linesOf($input)

The input can either be an instance of stubbles\streams\InputStream or a file name.

$lines = linesOf('somefile.txt')
        ->filter(/* callable which filters */)
        ->map(/* callable which maps the line to other content */);
foreach ($lines as $line) {
    processLine($line);
}

stubbles\streams\nonEmptyLinesOf($input)

Same as above, but already filters all empty lines.