bcremer/line-reader

Read large files line by line in a memory efficient (constant) way.

1.0.0 2017-11-21 16:34 UTC

README

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LineReader is a library to read large files line by line in a memory efficient (constant) way.

Install

Via Composer

$ composer require bcremer/line-reader

Usage

Given we have a textfile (some/file.txt) with lines like:

Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10

Also let's assume the namespace is imported to keep the examples dense:

use Bcremer\LineReader\LineReader;

Read forwards

foreach (LineReader::readLines('some/file.txt') as $line) {
    echo $line . "\n"
}

The output will be:

Line 1
Line 2
Line 3
Line 4
Line 5
...

To set an offset or a limit use the \LimitIterator:

$lineGenerator = LineReader::readLines('some/file.txt');
$lineGenerator = new \LimitIterator($lineGenerator, 2, 5);
foreach ($lineGenerator as $line) {
    echo $line . "\n"
}

Will output line 3 to 7

Line 3
Line 4
Line 5
Line 6
Line 7

Read backwards

foreach (LineReader::readLinesBackwards('some/file.txt') as $line) {
    echo $line;
}
Line 10
Line 9
Line 8
Line 7
Line 6
...

Example: Read the last 5 lines in forward order:

$lineGenerator = LineReader::readLinesBackwards('some/file.txt');
$lineGenerator = new \LimitIterator($lineGenerator, 0, 5);

$lines = array_reverse(iterator_to_array($lineGenerator));
foreach ($line as $line) {
    echo $line;
}
Line 6
Line 7
Line 8
Line 9
Line 10

Testing

$ composer test
$ TEST_MAX_LINES=200000 composer test

License

The MIT License (MIT). Please see License File for more information.