Merge pull request #1 from aldas/improve_api

improve api, cleanup and many other things

.travis.yml

@@ -7,7 +7,6 @@ cache:
         - $HOME/.composer/cache
 
 php:
-    - 7.0
     - 7.1
     - 7.2
 

README.md

@@ -1,4 +1,7 @@
 # Pure PHP RRDtool file reader
+[![Build Status](https://travis-ci.org/aldas/rrd-php-reader.svg?branch=master)](https://travis-ci.org/aldas/rrd-php-reader)
+[![codecov](https://codecov.io/gh/aldas/rrd-php-reader/branch/master/graph/badge.svg)](https://codecov.io/gh/aldas/rrd-php-reader)
+
 
 > Because on windows php ext-rrd can not read rrd files created on unix and vice versa.
 > See https://github.com/oetiker/rrdtool-1.x/issues/759
@@ -7,31 +10,46 @@ This library supports reading:
 * rrds created on 64bit linux from 64bit Windows
 * rrds created on 64bit Windows from 64bit Linux
 
-**Only meant to export/dump data out of rrd file. No support for consolidation function etc**
+**Only meant to export/dump data out of rrd file.**
 
-Original repository: http://javascriptrrd.sourceforge.net/
+This library is based on [javascriptRRD](http://javascriptrrd.sourceforge.net/)
 
 ## Example
 
+Convert RRD to CSV:  [rrd_to_csv.php](examples/rrd_to_csv.php)
+```
+$reader = RrdReader::createFromPath('path/to/my_rrd.rrd');
+
+$fp = fopen('output.csv', 'wb');
+$reader->outputAsCsv($fp, [
+    'ds' => 'value'
+]);
+fclose($fp);
 ```
-use RrdPhpReader\RrdReader;
 
+
+Filter rrd: [read_rrd.php](examples/read_rrd.php)
+```
 $reader = RrdReader::createFromPath('path/to/my_rrd.rrd');
 
-$data = $reader->setDs('value')->setRraIndex(0)->getAsArray();
+$traversable = $reader->getAll([
+    'ds' => 'value',
+    'row_filter_callback' => function (int $timestamp, float $value, RrdDs $ds, RraInfo $rra) {
+        return $value < 8;
+    }
+]);
+
+/** @var RrdRowValue $value */
+foreach ($traversable as $value) {
+    echo $value . PHP_EOL;
+}
 
 ```
 
-`$data` structure would be
+Output would be:
 ```
-[
-    'value' => [ <--- datasource as first level keys
-        0 => [   <--- rra index as key
-            1521054891 => 6,  <--- timestamp => value
-            1521054892 => 7,
-            1521054893 => 8,
-            1521054894 => 9,
-        ]
-    ]
-];
+timestamp=1521054891, value=6.000000, cf=AVERAGE, ds=value, step=1
+timestamp=1521054892, value=7.000000, cf=AVERAGE, ds=value, step=1
+timestamp=1521054891, value=6.000000, cf=MAX, ds=value, step=1
+timestamp=1521054892, value=7.000000, cf=MAX, ds=value, step=1
 ```