[Process] Add output / error output incremental getters

src/Symfony/Component/Process/Process.php

@@ -51,6 +51,8 @@ class Process
     private $pipes;
     private $process;
     private $status = self::STATUS_READY;
+    private $incrementalOutputOffset;
+    private $incrementalErrorOutputOffset;
 
     private $fileHandles;
     private $readBytes;
@@ -205,6 +207,8 @@ class Process
 
         $this->stdout = '';
         $this->stderr = '';
+        $this->incrementalOutputOffset = 0;
+        $this->incrementalErrorOutputOffset = 0;
         $callback = $this->buildCallback($callback);
 
         //Fix for PHP bug #51800: reading from STDOUT pipe hangs forever on Windows if the output is too big.
@@ -413,6 +417,24 @@ class Process
         return $this->stdout;
     }
 
+    /**
+     * Returns the output incrementally.
+     *
+     * In comparison with the getOutput method which always return the whole
+     * output, this one returns the new output since the last call.
+     *
+     * @return string The process output since the last call
+     */
+    public function getIncrementalOutput()
+    {
+        $data = $this->getOutput();
+
+        $latest = substr($data, $this->incrementalOutputOffset);
+        $this->incrementalOutputOffset = strlen($data);
+
+        return $latest;
+    }
+
     /**
      * Returns the current error output of the process (STDERR).
      *
@@ -427,6 +449,25 @@ class Process
         return $this->stderr;
     }
 
+    /**
+     * Returns the errorOutput incrementally.
+     *
+     * In comparison with the getErrorOutput method which always return the
+     * whole error output, this one returns the new error output since the last
+     * call.
+     *
+     * @return string The process error output since the last call
+     */
+    public function getIncrementalErrorOutput()
+    {
+        $data = $this->getErrorOutput();
+
+        $latest = substr($data, $this->incrementalErrorOutputOffset);
+        $this->incrementalErrorOutputOffset = strlen($data);
+
+        return $latest;
+    }
+
     /**
      * Returns the exit code returned by the process.
      *

src/Symfony/Component/Process/Tests/AbstractProcessTest.php

@@ -88,6 +88,44 @@ abstract class AbstractProcessTest extends \PHPUnit_Framework_TestCase
         $this->assertTrue($called, 'The callback should be executed with the output');
     }
 
+    public function testGetErrorOutput()
+    {
+        $p = new Process(sprintf('php -r %s', escapeshellarg('ini_set(\'display_errors\',\'on\');$n=0;while($n<3){echo $a;$n++;}')));
+
+        $p->run();
+        $this->assertEquals(3, preg_match_all('/PHP Notice/', $p->getErrorOutput(), $matches));
+    }
+
+    public function testGetIncrementalErrorOutput()
+    {
+        $p = new Process(sprintf('php -r %s', escapeshellarg('ini_set(\'display_errors\',\'on\');usleep(50000);$n=0;while($n<3){echo $a;$n++;}')));
+
+        $p->start();
+        while($p->isRunning()) {
+            $this->assertLessThanOrEqual(1, preg_match_all('/PHP Notice/', $p->getIncrementalOutput(), $matches));
+            usleep(20000);
+        }
+    }
+
+    public function testGetOutput()
+    {
+        $p = new Process(sprintf('php -r %s', escapeshellarg('$n=0;while($n<3){echo \' foo \';$n++;}')));
+
+        $p->run();
+        $this->assertEquals(3, preg_match_all('/foo/', $p->getOutput(), $matches));
+    }
+
+    public function testGetIncrementalOutput()
+    {
+        $p = new Process(sprintf('php -r %s', escapeshellarg('$n=0;while($n<3){echo \' foo \';usleep(50000);$n++;}')));
+
+        $p->start();
+        while($p->isRunning()) {
+            $this->assertLessThanOrEqual(1, preg_match_all('/foo/', $p->getIncrementalOutput(), $matches));
+            usleep(20000);
+        }
+    }
+
     public function testExitCodeCommandFailed()
     {
         if (defined('PHP_WINDOWS_VERSION_BUILD')) {