Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/lib/Drupal/Component/Gettext/PoHeader.php

@@ -0,0 +1,567 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Gettext\PoHeader.
+ */
+
+namespace Drupal\Component\Gettext;
+
+/**
+ * Gettext PO header handler.
+ *
+ * Possible Gettext PO header elements are explained in
+ * http://www.gnu.org/software/gettext/manual/gettext.html#Header-Entry,
+ * but we only support a subset of these directly.
+ *
+ * Example header:
+ *
+ * "Project-Id-Version: Drupal core (7.11)\n"
+ * "POT-Creation-Date: 2012-02-12 22:59+0000\n"
+ * "PO-Revision-Date: YYYY-mm-DD HH:MM+ZZZZ\n"
+ * "Language-Team: Catalan\n"
+ * "MIME-Version: 1.0\n"
+ * "Content-Type: text/plain; charset=utf-8\n"
+ * "Content-Transfer-Encoding: 8bit\n"
+ * "Plural-Forms: nplurals=2; plural=(n>1);\n"
+ */
+class PoHeader {
+
+  /**
+   * Language code.
+   *
+   * @var string
+   */
+  private $_langcode;
+
+  /**
+   * Formula for the plural form.
+   *
+   * @var string
+   */
+  private $_pluralForms;
+
+  /**
+   * Author(s) of the file.
+   *
+   * @var string
+   */
+  private $_authors;
+
+  /**
+   * Date the po file got created.
+   *
+   * @var string
+   */
+  private $_po_date;
+
+  /**
+   * Human readable language name.
+   *
+   * @var string
+   */
+  private $_languageName;
+
+  /**
+   * Name of the project the translation belongs to.
+   *
+   * @var string
+   */
+  private $_projectName;
+
+  /**
+   * Constructor, creates a PoHeader with default values.
+   *
+   * @param string $langcode
+   *   Language code.
+   */
+  public function __construct($langcode = NULL) {
+    $this->_langcode = $langcode;
+    // Ignore errors when run during site installation before
+    // date_default_timezone_set() is called.
+    $this->_po_date = @date("Y-m-d H:iO");
+    $this->_pluralForms = 'nplurals=2; plural=(n > 1);';
+  }
+
+  /**
+   * Gets the plural form.
+   *
+   * @return string
+   *   Plural form component from the header, for example:
+   *   'nplurals=2; plural=(n > 1);'.
+   */
+  function getPluralForms() {
+    return $this->_pluralForms;
+  }
+
+  /**
+   * Set the human readable language name.
+   *
+   * @param string $languageName
+   *   Human readable language name.
+   */
+  function setLanguageName($languageName) {
+    $this->_languageName = $languageName;
+  }
+
+  /**
+   * Gets the human readable language name.
+   *
+   * @return string
+   *   The human readable language name.
+   */
+  function getLanguageName() {
+    return $this->_languageName;
+  }
+
+  /**
+   * Set the project name.
+   *
+   * @param string $projectName
+   *   Human readable project name.
+   */
+  function setProjectName($projectName) {
+    $this->_projectName = $projectName;
+  }
+
+  /**
+   * Gets the project name.
+   *
+   * @return string
+   *   The human readable project name.
+   */
+  function getProjectName() {
+    return $this->_projectName;
+  }
+
+  /**
+   * Populate internal values from a string.
+   *
+   * @param string $header
+   *   Full header string with key-value pairs.
+   */
+  public function setFromString($header) {
+    // Get an array of all header values for processing.
+    $values = $this->parseHeader($header);
+
+    // There is only one value relevant for our header implementation when
+    // reading, and that is the plural formula.
+    if (!empty($values['Plural-Forms'])) {
+      $this->_pluralForms = $values['Plural-Forms'];
+    }
+  }
+
+  /**
+   * Generate a Gettext PO formatted header string based on data set earlier.
+   */
+  public function __toString() {
+    $output = '';
+
+    $isTemplate = empty($this->_languageName);
+
+    $output .= '# ' . ($isTemplate ? 'LANGUAGE' : $this->_languageName) . ' translation of ' . ($isTemplate ? 'PROJECT' : $this->_projectName) . "\n";
+    if (!empty($this->_authors)) {
+      $output .= '# Generated by ' . implode("\n# ", $this->_authors) . "\n";
+    }
+    $output .= "#\n";
+
+    // Add the actual header information.
+    $output .= "msgid \"\"\n";
+    $output .= "msgstr \"\"\n";
+    $output .= "\"Project-Id-Version: PROJECT VERSION\\n\"\n";
+    $output .= "\"POT-Creation-Date: " . $this->_po_date . "\\n\"\n";
+    $output .= "\"PO-Revision-Date: " . $this->_po_date . "\\n\"\n";
+    $output .= "\"Last-Translator: NAME <EMAIL@ADDRESS>\\n\"\n";
+    $output .= "\"Language-Team: LANGUAGE <EMAIL@ADDRESS>\\n\"\n";
+    $output .= "\"MIME-Version: 1.0\\n\"\n";
+    $output .= "\"Content-Type: text/plain; charset=utf-8\\n\"\n";
+    $output .= "\"Content-Transfer-Encoding: 8bit\\n\"\n";
+    $output .= "\"Plural-Forms: " . $this->_pluralForms . "\\n\"\n";
+    $output .= "\n";
+
+    return $output;
+  }
+
+  /**
+   * Parses a Plural-Forms entry from a Gettext Portable Object file header.
+   *
+   * @param string $pluralforms
+   *   The Plural-Forms entry value.
+   *
+   * @return
+   *   An indexed array of parsed plural formula data. Containing:
+   *   - 'nplurals': The number of plural forms defined by the plural formula.
+   *   - 'plurals': Array of plural positions keyed by plural value.
+   *
+   * @throws Exception
+   */
+  function parsePluralForms($pluralforms) {
+    $plurals = array();
+    // First, delete all whitespace.
+    $pluralforms = strtr($pluralforms, array(" " => "", "\t" => ""));
+
+    // Select the parts that define nplurals and plural.
+    $nplurals = strstr($pluralforms, "nplurals=");
+    if (strpos($nplurals, ";")) {
+      // We want the string from the 10th char, because "nplurals=" length is 9.
+      $nplurals = substr($nplurals, 9, strpos($nplurals, ";") - 9);
+    }
+    else {
+      return FALSE;
+    }
+    $plural = strstr($pluralforms, "plural=");
+    if (strpos($plural, ";")) {
+      // We want the string from the 8th char, because "plural=" length is 7.
+      $plural = substr($plural, 7, strpos($plural, ";") - 7);
+    }
+    else {
+      return FALSE;
+    }
+
+    // If the number of plurals is zero, we return a default result.
+    if ($nplurals == 0) {
+      return array($nplurals, array('default' => 0));
+    }
+
+    // Calculate possible plural positions of different plural values. All known
+    // plural formula's are repetitive above 100.
+    // For data compression we store the last position the array value
+    // changes and store it as default.
+    $element_stack = $this->parseArithmetic($plural);
+    if ($element_stack !== FALSE) {
+      for ($i = 0; $i <= 199; $i++) {
+        $plurals[$i] = $this->evaluatePlural($element_stack, $i);
+      }
+      $default = $plurals[$i - 1];
+      $plurals = array_filter($plurals, function ($value) use ($default) {
+        return ($value != $default);
+      });
+      $plurals['default'] = $default;
+
+      return array($nplurals, $plurals);
+    }
+    else {
+      throw new \Exception('The plural formula could not be parsed.');
+    }
+  }
+
+  /**
+   * Parses a Gettext Portable Object file header.
+   *
+   * @param string $header
+   *   A string containing the complete header.
+   *
+   * @return array
+   *   An associative array of key-value pairs.
+   */
+  private function parseHeader($header) {
+    $header_parsed = array();
+    $lines = array_map('trim', explode("\n", $header));
+    foreach ($lines as $line) {
+      if ($line) {
+        list($tag, $contents) = explode(":", $line, 2);
+        $header_parsed[trim($tag)] = trim($contents);
+      }
+    }
+    return $header_parsed;
+  }
+
+  /**
+   * Parses and sanitizes an arithmetic formula into a plural element stack.
+   *
+   * While parsing, we ensure, that the operators have the right
+   * precedence and associativity.
+   *
+   * @param string $string
+   *   A string containing the arithmetic formula.
+   *
+   * @return
+   *   A stack of values and operations to be evaluated.
+   */
+  private function parseArithmetic($string) {
+    // Operator precedence table.
+    $precedence = array("(" => -1, ")" => -1, "?" => 1, ":" => 1, "||" => 3, "&&" => 4, "==" => 5, "!=" => 5, "<" => 6, ">" => 6, "<=" => 6, ">=" => 6, "+" => 7, "-" => 7, "*" => 8, "/" => 8, "%" => 8);
+    // Right associativity.
+    $right_associativity = array("?" => 1, ":" => 1);
+
+    $tokens = $this->tokenizeFormula($string);
+
+    // Parse by converting into infix notation then back into postfix
+    // Operator stack - holds math operators and symbols.
+    $operator_stack = array();
+    // Element Stack - holds data to be operated on.
+    $element_stack = array();
+
+    foreach ($tokens as $token) {
+      $current_token = $token;
+
+      // Numbers and the $n variable are simply pushed into $element_stack.
+      if (is_numeric($token)) {
+        $element_stack[] = $current_token;
+      }
+      elseif ($current_token == "n") {
+        $element_stack[] = '$n';
+      }
+      elseif ($current_token == "(") {
+        $operator_stack[] = $current_token;
+      }
+      elseif ($current_token == ")") {
+        $topop = array_pop($operator_stack);
+        while (isset($topop) && ($topop != "(")) {
+          $element_stack[] = $topop;
+          $topop = array_pop($operator_stack);
+        }
+      }
+      elseif (!empty($precedence[$current_token])) {
+        // If it's an operator, then pop from $operator_stack into
+        // $element_stack until the precedence in $operator_stack is less
+        // than current, then push into $operator_stack.
+        $topop = array_pop($operator_stack);
+        while (isset($topop) && ($precedence[$topop] >= $precedence[$current_token]) && !(($precedence[$topop] == $precedence[$current_token]) && !empty($right_associativity[$topop]) && !empty($right_associativity[$current_token]))) {
+          $element_stack[] = $topop;
+          $topop = array_pop($operator_stack);
+        }
+        if ($topop) {
+          // Return element to top.
+          $operator_stack[] = $topop;
+        }
+        // Parentheses are not needed.
+        $operator_stack[] = $current_token;
+      }
+      else {
+        return FALSE;
+      }
+    }
+
+    // Flush operator stack.
+    $topop = array_pop($operator_stack);
+    while ($topop != NULL) {
+      $element_stack[] = $topop;
+      $topop = array_pop($operator_stack);
+    }
+    $return = $element_stack;
+
+    // Now validate stack.
+    $previous_size = count($element_stack) + 1;
+    while (count($element_stack) < $previous_size) {
+      $previous_size = count($element_stack);
+      for ($i = 2; $i < count($element_stack); $i++) {
+        $op = $element_stack[$i];
+        if (!empty($precedence[$op])) {
+          if ($op == ":") {
+            $f = $element_stack[$i - 2] . "):" . $element_stack[$i - 1] . ")";
+          }
+          elseif ($op == "?") {
+            $f = "(" . $element_stack[$i - 2] . "?(" . $element_stack[$i - 1];
+          }
+          else {
+            $f = "(" . $element_stack[$i - 2] . $op . $element_stack[$i - 1] . ")";
+          }
+          array_splice($element_stack, $i - 2, 3, $f);
+          break;
+        }
+      }
+    }
+
+    // If only one element is left, the number of operators is appropriate.
+    return count($element_stack) == 1 ? $return : FALSE;
+  }
+
+  /**
+   * Tokenize the formula.
+   *
+   * @param string $formula
+   *   A string containing the arithmetic formula.
+   *
+   * @return array
+   *   List of arithmetic tokens identified in the formula.
+   */
+  private function tokenizeFormula($formula) {
+    $formula = str_replace(" ", "", $formula);
+    $tokens = array();
+    for ($i = 0; $i < strlen($formula); $i++) {
+      if (is_numeric($formula[$i])) {
+        $num = $formula[$i];
+        $j = $i + 1;
+        while ($j < strlen($formula) && is_numeric($formula[$j])) {
+          $num .= $formula[$j];
+          $j++;
+        }
+        $i = $j - 1;
+        $tokens[] = $num;
+      }
+      elseif ($pos = strpos(" =<>!&|", $formula[$i])) {
+        $next = $formula[$i + 1];
+        switch ($pos) {
+          case 1:
+          case 2:
+          case 3:
+          case 4:
+            if ($next == '=') {
+              $tokens[] = $formula[$i] . '=';
+              $i++;
+            }
+            else {
+              $tokens[] = $formula[$i];
+            }
+            break;
+          case 5:
+            if ($next == '&') {
+              $tokens[] = '&&';
+              $i++;
+            }
+            else {
+              $tokens[] = $formula[$i];
+            }
+            break;
+          case 6:
+            if ($next == '|') {
+              $tokens[] = '||';
+              $i++;
+            }
+            else {
+              $tokens[] = $formula[$i];
+            }
+            break;
+        }
+      }
+      else {
+        $tokens[] = $formula[$i];
+      }
+    }
+    return $tokens;
+  }
+
+  /**
+   * Evaluate the plural element stack using a plural value.
+   *
+   * Using an element stack, which represents a plural formula, we calculate
+   * which plural string should be used for a given plural value.
+   *
+   * An example of plural formula parting and evaluation:
+   *   Plural formula: 'n!=1'
+   * This formula is parsed by parseArithmetic() to a stack (array) of elements:
+   *   array(
+   *     0 => '$n',
+   *     1 => '1',
+   *     2 => '!=',
+   *   );
+   * The evaluatePlural() method evaluates the $element_stack using the plural
+   * value $n. Before the actual evaluation, the '$n' in the array is replaced
+   * by the value of $n.
+   *   For example: $n = 2 results in:
+   *   array(
+   *     0 => '2',
+   *     1 => '1',
+   *     2 => '!=',
+   *   );
+   * The stack is processed until only one element is (the result) is left. In
+   * every iteration the top elements of the stack, up until the first operator,
+   * are evaluated. After evaluation the arguments and the operator itself are
+   * removed and replaced by the evaluation result. This is typically 2
+   * arguments and 1 element for the operator.
+   *   Because the operator is '!=' the example stack is evaluated as:
+   *   $f = (int) 2 != 1;
+   *   The resulting stack is:
+   *   array(
+   *     0 => 1,
+   *   );
+   * With only one element left in the stack (the final result) the loop is
+   * terminated and the result is returned.
+   *
+   * @param array $element_stack
+   *   Array of plural formula values and operators create by parseArithmetic().
+   * @param integer $n
+   *   The @count number for which we are determining the right plural position.
+   *
+   * @return integer
+   *   Number of the plural string to be used for the given plural value.
+   *
+   * @see parseArithmetic()
+   * @throws Exception
+   */
+  protected function evaluatePlural($element_stack, $n) {
+    $count = count($element_stack);
+    $limit = $count;
+    // Replace the '$n' value in the formula by the plural value.
+    for ($i = 0; $i < $count; $i++) {
+      if ($element_stack[$i] === '$n') {
+        $element_stack[$i] = $n;
+      }
+    }
+
+    // We process the stack until only one element is (the result) is left.
+    // We limit the number of evaluation cycles to prevent an endless loop in
+    // case the stack contains an error.
+    while (isset($element_stack[1])) {
+      for ($i = 2; $i < $count; $i++) {
+        // There's no point in checking non-symbols. Also, switch(TRUE) would
+        // match any case and so it would break.
+        if (is_bool($element_stack[$i]) || is_numeric($element_stack[$i])) {
+          continue;
+        }
+        $f = NULL;
+        $length = 3;
+        $delta = 2;
+        switch ($element_stack[$i]) {
+          case '==':
+            $f = $element_stack[$i - 2] == $element_stack[$i - 1];
+            break;
+          case '!=':
+            $f = $element_stack[$i - 2] != $element_stack[$i - 1];
+            break;
+          case '<=':
+            $f = $element_stack[$i - 2] <= $element_stack[$i - 1];
+            break;
+          case '>=':
+            $f = $element_stack[$i - 2] >= $element_stack[$i - 1];
+            break;
+          case '<':
+            $f = $element_stack[$i - 2] < $element_stack[$i - 1];
+            break;
+          case '>':
+            $f = $element_stack[$i - 2] > $element_stack[$i - 1];
+            break;
+          case '+':
+            $f = $element_stack[$i - 2] + $element_stack[$i - 1];
+            break;
+          case '-':
+            $f = $element_stack[$i - 2] - $element_stack[$i - 1];
+            break;
+          case '*':
+            $f = $element_stack[$i - 2] * $element_stack[$i - 1];
+            break;
+          case '/':
+            $f = $element_stack[$i - 2] / $element_stack[$i - 1];
+            break;
+          case '%':
+            $f = $element_stack[$i - 2] % $element_stack[$i - 1];
+            break;
+          case '&&':
+            $f = $element_stack[$i - 2] && $element_stack[$i - 1];
+            break;
+          case '||':
+            $f = $element_stack[$i - 2] || $element_stack[$i - 1];
+            break;
+          case ':':
+            $f = $element_stack[$i - 3] ? $element_stack[$i - 2] : $element_stack[$i - 1];
+            // This operator has 3 preceding elements, instead of the default 2.
+            $length = 5;
+            $delta = 3;
+            break;
+        }
+
+        // If the element is an operator we remove the processed elements and
+        // store the result.
+        if (isset($f)) {
+          array_splice($element_stack, $i - $delta, $length, $f);
+          break;
+        }
+      }
+    }
+    if (!$limit) {
+      throw new \Exception('The plural formula could not be evaluated.');
+    }
+    return (int) $element_stack[0];
+  }
+}

core/lib/Drupal/Component/Gettext/PoItem.php

@@ -0,0 +1,287 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Gettext\PoItem.
+ */
+
+namespace Drupal\Component\Gettext;
+
+/**
+ * PoItem handles one translation.
+ *
+ * @todo: This class contains some really old legacy code.
+ * @see https://www.drupal.org/node/1637662
+ */
+class PoItem {
+
+  /**
+   * The language code this translation is in.
+   *
+   * @car string
+   */
+  private $_langcode;
+
+  /**
+   * The context this translation belongs to.
+   *
+   * @var string
+   */
+  private $_context = '';
+
+  /**
+   * The source string or array of strings if it has plurals.
+   *
+   * @var string or array
+   * @see $_plural
+   */
+  private $_source;
+
+  /**
+   * Flag indicating if this translation has plurals.
+   *
+   * @var bool
+   */
+  private $_plural;
+
+  /**
+   * The comment of this translation.
+   *
+   * @var string
+   */
+  private $_comment;
+
+  /**
+   * The translation string or array of strings if it has plurals.
+   *
+   * @var string or array
+   * @see $_plural
+   */
+  private $_translation;
+
+  /**
+   * Gets the language code of the currently used language.
+   *
+   * @return string with langcode
+   */
+  function getLangcode() {
+    return $this->_langcode;
+  }
+
+  /**
+   * Set the language code of the current language.
+   *
+   * @param string $langcode
+   */
+  function setLangcode($langcode) {
+    $this->_langcode = $langcode;
+  }
+
+  /**
+   * Gets the context this translation belongs to.
+   *
+   * @return string $context
+   */
+  function getContext() {
+    return $this->_context;
+  }
+
+  /**
+   * Set the context this translation belongs to.
+   *
+   * @param string $context
+   */
+  function setContext($context) {
+    $this->_context = $context;
+  }
+
+  /**
+   * Gets the source string or the array of strings if the translation has
+   * plurals.
+   *
+   * @return string or array $translation
+   */
+  function getSource() {
+    return $this->_source;
+  }
+
+  /**
+   * Set the source string or the array of strings if the translation has
+   * plurals.
+   *
+   * @param string or array $source
+   */
+  function setSource($source) {
+    $this->_source = $source;
+  }
+
+  /**
+   * Gets the translation string or the array of strings if the translation has
+   * plurals.
+   *
+   * @return string or array $translation
+   */
+  function getTranslation() {
+    return $this->_translation;
+  }
+
+  /**
+   * Set the translation string or the array of strings if the translation has
+   * plurals.
+   *
+   * @param string or array $translation
+   */
+  function setTranslation($translation) {
+    $this->_translation = $translation;
+  }
+
+  /**
+   * Set if the translation has plural values.
+   *
+   * @param bool $plural
+   */
+  function setPlural($plural) {
+    $this->_plural = $plural;
+  }
+
+  /**
+   * Get if the translation has plural values.
+   *
+   * @return boolean $plural
+   */
+  function isPlural() {
+    return $this->_plural;
+  }
+
+  /**
+   * Gets the comment of this translation.
+   *
+   * @return String $comment
+   */
+  function getComment() {
+    return $this->_comment;
+  }
+
+  /**
+   * Set the comment of this translation.
+   *
+   * @param String $comment
+   */
+  function setComment($comment) {
+    $this->_comment = $comment;
+  }
+
+  /**
+   * Create the PoItem from a structured array.
+   *
+   * @param array values
+   */
+  public function setFromArray(array $values = array()) {
+    if (isset($values['context'])) {
+      $this->setContext($values['context']);
+    }
+    if (isset($values['source'])) {
+      $this->setSource($values['source']);
+    }
+    if (isset($values['translation'])) {
+      $this->setTranslation($values['translation']);
+    }
+    if (isset($values['comment'])){
+      $this->setComment($values['comment']);
+    }
+    if (isset($this->_source) &&
+        strpos($this->_source, LOCALE_PLURAL_DELIMITER) !== FALSE) {
+      $this->setSource(explode(LOCALE_PLURAL_DELIMITER, $this->_source));
+      $this->setTranslation(explode(LOCALE_PLURAL_DELIMITER, $this->_translation));
+      $this->setPlural(count($this->_translation) > 1);
+    }
+  }
+
+  /**
+   * Output the PoItem as a string.
+   */
+  public function __toString() {
+    return $this->formatItem();
+  }
+
+  /**
+   * Format the POItem as a string.
+   */
+  private function formatItem() {
+    $output = '';
+
+    // Format string context.
+    if (!empty($this->_context)) {
+      $output .= 'msgctxt ' . $this->formatString($this->_context);
+    }
+
+    // Format translation.
+    if ($this->_plural) {
+      $output .= $this->formatPlural();
+    }
+    else {
+      $output .= $this->formatSingular();
+    }
+
+    // Add one empty line to separate the translations.
+    $output .= "\n";
+
+    return $output;
+  }
+
+  /**
+   * Formats a plural translation.
+   */
+  private function formatPlural() {
+    $output = '';
+
+    // Format source strings.
+    $output .= 'msgid ' . $this->formatString($this->_source[0]);
+    $output .= 'msgid_plural ' . $this->formatString($this->_source[1]);
+
+    foreach ($this->_translation as $i => $trans) {
+      if (isset($this->_translation[$i])) {
+        $output .= 'msgstr[' . $i . '] ' . $this->formatString($trans);
+      }
+      else {
+        $output .= 'msgstr[' . $i . '] ""' . "\n";
+      }
+    }
+
+    return $output;
+  }
+
+  /**
+   * Formats a singular translation.
+   */
+  private function formatSingular() {
+    $output = '';
+    $output .= 'msgid ' . $this->formatString($this->_source);
+    $output .= 'msgstr ' . (isset($this->_translation) ? $this->formatString($this->_translation) : '""');
+    return $output;
+  }
+
+  /**
+   * Formats a string for output on multiple lines.
+   */
+  private function formatString($string) {
+    // Escape characters for processing.
+    $string = addcslashes($string, "\0..\37\\\"");
+
+    // Always include a line break after the explicit \n line breaks from
+    // the source string. Otherwise wrap at 70 chars to accommodate the extra
+    // format overhead too.
+    $parts = explode("\n", wordwrap(str_replace('\n', "\\n\n", $string), 70, " \n"));
+
+    // Multiline string should be exported starting with a "" and newline to
+    // have all lines aligned on the same column.
+    if (count($parts) > 1) {
+      return "\"\"\n\"" . implode("\"\n\"", $parts) . "\"\n";
+    }
+    // Single line strings are output on the same line.
+    else {
+      return "\"$parts[0]\"\n";
+    }
+  }
+
+}

core/lib/Drupal/Component/Gettext/PoMemoryWriter.php

@@ -0,0 +1,96 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Gettext\PoMemoryWriter.
+ */
+
+namespace Drupal\Component\Gettext;
+
+use Drupal\Component\Gettext\PoWriterInterface;
+use Drupal\Component\Gettext\PoHeader;
+use Drupal\Component\Gettext\PoItem;
+
+/**
+ * Defines a Gettext PO memory writer, to be used by the installer.
+ */
+class PoMemoryWriter implements PoWriterInterface {
+
+  /**
+   * Array to hold all PoItem elements.
+   *
+   * @var array
+   */
+  private $_items;
+
+  /**
+   * Constructor, initialize empty items.
+   */
+  function __construct() {
+    $this->_items = array();
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoWriterInterface::writeItem().
+   */
+  public function writeItem(PoItem $item) {
+    if (is_array($item->getSource())) {
+      $item->setSource(implode(LOCALE_PLURAL_DELIMITER, $item->getSource()));
+      $item->setTranslation(implode(LOCALE_PLURAL_DELIMITER, $item->getTranslation()));
+    }
+    $context = $item->getContext();
+    $this->_items[$context != NULL ? $context : ''][$item->getSource()] = $item->getTranslation();
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoWriterInterface::writeItems().
+   */
+  public function writeItems(PoReaderInterface $reader, $count = -1) {
+    $forever = $count == -1;
+    while (($count-- > 0 || $forever) && ($item = $reader->readItem())) {
+      $this->writeItem($item);
+    }
+  }
+
+  /**
+   * Get all stored PoItem's.
+   *
+   * @return array PoItem
+   */
+  public function getData() {
+    return $this->_items;
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoMetadataInterface:setLangcode().
+   *
+   * Not implemented. Not relevant for the MemoryWriter.
+   */
+  function setLangcode($langcode) {
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoMetadataInterface:getLangcode().
+   *
+   * Not implemented. Not relevant for the MemoryWriter.
+   */
+  function getLangcode() {
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoMetadataInterface:getHeader().
+   *
+   * Not implemented. Not relevant for the MemoryWriter.
+   */
+  function getHeader() {
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoMetadataInterface:setHeader().
+   *
+   * Not implemented. Not relevant for the MemoryWriter.
+   */
+  function setHeader(PoHeader $header) {
+  }
+
+}

core/lib/Drupal/Component/Gettext/PoMetadataInterface.php

@@ -0,0 +1,52 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Gettext\PoMetadataInterface.
+ */
+
+namespace Drupal\Component\Gettext;
+
+use Drupal\Component\Gettext\PoHeader;
+
+/**
+ * Methods required for both reader and writer implementations.
+ *
+ * @see \Drupal\Component\Gettext\PoReaderInterface
+ * @see \Drupal\Component\Gettext\PoWriterInterface
+ */
+interface PoMetadataInterface {
+
+  /**
+   * Set language code.
+   *
+   * @param string $langcode
+   *   Language code string.
+   */
+  public function setLangcode($langcode);
+
+  /**
+   * Get language code.
+   *
+   * @return string
+   *   Language code string.
+   */
+  public function getLangcode();
+
+  /**
+   * Set header metadata.
+   *
+   * @param \Drupal\Component\Gettext\PoHeader $header
+   *   Header object representing metadata in a PO header.
+   */
+  public function setHeader(PoHeader $header);
+
+  /**
+   * Get header metadata.
+   *
+   * @return \Drupal\Component\Gettext\PoHeader $header
+   *   Header instance representing metadata in a PO header.
+   */
+  public function getHeader();
+
+}

core/lib/Drupal/Component/Gettext/PoReaderInterface.php

@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Gettext\PoReaderInterface.
+ */
+
+namespace Drupal\Component\Gettext;
+
+use Drupal\Component\Gettext\PoMetadataInterface;
+
+/**
+ * Shared interface definition for all Gettext PO Readers.
+ */
+interface PoReaderInterface extends PoMetadataInterface {
+
+  /**
+   * Reads and returns a PoItem (source/translation pair).
+   *
+   * @return \Drupal\Component\Gettext\PoItem
+   *   Wrapper for item data instance.
+   */
+  public function readItem();
+
+}

core/lib/Drupal/Component/Gettext/PoStreamInterface.php

@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Gettext\PoStreamInterface.
+ */
+
+namespace Drupal\Component\Gettext;
+
+/**
+ * Common functions for file/stream based PO readers/writers.
+ *
+ * @see PoReaderInterface
+ * @see PoWriterInterface
+ */
+interface PoStreamInterface {
+
+  /**
+   * Open the stream. Set the URI for the stream earlier with setURI().
+   */
+  public function open();
+
+  /**
+   * Close the stream.
+   */
+  public function close();
+
+  /**
+   * Gets the URI of the PO stream that is being read or written.
+   *
+   * @return
+   *   URI string for this stream.
+   */
+  public function getURI();
+
+  /**
+   * Set the URI of the PO stream that is going to be read or written.
+   *
+   * @param $uri
+   *   URI string to set for this stream.
+   */
+  public function setURI($uri);
+
+}

core/lib/Drupal/Component/Gettext/PoStreamReader.php

@@ -0,0 +1,602 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Gettext\PoStreamReader.
+ */
+
+namespace Drupal\Component\Gettext;
+
+use Drupal\Component\Gettext\PoReaderInterface;
+use Drupal\Component\Gettext\PoStreamInterface;
+use Drupal\Component\Gettext\PoHeader;
+use Drupal\Component\Utility\SafeMarkup;
+
+/**
+ * Implements Gettext PO stream reader.
+ *
+ * The PO file format parsing is implemented according to the documentation at
+ * http://www.gnu.org/software/gettext/manual/gettext.html#PO-Files
+ */
+class PoStreamReader implements PoStreamInterface, PoReaderInterface {
+
+  /**
+   * Source line number of the stream being parsed.
+   *
+   * @var int
+   */
+  private $_line_number = 0;
+
+  /**
+   * Parser context for the stream reader state machine.
+   *
+   * Possible contexts are:
+   *  - 'COMMENT' (#)
+   *  - 'MSGID' (msgid)
+   *  - 'MSGID_PLURAL' (msgid_plural)
+   *  - 'MSGCTXT' (msgctxt)
+   *  - 'MSGSTR' (msgstr or msgstr[])
+   *  - 'MSGSTR_ARR' (msgstr_arg)
+   *
+   * @var string
+   */
+  private $_context = 'COMMENT';
+
+  /**
+   * Current entry being read. Incomplete.
+   *
+   * @var array
+   */
+  private $_current_item = array();
+
+  /**
+   * Current plural index for plural translations.
+   *
+   * @var int
+   */
+  private $_current_plural_index = 0;
+
+  /**
+   * URI of the PO stream that is being read.
+   *
+   * @var string
+   */
+  private $_uri = '';
+
+  /**
+   * Language code for the PO stream being read.
+   *
+   * @var string
+   */
+  private $_langcode = NULL;
+
+  /**
+   * File handle of the current PO stream.
+   *
+   * @var resource
+   */
+  private $_fd;
+
+  /**
+   * The PO stream header.
+   *
+   * @var \Drupal\Component\Gettext\PoHeader
+   */
+  private $_header;
+
+  /**
+   * Object wrapper for the last read source/translation pair.
+   *
+   * @var \Drupal\Component\Gettext\PoItem
+   */
+  private $_last_item;
+
+  /**
+   * Indicator of whether the stream reading is finished.
+   *
+   * @var bool
+   */
+  private $_finished;
+
+  /**
+   * Array of translated error strings recorded on reading this stream so far.
+   *
+   * @var array
+   */
+  private $_errors;
+
+  /**
+   * Implements Drupal\Component\Gettext\PoMetadataInterface::getLangcode().
+   */
+  public function getLangcode() {
+    return $this->_langcode;
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoMetadataInterface::setLangcode().
+   */
+  public function setLangcode($langcode) {
+    $this->_langcode = $langcode;
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoMetadataInterface::getHeader().
+   */
+  public function getHeader() {
+    return $this->_header;
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoMetadataInterface::setHeader().
+   *
+   * Not applicable to stream reading and therefore not implemented.
+   */
+  public function setHeader(PoHeader $header) {
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoStreamInterface::getURI().
+   */
+  public function getURI() {
+    return $this->_uri;
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoStreamInterface::setURI().
+   */
+  public function setURI($uri) {
+    $this->_uri = $uri;
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoStreamInterface::open().
+   *
+   * Opens the stream and reads the header. The stream is ready for reading
+   * items after.
+   *
+   * @throws Exception
+   *   If the URI is not yet set.
+   */
+  public function open() {
+    if (!empty($this->_uri)) {
+      $this->_fd = fopen($this->_uri, 'rb');
+      $this->readHeader();
+    }
+    else {
+      throw new \Exception('Cannot open stream without URI set.');
+    }
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoStreamInterface::close().
+   *
+   * @throws Exception
+   *   If the stream is not open.
+   */
+  public function close() {
+    if ($this->_fd) {
+      fclose($this->_fd);
+    }
+    else {
+      throw new \Exception('Cannot close stream that is not open.');
+    }
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoReaderInterface::readItem().
+   */
+  public function readItem() {
+    // Clear out the last item.
+    $this->_last_item = NULL;
+
+    // Read until finished with the stream or a complete item was identified.
+    while (!$this->_finished && is_null($this->_last_item)) {
+      $this->readLine();
+    }
+
+    return $this->_last_item;
+  }
+
+  /**
+   * Sets the seek position for the current PO stream.
+   *
+   * @param int $seek
+   *   The new seek position to set.
+   */
+  public function setSeek($seek) {
+    fseek($this->_fd, $seek);
+  }
+
+  /**
+   * Gets the pointer position of the current PO stream.
+   */
+  public function getSeek() {
+    return ftell($this->_fd);
+  }
+
+  /**
+   * Read the header from the PO stream.
+   *
+   * The header is a special case PoItem, using the empty string as source and
+   * key-value pairs as translation. We just reuse the item reader logic to
+   * read the header.
+   */
+  private function readHeader() {
+    $item = $this->readItem();
+    // Handle the case properly when the .po file is empty (0 bytes).
+    if (!$item) {
+      return;
+    }
+    $header = new PoHeader;
+    $header->setFromString(trim($item->getTranslation()));
+    $this->_header = $header;
+  }
+
+  /**
+   * Reads a line from the PO stream and stores data internally.
+   *
+   * Expands $this->_current_item based on new data for the current item. If
+   * this line ends the current item, it is saved with setItemFromArray() with
+   * data from $this->_current_item.
+   *
+   * An internal state machine is maintained in this reader using
+   * $this->_context as the reading state. PO items are in between COMMENT
+   * states (when items have at least one line or comment in between them) or
+   * indicated by MSGSTR or MSGSTR_ARR followed immediately by an MSGID or
+   * MSGCTXT (when items closely follow each other).
+   *
+   * @return
+   *   FALSE if an error was logged, NULL otherwise. The errors are considered
+   *   non-blocking, so reading can continue, while the errors are collected
+   *   for later presentation.
+   */
+  private function readLine() {
+    // Read a line and set the stream finished indicator if it was not
+    // possible anymore.
+    $line = fgets($this->_fd);
+    $this->_finished = ($line === FALSE);
+
+    if (!$this->_finished) {
+
+      if ($this->_line_number == 0) {
+        // The first line might come with a UTF-8 BOM, which should be removed.
+        $line = str_replace("\xEF\xBB\xBF", '', $line);
+        // Current plurality for 'msgstr[]'.
+        $this->_current_plural_index = 0;
+      }
+
+      // Track the line number for error reporting.
+      $this->_line_number++;
+
+      // Initialize common values for error logging.
+      $log_vars = array(
+        '%uri' => $this->getURI(),
+        '%line' => $this->_line_number,
+      );
+
+      // Trim away the linefeed. \\n might appear at the end of the string if
+      // another line continuing the same string follows. We can remove that.
+      $line = trim(strtr($line, array("\\\n" => "")));
+
+      if (!strncmp('#', $line, 1)) {
+        // Lines starting with '#' are comments.
+
+        if ($this->_context == 'COMMENT') {
+          // Already in comment context, add to current comment.
+          $this->_current_item['#'][] = substr($line, 1);
+        }
+        elseif (($this->_context == 'MSGSTR') || ($this->_context == 'MSGSTR_ARR')) {
+          // We are currently in string context, save current item.
+          $this->setItemFromArray($this->_current_item);
+
+          // Start a new entry for the comment.
+          $this->_current_item = array();
+          $this->_current_item['#'][] = substr($line, 1);
+
+          $this->_context = 'COMMENT';
+          return;
+        }
+        else {
+          // A comment following any other context is a syntax error.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: "msgstr" was expected but not found on line %line.', $log_vars);
+          return FALSE;
+        }
+        return;
+      }
+      elseif (!strncmp('msgid_plural', $line, 12)) {
+        // A plural form for the current source string.
+
+        if ($this->_context != 'MSGID') {
+          // A plural form can only be added to an msgid directly.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: "msgid_plural" was expected but not found on line %line.', $log_vars);
+          return FALSE;
+        }
+
+        // Remove 'msgid_plural' and trim away whitespace.
+        $line = trim(substr($line, 12));
+
+        // Only the plural source string is left, parse it.
+        $quoted = $this->parseQuoted($line);
+        if ($quoted === FALSE) {
+          // The plural form must be wrapped in quotes.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains a syntax error on line %line.', $log_vars);
+          return FALSE;
+        }
+
+        // Append the plural source to the current entry.
+        if (is_string($this->_current_item['msgid'])) {
+          // The first value was stored as string. Now we know the context is
+          // plural, it is converted to array.
+          $this->_current_item['msgid'] = array($this->_current_item['msgid']);
+        }
+        $this->_current_item['msgid'][] = $quoted;
+
+        $this->_context = 'MSGID_PLURAL';
+        return;
+      }
+      elseif (!strncmp('msgid', $line, 5)) {
+        // Starting a new message.
+
+        if (($this->_context == 'MSGSTR') || ($this->_context == 'MSGSTR_ARR')) {
+          // We are currently in string context, save current item.
+          $this->setItemFromArray($this->_current_item);
+
+          // Start a new context for the msgid.
+          $this->_current_item = array();
+        }
+        elseif ($this->_context == 'MSGID') {
+          // We are currently already in the context, meaning we passed an id with no data.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: "msgid" is unexpected on line %line.', $log_vars);
+          return FALSE;
+        }
+
+        // Remove 'msgid' and trim away whitespace.
+        $line = trim(substr($line, 5));
+
+        // Only the message id string is left, parse it.
+        $quoted = $this->parseQuoted($line);
+        if ($quoted === FALSE) {
+          // The message id must be wrapped in quotes.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: invalid format for "msgid" on line %line.', $log_vars, $log_vars);
+          return FALSE;
+        }
+
+        $this->_current_item['msgid'] = $quoted;
+        $this->_context = 'MSGID';
+        return;
+      }
+      elseif (!strncmp('msgctxt', $line, 7)) {
+        // Starting a new context.
+
+        if (($this->_context == 'MSGSTR') || ($this->_context == 'MSGSTR_ARR')) {
+          // We are currently in string context, save current item.
+          $this->setItemFromArray($this->_current_item);
+          $this->_current_item = array();
+        }
+        elseif (!empty($this->_current_item['msgctxt'])) {
+          // A context cannot apply to another context.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: "msgctxt" is unexpected on line %line.', $log_vars);
+          return FALSE;
+        }
+
+        // Remove 'msgctxt' and trim away whitespaces.
+        $line = trim(substr($line, 7));
+
+        // Only the msgctxt string is left, parse it.
+        $quoted = $this->parseQuoted($line);
+        if ($quoted === FALSE) {
+          // The context string must be quoted.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: invalid format for "msgctxt" on line %line.', $log_vars);
+          return FALSE;
+        }
+
+        $this->_current_item['msgctxt'] = $quoted;
+
+        $this->_context = 'MSGCTXT';
+        return;
+      }
+      elseif (!strncmp('msgstr[', $line, 7)) {
+        // A message string for a specific plurality.
+
+        if (($this->_context != 'MSGID') &&
+            ($this->_context != 'MSGCTXT') &&
+            ($this->_context != 'MSGID_PLURAL') &&
+            ($this->_context != 'MSGSTR_ARR')) {
+          // Plural message strings must come after msgid, msgxtxt,
+          // msgid_plural, or other msgstr[] entries.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: "msgstr[]" is unexpected on line %line.', $log_vars);
+          return FALSE;
+        }
+
+        // Ensure the plurality is terminated.
+        if (strpos($line, ']') === FALSE) {
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: invalid format for "msgstr[]" on line %line.', $log_vars);
+          return FALSE;
+        }
+
+        // Extract the plurality.
+        $frombracket = strstr($line, '[');
+        $this->_current_plural_index = substr($frombracket, 1, strpos($frombracket, ']') - 1);
+
+        // Skip to the next whitespace and trim away any further whitespace,
+        // bringing $line to the message text only.
+        $line = trim(strstr($line, " "));
+
+        $quoted = $this->parseQuoted($line);
+        if ($quoted === FALSE) {
+          // The string must be quoted.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: invalid format for "msgstr[]" on line %line.', $log_vars);
+          return FALSE;
+        }
+        if (!isset($this->_current_item['msgstr']) || !is_array($this->_current_item['msgstr'])) {
+          $this->_current_item['msgstr'] = array();
+        }
+
+        $this->_current_item['msgstr'][$this->_current_plural_index] = $quoted;
+
+        $this->_context = 'MSGSTR_ARR';
+        return;
+      }
+      elseif (!strncmp("msgstr", $line, 6)) {
+        // A string pair for an msgid (with optional context).
+
+        if (($this->_context != 'MSGID') && ($this->_context != 'MSGCTXT')) {
+          // Strings are only valid within an id or context scope.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: "msgstr" is unexpected on line %line.', $log_vars);
+          return FALSE;
+        }
+
+        // Remove 'msgstr' and trim away away whitespaces.
+        $line = trim(substr($line, 6));
+
+        // Only the msgstr string is left, parse it.
+        $quoted = $this->parseQuoted($line);
+        if ($quoted === FALSE) {
+          // The string must be quoted.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: invalid format for "msgstr" on line %line.', $log_vars);
+          return FALSE;
+        }
+
+        $this->_current_item['msgstr'] = $quoted;
+
+        $this->_context = 'MSGSTR';
+        return;
+      }
+      elseif ($line != '') {
+        // Anything that is not a token may be a continuation of a previous token.
+
+        $quoted = $this->parseQuoted($line);
+        if ($quoted === FALSE) {
+          // This string must be quoted.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: string continuation expected on line %line.', $log_vars);
+          return FALSE;
+        }
+
+        // Append the string to the current item.
+        if (($this->_context == 'MSGID') || ($this->_context == 'MSGID_PLURAL')) {
+          if (is_array($this->_current_item['msgid'])) {
+            // Add string to last array element for plural sources.
+            $last_index = count($this->_current_item['msgid']) - 1;
+            $this->_current_item['msgid'][$last_index] .= $quoted;
+          }
+          else {
+            // Singular source, just append the string.
+            $this->_current_item['msgid'] .= $quoted;
+          }
+        }
+        elseif ($this->_context == 'MSGCTXT') {
+          // Multiline context name.
+          $this->_current_item['msgctxt'] .= $quoted;
+        }
+        elseif ($this->_context == 'MSGSTR') {
+          // Multiline translation string.
+          $this->_current_item['msgstr'] .= $quoted;
+        }
+        elseif ($this->_context == 'MSGSTR_ARR') {
+          // Multiline plural translation string.
+          $this->_current_item['msgstr'][$this->_current_plural_index] .= $quoted;
+        }
+        else {
+          // No valid context to append to.
+          $this->_errors[] = SafeMarkup::format('The translation stream %uri contains an error: unexpected string on line %line.', $log_vars);
+          return FALSE;
+        }
+        return;
+      }
+    }
+
+    // Empty line read or EOF of PO stream, close out the last entry.
+    if (($this->_context == 'MSGSTR') || ($this->_context == 'MSGSTR_ARR')) {
+      $this->setItemFromArray($this->_current_item);
+      $this->_current_item = array();
+    }
+    elseif ($this->_context != 'COMMENT') {
+      $this->_errors[] = SafeMarkup::format('The translation stream %uri ended unexpectedly at line %line.', $log_vars);
+      return FALSE;
+    }
+  }
+
+  /**
+   * Store the parsed values as a PoItem object.
+   */
+  public function setItemFromArray($value) {
+    $plural = FALSE;
+
+    $comments = '';
+    if (isset($value['#'])) {
+      $comments = $this->shortenComments($value['#']);
+    }
+
+    if (is_array($value['msgstr'])) {
+      // Sort plural variants by their form index.
+      ksort($value['msgstr']);
+      $plural = TRUE;
+    }
+
+    $item = new PoItem();
+    $item->setContext(isset($value['msgctxt']) ? $value['msgctxt'] : '');
+    $item->setSource($value['msgid']);
+    $item->setTranslation($value['msgstr']);
+    $item->setPlural($plural);
+    $item->setComment($comments);
+    $item->setLangcode($this->_langcode);
+
+    $this->_last_item = $item;
+
+    $this->_context = 'COMMENT';
+  }
+
+  /**
+   * Parses a string in quotes.
+   *
+   * @param $string
+   *   A string specified with enclosing quotes.
+   *
+   * @return
+   *   The string parsed from inside the quotes.
+   */
+  function parseQuoted($string) {
+    if (substr($string, 0, 1) != substr($string, -1, 1)) {
+      // Start and end quotes must be the same.
+      return FALSE;
+    }
+    $quote = substr($string, 0, 1);
+    $string = substr($string, 1, -1);
+    if ($quote == '"') {
+      // Double quotes: strip slashes.
+      return stripcslashes($string);
+    }
+    elseif ($quote == "'") {
+      // Simple quote: return as-is.
+      return $string;
+    }
+    else {
+      // Unrecognized quote.
+      return FALSE;
+    }
+  }
+
+  /**
+   * Generates a short, one-string version of the passed comment array.
+   *
+   * @param $comment
+   *   An array of strings containing a comment.
+   *
+   * @return
+   *   Short one-string version of the comment.
+   */
+  private function shortenComments($comment) {
+    $comm = '';
+    while (count($comment)) {
+      $test = $comm . substr(array_shift($comment), 1) . ', ';
+      if (strlen($comm) < 130) {
+        $comm = $test;
+      }
+      else {
+        break;
+      }
+    }
+    return trim(substr($comm, 0, -2));
+  }
+
+}

core/lib/Drupal/Component/Gettext/PoStreamWriter.php

@@ -0,0 +1,168 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Gettext\PoStreamWriter.
+ */
+
+namespace Drupal\Component\Gettext;
+
+use Drupal\Component\Gettext\PoHeader;
+use Drupal\Component\Gettext\PoItem;
+use Drupal\Component\Gettext\PoReaderInterface;
+use Drupal\Component\Gettext\PoWriterInterface;
+use Drupal\Component\Gettext\PoStreamInterface;
+
+/**
+ * Defines a Gettext PO stream writer.
+ */
+class PoStreamWriter implements PoWriterInterface, PoStreamInterface {
+
+  /**
+   * URI of the PO stream that is being written.
+   *
+   * @var string
+   */
+  private $_uri;
+
+  /**
+   * The Gettext PO header.
+   *
+   * @var \Drupal\Component\Gettext\PoHeader
+   */
+  private $_header;
+
+  /**
+   * File handle of the current PO stream.
+   *
+   * @var resource
+   */
+  private $_fd;
+
+  /**
+   * Gets the PO header of the current stream.
+   *
+   * @return \Drupal\Component\Gettext\PoHeader
+   *   The Gettext PO header.
+   */
+  public function getHeader() {
+    return $this->_header;
+  }
+
+  /**
+   * Set the PO header for the current stream.
+   *
+   * @param \Drupal\Component\Gettext\PoHeader $header
+   *   The Gettext PO header to set.
+   */
+  public function setHeader(PoHeader $header) {
+    $this->_header = $header;
+  }
+
+  /**
+   * Gets the current language code used.
+   *
+   * @return string
+   *   The language code.
+   */
+  public function getLangcode() {
+    return $this->_langcode;
+  }
+
+  /**
+   * Set the language code.
+   *
+   * @param string $langcode
+   *   The language code.
+   */
+  public function setLangcode($langcode) {
+    $this->_langcode = $langcode;
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoStreamInterface::open().
+   */
+  public function open() {
+    // Open in write mode. Will overwrite the stream if it already exists.
+    $this->_fd = fopen($this->getURI(), 'w');
+    // Write the header at the start.
+    $this->writeHeader();
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoStreamInterface::close().
+   *
+   * @throws Exception
+   *   If the stream is not open.
+   */
+  public function close() {
+    if ($this->_fd) {
+      fclose($this->_fd);
+    }
+    else {
+      throw new Exception('Cannot close stream that is not open.');
+    }
+  }
+
+  /**
+   * Write data to the stream.
+   *
+   * @param string $data
+   *   Piece of string to write to the stream. If the value is not directly a
+   *   string, casting will happen in writing.
+   *
+   * @throws Exception
+   *   If writing the data is not possible.
+   */
+  private function write($data) {
+    $result = fputs($this->_fd, $data);
+    if ($result === FALSE) {
+      throw new Exception('Unable to write data: ' . substr($data, 0, 20));
+    }
+  }
+
+  /**
+   * Write the PO header to the stream.
+   */
+  private function writeHeader() {
+    $this->write($this->_header);
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoWriterInterface::writeItem().
+   */
+  public function writeItem(PoItem $item) {
+    $this->write($item);
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoWriterInterface::writeItems().
+   */
+  public function writeItems(PoReaderInterface $reader, $count = -1) {
+    $forever = $count == -1;
+    while (($count-- > 0 || $forever) && ($item = $reader->readItem())) {
+      $this->writeItem($item);
+    }
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoStreamInterface::getURI().
+   *
+   * @throws Exception
+   *   If the URI is not set.
+   */
+  public function getURI() {
+    if (empty($this->_uri)) {
+      throw new Exception('No URI set.');
+    }
+    return $this->_uri;
+  }
+
+  /**
+   * Implements Drupal\Component\Gettext\PoStreamInterface::setURI().
+   */
+  public function setURI($uri) {
+    $this->_uri = $uri;
+  }
+
+}

core/lib/Drupal/Component/Gettext/PoWriterInterface.php

@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Gettext\PoWriterInterface.
+ */
+
+namespace Drupal\Component\Gettext;
+
+use Drupal\Component\Gettext\PoMetadataInterface;
+use Drupal\Component\Gettext\PoItem;
+
+/**
+ * Shared interface definition for all Gettext PO Writers.
+ */
+interface PoWriterInterface extends PoMetadataInterface {
+
+  /**
+   * Writes the given item.
+   *
+   * @param PoItem $item
+   *   One specific item to write.
+   */
+  public function writeItem(PoItem $item);
+
+  /**
+   * Writes all or the given amount of items.
+   *
+   * @param PoReaderInterface $reader
+   *   Reader to read PoItems from.
+   * @param $count
+   *   Amount of items to read from $reader to write. If -1, all items are
+   *   read from $reader.
+   */
+  public function writeItems(PoReaderInterface $reader, $count = -1);
+
+}