From ca87bd7c79c17af6cdf804bc24f58fb20c41ad76 Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Sun, 2 Sep 2018 13:14:36 -0400
Subject: add documentation for all methods, add DeflateError, refactor
 VERSION_NEEDED, add maximum comment length check

---
 src/ZipStream.php | 641 +++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 610 insertions(+), 31 deletions(-)

(limited to 'src/ZipStream.php')

diff --git a/src/ZipStream.php b/src/ZipStream.php
index 33218b6..0f3a452 100644
--- a/src/ZipStream.php
+++ b/src/ZipStream.php
@@ -1,17 +1,53 @@
 <?php
 declare(strict_types = 1);
+/**
+ * Streamed, dynamically generated zip archives.
+ *
+ * @author Paul Duncan <pabs@pablotron.org>
+ * @copyright 2007-2018 Paul Duncan <pabs@pablotron.org>
+ * @license MIT
+ * @package Pablotron\ZipStream
+ */
 
 namespace Pablotron\ZipStream;
 
+/**
+ * Current version of ZipStream.
+ */
 const VERSION = '0.3.0';
 
+/**
+ * Version needed to extract.
+ * @internal
+ */
+const VERSION_NEEDED = 45;
+
+/**
+ * Valid compression methods.
+ */
 final class Methods {
+  /** Store file without compression. */
   const STORE = 0;
+
+  /** Store file using DEFLATE compression. */
   const DEFLATE = 8;
 };
 
+/**
+ * Base class for all exceptions raised by ZipStream.
+ */
 class Error extends \Exception { };
+
+/**
+ * Deflate context error.
+ */
+class DeflateError extends Error { };
+
+/**
+ * File related error.
+ */
 final class FileError extends Error {
+  /** @var string Name of fail in which error occurred. */
   public $file_name;
 
   public function __construct(string $file_name, string $message) {
@@ -20,7 +56,11 @@ final class FileError extends Error {
   }
 };
 
+/**
+ * Path validation error.
+ */
 final class PathError extends Error {
+  /** @var string string Invalid file name. */
   public $file_name;
 
   public function __construct(string $file_name, string $message) {
@@ -29,35 +69,126 @@ final class PathError extends Error {
   }
 };
 
+/**
+ * Abstract interface for stream output.
+ *
+ * @api
+ *
+ * @see FileWriter, HTTPResponseWriter
+ */
 interface Writer {
+  /**
+   * Set metadata for generated archive.
+   *
+   * @param string $key Metadata key (one of "name" or "type").
+   * @param string $val Metadata value.
+   *
+   * @return void
+   */
   public function set(string $key, string $val) : void;
-  public function open() : void ;
+
+  /**
+   * Flush metadata and begin streaming archive contents.
+   *
+   * @return void
+   */
+  public function open() : void;
+
+  /**
+   * Write archive contents.
+   *
+   * @param string $data Archive file data.
+   *
+   * @return void
+   */
   public function write(string $data) : void;
+
+  /**
+   * Finish writing archive data.
+   *
+   * @return void
+   */
   public function close() : void;
 };
 
+/**
+ * Stream generated archive as an HTTP response.
+ *
+ * @api
+ *
+ * Streams generated zip archive as an HTTP response.  This is the
+ * default writer used by ZipStream if none is provided.
+ *
+ * @see Writer
+ */
 final class HTTPResponseWriter implements Writer {
+  /**
+   * @var array Hash of metadata.
+   * @internal
+   */
   private $args = [];
 
+  /**
+   * Set metadata for generated archive.
+   *
+   * @param string $key Metadata key (one of "name" or "type").
+   * @param string $val Metadata value.
+   *
+   * @return void
+   */
   public function set(string $key, string $val) : void {
     $this->args[$key] = $val;
   }
 
+  /**
+   * Flush metadata and begin streaming archive contents.
+   *
+   * @todo
+   * @return void
+   */
   public function open() : void {
     # TODO: send http headers
   }
 
+  /**
+   * Write archive contents.
+   *
+   * @param string $data Archive file data.
+   *
+   * @return void
+   */
   public function write(string $data) : void {
     echo $data;
   }
 
+  /**
+   * Finish writing archive data.
+   *
+   * @return void
+   */
   public function close() : void {
     # ignore
   }
 };
 
+/**
+ * @api
+ *
+ * Stream generated archive to a local file.
+ *
+ * Streams generated zip archive to a local file.  This is the
+ * default writer used by ZipStream if none is provided.
+ *
+ * @see Writer
+ */
 final class FileWriter implements Writer {
+  /** @var string Output file path. */
   public $path;
+
+  /**
+   * @var resource Output file handle.
+   * @internal
+   */
   private $fh;
 
   const FILE_WRITER_STATE_INIT = 0;
@@ -65,15 +196,35 @@ final class FileWriter implements Writer {
   const FILE_WRITER_STATE_CLOSED = 2;
   const FILE_WRITER_STATE_ERROR = 3;
 
-  public function __construct($path) {
+  /**
+   * @api
+   *
+   * Create a new FileWriter.
+   *
+   * @param string $path Output file path.
+   */
+  public function __construct(string $path) {
     $this->state = self::FILE_WRITER_STATE_INIT;
     $this->path = $path;
   }
 
+  /**
+   * Set metadata for generated archive.
+   *
+   * @param string $key Metadata key (one of "name" or "type").
+   * @param string $val Metadata value.
+   *
+   * @return void
+   */
   public function set(string $key, string $val) : void {
     # ignore metadata
   }
 
+  /**
+   * Flush metadata and begin streaming archive contents.
+   *
+   * @return void
+   */
   public function open() : void {
     # open output file
     $this->fh = @fopen($this->path, 'wb');
@@ -85,6 +236,13 @@ final class FileWriter implements Writer {
     $this->state = self::FILE_WRITER_STATE_OPEN;
   }
 
+  /**
+   * Write archive contents.
+   *
+   * @param string $data Archive file data.
+   *
+   * @return void
+   */
   public function write(string $data) : void {
     # check state
     if ($this->state != self::FILE_WRITER_STATE_OPEN) {
@@ -101,6 +259,11 @@ final class FileWriter implements Writer {
     }
   }
 
+  /**
+   * Finish writing archive data.
+   *
+   * @return void
+   */
   public function close() : void {
     # check state
     if ($this->state == self::FILE_WRITER_STATE_CLOSED) {
@@ -117,10 +280,16 @@ final class FileWriter implements Writer {
   }
 };
 
-#
-# Convert a UNIX timestamp to a DOS time/date.
-#
+/**
+ * Convert a UNIX timestamp into DOS date and time components.
+ * @internal
+ */
 final class DateTime {
+  /**
+   * @var int $time Input UNIX timestamp.
+   * @var int $dos_time Output DOS timestamp.
+   * @var int $dos_date Output DOS datestamp.
+   */
   public $time,
          $dos_time,
          $dos_date;
@@ -134,8 +303,22 @@ final class DateTime {
     'seconds' => 0,
   ];
 
-  public function __construct($time) {
+  /**
+   * Convert a UNIX timestamp into DOS date and time components.
+   *
+   * @param int $time Input UNIX timestamp.
+   *
+   * @example
+   *   # create DateTime with current timestamp
+   *   $dt = new DateTime(time());
+   *
+   *   # print DOS date and time
+   *   echo "DOS time: {$dt->dos_time}\n";
+   *   echo "DOS date: {$dt->dos_date}\n";
+   */
+  public function __construct(int $time) {
     $this->time = $time;
+
     # get date array for timestamp
     $d = getdate($time);
 
@@ -152,15 +335,32 @@ final class DateTime {
   }
 };
 
+/**
+ * CRC32b hash context wrapper.
+ * @internal
+ */
 final class Hasher {
+  /** @var int $hash Output hash result. */
   public $hash;
+
+  /** @var object $ctx Internal hash context. */
   private $ctx;
 
+  /**
+   * Create a new Hasher.
+   */
   public function __construct() {
     $this->ctx = hash_init('crc32b');
   }
 
-  public function write($data) : void {
+  /**
+   * Write data to Hasher.
+   *
+   * @param string $data Input data.
+   * @return void
+   * @throw Error if called after close().
+   */
+  public function write(string $data) : void {
     if ($this->ctx !== null) {
       # update hash context
       hash_update($this->ctx, $data);
@@ -169,6 +369,14 @@ final class Hasher {
     }
   }
 
+  /**
+   * Create hash of input data.
+   *
+   * Finalize the internal has context and return a CRC32b hash of the
+   * given input data.
+   *
+   * @return int CRC32b hash of input data.
+   */
   public function close() : int {
     if ($this->ctx !== null) {
       # finalize hash context
@@ -190,67 +398,182 @@ final class Hasher {
   }
 };
 
+/**
+ * Abstract base class for data filter methods.
+ *
+ * @internal
+ * @see StoreFilter, DeflateFilter
+ */
 abstract class DataFilter {
+  /** @var Writer output writer */
   private $output;
 
+  /**
+   * Create a new DataFilter bound to the given Writer.
+   *
+   * @param Writer $output Output writer.
+   */
   public function __construct(Writer &$output) {
     $this->output = $output;
   }
 
+  /**
+   * Write data to data filter.
+   *
+   * @param string $data Output data.
+   * @return int Number of bytes written.
+   */
   public function write(string $data) : int {
     $this->output->write($data);
     return strlen($data);
   }
 
+  /**
+   * Close this data filter.
+   *
+   * @return int Number of bytes written.
+   */
   public abstract function close() : int;
 }
 
+/**
+ * Data filter for files using the store compression method.
+ *
+ * @internal
+ * @see DataFilter, DeflateFilter
+ */
 final class StoreFilter extends DataFilter {
+  /**
+   * Close this data filter.
+   *
+   * @return int Number of bytes written.
+   */
   public function close() : int {
     return 0;
   }
 };
 
+/**
+ * Data filter for files using the deflate compression method.
+ *
+ * @internal
+ *
+ * @see DataFilter, StoreFilter
+ */
 final class DeflateFilter extends DataFilter {
+  /** @var object $ctx Deflate context. */
   private $ctx;
 
+  /**
+   * Create a new DeflateFilter bound to the given Writer.
+   *
+   * @param Writer $output Output writer.
+   *
+   * @throw DeflateError If initializing deflate context fails.
+   */
   public function __construct(Writer &$output) {
+    # init parent
     parent::__construct($output);
 
+    # init deflate context, check for error
     $this->ctx = deflate_init(ZLIB_ENCODING_RAW);
     if ($this->ctx === false) {
-      throw new Error('deflate_init() failed');
+      throw new DeflateError('deflate_init() failed');
     }
   }
 
+  /**
+   * Write data to data filter.
+   *
+   * @param string $data Output data.
+   *
+   * @return int Number of bytes written.
+   *
+   * @throw DeflateError If writing to deflate context fails.
+   * @throw Error If this filter was already closed.
+   */
   public function write(string $data) : int {
+    # check state
+    if (!$this->ctx) {
+      # filter already closed
+      throw new Error('Filter already closed');
+    }
+
+    # write data to deflate context, check for error
     $compressed_data = deflate_add($this->ctx, $data, ZLIB_NO_FLUSH);
     if ($compressed_data === false) {
-      throw new Error('deflate_add() failed');
+      throw new DeflateError('deflate_add() failed');
     }
 
+    # pass data to parent
     return parent::write($compressed_data);
   }
 
+  /**
+   * Close this data filter.
+   *
+   * @return int Number of bytes written.
+   *
+   * @throw DeflateError If writing to deflate context fails.
+   * @throw Error If this filter was already closed.
+   */
   public function close() : int {
+    # check state
+    if (!$this->ctx) {
+      # filter already closed
+      throw new Error('Filter already closed');
+    }
+
+    # finalize context, flush remaining data
     $compressed_data = deflate_add($this->ctx, '', ZLIB_FINISH);
     if ($compressed_data === false) {
-      throw new Error('deflate_add() failed');
+      throw new DeflateError('deflate_add() failed');
     }
 
     # clear deflate context
     $this->ctx = null;
 
+    # write remaining data, return number of bytes written
     return parent::write($compressed_data);
   }
 };
 
+/**
+ * Internal representation for a zip file.
+ *
+ * @internal
+ *
+ * @see DataFilter, StoreFilter
+ */
 final class Entry {
   const ENTRY_STATE_INIT = 0;
   const ENTRY_STATE_DATA = 1;
   const ENTRY_STATE_CLOSED = 2;
   const ENTRY_STATE_ERROR = 3;
 
+  /**
+   * @var Writer $output
+   *   Reference to output writer.
+   * @var int $pos
+   *   Offset from start of file of entry local header.
+   * @var string $name
+   *   Name of file.
+   * @var int $method
+   *   Compression method.
+   * @var int $time
+   *   File creation time (UNIX timestamp).
+   * @var string $comment
+   *   File comment.
+   * @var int $uncompressed_size
+   *   Raw file size, in bytes.  Only valid after file has been
+   *   read completely.
+   * @var int $compressed_size
+   *   Compressed file size, in bytes.  Only valid after file has
+   *   been read completely.
+   * @var int $hash
+   *   CRC32b hash of file contents.  Only valid after file has
+   *   been read completely.
+   */
   public $output,
          $pos,
          $name,
@@ -261,11 +584,43 @@ final class Entry {
          $compressed_size,
          $hash;
 
+  /**
+   * @var int $len
+   *   File length, in bytes.  Only valid after file has been read
+   *   completely.
+   * @var DateTime $date_time
+   *   Date and time converter for this file.
+   * @var Hasher $hasher
+   *   Internal hasher for this file.
+   * @var int $state
+   *   Entry state.
+   */
   private $len,
           $date_time,
           $hasher,
           $state;
 
+  /**
+   * Create a new entry object.
+   *
+   * @internal
+   *
+   * @param Writer $output
+   *   Reference to output writer.
+   * @param int $pos
+   *   Offset from start of file of entry local header.
+   * @param string $name
+   *   Name of file.
+   * @param int $method
+   *   Compression method.
+   * @param int $time
+   *   File creation time (UNIX timestamp).
+   * @param string $comment
+   *   File comment.
+   *
+   * @throw Error if compression method is unknown.
+   * @throw PathError if compression method is unknown.
+   */
   public function __construct(
     Writer &$output,
     int $pos,
@@ -274,6 +629,9 @@ final class Entry {
     int $time,
     string $comment
   ) {
+    # set state
+    $this->state = self::ENTRY_STATE_INIT;
+
     $this->output = $output;
     $this->pos = $pos;
     $this->name = $name;
@@ -283,7 +641,6 @@ final class Entry {
 
     $this->uncompressed_size = 0;
     $this->compressed_size = 0;
-    $this->state = self::ENTRY_STATE_INIT;
     $this->len = 0;
     $this->date_time = new DateTime($time);
 
@@ -303,6 +660,17 @@ final class Entry {
     $this->check_path($name);
   }
 
+  /**
+   * Write data to file entry.
+   *
+   * @api
+   *
+   * @param string $data Output file data.
+   *
+   * @throw Error if entry state is invalid.
+   *
+   * @return int Number of bytes written to output.
+   */
   public function write(string &$data) : int {
     try {
       # check entry state
@@ -331,6 +699,15 @@ final class Entry {
   # local header methods #
   ########################
 
+  /**
+   * Write local file header.
+   *
+   * @internal
+   *
+   * @throw Error if entry state is invalid.
+   *
+   * @return int Number of bytes written to output.
+   */
   public function write_local_header() : int {
     # check state
     if ($this->state != self::ENTRY_STATE_INIT) {
@@ -353,6 +730,11 @@ final class Entry {
   const ENTRY_VERSION_NEEDED = 45;
   const ENTRY_BIT_FLAGS = 0b100000001000;
 
+  /**
+   * Create local file header for this entry.
+   *
+   * @return string Packed local file header.
+   */
   private function get_local_header() : string {
     # build extra data
     $extra_data = pack('vv',
@@ -363,7 +745,7 @@ final class Entry {
     # build and return local file header
     return pack('VvvvvvVVVvv',
       0x04034b50,                 # local file header signature (4 bytes)
-      self::ENTRY_VERSION_NEEDED, # version needed to extract (2 bytes)
+      VERSION_NEEDED,             # version needed to extract (2 bytes)
       self::ENTRY_BIT_FLAGS,      # general purpose bit flag (2 bytes)
       $this->method,              # compression method (2 bytes)
       $this->date_time->dos_time, # last mod file time (2 bytes)
@@ -380,6 +762,15 @@ final class Entry {
   # local footer methods #
   ########################
 
+  /**
+   * Write local file footer (e.g. data descriptor).
+   *
+   * @internal
+   *
+   * @throw Error if entry state is invalid.
+   *
+   * @return int Number of bytes written to output.
+   */
   public function write_local_footer() : int {
     # check state
     if ($this->state != self::ENTRY_STATE_DATA) {
@@ -407,6 +798,11 @@ final class Entry {
     return strlen($data);
   }
 
+  /**
+   * Create local file footer (data descriptor) for this entry.
+   *
+   * @return string Packed local file footer.
+   */
   private function get_local_footer() : string {
     return pack('VVPP',
       0x08074b50,                 # data descriptor signature (4 bytes)
@@ -420,25 +816,40 @@ final class Entry {
   # central header methods #
   ##########################
 
+  /**
+   * Write central directory entry for this file to output writer.
+   *
+   * @internal
+   *
+   * @return int Number of bytes written to output.
+   */
   public function write_central_header() : int {
     $data = $this->get_central_header();
     $this->output->write($data);
     return strlen($data);
   }
 
+  /**
+   * Create extra data for central directory entry for this file.
+   *
+   * @return string Packed extra data for central directory entry.
+   */
   private function get_central_extra_data() : string {
     $r = [];
 
+    # check uncompressed size for overflow
     if ($this->uncompressed_size >= 0xFFFFFFFF) {
       # append 64-bit uncompressed size
       $r[] = pack('P', $this->uncompressed_size);
     }
 
+    # check compressed size for overflow
     if ($this->compressed_size >= 0xFFFFFFFF) {
       # append 64-bit compressed size
       $r[] = pack('P', $this->compressed_size);
     }
 
+    # check offset for overflow
     if ($this->pos >= 0xFFFFFFFF) {
       # append 64-bit file offset
       $r[] = pack('P', $this->pos);
@@ -448,6 +859,7 @@ final class Entry {
     $r = join('', $r);
 
     if (strlen($r) > 0) {
+      # has overflow, so generate zip64 info
       $r = pack('vv',
         0x01,                     # zip64 ext. info extra tag (2 bytes)
         strlen($r)                # size of this extra block (2 bytes)
@@ -458,10 +870,15 @@ final class Entry {
     return $r;
   }
 
+  /**
+   * Create central directory entry for this file.
+   *
+   * @return string Packed central directory entry.
+   */
   private function get_central_header() : string {
     $extra_data = $this->get_central_extra_data();
 
-    # get sizes and offset
+    # get compressed size, uncompressed size, and offset
     $compressed_size = ($this->compressed_size >= 0xFFFFFFFF) ? 0xFFFFFFFF : $this->compressed_size;
     $uncompressed_size = ($this->uncompressed_size >= 0xFFFFFFFF) ? 0xFFFFFFFF : $this->uncompressed_size;
     $pos = ($this->pos >= 0xFFFFFFFF) ? 0xFFFFFFFF : $this->pos;
@@ -469,8 +886,8 @@ final class Entry {
     # pack and return central header
     return pack('VvvvvvvVVVvvvvvVV',
       0x02014b50,                 # central file header signature (4 bytes)
-      self::ENTRY_VERSION_NEEDED, # FIXME: version made by (2 bytes)
-      self::ENTRY_VERSION_NEEDED, # version needed to extract (2 bytes)
+      VERSION_NEEDED,             # FIXME: version made by (2 bytes)
+      VERSION_NEEDED,             # version needed to extract (2 bytes)
       self::ENTRY_BIT_FLAGS,      # general purpose bit flag (2 bytes)
       $this->method,              # compression method (2 bytes)
       $this->date_time->dos_time, # last mod file time (2 bytes)
@@ -492,6 +909,27 @@ final class Entry {
   # utility methods #
   ###################
 
+  /**
+   * Check file path.
+   *
+   * Verifies that the given file path satisfies the following
+   * constraints:
+   *
+   * * Path is not null.
+   * * Path not empty.
+   * * Path is less than 65535 bytes in length.
+   * * Path does not contain a leading slash.
+   * * Path does not contain a trailing slash.
+   * * Path does not contain double slashes.
+   * * Path does not contain backslashes.
+   * * Path is not a relative path.
+   *
+   * @param string $path Input file path.
+   *
+   * @return void
+   *
+   * @throw PathError if path is invalid.
+   */
   private function check_path(string $path) : void {
     # make sure path is non-null
     if (!$path) {
@@ -529,12 +967,19 @@ final class Entry {
     }
 
     # check for relative path
-    if (preg_match('/\.\./', $path)) {
+    if (preg_match('/^\.\.|\\/\.\.\\/|\.\.$/', $path)) {
       throw new PathError($path, "relative path");
     }
   }
 };
 
+/**
+ * Dynamically generate streamed zip file.
+ *
+ * @api
+ *
+ * {@example ../examples/01-simple.php}
+ */
 final class ZipStream {
   const STREAM_STATE_INIT = 0;
   const STREAM_STATE_ENTRY = 1;
@@ -544,13 +989,25 @@ final class ZipStream {
   # stream chunk size
   const READ_BUF_SIZE = 8192;
 
+  /** @var string Output archive name. */
   public $name;
+
+  /**
+   * @var array $args Hash of options.
+   * @var Writer $output output Writer.
+   * @var int $pos Current byte offset in output stream.
+   * @var array $entries Array of archive entries.
+   */
   private $args,
           $output,
           $pos = 0,
           $entries = [],
           $paths = [];
 
+  /**
+   * Default archive options.
+   * @internal
+   */
   static $ARCHIVE_DEFAULTS = [
     'method'  => Methods::DEFLATE,
     'comment' => '',
@@ -558,10 +1015,22 @@ final class ZipStream {
     'header'  => true,
   ];
 
+  /**
+   * Default file options.
+   * @internal
+   */
   static $FILE_DEFAULTS = [
     'comment' => '',
   ];
 
+  /**
+   * Create a new ZipStream object.
+   *
+   * @param string $name Output archive name.
+   * @param array $args Hash of output options (optional).
+   *
+   * {@example ../examples/01-simple.php}
+   */
   public function __construct(string $name, array &$args = []) {
     try {
       $this->state = self::STREAM_STATE_INIT;
@@ -591,17 +1060,41 @@ final class ZipStream {
     }
   }
 
+  /**
+   * Add file to output archive.
+   *
+   * @param string $dst_path Destination path in output archive.
+   * @param string $data File contents.
+   * @param array $args File options (optional).
+   *
+   * @return void
+   *
+   * {@example ../examples/01-simple.php}
+   */
   public function add_file(
     string $dst_path,
     string $data,
     array $args = []
-  ) {
+  ) : void {
     $this->add($dst_path, function(Entry &$e) use (&$data) {
       # write data
       $e->write($data);
     }, array_merge(self::$FILE_DEFAULTS, $args));
   }
 
+  /**
+   * Add file on the local file system to output archive.
+   *
+   * @param string $dst_path Destination path in output archive.
+   * @param string $src_path Path to input file.
+   * @param array $args File options (optional).
+   *
+   * @return void
+   *
+   * {@example ../examples/02-add_file_from_path.php}
+   *
+   * @throw FileError if the file could not be opened or read.
+   */
   public function add_file_from_path(
     string $dst_path,
     string $src_path,
@@ -632,6 +1125,20 @@ final class ZipStream {
     $this->add_stream($dst_path, $fh, $args);
   }
 
+  /**
+   * Add contents of resource stream to output archive.
+   *
+   * @param string $dst_path Destination path in output archive.
+   * @param resource $src Input resource stream.
+   * @param array $args File options (optional).
+   *
+   * @return void
+   *
+   * {@example ../examples/03-add_stream.php}
+   *
+   * @throw Error if $src is not a resource.
+   * @throw Error if the resource could not be read.
+   */
   public function add_stream(
     string $dst_path,
     &$src,
@@ -650,7 +1157,7 @@ final class ZipStream {
 
         # check for error
         if ($buf === false) {
-          throw new Error("file read error");
+          throw new Error("fread() error");
         }
 
         # write chunk to entry
@@ -664,6 +1171,20 @@ final class ZipStream {
     }, $args);
   }
 
+  /**
+   * Dynamically write file contents to output archive.
+   *
+   * @param string $dst_path Destination path in output archive.
+   * @param callable $cb Write callback.
+   * @param array $args File options (optional).
+   *
+   * @return void
+   *
+   * {@example ../examples/04-add.php}
+   *
+   * @throw Error if the archive is in an invalid state.
+   * @throw Error if the destination path already exists.
+   */
   public function add(
     string $dst_path,
     callable $cb,
@@ -724,6 +1245,15 @@ final class ZipStream {
     }
   }
 
+  /**
+   * Finalize the output stream.
+   *
+   * @return int Total number of bytes written.
+   *
+   * @throw Error if the archive is in an invalid state.
+   *
+   * {@example ../examples/01-simple.php}
+   */
   public function close() : int {
     try {
       if ($this->state != self::STREAM_STATE_INIT) {
@@ -768,6 +1298,15 @@ final class ZipStream {
     }
   }
 
+  /**
+   * Create an archive and send it using a single function.
+   *
+   * @param string $name Name of output archive.
+   * @param callable $cb Context callback.
+   * @param array $args Hash of archive options (optional).
+   *
+   * {@example ../examples/05-send.php}
+   */
   public static function send(
     string $name,
     callable $cb,
@@ -787,30 +1326,44 @@ final class ZipStream {
   # central directory record methods #
   ####################################
 
-  const VERSION_NEEDED = 45;
-
+  /**
+   * Get Zip64 end of Central Directory Record (CDR)
+   *
+   * @param int $cdr_pos CDR offset, in bytes.
+   * @param int $cdr_len Size of CDR, in bytes.
+   *
+   * @return string Packed Zip64 end of Central Directory Record.
+   */
   private function get_zip64_end_of_central_directory_record(
     int $cdr_pos,
     int $cdr_len
   ) : string {
+    # get entry count
     $num_entries = count($this->entries);
 
     return pack('VPvvVVPPPP',
       0x06064b50, # zip64 end of central dir signature (4 bytes)
       44,         # size of zip64 end of central directory record (8 bytes)
-      self::VERSION_NEEDED, # FIXME: version made by (2 bytes)
-      self::VERSION_NEEDED, # version needed to extract (2 bytes)
-      0,                    # number of this disk (4 bytes)
-      0,                    # number of the disk with the start of the central directory (4 bytes)
-      $num_entries,         # total number of entries in the central directory on this disk (8 bytes)
-      $num_entries,         # total number of entries in the central directory (8 bytes)
-      $cdr_len,             # size of the central directory  (8 bytes)
-      $cdr_pos              # offset of start of central directory with respect to the starting disk number (8 bytes)
+      VERSION_NEEDED, # FIXME: version made by (2 bytes)
+      VERSION_NEEDED, # version needed to extract (2 bytes)
+      0,              # number of this disk (4 bytes)
+      0,              # number of the disk with the start of the central directory (4 bytes)
+      $num_entries,   # total number of entries in the central directory on this disk (8 bytes)
+      $num_entries,   # total number of entries in the central directory (8 bytes)
+      $cdr_len,       # size of the central directory  (8 bytes)
+      $cdr_pos        # offset of start of central directory with respect to the starting disk number (8 bytes)
       # zip64 extensible data sector (variable size)
       # (FIXME: is extensible data sector needed?)
     );
   }
 
+  /**
+   * Get Zip64 End of Central Directory Record (CDR) Locator.
+   *
+   * @param int $zip64_cdr_pos Zip64 End of CDR offset, in bytes.
+   *
+   * @return string Packed Zip64 End of CDR Locator.
+   */
   private function get_zip64_end_of_central_directory_locator(
     int $zip64_cdr_pos
   ) : string {
@@ -822,22 +1375,34 @@ final class ZipStream {
     );
   }
 
+  /**
+   * Get End of Central Directory Record (CDR) Locator.
+   *
+   * @param int $cdr_pos CDR offset, in bytes.
+   * @param int $cdr_len CDR size, in bytes.
+   *
+   * @return string End of CDR Record.
+   */
   private function get_end_of_central_directory_record(
     int $cdr_pos,
     int $cdr_len
   ) : string {
-    # clamp num_entries
+    # get entry count
     $num_entries = count($this->entries);
     if ($num_entries >= 0xFFFF) {
+      # clamp entry count
       $num_entries = 0xFFFF;
     }
 
-    # clamp cdr_len and cdr_pos
+    # get/clamp cdr_len and cdr_pos
     $cdr_len = ($cdr_len >= 0xFFFFFFFF) ? 0xFFFFFFFF : $cdr_len;
     $cdr_pos = ($cdr_pos >= 0xFFFFFFFF) ? 0xFFFFFFFF : $cdr_pos;
 
-    # get comment
+    # get comment, check length
     $comment = $this->args['comment'];
+    if (strlen($comment) >= 65535) {
+      throw new Error('comment too long');
+    }
 
     return pack('VvvvvVVv',
       0x06054b50,       # end of central dir signature (4 bytes)
@@ -855,6 +1420,13 @@ final class ZipStream {
   # utility methods #
   ###################
 
+  /**
+   * Get UNIX timestamp for given entry.
+   *
+   * @param array $args Entry options.
+   *
+   * @return int UNIX timestamp.
+   */
   private function get_entry_time(array &$args) : int {
     if (isset($args['time'])) {
       return $args['time'];
@@ -865,6 +1437,13 @@ final class ZipStream {
     }
   }
 
+  /**
+   * Get compression method for given entry.
+   *
+   * @param array $args Entry options.
+   *
+   * @return int Compression method.
+   */
   private function get_entry_method(array &$args) : int {
     if (isset($args['method'])) {
       return $args['method'];
-- 
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