enmi-conf.org: comparison wp/wp-includes/class-avif-info.php

equal deleted inserted replaced

-:7b1b88e27a20
+:48c4eec2b7e6
+<?php
+/**
+* Copyright (c) 2021, Alliance for Open Media. All rights reserved
+*
+* This source code is subject to the terms of the BSD 2 Clause License and
+* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+* was not distributed with this source code in the LICENSE file, you can
+* obtain it at www.aomedia.org/license/software. If the Alliance for Open
+* Media Patent License 1.0 was not distributed with this source code in the
+* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
+*
+* Note: this class is from libavifinfo - https://aomedia.googlesource.com/libavifinfo/+/refs/heads/main/avifinfo.php at f509487.
+* It is used as a fallback to parse AVIF files when the server doesn't support AVIF,
+* primarily to identify the width and height of the image.
+*
+* Note PHP 8.2 added native support for AVIF, so this class can be removed when WordPress requires PHP 8.2.
+*/
+namespace Avifinfo;
+const FOUND     = 0; // Input correctly parsed and information retrieved.
+const NOT_FOUND = 1; // Input correctly parsed but information is missing or elsewhere.
+const TRUNCATED = 2; // Input correctly parsed until missing bytes to continue.
+const ABORTED   = 3; // Input correctly parsed until stopped to avoid timeout or crash.
+const INVALID   = 4; // Input incorrectly parsed.
+const MAX_SIZE      = 4294967295; // Unlikely to be insufficient to parse AVIF headers.
+const MAX_NUM_BOXES = 4096;       // Be reasonable. Avoid timeouts and out-of-memory.
+const MAX_VALUE     = 255;
+const MAX_TILES     = 16;
+const MAX_PROPS     = 32;
+const MAX_FEATURES  = 8;
+const UNDEFINED     = 0;          // Value was not yet parsed.
+/**
+* Reads an unsigned integer with most significant bits first.
+*
+* @param binary string $input     Must be at least $num_bytes-long.
+* @param int           $num_bytes Number of parsed bytes.
+* @return int                     Value.
+*/
+function read_big_endian( $input, $num_bytes ) {
+if ( $num_bytes == 1 ) {
+return unpack( 'C', $input ) [1];
+} else if ( $num_bytes == 2 ) {
+return unpack( 'n', $input ) [1];
+} else if ( $num_bytes == 3 ) {
+$bytes = unpack( 'C3', $input );
+return ( $bytes[1] << 16 ) | ( $bytes[2] << 8 ) | $bytes[3];
+} else { // $num_bytes is 4
+// This might fail to read unsigned values >= 2^31 on 32-bit systems.
+// See https://www.php.net/manual/en/function.unpack.php#106041
+return unpack( 'N', $input ) [1];
+}
+}
+/**
+* Reads bytes and advances the stream position by the same count.
+*
+* @param stream               $handle    Bytes will be read from this resource.
+* @param int                  $num_bytes Number of bytes read. Must be greater than 0.
+* @return binary string|false            The raw bytes or false on failure.
+*/
+function read( $handle, $num_bytes ) {
+$data = fread( $handle, $num_bytes );
+return ( $data !== false && strlen( $data ) >= $num_bytes ) ? $data : false;
+}
+/**
+* Advances the stream position by the given offset.
+*
+* @param stream $handle    Bytes will be skipped from this resource.
+* @param int    $num_bytes Number of skipped bytes. Can be 0.
+* @return bool             True on success or false on failure.
+*/
+// Skips 'num_bytes' from the 'stream'. 'num_bytes' can be zero.
+function skip( $handle, $num_bytes ) {
+return ( fseek( $handle, $num_bytes, SEEK_CUR ) == 0 );
+}
+//------------------------------------------------------------------------------
+// Features are parsed into temporary property associations.
+class Tile { // Tile item id <-> parent item id associations.
+public $tile_item_id;
+public $parent_item_id;
+}
+class Prop { // Property index <-> item id associations.
+public $property_index;
+public $item_id;
+}
+class Dim_Prop { // Property <-> features associations.
+public $property_index;
+public $width;
+public $height;
+}
+class Chan_Prop { // Property <-> features associations.
+public $property_index;
+public $bit_depth;
+public $num_channels;
+}
+class Features {
+public $has_primary_item = false; // True if "pitm" was parsed.
+public $has_alpha = false; // True if an alpha "auxC" was parsed.
+public $primary_item_id;
+public $primary_item_features = array( // Deduced from the data below.
+'width'        => UNDEFINED, // In number of pixels.
+'height'       => UNDEFINED, // Ignores mirror and rotation.
+'bit_depth'    => UNDEFINED, // Likely 8, 10 or 12 bits per channel per pixel.
+'num_channels' => UNDEFINED  // Likely 1, 2, 3 or 4 channels:
+//   (1 monochrome or 3 colors) + (0 or 1 alpha)
+);
+public $tiles = array(); // Tile[]
+public $props = array(); // Prop[]
+public $dim_props = array(); // Dim_Prop[]
+public $chan_props = array(); // Chan_Prop[]
+/**
+* Binds the width, height, bit depth and number of channels from stored internal features.
+*
+* @param int     $target_item_id Id of the item whose features will be bound.
+* @param int     $tile_depth     Maximum recursion to search within tile-parent relations.
+* @return Status                 FOUND on success or NOT_FOUND on failure.
+*/
+private function get_item_features( $target_item_id, $tile_depth ) {
+foreach ( $this->props as $prop ) {
+if ( $prop->item_id != $target_item_id ) {
+continue;
+}
+// Retrieve the width and height of the primary item if not already done.
+if ( $target_item_id == $this->primary_item_id &&
+( $this->primary_item_features['width'] == UNDEFINED ||
+$this->primary_item_features['height'] == UNDEFINED ) ) {
+foreach ( $this->dim_props as $dim_prop ) {
+if ( $dim_prop->property_index != $prop->property_index ) {
+continue;
+}
+$this->primary_item_features['width']  = $dim_prop->width;
+$this->primary_item_features['height'] = $dim_prop->height;
+if ( $this->primary_item_features['bit_depth'] != UNDEFINED &&
+$this->primary_item_features['num_channels'] != UNDEFINED ) {
+return FOUND;
+}
+break;
+}
+}
+// Retrieve the bit depth and number of channels of the target item if not
+// already done.
+if ( $this->primary_item_features['bit_depth'] == UNDEFINED ||
+$this->primary_item_features['num_channels'] == UNDEFINED ) {
+foreach ( $this->chan_props as $chan_prop ) {
+if ( $chan_prop->property_index != $prop->property_index ) {
+continue;
+}
+$this->primary_item_features['bit_depth']    = $chan_prop->bit_depth;
+$this->primary_item_features['num_channels'] = $chan_prop->num_channels;
+if ( $this->primary_item_features['width'] != UNDEFINED &&
+$this->primary_item_features['height'] != UNDEFINED ) {
+return FOUND;
+}
+break;
+}
+}
+}
+// Check for the bit_depth and num_channels in a tile if not yet found.
+if ( $tile_depth < 3 ) {
+foreach ( $this->tiles as $tile ) {
+if ( $tile->parent_item_id != $target_item_id ) {
+continue;
+}
+$status = $this->get_item_features( $tile->tile_item_id, $tile_depth + 1 );
+if ( $status != NOT_FOUND ) {
+return $status;
+}
+}
+}
+return NOT_FOUND;
+}
+/**
+* Finds the width, height, bit depth and number of channels of the primary item.
+*
+* @return Status FOUND on success or NOT_FOUND on failure.
+*/
+public function get_primary_item_features() {
+// Nothing to do without the primary item ID.
+if ( !$this->has_primary_item ) {
+return NOT_FOUND;
+}
+// Early exit.
+if ( empty( $this->dim_props ) || empty( $this->chan_props ) ) {
+return NOT_FOUND;
+}
+$status = $this->get_item_features( $this->primary_item_id, /*tile_depth=*/ 0 );
+if ( $status != FOUND ) {
+return $status;
+}
+// "auxC" is parsed before the "ipma" properties so it is known now, if any.
+if ( $this->has_alpha ) {
+++$this->primary_item_features['num_channels'];
+}
+return FOUND;
+}
+}
+//------------------------------------------------------------------------------
+class Box {
+public $size; // In bytes.
+public $type; // Four characters.
+public $version; // 0 or actual version if this is a full box.
+public $flags; // 0 or actual value if this is a full box.
+public $content_size; // 'size' minus the header size.
+/**
+* Reads the box header.
+*
+* @param stream  $handle              The resource the header will be parsed from.
+* @param int     $num_parsed_boxes    The total number of parsed boxes. Prevents timeouts.
+* @param int     $num_remaining_bytes The number of bytes that should be available from the resource.
+* @return Status                      FOUND on success or an error on failure.
+*/
+public function parse( $handle, &$num_parsed_boxes, $num_remaining_bytes = MAX_SIZE ) {
+// See ISO/IEC 14496-12:2012(E) 4.2
+$header_size = 8; // box 32b size + 32b type (at least)
+if ( $header_size > $num_remaining_bytes ) {
+return INVALID;
+}
+if ( !( $data = read( $handle, 8 ) ) ) {
+return TRUNCATED;
+}
+$this->size = read_big_endian( $data, 4 );
+$this->type = substr( $data, 4, 4 );
+// 'box->size==1' means 64-bit size should be read after the box type.
+// 'box->size==0' means this box extends to all remaining bytes.
+if ( $this->size == 1 ) {
+$header_size += 8;
+if ( $header_size > $num_remaining_bytes ) {
+return INVALID;
+}
+if ( !( $data = read( $handle, 8 ) ) ) {
+return TRUNCATED;
+}
+// Stop the parsing if any box has a size greater than 4GB.
+if ( read_big_endian( $data, 4 ) != 0 ) {
+return ABORTED;
+}
+// Read the 32 least-significant bits.
+$this->size = read_big_endian( substr( $data, 4, 4 ), 4 );
+} else if ( $this->size == 0 ) {
+$this->size = $num_remaining_bytes;
+}
+if ( $this->size < $header_size ) {
+return INVALID;
+}
+if ( $this->size > $num_remaining_bytes ) {
+return INVALID;
+}
+$has_fullbox_header = $this->type == 'meta' || $this->type == 'pitm' ||
+$this->type == 'ipma' || $this->type == 'ispe' ||
+$this->type == 'pixi' || $this->type == 'iref' ||
+$this->type == 'auxC';
+if ( $has_fullbox_header ) {
+$header_size += 4;
+}
+if ( $this->size < $header_size ) {
+return INVALID;
+}
+$this->content_size = $this->size - $header_size;
+// Avoid timeouts. The maximum number of parsed boxes is arbitrary.
+++$num_parsed_boxes;
+if ( $num_parsed_boxes >= MAX_NUM_BOXES ) {
+return ABORTED;
+}
+$this->version = 0;
+$this->flags   = 0;
+if ( $has_fullbox_header ) {
+if ( !( $data = read( $handle, 4 ) ) ) {
+return TRUNCATED;
+}
+$this->version = read_big_endian( $data, 1 );
+$this->flags   = read_big_endian( substr( $data, 1, 3 ), 3 );
+// See AV1 Image File Format (AVIF) 8.1
+// at https://aomediacodec.github.io/av1-avif/#avif-boxes (available when
+// https://github.com/AOMediaCodec/av1-avif/pull/170 is merged).
+$is_parsable = ( $this->type == 'meta' && $this->version <= 0 ) ||
+( $this->type == 'pitm' && $this->version <= 1 ) ||
+( $this->type == 'ipma' && $this->version <= 1 ) ||
+( $this->type == 'ispe' && $this->version <= 0 ) ||
+( $this->type == 'pixi' && $this->version <= 0 ) ||
+( $this->type == 'iref' && $this->version <= 1 ) ||
+( $this->type == 'auxC' && $this->version <= 0 );
+// Instead of considering this file as invalid, skip unparsable boxes.
+if ( !$is_parsable ) {
+$this->type = 'unknownversion';
+}
+}
+// print_r( $this ); // Uncomment to print all boxes.
+return FOUND;
+}
+}
+//------------------------------------------------------------------------------
+class Parser {
+private $handle; // Input stream.
+private $num_parsed_boxes = 0;
+private $data_was_skipped = false;
+public $features;
+function __construct( $handle ) {
+$this->handle   = $handle;
+$this->features = new Features();
+}
+/**
+* Parses an "ipco" box.
+*
+* "ispe" is used for width and height, "pixi" and "av1C" are used for bit depth
+* and number of channels, and "auxC" is used for alpha.
+*
+* @param stream  $handle              The resource the box will be parsed from.
+* @param int     $num_remaining_bytes The number of bytes that should be available from the resource.
+* @return Status                      FOUND on success or an error on failure.
+*/
+private function parse_ipco( $num_remaining_bytes ) {
+$box_index = 1; // 1-based index. Used for iterating over properties.
+do {
+$box    = new Box();
+$status = $box->parse( $this->handle, $this->num_parsed_boxes, $num_remaining_bytes );
+if ( $status != FOUND ) {
+return $status;
+}
+if ( $box->type == 'ispe' ) {
+// See ISO/IEC 23008-12:2017(E) 6.5.3.2
+if ( $box->content_size < 8 ) {
+return INVALID;
+}
+if ( !( $data = read( $this->handle, 8 ) ) ) {
+return TRUNCATED;
+}
+$width  = read_big_endian( substr( $data, 0, 4 ), 4 );
+$height = read_big_endian( substr( $data, 4, 4 ), 4 );
+if ( $width == 0 || $height == 0 ) {
+return INVALID;
+}
+if ( count( $this->features->dim_props ) <= MAX_FEATURES &&
+$box_index <= MAX_VALUE ) {
+$dim_prop_count = count( $this->features->dim_props );
+$this->features->dim_props[$dim_prop_count]                 = new Dim_Prop();
+$this->features->dim_props[$dim_prop_count]->property_index = $box_index;
+$this->features->dim_props[$dim_prop_count]->width          = $width;
+$this->features->dim_props[$dim_prop_count]->height         = $height;
+} else {
+$this->data_was_skipped = true;
+}
+if ( !skip( $this->handle, $box->content_size - 8 ) ) {
+return TRUNCATED;
+}
+} else if ( $box->type == 'pixi' ) {
+// See ISO/IEC 23008-12:2017(E) 6.5.6.2
+if ( $box->content_size < 1 ) {
+return INVALID;
+}
+if ( !( $data = read( $this->handle, 1 ) ) ) {
+return TRUNCATED;
+}
+$num_channels = read_big_endian( $data, 1 );
+if ( $num_channels < 1 ) {
+return INVALID;
+}
+if ( $box->content_size < 1 + $num_channels ) {
+return INVALID;
+}
+if ( !( $data = read( $this->handle, 1 ) ) ) {
+return TRUNCATED;
+}
+$bit_depth = read_big_endian( $data, 1 );
+if ( $bit_depth < 1 ) {
+return INVALID;
+}
+for ( $i = 1; $i < $num_channels; ++$i ) {
+if ( !( $data = read( $this->handle, 1 ) ) ) {
+return TRUNCATED;
+}
+// Bit depth should be the same for all channels.
+if ( read_big_endian( $data, 1 ) != $bit_depth ) {
+return INVALID;
+}
+if ( $i > 32 ) {
+return ABORTED; // Be reasonable.
+}
+}
+if ( count( $this->features->chan_props ) <= MAX_FEATURES &&
+$box_index <= MAX_VALUE && $bit_depth <= MAX_VALUE &&
+$num_channels <= MAX_VALUE ) {
+$chan_prop_count = count( $this->features->chan_props );
+$this->features->chan_props[$chan_prop_count]                 = new Chan_Prop();
+$this->features->chan_props[$chan_prop_count]->property_index = $box_index;
+$this->features->chan_props[$chan_prop_count]->bit_depth      = $bit_depth;
+$this->features->chan_props[$chan_prop_count]->num_channels   = $num_channels;
+} else {
+$this->data_was_skipped = true;
+}
+if ( !skip( $this->handle, $box->content_size - ( 1 + $num_channels ) ) ) {
+return TRUNCATED;
+}
+} else if ( $box->type == 'av1C' ) {
+// See AV1 Codec ISO Media File Format Binding 2.3.1
+// at https://aomediacodec.github.io/av1-isobmff/#av1c
+// Only parse the necessary third byte. Assume that the others are valid.
+if ( $box->content_size < 3 ) {
+return INVALID;
+}
+if ( !( $data = read( $this->handle, 3 ) ) ) {
+return TRUNCATED;
+}
+$byte          = read_big_endian( substr( $data, 2, 1 ), 1 );
+$high_bitdepth = ( $byte & 0x40 ) != 0;
+$twelve_bit    = ( $byte & 0x20 ) != 0;
+$monochrome    = ( $byte & 0x10 ) != 0;
+if ( $twelve_bit && !$high_bitdepth ) {
+return INVALID;
+}
+if ( count( $this->features->chan_props ) <= MAX_FEATURES &&
+$box_index <= MAX_VALUE ) {
+$chan_prop_count = count( $this->features->chan_props );
+$this->features->chan_props[$chan_prop_count]                 = new Chan_Prop();
+$this->features->chan_props[$chan_prop_count]->property_index = $box_index;
+$this->features->chan_props[$chan_prop_count]->bit_depth      =
+$high_bitdepth ? $twelve_bit ? 12 : 10 : 8;
+$this->features->chan_props[$chan_prop_count]->num_channels   = $monochrome ? 1 : 3;
+} else {
+$this->data_was_skipped = true;
+}
+if ( !skip( $this->handle, $box->content_size - 3 ) ) {
+return TRUNCATED;
+}
+} else if ( $box->type == 'auxC' ) {
+// See AV1 Image File Format (AVIF) 4
+// at https://aomediacodec.github.io/av1-avif/#auxiliary-images
+$kAlphaStr       = "urn:mpeg:mpegB:cicp:systems:auxiliary:alpha\0";
+$kAlphaStrLength = 44; // Includes terminating character.
+if ( $box->content_size >= $kAlphaStrLength ) {
+if ( !( $data = read( $this->handle, $kAlphaStrLength ) ) ) {
+return TRUNCATED;
+}
+if ( substr( $data, 0, $kAlphaStrLength ) == $kAlphaStr ) {
+// Note: It is unlikely but it is possible that this alpha plane does
+//       not belong to the primary item or a tile. Ignore this issue.
+$this->features->has_alpha = true;
+}
+if ( !skip( $this->handle, $box->content_size - $kAlphaStrLength ) ) {
+return TRUNCATED;
+}
+} else {
+if ( !skip( $this->handle, $box->content_size ) ) {
+return TRUNCATED;
+}
+}
+} else {
+if ( !skip( $this->handle, $box->content_size ) ) {
+return TRUNCATED;
+}
+}
+++$box_index;
+$num_remaining_bytes -= $box->size;
+} while ( $num_remaining_bytes > 0 );
+return NOT_FOUND;
+}
+/**
+* Parses an "iprp" box.
+*
+* The "ipco" box contain the properties which are linked to items by the "ipma" box.
+*
+* @param stream  $handle              The resource the box will be parsed from.
+* @param int     $num_remaining_bytes The number of bytes that should be available from the resource.
+* @return Status                      FOUND on success or an error on failure.
+*/
+private function parse_iprp( $num_remaining_bytes ) {
+do {
+$box    = new Box();
+$status = $box->parse( $this->handle, $this->num_parsed_boxes, $num_remaining_bytes );
+if ( $status != FOUND ) {
+return $status;
+}
+if ( $box->type == 'ipco' ) {
+$status = $this->parse_ipco( $box->content_size );
+if ( $status != NOT_FOUND ) {
+return $status;
+}
+} else if ( $box->type == 'ipma' ) {
+// See ISO/IEC 23008-12:2017(E) 9.3.2
+$num_read_bytes = 4;
+if ( $box->content_size < $num_read_bytes ) {
+return INVALID;
+}
+if ( !( $data = read( $this->handle, $num_read_bytes ) ) ) {
+return TRUNCATED;
+}
+$entry_count        = read_big_endian( $data, 4 );
+$id_num_bytes       = ( $box->version < 1 ) ? 2 : 4;
+$index_num_bytes    = ( $box->flags & 1 ) ? 2 : 1;
+$essential_bit_mask = ( $box->flags & 1 ) ? 0x8000 : 0x80;
+for ( $entry = 0; $entry < $entry_count; ++$entry ) {
+if ( $entry >= MAX_PROPS ||
+count( $this->features->props ) >= MAX_PROPS ) {
+$this->data_was_skipped = true;
+break;
+}
+$num_read_bytes += $id_num_bytes + 1;
+if ( $box->content_size < $num_read_bytes ) {
+return INVALID;
+}
+if ( !( $data = read( $this->handle, $id_num_bytes + 1 ) ) ) {
+return TRUNCATED;
+}
+$item_id           = read_big_endian(
+substr( $data, 0, $id_num_bytes ), $id_num_bytes );
+$association_count = read_big_endian(
+substr( $data, $id_num_bytes, 1 ), 1 );
+for ( $property = 0; $property < $association_count; ++$property ) {
+if ( $property >= MAX_PROPS ||
+count( $this->features->props ) >= MAX_PROPS ) {
+$this->data_was_skipped = true;
+break;
+}
+$num_read_bytes += $index_num_bytes;
+if ( $box->content_size < $num_read_bytes ) {
+return INVALID;
+}
+if ( !( $data = read( $this->handle, $index_num_bytes ) ) ) {
+return TRUNCATED;
+}
+$value          = read_big_endian( $data, $index_num_bytes );
+// $essential = ($value & $essential_bit_mask);  // Unused.
+$property_index = ( $value & ~$essential_bit_mask );
+if ( $property_index <= MAX_VALUE && $item_id <= MAX_VALUE ) {
+$prop_count = count( $this->features->props );
+$this->features->props[$prop_count]                 = new Prop();
+$this->features->props[$prop_count]->property_index = $property_index;
+$this->features->props[$prop_count]->item_id        = $item_id;
+} else {
+$this->data_was_skipped = true;
+}
+}
+if ( $property < $association_count ) {
+break; // Do not read garbage.
+}
+}
+// If all features are available now, do not look further.
+$status = $this->features->get_primary_item_features();
+if ( $status != NOT_FOUND ) {
+return $status;
+}
+// Mostly if 'data_was_skipped'.
+if ( !skip( $this->handle, $box->content_size - $num_read_bytes ) ) {
+return TRUNCATED;
+}
+} else {
+if ( !skip( $this->handle, $box->content_size ) ) {
+return TRUNCATED;
+}
+}
+$num_remaining_bytes -= $box->size;
+} while ( $num_remaining_bytes > 0 );
+return NOT_FOUND;
+}
+/**
+* Parses an "iref" box.
+*
+* The "dimg" boxes contain links between tiles and their parent items, which
+* can be used to infer bit depth and number of channels for the primary item
+* when the latter does not have these properties.
+*
+* @param stream  $handle              The resource the box will be parsed from.
+* @param int     $num_remaining_bytes The number of bytes that should be available from the resource.
+* @return Status                      FOUND on success or an error on failure.
+*/
+private function parse_iref( $num_remaining_bytes ) {
+do {
+$box    = new Box();
+$status = $box->parse( $this->handle, $this->num_parsed_boxes, $num_remaining_bytes );
+if ( $status != FOUND ) {
+return $status;
+}
+if ( $box->type == 'dimg' ) {
+// See ISO/IEC 14496-12:2015(E) 8.11.12.2
+$num_bytes_per_id = ( $box->version == 0 ) ? 2 : 4;
+$num_read_bytes   = $num_bytes_per_id + 2;
+if ( $box->content_size < $num_read_bytes ) {
+return INVALID;
+}
+if ( !( $data = read( $this->handle, $num_read_bytes ) ) ) {
+return TRUNCATED;
+}
+$from_item_id    = read_big_endian( $data, $num_bytes_per_id );
+$reference_count = read_big_endian( substr( $data, $num_bytes_per_id, 2 ), 2 );
+for ( $i = 0; $i < $reference_count; ++$i ) {
+if ( $i >= MAX_TILES ) {
+$this->data_was_skipped = true;
+break;
+}
+$num_read_bytes += $num_bytes_per_id;
+if ( $box->content_size < $num_read_bytes ) {
+return INVALID;
+}
+if ( !( $data = read( $this->handle, $num_bytes_per_id ) ) ) {
+return TRUNCATED;
+}
+$to_item_id = read_big_endian( $data, $num_bytes_per_id );
+$tile_count = count( $this->features->tiles );
+if ( $from_item_id <= MAX_VALUE && $to_item_id <= MAX_VALUE &&
+$tile_count < MAX_TILES ) {
+$this->features->tiles[$tile_count]                 = new Tile();
+$this->features->tiles[$tile_count]->tile_item_id   = $to_item_id;
+$this->features->tiles[$tile_count]->parent_item_id = $from_item_id;
+} else {
+$this->data_was_skipped = true;
+}
+}
+// If all features are available now, do not look further.
+$status = $this->features->get_primary_item_features();
+if ( $status != NOT_FOUND ) {
+return $status;
+}
+// Mostly if 'data_was_skipped'.
+if ( !skip( $this->handle, $box->content_size - $num_read_bytes ) ) {
+return TRUNCATED;
+}
+} else {
+if ( !skip( $this->handle, $box->content_size ) ) {
+return TRUNCATED;
+}
+}
+$num_remaining_bytes -= $box->size;
+} while ( $num_remaining_bytes > 0 );
+return NOT_FOUND;
+}
+/**
+* Parses a "meta" box.
+*
+* It looks for the primary item ID in the "pitm" box and recurses into other boxes
+* to find its features.
+*
+* @param stream  $handle              The resource the box will be parsed from.
+* @param int     $num_remaining_bytes The number of bytes that should be available from the resource.
+* @return Status                      FOUND on success or an error on failure.
+*/
+private function parse_meta( $num_remaining_bytes ) {
+do {
+$box    = new Box();
+$status = $box->parse( $this->handle, $this->num_parsed_boxes, $num_remaining_bytes );
+if ( $status != FOUND ) {
+return $status;
+}
+if ( $box->type == 'pitm' ) {
+// See ISO/IEC 14496-12:2015(E) 8.11.4.2
+$num_bytes_per_id = ( $box->version == 0 ) ? 2 : 4;
+if ( $num_bytes_per_id > $num_remaining_bytes ) {
+return INVALID;
+}
+if ( !( $data = read( $this->handle, $num_bytes_per_id ) ) ) {
+return TRUNCATED;
+}
+$primary_item_id = read_big_endian( $data, $num_bytes_per_id );
+if ( $primary_item_id > MAX_VALUE ) {
+return ABORTED;
+}
+$this->features->has_primary_item = true;
+$this->features->primary_item_id  = $primary_item_id;
+if ( !skip( $this->handle, $box->content_size - $num_bytes_per_id ) ) {
+return TRUNCATED;
+}
+} else if ( $box->type == 'iprp' ) {
+$status = $this->parse_iprp( $box->content_size );
+if ( $status != NOT_FOUND ) {
+return $status;
+}
+} else if ( $box->type == 'iref' ) {
+$status = $this->parse_iref( $box->content_size );
+if ( $status != NOT_FOUND ) {
+return $status;
+}
+} else {
+if ( !skip( $this->handle, $box->content_size ) ) {
+return TRUNCATED;
+}
+}
+$num_remaining_bytes -= $box->size;
+} while ( $num_remaining_bytes != 0 );
+// According to ISO/IEC 14496-12:2012(E) 8.11.1.1 there is at most one "meta".
+return INVALID;
+}
+/**
+* Parses a file stream.
+*
+* The file type is checked through the "ftyp" box.
+*
+* @return bool True if the input stream is an AVIF bitstream or false.
+*/
+public function parse_ftyp() {
+$box    = new Box();
+$status = $box->parse( $this->handle, $this->num_parsed_boxes );
+if ( $status != FOUND ) {
+return false;
+}
+if ( $box->type != 'ftyp' ) {
+return false;
+}
+// Iterate over brands. See ISO/IEC 14496-12:2012(E) 4.3.1
+if ( $box->content_size < 8 ) {
+return false;
+}
+for ( $i = 0; $i + 4 <= $box->content_size; $i += 4 ) {
+if ( !( $data = read( $this->handle, 4 ) ) ) {
+return false;
+}
+if ( $i == 4 ) {
+continue; // Skip minor_version.
+}
+if ( substr( $data, 0, 4 ) == 'avif' || substr( $data, 0, 4 ) == 'avis' ) {
+return skip( $this->handle, $box->content_size - ( $i + 4 ) );
+}
+if ( $i > 32 * 4 ) {
+return false; // Be reasonable.
+}
+}
+return false; // No AVIF brand no good.
+}
+/**
+* Parses a file stream.
+*
+* Features are extracted from the "meta" box.
+*
+* @return bool True if the main features of the primary item were parsed or false.
+*/
+public function parse_file() {
+$box = new Box();
+while ( $box->parse( $this->handle, $this->num_parsed_boxes ) == FOUND ) {
+if ( $box->type === 'meta' ) {
+if ( $this->parse_meta( $box->content_size ) != FOUND ) {
+return false;
+}
+return true;
+}
+if ( !skip( $this->handle, $box->content_size ) ) {
+return false;
+}
+}
+return false; // No "meta" no good.
+}
+}