%PDF-
%PDF-
Mini Shell
Mini Shell
<?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.
}
}
Zerion Mini Shell 1.0