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<?php
/**
* PEL: PHP Exif Library.
* A library with support for reading and
* writing all Exif headers in JPEG and TIFF images using PHP.
*
* Copyright (C) 2004, 2005, 2006, 2007 Martin Geisler.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program in the file COPYING; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301 USA
*/
namespace lsolesen\pel;
/**
* The window.
*
* @package PEL
*/
class PelDataWindow
{
/**
* The data held by this window.
*
* The string can contain any kind of data, including binary data.
*
* @var string
*/
private $data = '';
/**
* The byte order currently in use.
*
* This will be the byte order used when data is read using the for
* example the {@link getShort} function. It must be one of {@link
* PelConvert::LITTLE_ENDIAN} and {@link PelConvert::BIG_ENDIAN}.
*
* @var boolean
* @see PelDataWindow::setByteOrder, getByteOrder
*/
private $order;
/**
* The start of the current window.
*
* All offsets used for access into the data will count from this
* offset, effectively limiting access to a window starting at this
* byte.
*
* @var int
* @see PelDataWindow::setWindowStart
*/
private $start = 0;
/**
* The size of the current window.
*
* All offsets used for access into the data will be limited by this
* variable. A valid offset must be strictly less than this
* variable.
*
* @var int
* @see PelDataWindow::setWindowSize
*/
private $size = 0;
/**
* Construct a new data window with the data supplied.
*
* @param string|resource|\GDImage $data
* the data that this window will contain. This can
* either be given as a string (interpreted litteraly as a sequence
* of bytes) or a PHP image resource handle. The data will be copied
* into the new data window.
* @param boolean $endianess
* the initial byte order of the window. This must
* be either {@link PelConvert::LITTLE_ENDIAN} or {@link
* PelConvert::BIG_ENDIAN}. This will be used when integers are
* read from the data, and it can be changed later with {@link
* setByteOrder()}.
* @throws PelInvalidArgumentException if $data was of invalid type
*/
public function __construct($data = '', $endianess = PelConvert::LITTLE_ENDIAN)
{
if (is_string($data)) {
$this->data = $data;
} elseif ((is_resource($data) && get_resource_type($data) === 'gd') || (PHP_VERSION_ID >= 80000 && is_object($data) && $data instanceof \GDImage)) {
/*
* The ImageJpeg() function insists on printing the bytes
* instead of returning them in a more civil way as a string, so
* we have to buffer the output...
*/
ob_start();
ImageJpeg($data, null, Pel::getJPEGQuality());
$this->data = ob_get_clean();
} else {
throw new PelInvalidArgumentException('Bad type for $data: %s', gettype($data));
}
$this->order = $endianess;
$this->size = strlen($this->data);
}
/**
* Get the size of the data window.
*
* @return integer the number of bytes covered by the window. The
* allowed offsets go from 0 up to this number minus one.
* @see getBytes()
*/
public function getSize()
{
return $this->size;
}
/**
* Change the byte order of the data.
*
* @param boolean $order
* the new byte order. This must be either
* {@link PelConvert::LITTLE_ENDIAN} or {@link
* PelConvert::BIG_ENDIAN}.
*/
public function setByteOrder($order)
{
$this->order = $order;
}
/**
* Get the currently used byte order.
*
* @return boolean this will be either {@link
* PelConvert::LITTLE_ENDIAN} or {@link PelConvert::BIG_ENDIAN}.
*/
public function getByteOrder()
{
return $this->order;
}
/**
* Move the start of the window forward.
*
* @param integer $start
* the new start of the window. All new offsets will be
* calculated from this new start offset, and the size of the window
* will shrink to keep the end of the window in place.
* @throws PelDataWindowWindowException
*/
public function setWindowStart($start)
{
if ($start < 0 || $start > $this->size) {
throw new PelDataWindowWindowException('Window [%d, %d] does ' . 'not fit in window [0, %d]', $start, $this->size, $this->size);
}
$this->start += $start;
$this->size -= $start;
}
/**
* Adjust the size of the window.
* The size can only be made smaller.
*
* @param integer $size
* the desired size of the window. If the argument is
* negative, the window will be shrunk by the argument.
* @throws PelDataWindowWindowException
*/
public function setWindowSize($size)
{
if ($size < 0) {
$size += $this->size;
}
if ($size < 0 || $size > $this->size) {
throw new PelDataWindowWindowException('Window [0, %d] ' . 'does not fit in window [0, %d]', $size, $this->size);
}
$this->size = $size;
}
/**
* Make a new data window with the same data as the this window.
*
* @param integer|null $start
* if an integer is supplied, then it will be the start
* of the window in the clone. If left unspecified, then the clone
* will inherit the start from this object.
* @param integer|null $size
* if an integer is supplied, then it will be the size
* of the window in the clone. If left unspecified, then the clone
* will inherit the size from this object.
* @return PelDataWindow a new window that operates on the same data
* as this window, but (optionally) with a smaller window size.
* @throws PelDataWindowWindowException
*/
public function getClone($start = null, $size = null)
{
$c = clone $this;
if (is_int($start)) {
$c->setWindowStart($start);
}
if (is_int($size)) {
$c->setWindowSize($size);
}
return $c;
}
/**
* Validate an offset against the current window.
*
* @param integer $offset
* the offset to be validated. If the offset is negative
* or if it is greater than or equal to the current window size,
* then a {@link PelDataWindowOffsetException} is thrown.
* @return void if the offset is valid nothing is returned, if it is
* invalid a new {@link PelDataWindowOffsetException} is thrown.
* @throws PelDataWindowOffsetException
*/
private function validateOffset($offset)
{
if ($offset < 0 || $offset >= $this->size) {
throw new PelDataWindowOffsetException('Offset %d not within [%d, %d]', $offset, 0, $this->size - 1);
}
}
/**
* Return some or all bytes visible in the window.
*
* This method works just like the standard {@link substr()}
* function in PHP with the exception that it works within the
* window of accessible bytes and does strict range checking.
*
* @param integer|null $start
* the offset to the first byte returned. If a negative
* number is given, then the counting will be from the end of the
* window. Invalid offsets will result in a {@link
* PelDataWindowOffsetException} being thrown.
* @param integer|null $size
* the size of the sub-window. If a negative number is
* given, then that many bytes will be omitted from the result.
* @return string a subset of the bytes in the window. This will
* always return no more than {@link getSize()} bytes.
* @throws PelDataWindowOffsetException
*/
public function getBytes($start = null, $size = null)
{
if (is_int($start)) {
if ($start < 0) {
$start += $this->size;
}
$this->validateOffset($start);
} else {
$start = 0;
}
if (is_int($size)) {
if ($size <= 0) {
$size += $this->size - $start;
}
$this->validateOffset($start + $size);
} else {
$size = $this->size - $start;
}
return substr($this->data, $this->start + $start, $size);
}
/**
* Return an unsigned byte from the data.
*
* @param integer $offset
* the offset into the data. An offset of zero will
* return the first byte in the current allowed window. The last
* valid offset is equal to {@link getSize()}-1. Invalid offsets
* will result in a {@link PelDataWindowOffsetException} being
* thrown.
* @return integer the unsigned byte found at offset.
* @throws PelDataWindowOffsetException
*/
public function getByte($offset = 0)
{
/*
* Validate the offset --- this throws an exception if offset is
* out of range.
*/
$this->validateOffset($offset);
/* Translate the offset into an offset into the data. */
$offset += $this->start;
/* Return an unsigned byte. */
return PelConvert::bytesToByte($this->data, $offset);
}
/**
* Return a signed byte from the data.
*
* @param integer $offset
* the offset into the data. An offset of zero will
* return the first byte in the current allowed window. The last
* valid offset is equal to {@link getSize()}-1. Invalid offsets
* will result in a {@link PelDataWindowOffsetException} being
* thrown.
* @return integer the signed byte found at offset.
* @throws PelDataWindowOffsetException
*/
public function getSByte($offset = 0)
{
/*
* Validate the offset --- this throws an exception if offset is
* out of range.
*/
$this->validateOffset($offset);
/* Translate the offset into an offset into the data. */
$offset += $this->start;
/* Return a signed byte. */
return PelConvert::bytesToSByte($this->data, $offset);
}
/**
* Return an unsigned short read from the data.
*
* @param integer $offset
* the offset into the data. An offset of zero will
* return the first short available in the current allowed window.
* The last valid offset is equal to {@link getSize()}-2. Invalid
* offsets will result in a {@link PelDataWindowOffsetException}
* being thrown.
* @return integer the unsigned short found at offset.
* @throws PelDataWindowOffsetException
*/
public function getShort($offset = 0)
{
/*
* Validate the offset+1 to see if we can safely get two bytes ---
* this throws an exception if offset is out of range.
*/
$this->validateOffset($offset);
$this->validateOffset($offset + 1);
/* Translate the offset into an offset into the data. */
$offset += $this->start;
/* Return an unsigned short. */
return PelConvert::bytesToShort($this->data, $offset, $this->order);
}
/**
* Return a signed short read from the data.
*
* @param integer $offset
* the offset into the data. An offset of zero will
* return the first short available in the current allowed window.
* The last valid offset is equal to {@link getSize()}-2. Invalid
* offsets will result in a {@link PelDataWindowOffsetException}
* being thrown.
* @return integer the signed short found at offset.
* @throws PelDataWindowOffsetException
*/
public function getSShort($offset = 0)
{
/*
* Validate the offset+1 to see if we can safely get two bytes ---
* this throws an exception if offset is out of range.
*/
$this->validateOffset($offset);
$this->validateOffset($offset + 1);
/* Translate the offset into an offset into the data. */
$offset += $this->start;
/* Return a signed short. */
return PelConvert::bytesToSShort($this->data, $offset, $this->order);
}
/**
* Return an unsigned long read from the data.
*
* @param integer $offset
* the offset into the data. An offset of zero will
* return the first long available in the current allowed window.
* The last valid offset is equal to {@link getSize()}-4. Invalid
* offsets will result in a {@link PelDataWindowOffsetException}
* being thrown.
* @return integer the unsigned long found at offset.
* @throws PelDataWindowOffsetException
*/
public function getLong($offset = 0)
{
/*
* Validate the offset+3 to see if we can safely get four bytes
* --- this throws an exception if offset is out of range.
*/
$this->validateOffset($offset);
$this->validateOffset($offset + 3);
/* Translate the offset into an offset into the data. */
$offset += $this->start;
/* Return an unsigned long. */
return PelConvert::bytesToLong($this->data, $offset, $this->order);
}
/**
* Return a signed long read from the data.
*
* @param integer $offset
* the offset into the data. An offset of zero will
* return the first long available in the current allowed window.
* The last valid offset is equal to {@link getSize()}-4. Invalid
* offsets will result in a {@link PelDataWindowOffsetException}
* being thrown.
* @return integer the signed long found at offset.
* @throws PelDataWindowOffsetException
*/
public function getSLong($offset = 0)
{
/*
* Validate the offset+3 to see if we can safely get four bytes
* --- this throws an exception if offset is out of range.
*/
$this->validateOffset($offset);
$this->validateOffset($offset + 3);
/* Translate the offset into an offset into the data. */
$offset += $this->start;
/* Return a signed long. */
return PelConvert::bytesToSLong($this->data, $offset, $this->order);
}
/**
* Return an unsigned rational read from the data.
*
* @param integer $offset
* the offset into the data. An offset of zero will
* return the first rational available in the current allowed
* window. The last valid offset is equal to {@link getSize()}-8.
* Invalid offsets will result in a {@link
* PelDataWindowOffsetException} being thrown.
* @return array the unsigned rational found at offset. A rational
* number is represented as an array of two numbers: the enumerator
* and denominator. Both of these numbers will be unsigned longs.
* @throws PelDataWindowOffsetException
*/
public function getRational($offset = 0)
{
return [
$this->getLong($offset),
$this->getLong($offset + 4)
];
}
/**
* Return a signed rational read from the data.
*
* @param integer $offset
* the offset into the data. An offset of zero will
* return the first rational available in the current allowed
* window. The last valid offset is equal to {@link getSize()}-8.
* Invalid offsets will result in a {@link
* PelDataWindowOffsetException} being thrown.
* @return array the signed rational found at offset. A rational
* number is represented as an array of two numbers: the enumerator
* and denominator. Both of these numbers will be signed longs.
* @throws PelDataWindowOffsetException
*/
public function getSRational($offset = 0)
{
return [
$this->getSLong($offset),
$this->getSLong($offset + 4)
];
}
/**
* String comparison on substrings.
*
* @param integer $offset
* the offset into the data. An offset of zero will make
* the comparison start with the very first byte available in the
* window. The last valid offset is equal to {@link getSize()}
* minus the length of the string. If the string is too long, then
* a {@link PelDataWindowOffsetException} will be thrown.
* @param string $str
* the string to compare with.
* @return boolean true if the string given matches the data in the
* window, at the specified offset, false otherwise. The comparison
* will stop as soon as a mismatch if found.
* @throws PelDataWindowOffsetException
*/
public function strcmp($offset, $str)
{
/*
* Validate the offset of the final character we might have to
* check.
*/
$s = strlen($str);
$this->validateOffset($offset);
$this->validateOffset($offset + $s - 1);
/* Translate the offset into an offset into the data. */
$offset += $this->start;
/* Check each character, return as soon as the answer is known. */
for ($i = 0; $i < $s; $i ++) {
if ($this->data[$offset + $i] != $str[$i]) {
return false;
}
}
/* All characters matches each other, return true. */
return true;
}
/**
* Return a string representation of the data window.
*
* @return string a description of the window with information about
* the number of bytes accessible, the total number of bytes, and
* the window start and stop.
*/
public function __toString()
{
return Pel::fmt('DataWindow: %d bytes in [%d, %d] of %d bytes', $this->size, $this->start, $this->start + $this->size, strlen($this->data));
}
}