PHP Classes

File: application/modules/extensions/aws/Aws/Glacier/TreeHash.php

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File: application/modules/extensions/aws/Aws/Glacier/TreeHash.php
Role: Application script
Content type: text/plain
Description: Application script
Class: Pretty PHP S3 Files Manager
Web based interface to manage files in Amazon S3
Author: By
Last change:
Date: 8 years ago
Size: 3,398 bytes
 

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<?php
namespace Aws\Glacier;

use
Aws\HashInterface;

/**
 * Encapsulates the creation of a tree hash from streamed data
 */
class TreeHash implements HashInterface
{
    const
MB = 1048576;
    const
EMPTY_HASH = 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855';

   
/** @var string Algorithm used for hashing. */
   
private $algorithm;

   
/** @var string Buffered data that has not yet been hashed. */
   
private $buffer;

   
/** @var array Binary checksums from which the tree hash is derived. */
   
private $checksums = [];

   
/** @var string Resulting hash in binary form. */
   
private $hash;

    public function
__construct($algorithm = 'sha256')
    {
       
$this->algorithm = $algorithm;
       
$this->reset();
    }

   
/**
     * {@inheritdoc}
     * @throws \LogicException if the root tree hash is already calculated
     */
   
public function update($data)
    {
       
// Error if hash is already calculated.
       
if ($this->hash) {
            throw new \
LogicException('You may not add more data to a '
               
. 'complete tree hash.');
        }

       
// Buffer incoming data.
       
$this->buffer .= $data;

       
// When there is more than a MB of data, create a checksum.
       
while (strlen($this->buffer) >= self::MB) {
           
$data = substr($this->buffer, 0, self::MB);
           
$this->buffer = substr($this->buffer, self::MB) ?: '';
           
$this->checksums[] = hash($this->algorithm, $data, true);
        }

        return
$this;
    }

   
/**
     * Add a checksum to the tree hash directly
     *
     * @param string $checksum The checksum to add
     * @param bool $inBinaryForm TRUE if checksum is in binary form
     *
     * @return self
     * @throws \LogicException if the root tree hash is already calculated
     */
   
public function addChecksum($checksum, $inBinaryForm = false)
    {
       
// Error if hash is already calculated
       
if ($this->hash) {
            throw new \
LogicException('You may not add more checksums to a '
               
. 'complete tree hash.');
        }

       
// Convert the checksum to binary form if necessary
       
$this->checksums[] = $inBinaryForm ? $checksum : hex2bin($checksum);

        return
$this;
    }

    public function
complete()
    {
        if (!
$this->hash) {
           
// Clear out the remaining buffer.
           
if ($this->buffer) {
               
$this->checksums[] = hash($this->algorithm, $this->buffer, true);
               
$this->buffer = '';
            }

           
// If no hashes, add the EMPTY_HASH.
           
if (!$this->checksums) {
               
$this->checksums[] = hex2bin(self::EMPTY_HASH);
            }

           
// Perform hashes up the tree to arrive at the root checksum.
           
$hashes = $this->checksums;
            while (
count($hashes) > 1) {
               
$sets = array_chunk($hashes, 2);
               
$hashes = array();
                foreach (
$sets as $set) {
                   
$hashes[] = (count($set) === 1)
                        ?
$set[0]
                        :
hash($this->algorithm, $set[0] . $set[1], true);
                }
            }

           
$this->hash = $hashes[0];
        }

        return
$this->hash;
    }

    public function
reset()
    {
       
$this->hash = null;
       
$this->checksums = [];
       
$this->buffer = '';
    }
}