<?php

declare(strict_types=1);

namespace GuzzleHttp\Psr7;

use Psr\Http\Message\StreamInterface;

/**
 * Stream decorator that can cache previously read bytes from a sequentially
 * read stream.
 */
final class CachingStream implements StreamInterface
{
    use StreamDecoratorTrait;

    /** @var StreamInterface Stream being wrapped */
    private $remoteStream;

    /** @var int Number of bytes to skip reading due to a write on the buffer */
    private $skipReadBytes = 0;

    /**
     * @var StreamInterface
     */
    private $stream;

    /**
     * We will treat the buffer object as the body of the stream
     *
     * @param StreamInterface $stream Stream to cache. The cursor is assumed to be at the beginning of the stream.
     * @param StreamInterface $target Optionally specify where data is cached
     */
    public function __construct(
        StreamInterface $stream,
        StreamInterface $target = null
    ) {
        $this->remoteStream = $stream;
        $this->stream = $target ?: new Stream(Utils::tryFopen('php://temp', 'r+'));
    }

    public function getSize(): ?int
    {
        $remoteSize = $this->remoteStream->getSize();

        if (null === $remoteSize) {
            return null;
        }

        return max($this->stream->getSize(), $remoteSize);
    }

    public function rewind(): void
    {
        $this->seek(0);
    }

    public function seek($offset, $whence = SEEK_SET): void
    {
        if ($whence === SEEK_SET) {
            $byte = $offset;
        } elseif ($whence === SEEK_CUR) {
            $byte = $offset + $this->tell();
        } elseif ($whence === SEEK_END) {
            $size = $this->remoteStream->getSize();
            if ($size === null) {
                $size = $this->cacheEntireStream();
            }
            $byte = $size + $offset;
        } else {
            throw new \InvalidArgumentException('Invalid whence');
        }

        $diff = $byte - $this->stream->getSize();

        if ($diff > 0) {
            // Read the remoteStream until we have read in at least the amount
            // of bytes requested, or we reach the end of the file.
            while ($diff > 0 && !$this->remoteStream->eof()) {
                $this->read($diff);
                $diff = $byte - $this->stream->getSize();
            }
        } else {
            // We can just do a normal seek since we've already seen this byte.
            $this->stream->seek($byte);
        }
    }

    public function read($length): string
    {
        // Perform a regular read on any previously read data from the buffer
        $data = $this->stream->read($length);
        $remaining = $length - strlen($data);

        // More data was requested so read from the remote stream
        if ($remaining) {
            // If data was written to the buffer in a position that would have
            // been filled from the remote stream, then we must skip bytes on
            // the remote stream to emulate overwriting bytes from that
            // position. This mimics the behavior of other PHP stream wrappers.
            $remoteData = $this->remoteStream->read(
                $remaining + $this->skipReadBytes
            );

            if ($this->skipReadBytes) {
                $len = strlen($remoteData);
                $remoteData = substr($remoteData, $this->skipReadBytes);
                $this->skipReadBytes = max(0, $this->skipReadBytes - $len);
            }

            $data .= $remoteData;
            $this->stream->write($remoteData);
        }

        return $data;
    }

    public function write($string): int
    {
        // When appending to the end of the currently read stream, you'll want
        // to skip bytes from being read from the remote stream to emulate
        // other stream wrappers. Basically replacing bytes of data of a fixed
        // length.
        $overflow = (strlen($string) + $this->tell()) - $this->remoteStream->tell();
        if ($overflow > 0) {
            $this->skipReadBytes += $overflow;
        }

        return $this->stream->write($string);
    }

    public function eof(): bool
    {
        return $this->stream->eof() && $this->remoteStream->eof();
    }

    /**
     * Close both the remote stream and buffer stream
     */
    public function close(): void
    {
        $this->remoteStream->close();
        $this->stream->close();
    }

    private function cacheEntireStream(): int
    {
        $target = new FnStream(['write' => 'strlen']);
        Utils::copyToStream($this, $target);

        return $this->tell();
    }
}

• [D] Exception
• [F] AppendStream.php
  Delete
• [F] BufferStream.php
  Delete
• [F] CachingStream.php
  Delete
• [F] DroppingStream.php
  Delete
• [F] FnStream.php
  Delete
• [F] Header.php
  Delete
• [F] HttpFactory.php
  Delete
• [F] InflateStream.php
  Delete
• [F] LazyOpenStream.php
  Delete
• [F] LimitStream.php
  Delete
• [F] Message.php
  Delete
• [F] MessageTrait.php
  Delete
• [F] MimeType.php
  Delete
• [F] MultipartStream.php
  Delete
• [F] NoSeekStream.php
  Delete
• [F] PumpStream.php
  Delete
• [F] Query.php
  Delete
• [F] Request.php
  Delete
• [F] Response.php
  Delete
• [F] Rfc7230.php
  Delete
• [F] ServerRequest.php
  Delete
• [F] Stream.php
  Delete
• [F] StreamDecoratorTrait.php
  Delete
• [F] StreamWrapper.php
  Delete
• [F] UploadedFile.php
  Delete
• [F] Uri.php
  Delete
• [F] UriComparator.php
  Delete
• [F] UriNormalizer.php
  Delete
• [F] UriResolver.php
  Delete
• [F] Utils.php
  Delete

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Encryption is a process that transforms data into a secure format, known as ciphertext, which can only be deciphered using a specific decryption key. This means that even if data is intercepted during transmission, it remains unreadable and protected from unauthorized access. Encryption is essential in safeguarding sensitive payment information, such as credit card details and personal data, during online transactions.
Tokenization, on the other hand, involves substituting sensitive data with unique identifiers or "tokens." These tokens serve as placeholders and have no value outside of the specific transaction context. If intercepted, tokens are meaningless and cannot be used to access the original sensitive data. This method significantly reduces the risk of fraud and data breaches, as the actual payment information is not stored or transmitted.
Together, encryption and tokenization form a powerful security framework. Encryption ensures that data is protected during transmission, while tokenization minimizes the risk of exposing sensitive information by replacing it with secure, non-sensitive tokens.
These technologies are integral to modern payment platforms, providing a robust defense against cyber threats. By implementing advanced encryption and tokenization techniques, businesses can enhance the security of digital transactions, ensuring that users' financial and personal information remains safe. This comprehensive approach not only builds user trust but also fortifies the overall security infrastructure of digital payment systems. As cyber threats evolve, the continued advancement of encryption and tokenization will be crucial in maintaining secure and reliable payment processes.

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• Payment