spaces.php

aws/Aws/Glacier/TreeHash.php

@@ -0,0 +1,118 @@
+<?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 (strlen($this->buffer) > 0) {
+                $this->checksums[] = hash($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 = '';
+    }
+}