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-<?php
-/**
- * Packed - provides a 'packed object' object
- *
- * PHP version 5.3
- *
- * @category Git
- * @package Granite
- * @author Craig Roberts <craig0990@googlemail.com>
- * @license http://www.opensource.org/licenses/mit-license.php MIT Expat License
- * @link http://craig0990.github.com/Granite/
- */
-
-namespace Granite\Git\Object;
-use \UnexpectedValueException as UnexpectedValueException;
-
-/**
- * Packed represents a packed object in the Git repository
- *
- * @category Git
- * @package Granite
- * @author Craig Roberts <craig0990@googlemail.com>
- * @license http://www.opensource.org/licenses/mit-license.php MIT Expat License
- * @link http://craig0990.github.com/Granite/
- */
-class Packed extends Raw
-{
-
- /**
- * The name of the packfile being read
- */
- private $_packfile;
-
- /**
- * Added to the object size to make a 'best-guess' effort at how much compressed
- * data to read - should be reimplemented, ideally with streams.
- */
- const OBJ_PADDING = 512;
-
- /**
- * Reads the object data from the compressed data at $offset in $packfile
- *
- * @param string $packfile The path to the packfile
- * @param int $offset The offset of the object data
- */
- public function __construct($packfile, $offset)
- {
- $this->_packfile = $packfile;
-
- list($this->type, $this->size, $this->content)
- = $this->_readPackedObject($offset);
- }
-
- /**
- * Reads the object data at $this->_offset
- *
- * @param int $offset Offset of the object header
- *
- * @return array Containing the type, size and object data
- */
- private function _readPackedObject($offset)
- {
- $file = fopen($this->_packfile, 'rb');
- fseek($file, $offset);
- // Read the type and uncompressed size from the object header
- list($type, $size) = $this->_readHeader($file, $offset);
- $object_offset = ftell($file);
-
- if ($type == self::OBJ_OFS_DELTA || $type == self::OBJ_REF_DELTA) {
- return $this->_unpackDeltified(
- $file, $offset, $object_offset, $type, $size
- );
- }
-
- $content = gzuncompress(fread($file, $size + self::OBJ_PADDING), $size);
-
- return array($type, $size, $content);
- }
-
- /**
- * Reads a packed object header, returning the type and the size. For more
- * detailed information, refer to the @see tag.
- *
- * From the @see tag: "Each byte is really 7 bits of data, with the first bit
- * being used to say if that hunk is the last one or not before the data starts.
- * If the first bit is a 1, you will read another byte, otherwise the data starts
- * next. The first 3 bits in the first byte specifies the type of data..."
- *
- * @param handle $file File handle to read
- * @param int $offset Offset of the object header
- *
- * @return array Containing the type and the size
- * @see http://book.git-scm.com/7_the_packfile.html
- */
- private function _readHeader($file, $offset)
- {
- // Read the object header byte-by-byte
- fseek($file, $offset);
- $byte = ord(fgetc($file));
- /**
- * Bit-shift right by four, then ignore the first bit with a bitwise AND
- * This gives us the object type in binary:
- * 001 commit self::OBJ_COMMIT
- * 010 tree self::OBJ_TREE
- * 011 blob self::OBJ_BLOB
- * 100 tag self::OBJ_TAG
- * 110 offset delta self::OBJ_OFS_DELTA
- * 111 ref delta self::OBJ_REF_DELTA
- *
- * (000 is undefined, 101 is not currently in use)
- * See http://book.git-scm.com/7_the_packfile.html for details
- */
- $type = ($byte >> 4) & 0x07;
-
- // Read the last four bits of the first byte, used to find the size
- $size = $byte & 0x0F;
-
- /**
- * $shift initially set to four, since we use the last four bits of the first
- * byte
- *
- * $byte & 0x80 checks the initial bit is set to 1 (i.e. keep reading data)
- *
- * Finally, $shift is incremented by seven for each consecutive byte (because
- * we ignore the initial bit)
- */
- for ($shift = 4; $byte & 0x80; $shift += 7) {
- $byte = ord(fgetc($file));
- /**
- * The size is ANDed against 0x7F to strip the initial bit, then
- * bitshifted by left $shift (4 or 7, depending on whether it's the
- * initial byte) and ORed against the existing binary $size. This
- * continuously increments the $size variable.
- */
- $size |= (($byte & 0x7F) << $shift);
- }
-
- return array($type, $size);
- }
-
- /**
- * Unpacks a deltified object located at $offset in $file
- *
- * @param handle $file File handle to read
- * @param int $offset Offset of the object data
- * @param int $object_offset Offset of the object data, past the header
- * @param int $type The object type, either OBJ_REF_DELTA
- or OBJ_OFS_DELTA
- * @param int $size The expected size of the uncompressed data
- *
- * @return array Containing the type, size and object data
- */
- private function _unpackDeltified($file, $offset, $object_offset, $type, $size)
- {
- fseek($file, $object_offset);
-
- if ($type == self::OBJ_REF_DELTA) {
-
- $base_sha = bin2hex(fread($file, 20));
-
- $path = substr($this->_packfile, 0, strpos($this->_packfile, '.git')+5);
- $base = Raw::factory($path, $base_sha);
- $type = $base->type();
- $base = $base->content();
-
- $delta = gzuncompress(
- fread($file, $size + self::OBJ_PADDING), $size
- );
-
- $content = $this->_applyDelta($base, $delta);
-
- } elseif ($type == self::OBJ_OFS_DELTA) {
-
- // 20 = maximum varint size according to Glip
- $data = fread($file, $size + self::OBJ_PADDING + 20);
-
- list($base_offset, $length) = $this->_bigEndianNumber($data);
-
- $delta = gzuncompress(substr($data, $length), $size);
- unset($data);
-
- $base_offset = $offset - $base_offset;
- list($type, $size, $base) = $this->_readPackedObject($base_offset);
-
- $content = $this->_applyDelta($base, $delta);
-
- } else {
- throw new UnexpectedValueException(
- "Unknown type $type for deltified object"
- );
- }
-
- return array($type, strlen($content), $content);
- }
-
- /**
- * Applies the $delta byte-sequence to $base and returns the
- * resultant binary string.
- *
- * This code is modified from Grit (see below), the Ruby
- * implementation used for GitHub under an MIT license.
- *
- * @param string $base The base string for the delta to be applied to
- * @param string $delta The delta string to apply
- *
- * @return string The patched binary string
- * @see
- * https://github.com/mojombo/grit/blob/master/lib/grit/git-ruby/internal/pack.rb
- */
- private function _applyDelta($base, $delta)
- {
- $pos = 0;
- $src_size = $this->_varint($delta, $pos);
- $dst_size = $this->_varint($delta, $pos);
-
- if ($src_size !== strlen($base)) {
- throw new UnexpectedValueException(
- 'Expected base delta size ' . strlen($base) . ' does not match the expected '
- . "value $src_size"
- );
- }
-
- $dest = "";
- while ($pos < strlen($delta)) {
- $byte = ord($delta{$pos++});
-
- if ($byte & 0x80) {
- /* copy a part of $base */
- $offset = 0;
- if ($byte & 0x01) $offset = ord($delta{$pos++});
- if ($byte & 0x02) $offset |= ord($delta{$pos++}) << 8;
- if ($byte & 0x04) $offset |= ord($delta{$pos++}) << 16;
- if ($byte & 0x08) $offset |= ord($delta{$pos++}) << 24;
- $length = 0;
- if ($byte & 0x10) $length = ord($delta{$pos++});
- if ($byte & 0x20) $length |= ord($delta{$pos++}) << 8;
- if ($byte & 0x40) $length |= ord($delta{$pos++}) << 16;
- if ($length == 0) $length = 0x10000;
- $dest .= substr($base, $offset, $length);
- } else {
- /* take the next $byte bytes as they are */
- $dest .= substr($delta, $pos, $byte);
- $pos += $byte;
- }
- }
-
- if (strlen($dest) !== $dst_size) {
- throw new UnexpectedValueException(
- "Deltified string expected to be $dst_size bytes, but actually "
- . strlen($dest) . ' bytes'
- );
- }
-
- return $dest;
- }
-
- /**
- * Parse a Git varint (variable-length integer). Used in the `_applyDelta()`
- * method to read the delta header.
- *
- * @param string $string The string to parse
- * @param int &$pos The position in the string to read from
- *
- * @return int The integer value
- */
- private function _varint($string, &$pos = 0)
- {
- $varint = 0;
- $bitmask = 0x80;
- for ($i = 0; $bitmask & 0x80; $i += 7) {
- $bitmask = ord($string{$pos++});
- $varint |= (($bitmask & 0x7F) << $i);
- }
- return $varint;
- }
-
- /**
- * Decodes a big endian modified base 128 number (refer to @see tag); this only
- * appears to be used in one place, the offset delta in packfiles. The offset
- * is the number of bytes to seek back from the start of the delta object to find
- * the base object.
- *
- * This code has been implemented using the C code given in the @see tag below.
- *
- * @param string &$data The data to read from and decode the number
- *
- * @return Array Containing the base offset (number of bytes to seek back) and
- * the length to use when reading the delta
- * @see http://git.rsbx.net/Documents/Git_Data_Formats.txt
- */
- private function _bigEndianNumber(&$data)
- {
- $i = 0;
- $byte = ord($data{$i++});
- $number = $byte & 0x7F;
- while ($byte & 0x80) {
- $byte = ord($data{$i++});
- $number = (($number + 1) << 7) | ($byte & 0x7F);
- }
-
- return array($number, $i);
- }
-
-}
generated by cgit v1.2.3 (git 2.39.1) at 2025-06-02 03:04:19 +0000