/**
* Search the index for a pack offset
*
* @param resource $index file pointer to index
* @param string $hash hash to find
* @param int $low low bound offset
* @param int $high high bound offset
* @return int|boolean pack offset or false if not found
*/
public function SearchIndex($index, $hash, $low, $high)
{
/*
* index v2 structure:
* magic and version - 2*4 bytes
* fanout table - 256*4 bytes
* sha listing - 20*count bytes
* crc checksums - 4*count bytes
* offsets - 4*count bytes
*/
/*
* get the object count from fanout[255]
*/
fseek($index, 8 + 4 * 255);
$objectCount = GitPHP_Pack::fuint32($index);
/*
* binary search for the index of the hash in the sha listing
* between cur and after from the fanout
*/
$objIndex = false;
while ($low <= $high) {
$mid = $low + $high >> 1;
fseek($index, 8 + 4 * 256 + 20 * $mid);
$binName = fread($index, 20);
$name = bin2hex($binName);
$cmp = strcmp($hash, $name);
if ($cmp < 0) {
$high = $mid - 1;
} else {
if ($cmp > 0) {
$low = $mid + 1;
} else {
$objIndex = $mid;
break;
}
}
}
if ($objIndex === false) {
return false;
}
/*
* get the offset from the same index in the offset table
*/
fseek($index, 8 + 4 * 256 + 24 * $objectCount + 4 * $objIndex);
$offset = GitPHP_Pack::fuint32($index);
if ($offset & 0x80000000) {
throw new Exception('64-bit offsets not implemented');
}
return $offset;
}
/**
* Tests if a pack file is valid
*
* @return boolean true if valid
*/
public function Valid()
{
if (!$this->validated) {
$this->validated = true;
$this->valid = false;
$pack = fopen($this->path, 'rb');
flock($pack, LOCK_SH);
$magic = fread($pack, 4);
$version = GitPHP_Pack::fuint32($pack);
if ($magic == 'PACK' && $version == 2) {
$this->valid = true;
}
flock($pack, LOCK_UN);
fclose($pack);
}
return $this->valid;
}
/**
* Find hashes in index matching a prefix
*
* @param resource $index file pointer to index
* @param string $prefix hash prefix
* @param int $low low bound offset
* @param int $high high bound offset
* @return string[] matching hashes
*/
public function FindHashes($index, $prefix, $low, $high)
{
$matches = array();
$range = $high - $low;
$prefixlen = strlen($prefix);
fseek($index, 4 * 256 + 24 * $low);
for ($i = 0; $i < $range; $i++) {
GitPHP_Pack::fuint32($index);
// offset
$binName = fread($index, 20);
$name = bin2hex($binName);
$cmp = substr_compare($name, $prefix, 0, $prefixlen);
if ($cmp === 0) {
$matches[] = $name;
} else {
if ($cmp > 0) {
break;
}
}
}
return $matches;
}
/**
* Reads and unpacks the next 32 bit integer
*
* @return int integer
* @param resource $handle file handle
*/
public static function fuint32($handle)
{
return GitPHP_Pack::uint32(fread($handle, 4));
}
