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libphutil/src/utils/PhutilRope.php
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PhutilRope.php
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<?php
/**
* String-like object which reduces the cost of managing large strings. This
* is particularly useful for buffering large amounts of data that is being
* passed to `fwrite()`.
*/
final class PhutilRope extends Phobject {
private $length = 0;
private $buffers = array();
// This is is arbitrary, it's just the maximum size I'm reliably able to
// fwrite() to a pipe on OSX. In theory, we could tune this slightly based
// on the pipe buffer size, but any value similar to this shouldn't affect
// performance much.
private $segmentSize = 16384;
/**
* Append a string to the rope.
*
* @param string String to append.
* @return this
*/
public function append($string) {
if (!strlen($string)) {
return $this;
}
$len = strlen($string);
$this->length += $len;
if ($len <= $this->segmentSize) {
$this->buffers[] = $string;
} else {
for ($cursor = 0; $cursor < $len; $cursor += $this->segmentSize) {
$this->buffers[] = substr($string, $cursor, $this->segmentSize);
}
}
return $this;
}
/**
* Get the length of the rope.
*
* @return int Length of the rope in bytes.
*/
public function getByteLength() {
return $this->length;
}
/**
* Get an arbitrary, nonempty prefix of the rope.
*
* @return string Some rope prefix.
*/
public function getAnyPrefix() {
$result = reset($this->buffers);
if ($result === false) {
return null;
}
return $result;
}
/**
* Get prefix bytes of the rope, up to some maximum size.
*
* @param int Maximum number of bytes to read.
* @return string Bytes.
*/
public function getPrefixBytes($length) {
$result = array();
$remaining_bytes = $length;
foreach ($this->buffers as $buf) {
$length = strlen($buf);
if ($length <= $remaining_bytes) {
$result[] = $buf;
$remaining_bytes -= $length;
} else {
$result[] = substr($buf, 0, $remaining_bytes);
$remaining_bytes = 0;
}
if (!$remaining_bytes) {
break;
}
}
return implode('', $result);
}
/**
* Return the entire rope as a normal string.
*
* @return string Normal string.
*/
public function getAsString() {
return implode('', $this->buffers);
}
/**
* Remove a specified number of bytes from the head of the rope.
*
* @param int Bytes to remove.
* @return this
*/
public function removeBytesFromHead($remove) {
if ($remove <= 0) {
throw new InvalidArgumentException(
pht('Length must be larger than 0!'));
}
$remaining_bytes = $remove;
foreach ($this->buffers as $key => $buf) {
$len = strlen($buf);
if ($len <= $remaining_bytes) {
unset($this->buffers[$key]);
$remaining_bytes -= $len;
if (!$remaining_bytes) {
break;
}
} else {
$this->buffers[$key] = substr($buf, $remaining_bytes);
break;
}
}
if ($this->buffers) {
$this->length -= $remove;
} else {
$this->length = 0;
}
return $this;
}
}
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