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+<?php
+/**
+ * Efficient concatenated text storage.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+
+/**
+ * Base class for general text storage via the "object" flag in old_flags, or
+ * two-part external storage URLs. Used for represent efficient concatenated
+ * storage, and migration-related pointer objects.
+ */
+interface HistoryBlob {
+ /**
+ * Adds an item of text, returns a stub object which points to the item.
+ * You must call setLocation() on the stub object before storing it to the
+ * database
+ *
+ * @param string $text
+ *
+ * @return string The key for getItem()
+ */
+ function addItem( $text );
+
+ /**
+ * Get item by key, or false if the key is not present
+ *
+ * @param string $key
+ *
+ * @return string|bool
+ */
+ function getItem( $key );
+
+ /**
+ * Set the "default text"
+ * This concept is an odd property of the current DB schema, whereby each text item has a revision
+ * associated with it. The default text is the text of the associated revision. There may, however,
+ * be other revisions in the same object.
+ *
+ * Default text is not required for two-part external storage URLs.
+ *
+ * @param string $text
+ */
+ function setText( $text );
+
+ /**
+ * Get default text. This is called from Revision::getRevisionText()
+ *
+ * @return string
+ */
+ function getText();
+}
+
+/**
+ * Concatenated gzip (CGZ) storage
+ * Improves compression ratio by concatenating like objects before gzipping
+ */
+class ConcatenatedGzipHistoryBlob implements HistoryBlob {
+ public $mVersion = 0, $mCompressed = false, $mItems = [], $mDefaultHash = '';
+ public $mSize = 0;
+ public $mMaxSize = 10000000;
+ public $mMaxCount = 100;
+
+ public function __construct() {
+ if ( !function_exists( 'gzdeflate' ) ) {
+ throw new MWException( "Need zlib support to read or write this "
+ . "kind of history object (ConcatenatedGzipHistoryBlob)\n" );
+ }
+ }
+
+ /**
+ * @param string $text
+ * @return string
+ */
+ public function addItem( $text ) {
+ $this->uncompress();
+ $hash = md5( $text );
+ if ( !isset( $this->mItems[$hash] ) ) {
+ $this->mItems[$hash] = $text;
+ $this->mSize += strlen( $text );
+ }
+ return $hash;
+ }
+
+ /**
+ * @param string $hash
+ * @return array|bool
+ */
+ public function getItem( $hash ) {
+ $this->uncompress();
+ if ( array_key_exists( $hash, $this->mItems ) ) {
+ return $this->mItems[$hash];
+ } else {
+ return false;
+ }
+ }
+
+ /**
+ * @param string $text
+ * @return void
+ */
+ public function setText( $text ) {
+ $this->uncompress();
+ $this->mDefaultHash = $this->addItem( $text );
+ }
+
+ /**
+ * @return array|bool
+ */
+ public function getText() {
+ $this->uncompress();
+ return $this->getItem( $this->mDefaultHash );
+ }
+
+ /**
+ * Remove an item
+ *
+ * @param string $hash
+ */
+ public function removeItem( $hash ) {
+ $this->mSize -= strlen( $this->mItems[$hash] );
+ unset( $this->mItems[$hash] );
+ }
+
+ /**
+ * Compress the bulk data in the object
+ */
+ public function compress() {
+ if ( !$this->mCompressed ) {
+ $this->mItems = gzdeflate( serialize( $this->mItems ) );
+ $this->mCompressed = true;
+ }
+ }
+
+ /**
+ * Uncompress bulk data
+ */
+ public function uncompress() {
+ if ( $this->mCompressed ) {
+ $this->mItems = unserialize( gzinflate( $this->mItems ) );
+ $this->mCompressed = false;
+ }
+ }
+
+ /**
+ * @return array
+ */
+ function __sleep() {
+ $this->compress();
+ return [ 'mVersion', 'mCompressed', 'mItems', 'mDefaultHash' ];
+ }
+
+ function __wakeup() {
+ $this->uncompress();
+ }
+
+ /**
+ * Helper function for compression jobs
+ * Returns true until the object is "full" and ready to be committed
+ *
+ * @return bool
+ */
+ public function isHappy() {
+ return $this->mSize < $this->mMaxSize
+ && count( $this->mItems ) < $this->mMaxCount;
+ }
+}
+
+/**
+ * Pointer object for an item within a CGZ blob stored in the text table.
+ */
+class HistoryBlobStub {
+ /**
+ * @var array One-step cache variable to hold base blobs; operations that
+ * pull multiple revisions may often pull multiple times from the same
+ * blob. By keeping the last-used one open, we avoid redundant
+ * unserialization and decompression overhead.
+ */
+ protected static $blobCache = [];
+
+ /** @var int */
+ public $mOldId;
+
+ /** @var string */
+ public $mHash;
+
+ /** @var string */
+ public $mRef;
+
+ /**
+ * @param string $hash The content hash of the text
+ * @param int $oldid The old_id for the CGZ object
+ */
+ function __construct( $hash = '', $oldid = 0 ) {
+ $this->mHash = $hash;
+ }
+
+ /**
+ * Sets the location (old_id) of the main object to which this object
+ * points
+ * @param int $id
+ */
+ function setLocation( $id ) {
+ $this->mOldId = $id;
+ }
+
+ /**
+ * Sets the location (old_id) of the referring object
+ * @param string $id
+ */
+ function setReferrer( $id ) {
+ $this->mRef = $id;
+ }
+
+ /**
+ * Gets the location of the referring object
+ * @return string
+ */
+ function getReferrer() {
+ return $this->mRef;
+ }
+
+ /**
+ * @return string|false
+ */
+ function getText() {
+ if ( isset( self::$blobCache[$this->mOldId] ) ) {
+ $obj = self::$blobCache[$this->mOldId];
+ } else {
+ $dbr = wfGetDB( DB_REPLICA );
+ $row = $dbr->selectRow(
+ 'text',
+ [ 'old_flags', 'old_text' ],
+ [ 'old_id' => $this->mOldId ]
+ );
+
+ if ( !$row ) {
+ return false;
+ }
+
+ $flags = explode( ',', $row->old_flags );
+ if ( in_array( 'external', $flags ) ) {
+ $url = $row->old_text;
+ $parts = explode( '://', $url, 2 );
+ if ( !isset( $parts[1] ) || $parts[1] == '' ) {
+ return false;
+ }
+ $row->old_text = ExternalStore::fetchFromURL( $url );
+
+ }
+
+ if ( !in_array( 'object', $flags ) ) {
+ return false;
+ }
+
+ if ( in_array( 'gzip', $flags ) ) {
+ // This shouldn't happen, but a bug in the compress script
+ // may at times gzip-compress a HistoryBlob object row.
+ $obj = unserialize( gzinflate( $row->old_text ) );
+ } else {
+ $obj = unserialize( $row->old_text );
+ }
+
+ if ( !is_object( $obj ) ) {
+ // Correct for old double-serialization bug.
+ $obj = unserialize( $obj );
+ }
+
+ // Save this item for reference; if pulling many
+ // items in a row we'll likely use it again.
+ $obj->uncompress();
+ self::$blobCache = [ $this->mOldId => $obj ];
+ }
+
+ return $obj->getItem( $this->mHash );
+ }
+
+ /**
+ * Get the content hash
+ *
+ * @return string
+ */
+ function getHash() {
+ return $this->mHash;
+ }
+}
+
+/**
+ * To speed up conversion from 1.4 to 1.5 schema, text rows can refer to the
+ * leftover cur table as the backend. This avoids expensively copying hundreds
+ * of megabytes of data during the conversion downtime.
+ *
+ * Serialized HistoryBlobCurStub objects will be inserted into the text table
+ * on conversion if $wgLegacySchemaConversion is set to true.
+ */
+class HistoryBlobCurStub {
+ /** @var int */
+ public $mCurId;
+
+ /**
+ * @param int $curid The cur_id pointed to
+ */
+ function __construct( $curid = 0 ) {
+ $this->mCurId = $curid;
+ }
+
+ /**
+ * Sets the location (cur_id) of the main object to which this object
+ * points
+ *
+ * @param int $id
+ */
+ function setLocation( $id ) {
+ $this->mCurId = $id;
+ }
+
+ /**
+ * @return string|bool
+ */
+ function getText() {
+ $dbr = wfGetDB( DB_REPLICA );
+ $row = $dbr->selectRow( 'cur', [ 'cur_text' ], [ 'cur_id' => $this->mCurId ] );
+ if ( !$row ) {
+ return false;
+ }
+ return $row->cur_text;
+ }
+}
+
+/**
+ * Diff-based history compression
+ * Requires xdiff 1.5+ and zlib
+ */
+class DiffHistoryBlob implements HistoryBlob {
+ /** @var array Uncompressed item cache */
+ public $mItems = [];
+
+ /** @var int Total uncompressed size */
+ public $mSize = 0;
+
+ /**
+ * @var array Array of diffs. If a diff D from A to B is notated D = B - A,
+ * and Z is an empty string:
+ *
+ * { item[map[i]] - item[map[i-1]] where i > 0
+ * diff[i] = {
+ * { item[map[i]] - Z where i = 0
+ */
+ public $mDiffs;
+
+ /** @var array The diff map, see above */
+ public $mDiffMap;
+
+ /** @var int The key for getText()
+ */
+ public $mDefaultKey;
+
+ /** @var string Compressed storage */
+ public $mCompressed;
+
+ /** @var bool True if the object is locked against further writes */
+ public $mFrozen = false;
+
+ /**
+ * @var int The maximum uncompressed size before the object becomes sad
+ * Should be less than max_allowed_packet
+ */
+ public $mMaxSize = 10000000;
+
+ /** @var int The maximum number of text items before the object becomes sad */
+ public $mMaxCount = 100;
+
+ /** Constants from xdiff.h */
+ const XDL_BDOP_INS = 1;
+ const XDL_BDOP_CPY = 2;
+ const XDL_BDOP_INSB = 3;
+
+ function __construct() {
+ if ( !function_exists( 'gzdeflate' ) ) {
+ throw new MWException( "Need zlib support to read or write DiffHistoryBlob\n" );
+ }
+ }
+
+ /**
+ * @throws MWException
+ * @param string $text
+ * @return int
+ */
+ function addItem( $text ) {
+ if ( $this->mFrozen ) {
+ throw new MWException( __METHOD__ . ": Cannot add more items after sleep/wakeup" );
+ }
+
+ $this->mItems[] = $text;
+ $this->mSize += strlen( $text );
+ $this->mDiffs = null; // later
+ return count( $this->mItems ) - 1;
+ }
+
+ /**
+ * @param string $key
+ * @return string
+ */
+ function getItem( $key ) {
+ return $this->mItems[$key];
+ }
+
+ /**
+ * @param string $text
+ */
+ function setText( $text ) {
+ $this->mDefaultKey = $this->addItem( $text );
+ }
+
+ /**
+ * @return string
+ */
+ function getText() {
+ return $this->getItem( $this->mDefaultKey );
+ }
+
+ /**
+ * @throws MWException
+ */
+ function compress() {
+ if ( !function_exists( 'xdiff_string_rabdiff' ) ) {
+ throw new MWException( "Need xdiff 1.5+ support to write DiffHistoryBlob\n" );
+ }
+ if ( isset( $this->mDiffs ) ) {
+ // Already compressed
+ return;
+ }
+ if ( !count( $this->mItems ) ) {
+ // Empty
+ return;
+ }
+
+ // Create two diff sequences: one for main text and one for small text
+ $sequences = [
+ 'small' => [
+ 'tail' => '',
+ 'diffs' => [],
+ 'map' => [],
+ ],
+ 'main' => [
+ 'tail' => '',
+ 'diffs' => [],
+ 'map' => [],
+ ],
+ ];
+ $smallFactor = 0.5;
+
+ $mItemsCount = count( $this->mItems );
+ for ( $i = 0; $i < $mItemsCount; $i++ ) {
+ $text = $this->mItems[$i];
+ if ( $i == 0 ) {
+ $seqName = 'main';
+ } else {
+ $mainTail = $sequences['main']['tail'];
+ if ( strlen( $text ) < strlen( $mainTail ) * $smallFactor ) {
+ $seqName = 'small';
+ } else {
+ $seqName = 'main';
+ }
+ }
+ $seq =& $sequences[$seqName];
+ $tail = $seq['tail'];
+ $diff = $this->diff( $tail, $text );
+ $seq['diffs'][] = $diff;
+ $seq['map'][] = $i;
+ $seq['tail'] = $text;
+ }
+ unset( $seq ); // unlink dangerous alias
+
+ // Knit the sequences together
+ $tail = '';
+ $this->mDiffs = [];
+ $this->mDiffMap = [];
+ foreach ( $sequences as $seq ) {
+ if ( !count( $seq['diffs'] ) ) {
+ continue;
+ }
+ if ( $tail === '' ) {
+ $this->mDiffs[] = $seq['diffs'][0];
+ } else {
+ $head = $this->patch( '', $seq['diffs'][0] );
+ $this->mDiffs[] = $this->diff( $tail, $head );
+ }
+ $this->mDiffMap[] = $seq['map'][0];
+ $diffsCount = count( $seq['diffs'] );
+ for ( $i = 1; $i < $diffsCount; $i++ ) {
+ $this->mDiffs[] = $seq['diffs'][$i];
+ $this->mDiffMap[] = $seq['map'][$i];
+ }
+ $tail = $seq['tail'];
+ }
+ }
+
+ /**
+ * @param string $t1
+ * @param string $t2
+ * @return string
+ */
+ function diff( $t1, $t2 ) {
+ # Need to do a null concatenation with warnings off, due to bugs in the current version of xdiff
+ # "String is not zero-terminated"
+ Wikimedia\suppressWarnings();
+ $diff = xdiff_string_rabdiff( $t1, $t2 ) . '';
+ Wikimedia\restoreWarnings();
+ return $diff;
+ }
+
+ /**
+ * @param string $base
+ * @param string $diff
+ * @return bool|string
+ */
+ function patch( $base, $diff ) {
+ if ( function_exists( 'xdiff_string_bpatch' ) ) {
+ Wikimedia\suppressWarnings();
+ $text = xdiff_string_bpatch( $base, $diff ) . '';
+ Wikimedia\restoreWarnings();
+ return $text;
+ }
+
+ # Pure PHP implementation
+
+ $header = unpack( 'Vofp/Vcsize', substr( $diff, 0, 8 ) );
+
+ # Check the checksum if hash extension is available
+ $ofp = $this->xdiffAdler32( $base );
+ if ( $ofp !== false && $ofp !== substr( $diff, 0, 4 ) ) {
+ wfDebug( __METHOD__ . ": incorrect base checksum\n" );
+ return false;
+ }
+ if ( $header['csize'] != strlen( $base ) ) {
+ wfDebug( __METHOD__ . ": incorrect base length\n" );
+ return false;
+ }
+
+ $p = 8;
+ $out = '';
+ while ( $p < strlen( $diff ) ) {
+ $x = unpack( 'Cop', substr( $diff, $p, 1 ) );
+ $op = $x['op'];
+ ++$p;
+ switch ( $op ) {
+ case self::XDL_BDOP_INS:
+ $x = unpack( 'Csize', substr( $diff, $p, 1 ) );
+ $p++;
+ $out .= substr( $diff, $p, $x['size'] );
+ $p += $x['size'];
+ break;
+ case self::XDL_BDOP_INSB:
+ $x = unpack( 'Vcsize', substr( $diff, $p, 4 ) );
+ $p += 4;
+ $out .= substr( $diff, $p, $x['csize'] );
+ $p += $x['csize'];
+ break;
+ case self::XDL_BDOP_CPY:
+ $x = unpack( 'Voff/Vcsize', substr( $diff, $p, 8 ) );
+ $p += 8;
+ $out .= substr( $base, $x['off'], $x['csize'] );
+ break;
+ default:
+ wfDebug( __METHOD__ . ": invalid op\n" );
+ return false;
+ }
+ }
+ return $out;
+ }
+
+ /**
+ * Compute a binary "Adler-32" checksum as defined by LibXDiff, i.e. with
+ * the bytes backwards and initialised with 0 instead of 1. See T36428.
+ *
+ * @param string $s
+ * @return string|bool False if the hash extension is not available
+ */
+ function xdiffAdler32( $s ) {
+ if ( !function_exists( 'hash' ) ) {
+ return false;
+ }
+
+ static $init;
+ if ( $init === null ) {
+ $init = str_repeat( "\xf0", 205 ) . "\xee" . str_repeat( "\xf0", 67 ) . "\x02";
+ }
+
+ // The real Adler-32 checksum of $init is zero, so it initialises the
+ // state to zero, as it is at the start of LibXDiff's checksum
+ // algorithm. Appending the subject string then simulates LibXDiff.
+ return strrev( hash( 'adler32', $init . $s, true ) );
+ }
+
+ function uncompress() {
+ if ( !$this->mDiffs ) {
+ return;
+ }
+ $tail = '';
+ $mDiffsCount = count( $this->mDiffs );
+ for ( $diffKey = 0; $diffKey < $mDiffsCount; $diffKey++ ) {
+ $textKey = $this->mDiffMap[$diffKey];
+ $text = $this->patch( $tail, $this->mDiffs[$diffKey] );
+ $this->mItems[$textKey] = $text;
+ $tail = $text;
+ }
+ }
+
+ /**
+ * @return array
+ */
+ function __sleep() {
+ $this->compress();
+ if ( !count( $this->mItems ) ) {
+ // Empty object
+ $info = false;
+ } else {
+ // Take forward differences to improve the compression ratio for sequences
+ $map = '';
+ $prev = 0;
+ foreach ( $this->mDiffMap as $i ) {
+ if ( $map !== '' ) {
+ $map .= ',';
+ }
+ $map .= $i - $prev;
+ $prev = $i;
+ }
+ $info = [
+ 'diffs' => $this->mDiffs,
+ 'map' => $map
+ ];
+ }
+ if ( isset( $this->mDefaultKey ) ) {
+ $info['default'] = $this->mDefaultKey;
+ }
+ $this->mCompressed = gzdeflate( serialize( $info ) );
+ return [ 'mCompressed' ];
+ }
+
+ function __wakeup() {
+ // addItem() doesn't work if mItems is partially filled from mDiffs
+ $this->mFrozen = true;
+ $info = unserialize( gzinflate( $this->mCompressed ) );
+ unset( $this->mCompressed );
+
+ if ( !$info ) {
+ // Empty object
+ return;
+ }
+
+ if ( isset( $info['default'] ) ) {
+ $this->mDefaultKey = $info['default'];
+ }
+ $this->mDiffs = $info['diffs'];
+ if ( isset( $info['base'] ) ) {
+ // Old format
+ $this->mDiffMap = range( 0, count( $this->mDiffs ) - 1 );
+ array_unshift( $this->mDiffs,
+ pack( 'VVCV', 0, 0, self::XDL_BDOP_INSB, strlen( $info['base'] ) ) .
+ $info['base'] );
+ } else {
+ // New format
+ $map = explode( ',', $info['map'] );
+ $cur = 0;
+ $this->mDiffMap = [];
+ foreach ( $map as $i ) {
+ $cur += $i;
+ $this->mDiffMap[] = $cur;
+ }
+ }
+ $this->uncompress();
+ }
+
+ /**
+ * Helper function for compression jobs
+ * Returns true until the object is "full" and ready to be committed
+ *
+ * @return bool
+ */
+ function isHappy() {
+ return $this->mSize < $this->mMaxSize
+ && count( $this->mItems ) < $this->mMaxCount;
+ }
+
+}
+
+// phpcs:ignore Generic.CodeAnalysis.UnconditionalIfStatement.Found
+if ( false ) {
+ // Blobs generated by MediaWiki < 1.5 on PHP 4 were serialized with the
+ // class name coerced to lowercase. We can improve efficiency by adding
+ // autoload entries for the lowercase variants of these classes (T166759).
+ // The code below is never executed, but it is picked up by the AutoloadGenerator
+ // parser, which scans for class_alias() calls.
+ class_alias( ConcatenatedGzipHistoryBlob::class, 'concatenatedgziphistoryblob' );
+ class_alias( HistoryBlobCurStub::class, 'historyblobcurstub' );
+ class_alias( HistoryBlobStub::class, 'historyblobstub' );
+}
generated by cgit v1.2.1 (git 2.18.0) at 2024-05-05 00:31:19 +0000