DBABagOStuff.php

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<?php
class DBABagOStuff extends BagOStuff {
        var $mHandler, $mFile, $mReader, $mWriter, $mDisabled;

        public function __construct( $params ) {
                global $wgDBAhandler;

                if ( !isset( $params['dir'] ) ) {
                        $params['dir'] = wfTempDir();
                }

                $this->mFile = $params['dir'] . '/mw-cache-' . wfWikiID() . '.db';
                wfDebug( __CLASS__ . ": using cache file {$this->mFile}\n" );
                $this->mHandler = $wgDBAhandler;
        }

        protected function encode( $value, $expiry ) {
                # Convert to absolute time
                $expiry = $this->convertExpiry( $expiry );

                return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value );
        }

        protected function decode( $blob ) {
                if ( !is_string( $blob ) ) {
                        return array( false, 0 );
                } else {
                        return array(
                                unserialize( substr( $blob, 11 ) ),
                                intval( substr( $blob, 0, 10 ) )
                        );
                }
        }

        protected function getReader() {
                if ( file_exists( $this->mFile ) ) {
                        $handle = dba_open( $this->mFile, 'rl', $this->mHandler );
                } else {
                        $handle = $this->getWriter();
                }

                if ( !$handle ) {
                        wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
                }

                return $handle;
        }

        protected function getWriter() {
                $handle = dba_open( $this->mFile, 'cl', $this->mHandler );

                if ( !$handle ) {
                        wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
                }

                return $handle;
        }

        public function get( $key, &$casToken = null ) {
                wfProfileIn( __METHOD__ );
                wfDebug( __METHOD__ . "($key)\n" );

                $handle = $this->getReader();
                if ( !$handle ) {
                        wfProfileOut( __METHOD__ );
                        return false;
                }

                $val = dba_fetch( $key, $handle );
                list( $val, $expiry ) = $this->decode( $val );

                # Must close ASAP because locks are held
                dba_close( $handle );

                if ( $val !== false && $expiry && $expiry < time() ) {
                        # Key is expired, delete it
                        $handle = $this->getWriter();
                        dba_delete( $key, $handle );
                        dba_close( $handle );
                        wfDebug( __METHOD__ . ": $key expired\n" );
                        $val = false;
                }

                $casToken = $val;

                wfProfileOut( __METHOD__ );

                return $val;
        }

        public function set( $key, $value, $exptime = 0 ) {
                wfProfileIn( __METHOD__ );
                wfDebug( __METHOD__ . "($key)\n" );

                $blob = $this->encode( $value, $exptime );

                $handle = $this->getWriter();
                if ( !$handle ) {
                        wfProfileOut( __METHOD__ );
                        return false;
                }

                $ret = dba_replace( $key, $blob, $handle );
                dba_close( $handle );

                wfProfileOut( __METHOD__ );
                return $ret;
        }

        public function cas( $casToken, $key, $value, $exptime = 0 ) {
                wfProfileIn( __METHOD__ );
                wfDebug( __METHOD__ . "($key)\n" );

                $blob = $this->encode( $value, $exptime );

                $handle = $this->getWriter();
                if ( !$handle ) {
                        wfProfileOut( __METHOD__ );
                        return false;
                }

                // DBA is locked to any other write connection, so we can safely
                // compare the current & previous value before saving new value
                $val = dba_fetch( $key, $handle );
                list( $val, $exptime ) = $this->decode( $val );
                if ( $casToken !== $val ) {
                        dba_close( $handle );
                        wfProfileOut( __METHOD__ );
                        return false;
                }

                $ret = dba_replace( $key, $blob, $handle );
                dba_close( $handle );

                wfProfileOut( __METHOD__ );
                return $ret;
        }

        public function delete( $key, $time = 0 ) {
                wfProfileIn( __METHOD__ );
                wfDebug( __METHOD__ . "($key)\n" );

                $handle = $this->getWriter();
                if ( !$handle ) {
                        wfProfileOut( __METHOD__ );
                        return false;
                }

                $ret = !dba_exists( $key, $handle ) || dba_delete( $key, $handle );
                dba_close( $handle );

                wfProfileOut( __METHOD__ );
                return $ret;
        }

        public function add( $key, $value, $exptime = 0 ) {
                wfProfileIn( __METHOD__ );

                $blob = $this->encode( $value, $exptime );

                $handle = $this->getWriter();

                if ( !$handle ) {
                        wfProfileOut( __METHOD__ );
                        return false;
                }

                $ret = dba_insert( $key, $blob, $handle );

                # Insert failed, check to see if it failed due to an expired key
                if ( !$ret ) {
                        list( , $expiry ) = $this->decode( dba_fetch( $key, $handle ) );

                        if ( $expiry && $expiry < time() ) {
                                # Yes expired, delete and try again
                                dba_delete( $key, $handle );
                                $ret = dba_insert( $key, $blob, $handle );
                                # This time if it failed then it will be handled by the caller like any other race
                        }
                }

                dba_close( $handle );

                wfProfileOut( __METHOD__ );
                return $ret;
        }

        public function incr( $key, $step = 1 ) {
                wfProfileIn( __METHOD__ );

                $handle = $this->getWriter();

                if ( !$handle ) {
                        wfProfileOut( __METHOD__ );
                        return false;
                }

                list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
                if ( $value !== false ) {
                        if ( $expiry && $expiry < time() ) {
                                # Key is expired, delete it
                                dba_delete( $key, $handle );
                                wfDebug( __METHOD__ . ": $key expired\n" );
                                $value = false;
                        } else {
                                $value += $step;
                                $blob = $this->encode( $value, $expiry );

                                $ret = dba_replace( $key, $blob, $handle );
                                $value = $ret ? $value : false;
                        }
                }

                dba_close( $handle );

                wfProfileOut( __METHOD__ );

                return ( $value === false ) ? false : (int)$value;
        }
}