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;
    }
}