[apple/xnu.git] / bsd / hfs / hfscommon / BTree / BTreeScanner.c

/*
 * Copyright (c) 1996-2005 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 *
 *      @(#)BTreeScanner.c
 */
#include <sys/kernel.h>
#include "../../hfs_endian.h"

#include "../headers/BTreeScanner.h"

static int FindNextLeafNode(    BTScanState *scanState, Boolean avoidIO );
static int ReadMultipleNodes(   BTScanState *scanState );


//_________________________________________________________________________________
//
//      Routine:        BTScanNextRecord
//
//      Purpose:        Return the next leaf record in a scan.
//
//      Inputs:
//              scanState               Scanner's current state
//              avoidIO                 If true, don't do any I/O to refill the buffer
//
//      Outputs:
//              key                             Key of found record (points into buffer)
//              data                    Data of found record (points into buffer)
//              dataSize                Size of data in found record
//
//      Result:
//              noErr                   Found a valid record
//              btNotFound              No more records
//              ???                             Needed to do I/O to get next node, but avoidIO set
//
//      Notes:
//              This routine returns pointers to the found record's key and data.  It
//              does not copy the key or data to a caller-supplied buffer (like
//              GetBTreeRecord would).  The caller must not modify the key or data.
//_________________________________________________________________________________

int BTScanNextRecord(   BTScanState *   scanState,
                                                Boolean                 avoidIO,
                                                void * *                key,
                                                void * *                data,
                                                u_int32_t *             dataSize  )
{
        int                             err;
        u_int16_t               dataSizeShort;
        
        err = noErr;

        //
        //      If this is the first call, there won't be any nodes in the buffer, so go
        //      find the first first leaf node (if any).
        //      
        if ( scanState->nodesLeftInBuffer == 0 )
        {
                err = FindNextLeafNode( scanState, avoidIO );
        }

        while ( err == noErr ) 
        { 
                //      See if we have a record in the current node
                err = GetRecordByIndex( scanState->btcb, scanState->currentNodePtr, 
                                                                scanState->recordNum, (KeyPtr *) key, 
                                                                (UInt8 **) data, &dataSizeShort  );

                if ( err == noErr )
                {
                        ++scanState->recordsFound;
                        ++scanState->recordNum;
                        if (dataSize != NULL)
                                *dataSize = dataSizeShort;
                        return noErr;
                }
                else if (err > 0)
                {
                        //      We didn't get the node through the cache, so we can't invalidate it.
                        //XXX Should we do something else to avoid seeing the same record again?
                        return err;
                }
                
                //      We're done with the current node.  See if we've returned all the records
                if ( scanState->recordsFound >= scanState->btcb->leafRecords )
                {
                        return btNotFound;
                }

                //      Move to the first record of the next leaf node
                scanState->recordNum = 0; 
                err = FindNextLeafNode( scanState, avoidIO );
        }
        
        //
        //      If we got an EOF error from FindNextLeafNode, then there are no more leaf
        //      records to be found.
        //
        if ( err == fsEndOfIterationErr )
                err = btNotFound;
        
        return err;
        
} /* BTScanNextRecord */


//_________________________________________________________________________________
//
//      Routine:        FindNextLeafNode
//
//      Purpose:        Point to the next leaf node in the buffer.  Read more nodes
//                              into the buffer if needed (and allowed).
//
//      Inputs:
//              scanState               Scanner's current state
//              avoidIO                 If true, don't do any I/O to refill the buffer
//
//      Result:
//              noErr                   Found a valid record
//              fsEndOfIterationErr     No more nodes in file
//              ???                             Needed to do I/O to get next node, but avoidIO set
//_________________________________________________________________________________

static int FindNextLeafNode(    BTScanState *scanState, Boolean avoidIO )
{
        int err;
        BlockDescriptor block;
        FileReference fref;
        
        err = noErr;            // Assume everything will be OK
        
        while ( 1 ) 
        {
                if ( scanState->nodesLeftInBuffer == 0 ) 
                {
                        //      Time to read some more nodes into the buffer
                        if ( avoidIO ) 
                        {
                                return fsBTTimeOutErr;
                        }
                        else 
                        {
                                //      read some more nodes into buffer
                                err = ReadMultipleNodes( scanState );
                                if ( err != noErr ) 
                                        break;
                        }
                }
                else 
                {
                        //      Adjust the node counters and point to the next node in the buffer
                        ++scanState->nodeNum;
                        --scanState->nodesLeftInBuffer;
                        
                        //      If we've looked at all nodes in the tree, then we're done
                        if ( scanState->nodeNum >= scanState->btcb->totalNodes )
                                return fsEndOfIterationErr;

                        if ( scanState->nodesLeftInBuffer == 0 )
                        {
                                scanState->recordNum = 0; 
                                continue; 
                        }

                        (u_int8_t *) scanState->currentNodePtr += scanState->btcb->nodeSize;
                }
                
                /* Fake a BlockDescriptor */
                block.blockHeader = NULL;       /* No buffer cache buffer */
                block.buffer = scanState->currentNodePtr;
                block.blockNum = scanState->nodeNum;
                block.blockSize = scanState->btcb->nodeSize;
                block.blockReadFromDisk = 1;
                block.isModified = 0;
                
                fref = scanState->btcb->fileRefNum;
                
                /* This node was read from disk, so it must be swapped/checked. */
                err = hfs_swap_BTNode(&block, fref, kSwapBTNodeBigToHost);
                if ( err != noErr ) {
                        printf("FindNextLeafNode: Error from hfs_swap_BTNode (node %u)\n", scanState->nodeNum);
                        continue;
                }

                if ( scanState->currentNodePtr->kind == kBTLeafNode )
                        break;
        }
        
        return err;
        
} /* FindNextLeafNode */


//_________________________________________________________________________________
//
//      Routine:        ReadMultipleNodes
//
//      Purpose:        Read one or more nodes into the buffer.
//
//      Inputs:
//              theScanStatePtr         Scanner's current state
//
//      Result:
//              noErr                           One or nodes were read
//              fsEndOfIterationErr             No nodes left in file, none in buffer
//_________________________________________________________________________________

static int ReadMultipleNodes( BTScanState *theScanStatePtr )
{
        int                                             myErr = E_NONE;
        BTreeControlBlockPtr    myBTreeCBPtr;
        daddr64_t                               myPhyBlockNum;
        u_int32_t                               myBufferSize;
        struct vnode *                  myDevPtr;
        int                                             myBlockRun;
        u_int32_t                               myBlocksInBufferCount;

        // release old buffer if we have one
        if ( theScanStatePtr->bufferPtr != NULL )
        {
                buf_markinvalid(theScanStatePtr->bufferPtr);
                buf_brelse( theScanStatePtr->bufferPtr );
                theScanStatePtr->bufferPtr = NULL;
                theScanStatePtr->currentNodePtr = NULL;
        }
        
        myBTreeCBPtr = theScanStatePtr->btcb;
                        
        // map logical block in catalog btree file to physical block on volume
        myErr = hfs_bmap(myBTreeCBPtr->fileRefNum, theScanStatePtr->nodeNum, 
                         &myDevPtr, &myPhyBlockNum, &myBlockRun);
        if ( myErr != E_NONE )
        {
                goto ExitThisRoutine;
        }

        // bmap block run gives us the remaining number of valid blocks (number of blocks 
        // minus the first).  so if there are 10 valid blocks our run number will be 9.
        // blocks, in our case is the same as nodes (both are 4K)
        myBlocksInBufferCount = (theScanStatePtr->bufferSize / myBTreeCBPtr->nodeSize );
        myBufferSize = theScanStatePtr->bufferSize;
        if ( (myBlockRun + 1) < myBlocksInBufferCount )
        {
                myBufferSize = (myBlockRun + 1) * myBTreeCBPtr->nodeSize;
        }
        
        // now read blocks from the device 
        myErr = (int)buf_bread(myDevPtr, 
                               myPhyBlockNum, 
                               myBufferSize,  
                               NOCRED, 
                               &theScanStatePtr->bufferPtr );
        if ( myErr != E_NONE )
        {
                goto ExitThisRoutine;
        }

        theScanStatePtr->nodesLeftInBuffer = buf_count(theScanStatePtr->bufferPtr) / theScanStatePtr->btcb->nodeSize;
        theScanStatePtr->currentNodePtr = (BTNodeDescriptor *) buf_dataptr(theScanStatePtr->bufferPtr);

ExitThisRoutine:
        return myErr;
        
} /* ReadMultipleNodes */



//_________________________________________________________________________________
//
//      Routine:        BTScanInitialize
//
//      Purpose:        Prepare to start a new BTree scan, or resume a previous one.
//
//      Inputs:
//              btreeFile               The B-Tree's file control block
//              startingNode    Initial node number
//              startingRecord  Initial record number within node
//              recordsFound    Number of valid records found so far
//              bufferSize              Size (in bytes) of buffer
//
//      Outputs:
//              scanState               Scanner's current state; pass to other scanner calls
//
//      Notes:
//              To begin a new scan and see all records in the B-Tree, pass zeroes for
//              startingNode, startingRecord, and recordsFound.
//
//              To resume a scan from the point of a previous BTScanTerminate, use the
//              values returned by BTScanTerminate as input for startingNode, startingRecord,
//              and recordsFound.
//
//              When resuming a scan, the caller should check the B-tree's write count.  If
//              it is different from the write count when the scan was terminated, then the
//              tree may have changed and the current state may be incorrect.  In particular,
//              you may see some records more than once, or never see some records.  Also,
//              the scanner may not be able to detect when all leaf records have been seen,
//              and will have to scan through many empty nodes.
//
//              XXXÊPerhaps the write count should be managed by BTScanInitialize and
//              XXX BTScanTerminate?  This would avoid the caller having to peek at
//              XXX internal B-Tree structures.
//_________________________________________________________________________________

int             BTScanInitialize(       const FCB *             btreeFile,
                                                        u_int32_t               startingNode,
                                                        u_int32_t               startingRecord,
                                                        u_int32_t               recordsFound,
                                                        u_int32_t               bufferSize,
                                                        BTScanState     *       scanState     )
{
        BTreeControlBlock       *btcb;
        
        //
        //      Make sure this is a valid B-Tree file
        //
        btcb = (BTreeControlBlock *) btreeFile->fcbBTCBPtr;
        if (btcb == NULL)
                return fsBTInvalidFileErr;
        
        //
        //      Make sure buffer size is big enough, and a multiple of the
        //      B-Tree node size
        //
        if ( bufferSize < btcb->nodeSize )
                return paramErr;
        bufferSize = (bufferSize / btcb->nodeSize) * btcb->nodeSize;

        //
        //      Set up the scanner's state
        //
        scanState->bufferSize                   = bufferSize;
        scanState->bufferPtr                    = NULL;
        scanState->btcb                                 = btcb;
        scanState->nodeNum                              = startingNode;
        scanState->recordNum                    = startingRecord;
        scanState->currentNodePtr               = NULL;
        scanState->nodesLeftInBuffer    = 0;            // no nodes currently in buffer
        scanState->recordsFound                 = recordsFound;
        microuptime(&scanState->startTime);                     // initialize our throttle
                
        return noErr;
        
} /* BTScanInitialize */


//_________________________________________________________________________________
//
//      Routine:        BTScanTerminate
//
//      Purpose:        Return state information about a scan so that it can be resumed
//                              later via BTScanInitialize.
//
//      Inputs:
//              scanState               Scanner's current state
//
//      Outputs:
//              nextNode                Node number to resume a scan (pass to BTScanInitialize)
//              nextRecord              Record number to resume a scan (pass to BTScanInitialize)
//              recordsFound    Valid records seen so far (pass to BTScanInitialize)
//_________________________________________________________________________________

int      BTScanTerminate(       BTScanState *           scanState,
                                                u_int32_t *                     startingNode,
                                                u_int32_t *                     startingRecord,
                                                u_int32_t *                     recordsFound    )
{
        *startingNode   = scanState->nodeNum;
        *startingRecord = scanState->recordNum;
        *recordsFound   = scanState->recordsFound;

        if ( scanState->bufferPtr != NULL )
        {
                buf_markinvalid(scanState->bufferPtr);
                buf_brelse( scanState->bufferPtr );
                scanState->bufferPtr = NULL;
                scanState->currentNodePtr = NULL;
        }
        
        return noErr;
        
} /* BTScanTerminate */