/* * Copyright (c) 2000 Apple Computer, Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * The contents of this file constitute Original Code as defined in and * are subject to the Apple Public Source License Version 1.1 (the * "License"). You may not use this file except in compliance with the * License. Please obtain a copy of the License at * http://www.apple.com/publicsource and read it before using this file. * * This 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 OR NON-INFRINGEMENT. Please see the * License for the specific language governing rights and limitations * under the License. * * @APPLE_LICENSE_HEADER_END@ */ /* File: VolumeAllocation.c Contains: Routines for accessing and modifying the volume bitmap. Version: HFS Plus 1.0 Copyright: © 1996-2000 by Apple Computer, Inc., all rights reserved. File Ownership: DRI: Mark Day Other Contact: Greg Parks Technology: HFS+ Writers: (djb) Don Brady (DSH) Deric Horn (msd) Mark Day Change History (most recent first): <MacOSX> 1/22/2000 djb Removed unused BlockCheck and BlockVerifyAllocated routines. <MacOSX> 4/27/98 djb Remove references to unused/legacy vcbFreeBks. <MacOSX> 4/27/98 djb Remove unneccessary DebugStr in BlockVerifyAllocated. <MacOSX> 4/17/98 djb Add VCB locking. <MacOSX> 4/13/98 djb Add RequireFileLock checking to ReadBitmapBlock. <MacOSX> 3/31/98 djb Sync up with final HFSVolumes.h header file. <12> 1 0/31/97 DSH Modify BlockVerifyAllocated() so DFA can call without actually writing to the disk. <CS11> 10/20/97 msd The way BlockAllocate rounds up to a multiple of the clump size is wrong. ExtendFileC should do the round-up and pass the result into BlockAllocate. Removed the fcb parameter to BlockAllocate; added a bytesMaximum parameter. <CS10> 10/17/97 msd Conditionalize DebugStrs. <CS9> 9/4/97 djb Add logging to BlockAllocate. <CS8> 9/4/97 msd Add a histogram of allocation sizes. Use DEBUG_BUILD instead of VSM_DEBUG to generate DebugStr messages. <CS7> 8/14/97 msd Bug 1662332. Don't mark blocks dirty in UpdateFreeCount. In BlockVerifyAllocated, only mark blocks dirty if they've actually changed. <CS6> 7/16/97 DSH FilesInternal.i renamed FileMgrInternal.i to avoid name collision <CS5> 7/8/97 DSH Loading PrecompiledHeaders from define passed in on C line <CS4> 6/12/97 msd Export BlockAllocateAny and UpdateVCBFreeBlks. <3> 5/8/97 DSH Added comments and ascii diagram of new BlockFindContiguous() algorithm. <2> 5/7/97 DSH New faster BlockFindContiguous algorithm. It searches backwards until a dirty bit is found instead of forwards. <CS1> 4/25/97 djb first checked in <HFS21> 4/14/97 msd Fix UpdateVCBFreeBlks so free space calculation doesn't overflow on volumes bigger than 4GB. <HFS20> 4/4/97 djb Get in sync with volume format changes. <HFS19> 1/27/97 msd Speed up BlockCheck and UpdateFreeCount. Removed DebugStr from BlockCheck; there are now DebugStr's in BlockVerifyAllocated, before the bitmap gets fixed (so potential problems can be debugged easier). Adjusted comments about internal routines. Changed names of "Fast" routines back to their original names (since the originals are now removed). <HFS18> 1/24/97 msd Speed up allocation and deallocation. <HFS17> 1/21/97 msd Add instrumentation for function entry/exit. BlockAllocate and ReadBitMapBlock use the event tag to log bytes requested and block number (respectively). <HFS16> 1/15/97 djb Add HFS+ supprt to BlockCheck (for MountCheck). <HFS15> 1/13/97 DSH Use vcb->nextAllocation instead of vcbAllocPtr. <HFS14> 1/9/97 djb UpdateVCBFreeBlks is not converting correctly. <HFS13> 1/6/97 djb Use vcb's allocationsRefNum to access allocation file. <HFS12> 1/2/97 DSH Added UpdateVCBFreeBlks() to update vcbFreeBks whenever we update vcb->freeblocks. <HFS11> 12/19/96 DSH All refs to VCB are now refs to ExtendedVCB <HFS10> 12/12/96 msd DivideAndRoundUp should not be declared as static. <HFS9> 12/10/96 msd Check PRAGMA_LOAD_SUPPORTED before loading precompiled headers. <HFS8> 12/4/96 DSH PrecompiledHeaders <HFS7> 11/27/96 djb Added AllocateFreeSpace for HFS wrapper support. <HFS6> 11/27/96 msd Changed ReadBitmapBlock to read from HFS+ allocation file. Temporarily uses the vcbVBMSt field of the VCB as the allocation file's refnum until extended VCB changes are checked in. <HFS5> 11/26/96 msd VSM and FileExtentMapping routines use FCB instead of FCBRec. <HFS4> 11/20/96 DSH Changed a parameter in GetBlock_glue, so I also changed the caller. <HFS3> 11/20/96 msd Include FilesInternal.h. Remove definition of MarkVCBDirty (since it is now in FilesInternal.h). <HFS2> 11/12/96 msd Need to bound allocations to be within the last allocation block of the volume (function AllocateAt). <HFS1> 11/11/96 msd first checked in */ /* Public routines: BlockAllocate Allocate space on a volume. Can allocate space contiguously. If not contiguous, then allocation may be less than what was asked for. Returns the starting block number, and number of blocks. (Will only do a single extent???) BlockDeallocate Deallocate a contiguous run of allocation blocks. UpdateFreeCount Computes the number of free allocation blocks on a volume. The vcb's free block count is updated. AllocateFreeSpace Allocates all the remaining free space (used for embedding HFS+ volumes). BlockAllocateAny Find and allocate a contiguous range of blocks up to a given size. The first range of contiguous free blocks found are allocated, even if there are fewer blocks than requested (and even if a contiguous range of blocks of the given size exists elsewhere). UpdateVCBFreeBlks Given an ExtenddVCB, calculate the vcbFreeBks value so that vcbFreeBks*vcbAlBlkSiz == freeBlocks*blockSize. Internal routines: BlockMarkFree Mark a contiguous range of blocks as free. The corresponding bits in the volume bitmap will be cleared. BlockMarkAllocated Mark a contiguous range of blocks as allocated. The cor- responding bits in the volume bitmap are set. Also tests to see if any of the blocks were previously unallocated. FindContiguous Find a contiguous range of blocks of a given size. The caller specifies where to begin the search (by block number). The block number of the first block in the range is returned. BlockAllocateContig Find and allocate a contiguous range of blocks of a given size. If a contiguous range of free blocks of the given size isn't found, then the allocation fails (i.e. it is "all or nothing"). ReadBitmapBlock Given an allocation block number, read the bitmap block that contains that allocation block into a caller-supplied buffer. */ #include "../../hfs_macos_defs.h" #include <sys/types.h> #include <sys/buf.h> #include <sys/systm.h> #include "../../hfs.h" #include "../../hfs_dbg.h" #include "../../hfs_format.h" #include "../../hfs_endian.h" #include "../headers/FileMgrInternal.h" #include "../headers/HFSInstrumentation.h" #define EXPLICIT_BUFFER_RELEASES 1 enum { kBitsPerByte = 8, kBitsPerWord = 32, kWordsPerBlock = 128, kBytesPerBlock = 512, kBitsPerBlock = 4096, kBitsWithinWordMask = kBitsPerWord-1, kBitsWithinBlockMask = kBitsPerBlock-1, kWordsWithinBlockMask = kWordsPerBlock-1, kExtentsPerRecord = 3 }; #define kLowBitInWordMask 0x00000001ul #define kHighBitInWordMask 0x80000000ul #define kAllBitsSetInWord 0xFFFFFFFFul static OSErr ReadBitmapBlock( ExtendedVCB *vcb, UInt32 block, UInt32 **buffer); static OSErr BlockAllocateContig( ExtendedVCB *vcb, UInt32 startingBlock, UInt32 minBlocks, UInt32 maxBlocks, UInt32 *actualStartBlock, UInt32 *actualNumBlocks); static OSErr BlockFindContiguous( ExtendedVCB *vcb, UInt32 startingBlock, UInt32 endingBlock, UInt32 minBlocks, UInt32 maxBlocks, UInt32 *actualStartBlock, UInt32 *actualNumBlocks); static OSErr BlockMarkAllocated( ExtendedVCB *vcb, UInt32 startingBlock, UInt32 numBlocks); static OSErr BlockMarkFree( ExtendedVCB *vcb, UInt32 startingBlock, UInt32 numBlocks); /* ;________________________________________________________________________________ ; ; Routine: BlkAlloc ; ; Function: Allocate space on a volume. If contiguous allocation is requested, ; at least the requested number of bytes will be allocated or an ; error will be returned. If contiguous allocation is not forced, ; the space will be allocated at the first free fragment following ; the requested starting allocation block. If there is not enough ; room there, a block of less than the requested size will be ; allocated. ; ; If the requested starting block is 0 (for new file allocations), ; the volume's allocation block pointer will be used as a starting ; point. ; ; All requests will be rounded up to the next highest clump size, as ; indicated in the file's FCB. ; ; Input Arguments: ; vcb - Pointer to ExtendedVCB for the volume to allocate space on ; fcb - Pointer to FCB for the file for which storage is being allocated ; startingBlock - Preferred starting allocation block, 0 = no preference ; forceContiguous - Force contiguous flag - if bit 0 set (NE), allocation is contiguous ; or an error is returned ; bytesRequested - Number of bytes requested. If the allocation is non-contiguous, ; less than this may actually be allocated ; bytesMaximum - The maximum number of bytes to allocate. If there is additional free ; space after bytesRequested, then up to bytesMaximum bytes should really ; be allocated. (Used by ExtendFileC to round up allocations to a multiple ; of the file's clump size.) ; ; Output: ; (result) - Error code, zero for successful allocation ; *startBlock - Actual starting allocation block ; *actualBlocks - Actual number of allocation blocks allocated ; ; Side effects: ; The volume bitmap is read and updated; the volume bitmap cache may be changed. ; ; Modification history: ; <06Oct85> PWD Changed to check for errors after calls to ReadBM and NextWord ; Relocated call to MarkBlock in allocation loop ; Changed to call NextBit ; <21Oct85> PWD Changed to check VCBFreeBks before attempting to allocate any block. ; Speed up scan for free space by checking for all 1's. ;________________________________________________________________________________ */ OSErr BlockAllocate ( ExtendedVCB *vcb, /* which volume to allocate space on */ UInt32 startingBlock, /* preferred starting block, or 0 for no preference */ SInt64 bytesRequested, /* desired number of BYTES to allocate */ SInt64 bytesMaximum, /* maximum number of bytes to allocate */ Boolean forceContiguous, /* non-zero to force contiguous allocation and to force */ /* bytesRequested bytes to actually be allocated */ UInt32 *actualStartBlock, /* actual first block of allocation */ UInt32 *actualNumBlocks) /* number of blocks actually allocated; if forceContiguous */ /* was zero, then this may represent fewer than bytesRequested */ /* bytes */ { OSErr err; UInt32 minBlocks; // minimum number of allocation blocks requested UInt32 maxBlocks; // number of allocation blocks requested, rounded to clump size Boolean updateAllocPtr = false; // true if nextAllocation needs to be updated LogStartTime(kTraceBlockAllocate); #if HFSInstrumentation InstSplitHistogramClassRef histogram; InstTraceClassRef trace; InstEventTag eventTag; err = InstCreateTraceClass(kInstRootClassRef, "HFS:VSM:BlockAllocate", 'hfs+', kInstEnableClassMask, &trace); if (err != noErr) DebugStr("\pError from InstCreateTraceClass"); err = InstCreateSplitHistogramClass(kInstRootClassRef, "HFS:VSM:BlockAllocate size", 0, 512, 16384, 262144, 16384, kInstEnableClassMask, &histogram); if (err != noErr) DebugStr("\pError from InstCreateHistogramClass"); eventTag = bytesRequested; // a cheap way to get bytesRequested into the log InstLogTraceEvent( trace, eventTag, kInstStartEvent); InstUpdateHistogram( histogram, bytesRequested, 1); #endif // // Initialize outputs in case we get an error // *actualStartBlock = 0; *actualNumBlocks = 0; // // Compute the number of allocation blocks requested, and maximum // minBlocks = FileBytesToBlocks(bytesRequested, vcb->blockSize); maxBlocks = FileBytesToBlocks(bytesMaximum, vcb->blockSize); // // If the disk is already full, don't bother. // if (vcb->freeBlocks == 0) { err = dskFulErr; goto Exit; } if (forceContiguous && vcb->freeBlocks < minBlocks) { err = dskFulErr; goto Exit; } // // If caller didn't specify a starting block number, then use the volume's // next block to allocate from. // if (startingBlock == 0) { VCB_LOCK(vcb); startingBlock = vcb->nextAllocation; VCB_UNLOCK(vcb); updateAllocPtr = true; } // // If the request must be contiguous, then find a sequence of free blocks // that is long enough. Otherwise, find the first free block. // if (forceContiguous) { err = BlockAllocateContig(vcb, startingBlock, minBlocks, maxBlocks, actualStartBlock, actualNumBlocks); } else { err = BlockAllocateAny(vcb, startingBlock, vcb->totalBlocks, maxBlocks, actualStartBlock, actualNumBlocks); if (err == dskFulErr) { err = BlockAllocateAny(vcb, 0, startingBlock, maxBlocks, actualStartBlock, actualNumBlocks); }; } if (err == noErr) { // // If we used the volume's roving allocation pointer, then we need to update it. // Adding in the length of the current allocation might reduce the next allocate // call by avoiding a re-scan of the already allocated space. However, the clump // just allocated can quite conceivably end up being truncated or released when // the file is closed or its EOF changed. Leaving the allocation pointer at the // start of the last allocation will avoid unnecessary fragmentation in this case. // VCB_LOCK(vcb); if (updateAllocPtr) vcb->nextAllocation = *actualStartBlock; // // Update the number of free blocks on the volume // vcb->freeBlocks -= *actualNumBlocks; VCB_UNLOCK(vcb); UpdateVCBFreeBlks( vcb ); MarkVCBDirty(vcb); } Exit: #if HFSInstrumentation InstLogTraceEvent( trace, eventTag, kInstEndEvent); #endif LogEndTime(kTraceBlockAllocate, err); return err; } /* ;________________________________________________________________________________ ; ; Routine: UpdateVCBFreeBlks ; ; Function: Whenever the freeBlocks field in the ExtendedVCB is updated, ; we must also recalculate the (UInt16) vcbFreeBks field in the ; traditional HFS VCB structure. ; ; Input Arguments: ; vcb - Pointer to ExtendedVCB for the volume to free space on ;________________________________________________________________________________ */ void UpdateVCBFreeBlks( ExtendedVCB *vcb ) { #if DEBUG_BUILD if ( vcb->vcbSigWord == kHFSSigWord && vcb->freeBlocks > 0xFFFF ) DebugStr("\p UpdateVCBFreeBlks: freeBlocks overflow!"); #endif } /* ;________________________________________________________________________________ ; ; Routine: BlkDealloc ; ; Function: Update the bitmap to deallocate a run of disk allocation blocks ; ; Input Arguments: ; vcb - Pointer to ExtendedVCB for the volume to free space on ; firstBlock - First allocation block to be freed ; numBlocks - Number of allocation blocks to free up (must be > 0!) ; ; Output: ; (result) - Result code ; ; Side effects: ; The volume bitmap is read and updated; the volume bitmap cache may be changed. ; ; Modification history: ; ; <06Oct85> PWD Changed to check for error after calls to ReadBM and NextWord ; Now calls NextBit to read successive bits from the bitmap ;________________________________________________________________________________ */ OSErr BlockDeallocate ( ExtendedVCB *vcb, // Which volume to deallocate space on UInt32 firstBlock, // First block in range to deallocate UInt32 numBlocks) // Number of contiguous blocks to deallocate { OSErr err; #if HFSInstrumentation InstTraceClassRef trace; InstEventTag eventTag; err = InstCreateTraceClass(kInstRootClassRef, "HFS:VSM:BlockDeallocate", 'hfs+', kInstEnableClassMask, &trace); if (err != noErr) DebugStr("\pError from InstCreateTraceClass"); eventTag = InstCreateEventTag(); InstLogTraceEvent( trace, eventTag, kInstStartEvent); #endif // // If no blocks to deallocate, then exit early // if (numBlocks == 0) { err = noErr; goto Exit; } // // Call internal routine to free the sequence of blocks // err = BlockMarkFree(vcb, firstBlock, numBlocks); if (err) goto Exit; // // Update the volume's free block count, and mark the VCB as dirty. // VCB_LOCK(vcb); vcb->freeBlocks += numBlocks; VCB_UNLOCK(vcb); UpdateVCBFreeBlks( vcb ); MarkVCBDirty(vcb); Exit: #if HFSInstrumentation InstLogTraceEvent( trace, eventTag, kInstEndEvent); #endif return err; } /* ;_______________________________________________________________________ ; ; Routine: UpdateFree ; Arguments: vcb -- ExtendedVCB for volume ; ; Called By: MountVol ; Function: This routine is used as part of the MountVol consistency check ; to figure out the number of free allocation blocks in the volume. ; ; Modification History: ; <08Sep85> LAK New today. ; <06Oct85> PWD Added explicit check for errors after calls to ReadBM, NextWord ; Now calls NextBit. ;_______________________________________________________________________ */ OSErr UpdateFreeCount ( ExtendedVCB *vcb) // Volume whose free block count should be updated { OSErr err; register UInt32 wordsLeft; // Number of words left in this bitmap block register UInt32 numBlocks; // Number of blocks left to scan register UInt32 freeCount; // Running count of free blocks found so far register UInt32 temp; UInt32 blockNum; // Block number of first block in this bitmap block UInt32 *buffer = NULL; // Pointer to bitmap block register UInt32 *currentWord; // Pointer to current word in bitmap block #if HFSInstrumentation InstTraceClassRef trace; InstEventTag eventTag; err = InstCreateTraceClass(kInstRootClassRef, "HFS:VSM:UpdateFreeCount", 'hfs+', kInstEnableClassMask, &trace); if (err != noErr) DebugStr("\pError from InstCreateTraceClass"); eventTag = InstCreateEventTag(); InstLogTraceEvent( trace, eventTag, kInstStartEvent); #endif // // Pre-read the first bitmap block // err = ReadBitmapBlock(vcb, 0, &buffer); if (err != noErr) goto Exit; // // Initialize buffer stuff // currentWord = buffer; wordsLeft = kWordsPerBlock; numBlocks = vcb->totalBlocks; freeCount = 0; blockNum = 0; // // Scan whole words first // while (numBlocks >= kBitsPerWord) { // See if it's time to move to the next bitmap block if (wordsLeft == 0) { // Read in the next bitmap block blockNum += kBitsPerBlock; // generate a block number in the next bitmap block #if EXPLICIT_BUFFER_RELEASES err = RelBlock_glue((Ptr)buffer, rbDefault); if (err != noErr) goto Exit; buffer = NULL; #endif err = ReadBitmapBlock(vcb, blockNum, &buffer); if (err != noErr) goto Exit; // Readjust currentWord, wordsLeft currentWord = buffer; wordsLeft = kWordsPerBlock; } // We count free blocks by inverting the word in the bitmap and counting set bits. temp = ~(*currentWord); while (temp) { ++freeCount; temp &= temp-1; // this clears least significant bit that is currently set } numBlocks -= kBitsPerWord; ++currentWord; // move to next word --wordsLeft; // one less word left in this block } // // Check any remaining blocks. // if (numBlocks != 0) { if (wordsLeft == 0) { // Read in the next bitmap block blockNum += kBitsPerBlock; // generate a block number in the next bitmap block #if EXPLICIT_BUFFER_RELEASES err = RelBlock_glue((Ptr)buffer, rbDefault); if (err != noErr) goto Exit; buffer = NULL; #endif err = ReadBitmapBlock(vcb, blockNum, &buffer); if (err != noErr) goto Exit; // Readjust currentWord, wordsLeft currentWord = buffer; wordsLeft = kWordsPerBlock; } // We count free blocks by inverting the word in the bitmap and counting set bits. temp = SWAP_BE32 (~(*currentWord)); while (numBlocks != 0) { if (temp & kHighBitInWordMask) ++freeCount; temp <<= 1; --numBlocks; } } VCB_LOCK(vcb); vcb->freeBlocks = freeCount; VCB_UNLOCK(vcb); UpdateVCBFreeBlks( vcb ); Exit: #if EXPLICIT_BUFFER_RELEASES if (buffer) { (void)RelBlock_glue((Ptr)buffer, rbDefault); /* Ignore any additional errors */ }; #endif #if HFSInstrumentation InstLogTraceEvent( trace, eventTag, kInstEndEvent); #endif return err; } /* ;_______________________________________________________________________ ; ; Routine: AllocateFreeSpace ; Arguments: vcb -- ExtendedVCB for volume ; ; Called By: HFSDiskInitComponent ; Function: This routine is used as part of DiskInit to create an ; embedded HFS+ volume. ; ; Note: Assumes that the free space is contiguous (true for a freshly erased disk) ;_______________________________________________________________________ */ OSErr AllocateFreeSpace ( ExtendedVCB *vcb, // Volume whose free space is about to be expropriated UInt32 *startBlock, // return where free space starts UInt32 *actualBlocks) // return the number of blocks in free space { OSErr err; err = BlockAllocateAny(vcb, 0, vcb->totalBlocks, vcb->freeBlocks, startBlock, actualBlocks); if (err == noErr) { VCB_LOCK(vcb); vcb->freeBlocks = 0; // sorry, no more blocks left! VCB_UNLOCK(vcb); MarkVCBDirty(vcb); } return err; } /* ;_______________________________________________________________________ ; ; Routine: FileBytesToBlocks ; ; Function: Divide numerator by denominator, rounding up the result if there ; was a remainder. This is frequently used for computing the number ; of whole and/or partial blocks used by some count of bytes. ; Actuall divides a 64 bit by a 32 bit into a 32bit result ; ; CAREFULL!!! THIS CAN CAUSE OVERFLOW....USER BEWARE!!! ;_______________________________________________________________________ */ UInt32 FileBytesToBlocks( SInt64 numerator, UInt32 denominator) { UInt32 quotient; quotient = (UInt32)(numerator / denominator); if (quotient * denominator != numerator) quotient++; return quotient; } /* ;_______________________________________________________________________ ; ; Routine: ReadBitmapBlock ; ; Function: Read in a bitmap block corresponding to a given allocation ; block. Return a pointer to the bitmap block. ; ; Inputs: ; vcb -- Pointer to ExtendedVCB ; block -- Allocation block whose bitmap block is desired ; ; Outputs: ; buffer -- Pointer to bitmap block corresonding to "block" ;_______________________________________________________________________ */ static OSErr ReadBitmapBlock( ExtendedVCB *vcb, UInt32 block, UInt32 **buffer) { OSErr err; #if HFSInstrumentation InstTraceClassRef trace; InstEventTag eventTag; err = InstCreateTraceClass(kInstRootClassRef, "HFS:VSM:ReadBitmapBlock", 'hfs+', kInstEnableClassMask, &trace); if (err != noErr) DebugStr("\pError from InstCreateTraceClass"); eventTag = block; // a cheap way to get the block number into the log InstLogTraceEvent( trace, eventTag, kInstStartEvent); #endif err = noErr; REQUIRE_FILE_LOCK(vcb->extentsRefNum, false); /* bitmap blocks are covered by the Extents B-tree lock */ if (vcb->vcbSigWord == kHFSSigWord) { // // HFS: Turn block number into physical block offset within the // bitmap, and then the physical block within the volume. // block /= kBitsPerBlock; // block offset within bitmap block += vcb->vcbVBMSt; // block within whole volume } else { FCB *allocFile; daddr_t startBlock; size_t availableBytes; // // HFS+: Read from allocation file. We simply convert the block number into a byte // offset within the allocation file and then determine which block that byte is in. // allocFile = GetFileControlBlock(vcb->allocationsRefNum); // // Find out which physical block holds byte #offset in allocation file. Note that we // map only 1 byte (the one we asked for). // err = MapFileBlockC(vcb, allocFile, (size_t)1, (off_t)(block/kBitsPerByte), &startBlock, &availableBytes); block = startBlock; } if (err == noErr) { err = GetBlock_glue( #if EXPLICIT_BUFFER_RELEASES 0, // No options #else gbReleaseMask, // Release block immediately. We only work on one // block at a time. Call MarkBlock later if dirty. #endif block, // Physical block on volume (Ptr *) buffer, // A place to return the buffer pointer kNoFileReference, // Not a file read vcb); // Volume to read from } #if HFSInstrumentation InstLogTraceEvent( trace, eventTag, kInstEndEvent); #endif return err; } /* _______________________________________________________________________ Routine: BlockAllocateContig Function: Allocate a contiguous group of allocation blocks. The allocation is all-or-nothing. The caller guarantees that there are enough free blocks (though they may not be contiguous, in which case this call will fail). Inputs: vcb Pointer to volume where space is to be allocated startingBlock Preferred first block for allocation minBlocks Minimum number of contiguous blocks to allocate maxBlocks Maximum number of contiguous blocks to allocate Outputs: actualStartBlock First block of range allocated, or 0 if error actualNumBlocks Number of blocks allocated, or 0 if error _______________________________________________________________________ */ static OSErr BlockAllocateContig( ExtendedVCB *vcb, UInt32 startingBlock, UInt32 minBlocks, UInt32 maxBlocks, UInt32 *actualStartBlock, UInt32 *actualNumBlocks) { OSErr err; // // Find a contiguous group of blocks at least minBlocks long. // Determine the number of contiguous blocks available (up // to maxBlocks). // err = BlockFindContiguous(vcb, startingBlock, vcb->totalBlocks, minBlocks, maxBlocks, actualStartBlock, actualNumBlocks); if (err == dskFulErr) { //€€ Should constrain the endingBlock here, so we don't bother looking for ranges //€€ that start after startingBlock, since we already checked those. err = BlockFindContiguous(vcb, 0, vcb->totalBlocks, minBlocks, maxBlocks, actualStartBlock, actualNumBlocks); } if (err != noErr) goto Exit; // // Now mark those blocks allocated. // err = BlockMarkAllocated(vcb, *actualStartBlock, *actualNumBlocks); Exit: if (err != noErr) { *actualStartBlock = 0; *actualNumBlocks = 0; } return err; } extern OSErr LookupBufferMapping(caddr_t bufferAddress, struct buf **bpp, int *mappingIndexPtr); /* _______________________________________________________________________ Routine: BlockAllocateAny Function: Allocate one or more allocation blocks. If there are fewer free blocks than requested, all free blocks will be allocated. The caller guarantees that there is at least one free block. Inputs: vcb Pointer to volume where space is to be allocated startingBlock Preferred first block for allocation endingBlock Last block to check + 1 maxBlocks Maximum number of contiguous blocks to allocate Outputs: actualStartBlock First block of range allocated, or 0 if error actualNumBlocks Number of blocks allocated, or 0 if error _______________________________________________________________________ */ OSErr BlockAllocateAny( ExtendedVCB *vcb, UInt32 startingBlock, register UInt32 endingBlock, UInt32 maxBlocks, UInt32 *actualStartBlock, UInt32 *actualNumBlocks) { OSErr err; register UInt32 block; // current block number register UInt32 currentWord; // Pointer to current word within bitmap block register UInt32 bitMask; // Word with given bits already set (ready to OR in) register UInt32 wordsLeft; // Number of words left in this bitmap block UInt32 *buffer = NULL; UInt32 *currCache = NULL; #if HFS_DIAGNOSTIC struct buf *bp = NULL; int mappingEntry; #endif // Since this routine doesn't wrap around if (maxBlocks > (endingBlock - startingBlock)) { maxBlocks = endingBlock - startingBlock; } DBG_TREE (("\nAllocating starting at %ld, maxblocks %ld\n", startingBlock, maxBlocks)); // // Pre-read the first bitmap block // err = ReadBitmapBlock(vcb, startingBlock, &currCache); DBG_TREE (("\n1. Read bit map at %ld, buffer is 0x%x\n", startingBlock, (int)currCache)); if (err != noErr) goto Exit; buffer = currCache; MarkBlock_glue((Ptr) currCache); // this block will be dirty DBG_ASSERT(! LookupBufferMapping((caddr_t)currCache, &bp, &mappingEntry)); // // Set up the current position within the block // { UInt32 wordIndexInBlock; wordIndexInBlock = (startingBlock & kBitsWithinBlockMask) / kBitsPerWord; buffer += wordIndexInBlock; wordsLeft = kWordsPerBlock - wordIndexInBlock; currentWord = SWAP_BE32 (*buffer); bitMask = kHighBitInWordMask >> (startingBlock & kBitsWithinWordMask); } // // Find the first unallocated block // block=startingBlock; while (block < endingBlock) { if ((currentWord & bitMask) == 0) break; // Next bit ++block; bitMask >>= 1; if (bitMask == 0) { // Next word bitMask = kHighBitInWordMask; ++buffer; if (--wordsLeft == 0) { // Next block #if EXPLICIT_BUFFER_RELEASES DBG_ASSERT(! LookupBufferMapping((caddr_t)currCache, &bp, &mappingEntry)); err = RelBlock_glue((Ptr)currCache, rbDefault); if (err != noErr) goto Exit; buffer = currCache = NULL; #endif err = ReadBitmapBlock(vcb, block, &currCache); if (err != noErr) goto Exit; buffer = currCache; DBG_TREE (("\n2. Read bit map at %ld, buffer is 0x%x\n", block, (int)currCache)); DBG_ASSERT(! LookupBufferMapping((caddr_t)currCache, &bp, &mappingEntry)); MarkBlock_glue((Ptr) currCache); // this block will be dirty wordsLeft = kWordsPerBlock; } currentWord = SWAP_BE32 (*buffer); } } // Did we get to the end of the bitmap before finding a free block? // If so, then couldn't allocate anything. if (block == endingBlock) { err = dskFulErr; goto Exit; } // Return the first block in the allocated range *actualStartBlock = block; // If we could get the desired number of blocks before hitting endingBlock, // then adjust endingBlock so we won't keep looking. Ideally, the comparison // would be (block + maxBlocks) < endingBlock, but that could overflow. The // comparison below yields identical results, but without overflow. if (block < (endingBlock-maxBlocks)) { endingBlock = block + maxBlocks; // if we get this far, we've found enough } // // Allocate all of the consecutive blocks // while ((currentWord & bitMask) == 0) { // Allocate this block currentWord |= bitMask; // Move to the next block. If no more, then exit. ++block; if (block == endingBlock) break; // Next bit bitMask >>= 1; if (bitMask == 0) { *buffer = SWAP_BE32 (currentWord); // update value in bitmap // Next word bitMask = kHighBitInWordMask; ++buffer; if (--wordsLeft == 0) { // Next block #if EXPLICIT_BUFFER_RELEASES DBG_ASSERT(! LookupBufferMapping((caddr_t)currCache, &bp, &mappingEntry)); err = RelBlock_glue((Ptr)currCache, rbDefault); if (err != noErr) goto Exit; buffer = currCache = NULL; #endif err = ReadBitmapBlock(vcb, block, &currCache); if (err != noErr) goto Exit; buffer = currCache; DBG_TREE (("\n3. Read bit map at %ld, buffer is 0x%x\n", block, (int)currCache)); DBG_ASSERT(! LookupBufferMapping((caddr_t)currCache, &bp, &mappingEntry)); MarkBlock_glue((Ptr) currCache); // this block will be dirty wordsLeft = kWordsPerBlock; } currentWord = SWAP_BE32 (*buffer); } } *buffer = SWAP_BE32 (currentWord); // update the last change Exit: if (err == noErr) { *actualNumBlocks = block - *actualStartBlock; } else { *actualStartBlock = 0; *actualNumBlocks = 0; } #if EXPLICIT_BUFFER_RELEASES if (currCache) { DBG_ASSERT(! LookupBufferMapping((caddr_t)currCache, &bp, &mappingEntry)); (void)RelBlock_glue((Ptr)currCache, rbDefault); /* Ignore any additional errors */ }; #endif return err; } /* _______________________________________________________________________ Routine: BlockMarkAllocated Function: Mark a contiguous group of blocks as allocated (set in the bitmap). It assumes those bits are currently marked deallocated (clear in the bitmap). Inputs: vcb Pointer to volume where space is to be allocated startingBlock First block number to mark as allocated numBlocks Number of blocks to mark as allocated _______________________________________________________________________ */ static OSErr BlockMarkAllocated( ExtendedVCB *vcb, UInt32 startingBlock, register UInt32 numBlocks) { OSErr err; register UInt32 *currentWord; // Pointer to current word within bitmap block register UInt32 wordsLeft; // Number of words left in this bitmap block register UInt32 bitMask; // Word with given bits already set (ready to OR in) UInt32 firstBit; // Bit index within word of first bit to allocate UInt32 numBits; // Number of bits in word to allocate UInt32 *buffer = NULL; #if HFSInstrumentation InstTraceClassRef trace; InstEventTag eventTag; err = InstCreateTraceClass(kInstRootClassRef, "HFS:VSM:BlockMarkAllocated", 'hfs+', kInstEnableClassMask, &trace); if (err != noErr) DebugStr("\pError from InstCreateTraceClass"); eventTag = InstCreateEventTag(); InstLogTraceEvent( trace, eventTag, kInstStartEvent); #endif // // Pre-read the bitmap block containing the first word of allocation // err = ReadBitmapBlock(vcb, startingBlock, &buffer); if (err != noErr) goto Exit; MarkBlock_glue((Ptr) buffer); // this block will be dirty // // Initialize currentWord, and wordsLeft. // { UInt32 wordIndexInBlock; wordIndexInBlock = (startingBlock & kBitsWithinBlockMask) / kBitsPerWord; currentWord = buffer + wordIndexInBlock; wordsLeft = kWordsPerBlock - wordIndexInBlock; } // // If the first block to allocate doesn't start on a word // boundary in the bitmap, then treat that first word // specially. // firstBit = startingBlock % kBitsPerWord; if (firstBit != 0) { bitMask = kAllBitsSetInWord >> firstBit; // turn off all bits before firstBit numBits = kBitsPerWord - firstBit; // number of remaining bits in this word if (numBits > numBlocks) { numBits = numBlocks; // entire allocation is inside this one word bitMask &= ~(kAllBitsSetInWord >> (firstBit + numBits)); // turn off bits after last } #if DEBUG_BUILD if ((*currentWord & SWAP_BE32 (bitMask)) != 0) { DebugStr("\pFATAL: blocks already allocated!"); //err = fsDSIntErr; //goto Exit; } #endif *currentWord |= SWAP_BE32 (bitMask); // set the bits in the bitmap numBlocks -= numBits; // adjust number of blocks left to allocate ++currentWord; // move to next word --wordsLeft; // one less word left in this block } // // Allocate whole words (32 blocks) at a time. // bitMask = kAllBitsSetInWord; // put this in a register for 68K while (numBlocks >= kBitsPerWord) { if (wordsLeft == 0) { // Read in the next bitmap block startingBlock += kBitsPerBlock; // generate a block number in the next bitmap block #if EXPLICIT_BUFFER_RELEASES err = RelBlock_glue((Ptr)buffer, rbDefault); if (err != noErr) goto Exit; buffer = NULL; #endif err = ReadBitmapBlock(vcb, startingBlock, &buffer); if (err != noErr) goto Exit; MarkBlock_glue((Ptr) buffer); // this block will be dirty // Readjust currentWord and wordsLeft currentWord = buffer; wordsLeft = kWordsPerBlock; } #if DEBUG_BUILD if (*currentWord != 0) { DebugStr("\pFATAL: blocks already allocated!"); //err = fsDSIntErr; //goto Exit; } #endif *currentWord = SWAP_BE32 (bitMask); numBlocks -= kBitsPerWord; ++currentWord; // move to next word --wordsLeft; // one less word left in this block } // // Allocate any remaining blocks. // if (numBlocks != 0) { bitMask = ~(kAllBitsSetInWord >> numBlocks); // set first numBlocks bits if (wordsLeft == 0) { // Read in the next bitmap block startingBlock += kBitsPerBlock; // generate a block number in the next bitmap block #if EXPLICIT_BUFFER_RELEASES err = RelBlock_glue((Ptr)buffer, rbDefault); if (err != noErr) goto Exit; buffer = NULL; #endif err = ReadBitmapBlock(vcb, startingBlock, &buffer); if (err != noErr) goto Exit; MarkBlock_glue((Ptr) buffer); // this block will be dirty // Readjust currentWord and wordsLeft currentWord = buffer; wordsLeft = kWordsPerBlock; } #if DEBUG_BUILD if ((*currentWord & SWAP_BE32 (bitMask)) != 0) { DebugStr("\pFATAL: blocks already allocated!"); //err = fsDSIntErr; //goto Exit; } #endif *currentWord |= SWAP_BE32 (bitMask); // set the bits in the bitmap // No need to update currentWord or wordsLeft } Exit: #if EXPLICIT_BUFFER_RELEASES if (buffer) { (void)RelBlock_glue((Ptr)buffer, rbDefault); /* Ignore any additional errors */ }; #endif #if HFSInstrumentation InstLogTraceEvent( trace, eventTag, kInstEndEvent); #endif return err; } /* _______________________________________________________________________ Routine: BlockMarkFree Function: Mark a contiguous group of blocks as free (clear in the bitmap). It assumes those bits are currently marked allocated (set in the bitmap). Inputs: vcb Pointer to volume where space is to be freed startingBlock First block number to mark as freed numBlocks Number of blocks to mark as freed _______________________________________________________________________ */ static OSErr BlockMarkFree( ExtendedVCB *vcb, UInt32 startingBlock, register UInt32 numBlocks) { OSErr err; register UInt32 *currentWord; // Pointer to current word within bitmap block register UInt32 wordsLeft; // Number of words left in this bitmap block register UInt32 bitMask; // Word with given bits already set (ready to OR in) UInt32 firstBit; // Bit index within word of first bit to allocate UInt32 numBits; // Number of bits in word to allocate UInt32 *buffer = NULL; #if HFSInstrumentation InstTraceClassRef trace; InstEventTag eventTag; err = InstCreateTraceClass(kInstRootClassRef, "HFS:VSM:BlockMarkFree", 'hfs+', kInstEnableClassMask, &trace); if (err != noErr) DebugStr("\pError from InstCreateTraceClass"); eventTag = InstCreateEventTag(); InstLogTraceEvent( trace, eventTag, kInstStartEvent); #endif // // Pre-read the bitmap block containing the first word of allocation // err = ReadBitmapBlock(vcb, startingBlock, &buffer); if (err != noErr) goto Exit; MarkBlock_glue((Ptr) buffer); // this block will be dirty // // Initialize currentWord, and wordsLeft. // { UInt32 wordIndexInBlock; wordIndexInBlock = (startingBlock & kBitsWithinBlockMask) / kBitsPerWord; currentWord = buffer + wordIndexInBlock; wordsLeft = kWordsPerBlock - wordIndexInBlock; } // // If the first block to free doesn't start on a word // boundary in the bitmap, then treat that first word // specially. // firstBit = startingBlock % kBitsPerWord; if (firstBit != 0) { bitMask = kAllBitsSetInWord >> firstBit; // turn off all bits before firstBit numBits = kBitsPerWord - firstBit; // number of remaining bits in this word if (numBits > numBlocks) { numBits = numBlocks; // entire allocation is inside this one word bitMask &= ~(kAllBitsSetInWord >> (firstBit + numBits)); // turn off bits after last } #if DEBUG_BUILD if ((*currentWord & SWAP_BE32 (bitMask)) != SWAP_BE32 (bitMask)) { DebugStr("\pFATAL: blocks not allocated!"); //err = fsDSIntErr; //goto Exit; } #endif *currentWord &= SWAP_BE32 (~bitMask); // clear the bits in the bitmap numBlocks -= numBits; // adjust number of blocks left to free ++currentWord; // move to next word --wordsLeft; // one less word left in this block } // // Allocate whole words (32 blocks) at a time. // while (numBlocks >= kBitsPerWord) { if (wordsLeft == 0) { // Read in the next bitmap block startingBlock += kBitsPerBlock; // generate a block number in the next bitmap block #if EXPLICIT_BUFFER_RELEASES err = RelBlock_glue((Ptr)buffer, rbDefault); if (err != noErr) goto Exit; buffer = NULL; #endif err = ReadBitmapBlock(vcb, startingBlock, &buffer); if (err != noErr) goto Exit; MarkBlock_glue((Ptr) buffer); // this block will be dirty // Readjust currentWord and wordsLeft currentWord = buffer; wordsLeft = kWordsPerBlock; } #if DEBUG_BUILD if (*currentWord != SWAP_BE32 (kAllBitsSetInWord)) { DebugStr("\pFATAL: blocks not allocated!"); //err = fsDSIntErr; //goto Exit; } #endif *currentWord = 0; // clear the entire word numBlocks -= kBitsPerWord; ++currentWord; // move to next word --wordsLeft; // one less word left in this block } // // Allocate any remaining blocks. // if (numBlocks != 0) { bitMask = ~(kAllBitsSetInWord >> numBlocks); // set first numBlocks bits if (wordsLeft == 0) { // Read in the next bitmap block startingBlock += kBitsPerBlock; // generate a block number in the next bitmap block #if EXPLICIT_BUFFER_RELEASES err = RelBlock_glue((Ptr)buffer, rbDefault); if (err != noErr) goto Exit; buffer = NULL; #endif err = ReadBitmapBlock(vcb, startingBlock, &buffer); if (err != noErr) goto Exit; MarkBlock_glue((Ptr) buffer); // this block will be dirty // Readjust currentWord and wordsLeft currentWord = buffer; wordsLeft = kWordsPerBlock; } #if DEBUG_BUILD if ((*currentWord & SWAP_BE32 (bitMask)) != SWAP_BE32 (bitMask)) { DebugStr("\pFATAL: blocks not allocated!"); //err = fsDSIntErr; //goto Exit; } #endif *currentWord &= SWAP_BE32 (~bitMask); // clear the bits in the bitmap // No need to update currentWord or wordsLeft } Exit: #if EXPLICIT_BUFFER_RELEASES if (buffer) { (void)RelBlock_glue((Ptr)buffer, rbDefault); /* Ignore any additional errors */ }; #endif #if HFSInstrumentation InstLogTraceEvent( trace, eventTag, kInstEndEvent); #endif return err; } /* _______________________________________________________________________ Routine: BlockFindContiguous Function: Find a contiguous range of blocks that are free (bits clear in the bitmap). If a contiguous range of the minimum size can't be found, an error will be returned. €€ It would be nice if we could skip over whole words €€ with all bits set. €€ When we find a bit set, and are about to set freeBlocks €€ to 0, we should check to see whether there are still €€ minBlocks bits left in the bitmap. Inputs: vcb Pointer to volume where space is to be allocated startingBlock Preferred first block of range endingBlock Last possible block in range + 1 minBlocks Minimum number of blocks needed. Must be > 0. maxBlocks Maximum (ideal) number of blocks desired Outputs: actualStartBlock First block of range found, or 0 if error actualNumBlocks Number of blocks found, or 0 if error _______________________________________________________________________ */ /* _________________________________________________________________________________________ (DSH) 5/8/97 Description of BlockFindContiguous() algorithm Finds a contiguous range of free blocks by searching back to front. This allows us to skip ranges of bits knowing that they are not candidates for a match because they are too small. The below ascii diagrams illustrate the algorithm in action. Representation of a piece of a volume bitmap file If BlockFindContiguous() is called with minBlocks == 10, maxBlocks == 20 Fig. 1 initialization of variables, "<--" represents direction of travel startingBlock (passed in) | 1 0 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 | <--| stopBlock currentBlock freeBlocks == 0 countedFreeBlocks == 0 Fig. 2 dirty bit found 1 0 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 | | stopBlock currentBlock freeBlocks == 3 countedFreeBlocks == 0 Fig. 3 reset variables to search for remainder of minBlocks 1 0 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 |_________________| | | Unsearched stopBlock currentBlock freeBlocks == 0 countedFreeBlocks == 3 Fig. 4 minBlocks contiguous blocks found, *actualStartBlock is set 1 0 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 |_________________| | Unsearched stopBlock freeBlocks == 7 currentBlock countedFreeBlocks == 3 Fig. 5 Now run it forwards trying to accumalate up to maxBlocks if possible 1 0 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 |_________________| | --> Unsearched currentBlock *actualNumBlocks == 10 Fig. 6 Dirty bit is found, return actual number of contiguous blocks found 1 0 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 |_________________| | Unsearched currentBlock *actualNumBlocks == 16 _________________________________________________________________________________________ */ static OSErr BlockFindContiguous( ExtendedVCB *vcb, UInt32 startingBlock, register UInt32 endingBlock, UInt32 minBlocks, UInt32 maxBlocks, UInt32 *actualStartBlock, UInt32 *actualNumBlocks) { OSErr err; register UInt32 bitMask; // mask of bit within word for currentBlock register UInt32 tempWord; // bitmap word currently being examined register UInt32 freeBlocks; // number of contiguous free blocks so far register UInt32 currentBlock; // block number we're currently examining UInt32 wordsLeft; // words remaining in bitmap block UInt32 *buffer = NULL; register UInt32 *currentWord; UInt32 stopBlock; // when all blocks until stopBlock are free, we found enough UInt32 countedFreeBlocks; // how many contiguous free block behind stopBlock UInt32 currentSector; // which allocations file sector #if HFSInstrumentation InstTraceClassRef trace; InstEventTag eventTag; err = InstCreateTraceClass(kInstRootClassRef, "HFS:VSM:BlockFindContiguous", 'hfs+', kInstEnableClassMask, &trace); if (err != noErr) DebugStr("\pError from InstCreateTraceClass"); eventTag = InstCreateEventTag(); InstLogTraceEvent( trace, eventTag, kInstStartEvent); #endif if ((endingBlock - startingBlock) < minBlocks) { // The set of blocks we're checking is smaller than the minimum number // of blocks, so we couldn't possibly find a good range. err = dskFulErr; goto Exit; } // Search for min blocks from back to front. // If min blocks is found, advance the allocation pointer up to max blocks // // Pre-read the bitmap block containing currentBlock // stopBlock = startingBlock; currentBlock = startingBlock + minBlocks - 1; // (-1) to include startingBlock err = ReadBitmapBlock( vcb, currentBlock, &buffer ); if ( err != noErr ) goto Exit; // // Init buffer, currentWord, wordsLeft, and bitMask // { UInt32 wordIndexInBlock; wordIndexInBlock = ( currentBlock & kBitsWithinBlockMask ) / kBitsPerWord; currentWord = buffer + wordIndexInBlock; wordsLeft = wordIndexInBlock; tempWord = SWAP_BE32 (*currentWord); bitMask = kHighBitInWordMask >> ( currentBlock & kBitsWithinWordMask ); currentSector = currentBlock / kBitsPerBlock; } // // Look for maxBlocks free blocks. If we find an allocated block, // see if we've found minBlocks. // freeBlocks = 0; countedFreeBlocks = 0; while ( currentBlock >= stopBlock ) { // Check current bit if ((tempWord & bitMask) == 0) { ++freeBlocks; } else // Used bitmap block found { if ( ( freeBlocks + countedFreeBlocks ) >= minBlocks ) { break; // Found enough } else { // We found a dirty bit, so we want to check if the next (minBlocks-freeBlocks) blocks // are free beyond what we have already checked. At Fig.2 setting up for Fig.3 stopBlock = currentBlock + 1 + freeBlocks; // Advance stop condition currentBlock += minBlocks; if ( currentBlock >= endingBlock ) break; countedFreeBlocks = freeBlocks; freeBlocks = 0; // Not enough; look for another range if ( currentSector != currentBlock / kBitsPerBlock ) { #if EXPLICIT_BUFFER_RELEASES err = RelBlock_glue((Ptr)buffer, rbDefault); if (err != noErr) goto Exit; buffer = NULL; #endif err = ReadBitmapBlock( vcb, currentBlock, &buffer ); if (err != noErr) goto Exit; currentSector = currentBlock / kBitsPerBlock; } wordsLeft = ( currentBlock & kBitsWithinBlockMask ) / kBitsPerWord; currentWord = buffer + wordsLeft; tempWord = SWAP_BE32 (*currentWord); bitMask = kHighBitInWordMask >> ( currentBlock & kBitsWithinWordMask ); continue; // Back to the while loop } } // Move to next bit --currentBlock; bitMask <<= 1; if (bitMask == 0) // On a word boundry, start masking words { bitMask = kLowBitInWordMask; // Move to next word NextWord: if ( wordsLeft != 0 ) { --currentWord; --wordsLeft; } else { // Read in the next bitmap block #if EXPLICIT_BUFFER_RELEASES err = RelBlock_glue((Ptr)buffer, rbDefault); if (err != noErr) goto Exit; buffer = NULL; #endif err = ReadBitmapBlock( vcb, currentBlock, &buffer ); if (err != noErr) goto Exit; // Adjust currentWord, wordsLeft, currentSector currentSector = currentBlock / kBitsPerBlock; currentWord = buffer + kWordsPerBlock - 1; // Last word in buffer wordsLeft = kWordsPerBlock - 1; } tempWord = SWAP_BE32 (*currentWord); // Grab the current word // // If we found a whole word of free blocks, quickly skip over it. // NOTE: we could actually go beyond the end of the bitmap if the // number of allocation blocks on the volume is not a multiple of // 32. If this happens, we'll adjust currentBlock and freeBlocks // after the loop. // if ( tempWord == 0 ) { freeBlocks += kBitsPerWord; currentBlock -= kBitsPerWord; if ( freeBlocks + countedFreeBlocks >= minBlocks ) break; // Found enough goto NextWord; } } } if ( freeBlocks + countedFreeBlocks < minBlocks ) { *actualStartBlock = 0; *actualNumBlocks = 0; err = dskFulErr; goto Exit; } // // When we get here, we know we've found minBlocks continuous space. // At Fig.4, setting up for Fig.5 // From here we do a forward search accumalating additional free blocks. // *actualNumBlocks = minBlocks; *actualStartBlock = stopBlock - countedFreeBlocks; // ActualStartBlock is set to return to the user currentBlock = *actualStartBlock + minBlocks; // Right after found free space // Now lets see if we can run the actualNumBlocks number all the way up to maxBlocks if ( currentSector != currentBlock / kBitsPerBlock ) { #if EXPLICIT_BUFFER_RELEASES err = RelBlock_glue((Ptr)buffer, rbDefault); if (err != noErr) goto Exit; buffer = NULL; #endif err = ReadBitmapBlock( vcb, currentBlock, &buffer ); if (err != noErr) { err = noErr; // We already found the space goto Exit; } currentSector = currentBlock / kBitsPerBlock; } // // Init buffer, currentWord, wordsLeft, and bitMask // { UInt32 wordIndexInBlock; wordIndexInBlock = (currentBlock & kBitsWithinBlockMask) / kBitsPerWord; currentWord = buffer + wordIndexInBlock; tempWord = SWAP_BE32 (*currentWord); wordsLeft = kWordsPerBlock - wordIndexInBlock; bitMask = kHighBitInWordMask >> (currentBlock & kBitsWithinWordMask); } if ( *actualNumBlocks < maxBlocks ) { while ( currentBlock < endingBlock ) { if ( (tempWord & bitMask) == 0 ) { *actualNumBlocks += 1; if ( *actualNumBlocks == maxBlocks ) break; } else { break; } // Move to next bit ++currentBlock; bitMask >>= 1; if (bitMask == 0) { bitMask = kHighBitInWordMask; ++currentWord; if ( --wordsLeft == 0) { #if EXPLICIT_BUFFER_RELEASES err = RelBlock_glue((Ptr)buffer, rbDefault); if (err != noErr) goto Exit; buffer = NULL; #endif err = ReadBitmapBlock(vcb, currentBlock, &buffer); if (err != noErr) break; // Adjust currentWord, wordsLeft currentWord = buffer; wordsLeft = kWordsPerBlock; } tempWord = SWAP_BE32 (*currentWord); // grab the current word } } } Exit: #if EXPLICIT_BUFFER_RELEASES if (buffer) { (void)RelBlock_glue((Ptr)buffer, rbDefault); /* Ignore any additional errors */ }; #endif #if HFSInstrumentation InstLogTraceEvent( trace, eventTag, kInstEndEvent); #endif return err; }