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366 lines
9.5 KiB
C
366 lines
9.5 KiB
C
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/*
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File: DiskCacheList.c
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Contains: Code for maintaining the disk cache lists. Caches are maintained in two
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linked lists. The offset list is sorted in physical file offset order.
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The date list is stored in most recently used to least recently used
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order.
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An empty array of disk cache entries is maintained inside of the disk
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cache map for disk cache storage. The array isn't dynamically allocated
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since we can't allocate memory if called during a purge procedure (the
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array is tiny compared to the size of the font cache file for all you
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chronic-byte-twiddling-weenies).
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The routines in this file are cake so I'm going to spare myself the pain
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documenting them.
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Written by: John Farmer
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Copyright: © 1991-1992 by Apple Computer, Inc., all rights reserved.
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Change History (most recent first):
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<3> 3/27/92 DTY #1024868: Delete inclusion of Assertion.h, since this file
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doesn’t use these routines.
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<2> 1/29/92 JSM Fix bug #1020958. In InsertDiskCache(), if we were inserting a
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new cache just before one we were about to delete because
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FindFirstFreeCache() didn't find a free cache, fNextOffsetIndex
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for the new entry would point to itself, causing the linked list
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to loop back on itself.
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<1> 7/17/91 jlf Split these routines out of DiskCacheExtensions.c
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*/
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// Include Statements
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#include "BaseIncludes.h"
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#include "DiskCacheList.proto"
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/* --------------------------------------------------------------------------------------
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Routine: cacheIndex = FindFirstFreeCache( diskCacheMapHandle )
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Purpose:
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Warnings: None
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----------------------------------------------------------------------------------- */
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DiskCacheIndex FindFirstFreeCache( DiskCacheMapStructureHandle diskCacheMapHandle )
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{
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// Locals
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Boolean freeCacheNotFound;
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DiskCacheIndex cacheIndex, cacheCount;
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cacheIndex = 0;
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freeCacheNotFound = true;
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cacheCount = (*diskCacheMapHandle)->fMaximumDiskCacheCount;
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while ( freeCacheNotFound && (cacheIndex < cacheCount) ) {
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if ( (*diskCacheMapHandle)->fDiskCache[cacheIndex].fCacheIsFree ) {
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freeCacheNotFound = false;
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} else {
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cacheIndex++;
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}
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}
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return ( freeCacheNotFound ? kDiskCacheNotFound : cacheIndex );
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}
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/* --------------------------------------------------------------------------------------
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Routine: InsertDiskCacheIntoOffsetList( cacheIndex, nextCacheIndex, diskCacheMapHandle )
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Purpose:
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Warnings: None
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----------------------------------------------------------------------------------- */
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void InsertDiskCacheIntoOffsetList( DiskCacheIndex cacheIndex, DiskCacheIndex nextCacheIndex, DiskCacheMapStructureHandle diskCacheMapHandle )
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{
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// Locals
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DiskCacheIndex previousCacheIndex;
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DiskCacheEntryStructure *cachePointer;
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if ( nextCacheIndex == kDiskCacheNotFound ) {
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previousCacheIndex = (*diskCacheMapHandle)->fLastOffsetIndex;
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(*diskCacheMapHandle)->fLastOffsetIndex = cacheIndex;
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} else {
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previousCacheIndex = (*diskCacheMapHandle)->fDiskCache[nextCacheIndex].fPreviousOffsetIndex;
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(*diskCacheMapHandle)->fDiskCache[nextCacheIndex].fPreviousOffsetIndex = cacheIndex;
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}
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if ( previousCacheIndex == kDiskCacheNotFound ) {
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(*diskCacheMapHandle)->fFirstOffsetIndex = cacheIndex;
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} else {
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(*diskCacheMapHandle)->fDiskCache[previousCacheIndex].fNextOffsetIndex = cacheIndex;
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}
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cachePointer = &(*diskCacheMapHandle)->fDiskCache[cacheIndex];
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cachePointer->fPreviousOffsetIndex = previousCacheIndex;
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cachePointer->fNextOffsetIndex = nextCacheIndex;
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}
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/* --------------------------------------------------------------------------------------
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Routine: InsertDiskCacheIntoDateList( cacheIndex, nextCacheIndex, diskCacheMapHandle )
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Purpose:
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Warnings: None
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----------------------------------------------------------------------------------- */
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void InsertDiskCacheIntoDateList( DiskCacheIndex cacheIndex, DiskCacheIndex nextCacheIndex, DiskCacheMapStructureHandle diskCacheMapHandle )
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{
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// Locals
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DiskCacheIndex previousCacheIndex;
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DiskCacheEntryStructure *cachePointer;
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if ( nextCacheIndex == kDiskCacheNotFound ) {
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previousCacheIndex = (*diskCacheMapHandle)->fLastDateIndex;
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(*diskCacheMapHandle)->fLastDateIndex = cacheIndex;
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} else {
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previousCacheIndex = (*diskCacheMapHandle)->fDiskCache[nextCacheIndex].fPreviousDateIndex;
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(*diskCacheMapHandle)->fDiskCache[nextCacheIndex].fPreviousDateIndex = cacheIndex;
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}
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if ( previousCacheIndex == kDiskCacheNotFound ) {
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(*diskCacheMapHandle)->fFirstDateIndex = cacheIndex;
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} else {
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(*diskCacheMapHandle)->fDiskCache[previousCacheIndex].fNextDateIndex = cacheIndex;
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}
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cachePointer = &(*diskCacheMapHandle)->fDiskCache[cacheIndex];
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cachePointer->fPreviousDateIndex = previousCacheIndex;
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cachePointer->fNextDateIndex = nextCacheIndex;
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}
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/* --------------------------------------------------------------------------------------
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Routine: error = InsertDiskCache( &cacheIndex, nextCacheIndex, diskCache, diskCacheMapHandle )
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Purpose:
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Warnings: None
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----------------------------------------------------------------------------------- */
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OSErr InsertDiskCache( DiskCacheIndex *cacheIndexPointer, DiskCacheIndex nextCacheIndex, DiskCacheEntryStructure sourceCacheEntry, DiskCacheMapStructureHandle diskCacheMapHandle )
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{
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// Locals
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OSErr error;
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error = noErr;
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*cacheIndexPointer = FindFirstFreeCache( diskCacheMapHandle );
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if ( *cacheIndexPointer == kDiskCacheNotFound ) {
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*cacheIndexPointer = (*diskCacheMapHandle)->fLastDateIndex;
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/* <2> */
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if (*cacheIndexPointer == nextCacheIndex)
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{
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// we're deleting the cache after the one we're about to insert, so we need to update nextCacheIndex
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nextCacheIndex = (*diskCacheMapHandle)->fDiskCache[nextCacheIndex].fNextOffsetIndex;
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}
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/* <2> */
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error = RemoveDiskCache( *cacheIndexPointer, diskCacheMapHandle );
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}
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if ( error == noErr ) {
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sourceCacheEntry.fCacheIsFree = false;
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(*diskCacheMapHandle)->fDiskCache[*cacheIndexPointer] = sourceCacheEntry;
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(*diskCacheMapHandle)->fDiskCacheCount++;
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InsertDiskCacheIntoOffsetList( *cacheIndexPointer, nextCacheIndex, diskCacheMapHandle );
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InsertDiskCacheIntoDateList( *cacheIndexPointer, (*diskCacheMapHandle)->fFirstDateIndex, diskCacheMapHandle );
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}
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return( error );
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}
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/* --------------------------------------------------------------------------------------
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Routine: RemoveDiskCacheFromOffsetList( cacheIndex, diskCacheMapHandle )
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Purpose:
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Warnings: None
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----------------------------------------------------------------------------------- */
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void RemoveDiskCacheFromOffsetList( DiskCacheIndex cacheIndex, DiskCacheMapStructureHandle diskCacheMapHandle )
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{
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// Locals
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DiskCacheIndex previousCacheIndex, nextCacheIndex;
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DiskCacheEntryStructurePointer cacheEntryPointer;
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cacheEntryPointer = &(*diskCacheMapHandle)->fDiskCache[cacheIndex];
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previousCacheIndex = cacheEntryPointer->fPreviousOffsetIndex;
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nextCacheIndex = cacheEntryPointer->fNextOffsetIndex;
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if ( previousCacheIndex == kDiskCacheNotFound ) {
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(*diskCacheMapHandle)->fFirstOffsetIndex = nextCacheIndex;
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} else {
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(*diskCacheMapHandle)->fDiskCache[previousCacheIndex].fNextOffsetIndex = nextCacheIndex;
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}
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if ( nextCacheIndex == kDiskCacheNotFound ) {
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(*diskCacheMapHandle)->fLastOffsetIndex = previousCacheIndex;
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} else {
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(*diskCacheMapHandle)->fDiskCache[nextCacheIndex].fPreviousOffsetIndex = previousCacheIndex;
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}
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}
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/* --------------------------------------------------------------------------------------
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Routine: RemoveDiskCacheFromDateList( cacheIndex, diskCacheMapHandle )
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Purpose:
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Warnings: None
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----------------------------------------------------------------------------------- */
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void RemoveDiskCacheFromDateList( DiskCacheIndex cacheIndex, DiskCacheMapStructureHandle diskCacheMapHandle )
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{
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// Locals
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DiskCacheIndex previousCacheIndex, nextCacheIndex;
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DiskCacheEntryStructurePointer cacheEntryPointer;
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cacheEntryPointer = &(*diskCacheMapHandle)->fDiskCache[cacheIndex];
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previousCacheIndex = cacheEntryPointer->fPreviousDateIndex;
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nextCacheIndex = cacheEntryPointer->fNextDateIndex;
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if ( previousCacheIndex == kDiskCacheNotFound ) {
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(*diskCacheMapHandle)->fFirstDateIndex = nextCacheIndex;
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} else {
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(*diskCacheMapHandle)->fDiskCache[previousCacheIndex].fNextDateIndex = nextCacheIndex;
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}
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if ( nextCacheIndex == kDiskCacheNotFound ) {
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(*diskCacheMapHandle)->fLastDateIndex = previousCacheIndex;
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} else {
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(*diskCacheMapHandle)->fDiskCache[nextCacheIndex].fPreviousDateIndex = previousCacheIndex;
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}
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}
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/* --------------------------------------------------------------------------------------
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Routine: error = RemoveDiskCache( cacheIndex, diskCacheMapHandle )
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Purpose:
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Warnings: None
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----------------------------------------------------------------------------------- */
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OSErr RemoveDiskCache( DiskCacheIndex cacheIndex, DiskCacheMapStructureHandle diskCacheMapHandle )
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{
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// Locals
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OSErr error;
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DiskCacheEntryStructurePointer destinationCacheEntryPointer;
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error = noErr;
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destinationCacheEntryPointer = &(*diskCacheMapHandle)->fDiskCache[cacheIndex];
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destinationCacheEntryPointer->fCacheIsFree = true;
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(*diskCacheMapHandle)->fDiskCacheCount--;
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RemoveDiskCacheFromOffsetList( cacheIndex, diskCacheMapHandle );
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RemoveDiskCacheFromDateList( cacheIndex, diskCacheMapHandle );
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return( error );
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}
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