OOCacheManager.m

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/*
 
OOCacheManager.m
 
Oolite
Copyright (C) 2004-2013 Giles C Williams and contributors
 
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
 
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301, USA.
 
*/
 
#import "OOCacheManager.h"
#import "OOPListParsing.h"
#import "OODeepCopy.h"
#import "OOCollectionExtractors.h"
#import "OOJavaScriptEngine.h"
#import "NSFileManagerOOExtensions.h"
 
 
#define WRITE_ASYNC             1
#define PROFILE_WRITES          0
 
 
// Use the (presumed) most efficient plist format for each platform.
#if OOLITE_MAC_OS_X
#define CACHE_PLIST_FORMAT  NSPropertyListBinaryFormat_v1_0
#else
#define CACHE_PLIST_FORMAT  NSPropertyListGNUstepBinaryFormat
#endif
 
 
#if WRITE_ASYNC
#import "OOAsyncWorkManager.h"
#endif
#if PROFILE_WRITES
#import "OOProfilingStopwatch.h"
#endif
 
 
static NSString * const kOOLogDataCacheFound                = @"dataCache.found";
static NSString * const kOOLogDataCacheNotFound             = @"dataCache.notFound";
static NSString * const kOOLogDataCacheRebuild              = @"dataCache.rebuild";
static NSString * const kOOLogDataCacheWriteSuccess         = @"dataCache.write.success";
static NSString * const kOOLogDataCacheWriteFailed          = @"dataCache.write.failed";
static NSString * const kOOLogDataCacheRetrieveSuccess      = @"dataCache.retrieve.success";
static NSString * const kOOLogDataCacheRetrieveFailed       = @"dataCache.retrieve.failed";
static NSString * const kOOLogDataCacheSetSuccess           = @"dataCache.set.success";
static NSString * const kOOLogDataCacheSetFailed            = @"dataCache.set.failed";
static NSString * const kOOLogDataCacheRemoveSuccess        = @"dataCache.remove.success";
static NSString * const kOOLogDataCacheClearSuccess         = @"dataCache.clear.success";
static NSString * const kOOLogDataCacheBuildPathError       = @"dataCache.write.buildPath.failed";
static NSString * const kOOLogDataCacheSerializationError   = @"dataCache.write.serialize.failed";
 
static NSString * const kCacheKeyVersion                    = @"version";
static NSString * const kCacheKeyEndianTag                  = @"endian tag";
static NSString * const kCacheKeyFormatVersion              = @"format version";
static NSString * const kCacheKeyCaches                     = @"caches";
 
 
enum
{
    kEndianTagValue         = 0x0123456789ABCDEFULL,
    kFormatVersionValue     = 219
};
 
 
static OOCacheManager *sSingleton = nil;
 
 
@interface OOCacheManager (Private)
 
- (void)loadCache;
- (void)write;
- (void)clear;
- (BOOL)dirty;
- (void)markClean;
 
- (NSDictionary *)loadDict;
- (BOOL)writeDict:(NSDictionary *)inDict;
 
- (void)buildCachesFromDictionary:(NSDictionary *)inDict;
- (NSDictionary *)dictionaryOfCaches;
 
- (BOOL)directoryExists:(NSString *)inPath create:(BOOL)inCreate;
 
@end
 
 
@interface OOCacheManager (PlatformSpecific)
 
- (NSString *)cachePathCreatingIfNecessary:(BOOL)inCreate;
 
@end
 
 
#if WRITE_ASYNC
@interface OOAsyncCacheWriter: NSObject <OOAsyncWorkTask>
{
@private
    NSDictionary            *_cacheContents;
}
 
- (id) initWithCacheContents:(NSDictionary *)cacheContents;
 
@end
#endif
 
 
@implementation OOCacheManager
 
- (id)init
{
    self = [super init];
    if (self != nil)
    {
        _permitWrites = YES;
        [self loadCache];
    }
    return self;
}
 
 
- (void)dealloc
{
    [self clear];
    
    [super dealloc];
}
 
 
- (NSString *)description
{
    return [NSString stringWithFormat:@"<%@ %p>{dirty=%s}", [self class], self, [self dirty] ? "yes" : "no"];
}
 
 
+ (OOCacheManager *) sharedCache
{
    // NOTE: assumes single-threaded access.
    if (sSingleton == nil)
    {
        sSingleton = [[self alloc] init];
    }
    
    return sSingleton;
}
 
 
- (id)objectForKey:(NSString *)inKey inCache:(NSString *)inCacheKey
{
    NSMutableDictionary     *cache = nil;
    id                      result = nil;
    
    NSParameterAssert(inKey != nil && inCacheKey != nil);
    
    cache = [_caches objectForKey:inCacheKey];
    if (cache != nil)
    {
        result = [cache objectForKey:inKey];
        if (result != nil)
        {
            OODebugLog(kOOLogDataCacheRetrieveSuccess, @"Retrieved \"%@\" cache object %@.", inCacheKey, inKey);
        }
        else
        {
            OODebugLog(kOOLogDataCacheRetrieveFailed, @"Failed to retrieve \"%@\" cache object %@ -- no such entry.", inCacheKey, inKey);
        }
    }
    else
    {
        OODebugLog(kOOLogDataCacheRetrieveFailed, @"Failed to retrieve \"%@\" cache object %@ -- no such cache.", inCacheKey, inKey);
    }
    
    return result;
}
 
 
 
- (void)setObject:(id)inObject forKey:(NSString *)inKey inCache:(NSString *)inCacheKey
{
    NSMutableDictionary     *cache = nil;
    
    NSParameterAssert(inObject != nil && inKey != nil && inCacheKey != nil);
    
    if (EXPECT_NOT(_caches == nil))  return;
    
    cache = [_caches objectForKey:inCacheKey];
    if (cache == nil)
    {
        cache = [NSMutableDictionary dictionary];
        if (cache == nil)
        {
            OODebugLog(kOOLogDataCacheSetFailed, @"Failed to create cache for key \"%@\".", inCacheKey);
            return;
        }
        [_caches setObject:cache forKey:inCacheKey];
    }
    
    [cache setObject:inObject forKey:inKey];
    _dirty = YES;
    OODebugLog(kOOLogDataCacheSetSuccess, @"Updated entry %@ in cache \"%@\".", inKey, inCacheKey);
}
 
 
- (void)removeObjectForKey:(NSString *)inKey inCache:(NSString *)inCacheKey
{
    NSMutableDictionary     *cache = nil;
    
    NSParameterAssert(inKey != nil && inCacheKey != nil);
    
    cache = [_caches objectForKey:inCacheKey];
    if (cache != nil)
    {
        if (nil != [cache objectForKey:inKey])
        {
            [cache removeObjectForKey:inKey];
            _dirty = YES;
            OODebugLog(kOOLogDataCacheRemoveSuccess, @"Removed entry keyed %@ from cache \"%@\".", inKey, inCacheKey);
        }
        else
        {
            OODebugLog(kOOLogDataCacheRemoveSuccess, @"No need to remove non-existent entry keyed %@ from cache \"%@\".", inKey, inCacheKey);
        }
    }
    else
    {
        OODebugLog(kOOLogDataCacheRemoveSuccess, @"No need to remove entry keyed %@ from non-existent cache \"%@\".", inKey, inCacheKey);
    }
}
 
 
- (void)clearCache:(NSString *)inCacheKey
{
    NSParameterAssert(inCacheKey != nil);
    
    if (nil != [_caches objectForKey:inCacheKey])
    {
        [_caches removeObjectForKey:inCacheKey];
        _dirty = YES;
        OODebugLog(kOOLogDataCacheClearSuccess, @"Cleared cache \"%@\".", inCacheKey);
    }
    else
    {
        OODebugLog(kOOLogDataCacheClearSuccess, @"No need to clear non-existent cache \"%@\".", inCacheKey);
    }
}
 
 
- (void)clearAllCaches
{
    [self clear];
    _caches = [[NSMutableDictionary alloc] init];
    _dirty = YES;
}
 
 
- (void) reloadAllCaches
{
    [self clear];
    [self loadCache];
}
 
 
- (void)flush
{
    if (_permitWrites && [self dirty] && _scheduledWrite == nil)
    {
        [self write];
        [self markClean];
    }
}
 
 
- (void)finishOngoingFlush
{
#if WRITE_ASYNC
    [[OOAsyncWorkManager sharedAsyncWorkManager] waitForTaskToComplete:_scheduledWrite];
#endif
}
 
 
- (void)setAllowCacheWrites:(BOOL)flag
{
    _permitWrites = (flag != NO);
}
 
 
- (NSString *)cacheDirectoryPathCreatingIfNecessary:(BOOL)create
{
    /*  Construct the path to the directory for cache files, which is:
            ~/Library/Caches/org.aegidian.oolite/
            or
            ~/GNUStep/Library/Caches/org.aegidian.oolite/
        In addition to generally being the right place to put caches,
        ~/Library/Caches has the particular advantage of not being indexed by
        Spotlight or backed up by Time Machine.
    */
    NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    if (![self directoryExists:cachePath create:create]) return nil;
 
#if !OOLITE_MAC_OS_X
    // the old cache file on GNUstep was one level up, so remove it if it exists
    [[NSFileManager defaultManager] removeFileAtPath:[cachePath stringByAppendingPathComponent:@"Oolite-cache.plist"] handler:nil];
#endif
 
    cachePath = [cachePath stringByAppendingPathComponent:@"org.aegidian.oolite"];
    if (![self directoryExists:cachePath create:create]) return nil;
    return cachePath;
}
 
@end
 
 
@implementation OOCacheManager (Private)
 
- (void)loadCache
{
    NSDictionary            *cache = nil;
    NSString                *cacheVersion = nil;
    NSString                *ooliteVersion = nil;
    NSData                  *endianTag = nil;
    NSNumber                *formatVersion = nil;
    BOOL                    accept = YES;
    uint64_t                endianTagValue = 0;
    
    ooliteVersion = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleVersion"];
    
    [self clear];
    
    cache = [self loadDict];
    if (cache != nil)
    {
        // We have a cache
        OOLog(kOOLogDataCacheFound, @"%@", @"Found data cache.");
        OOLogIndentIf(kOOLogDataCacheFound);
        
        cacheVersion = [cache objectForKey:kCacheKeyVersion];
        if (![cacheVersion isEqual:ooliteVersion])
        {
            OOLog(kOOLogDataCacheRebuild, @"Data cache version (%@) does not match Oolite version (%@), rebuilding cache.", cacheVersion, ooliteVersion);
            accept = NO;
        }
        
        formatVersion = [cache objectForKey:kCacheKeyFormatVersion];
        if (accept && [formatVersion unsignedIntValue] != kFormatVersionValue)
        {
            OOLog(kOOLogDataCacheRebuild, @"Data cache format (%@) is not supported format (%u), rebuilding cache.", formatVersion, kFormatVersionValue);
            accept = NO;
        }
        
        if (accept)
        {
            endianTag = [cache objectForKey:kCacheKeyEndianTag];
            if (![endianTag isKindOfClass:[NSData class]] || [endianTag length] != sizeof endianTagValue)
            {
                OOLog(kOOLogDataCacheRebuild, @"%@", @"Data cache endian tag is invalid, rebuilding cache.");
                accept = NO;
            }
            else
            {
                endianTagValue = *(const uint64_t *)[endianTag bytes];
                if (endianTagValue != kEndianTagValue)
                {
                    OOLog(kOOLogDataCacheRebuild, @"%@", @"Data cache endianness is inappropriate for this system, rebuilding cache.");
                    accept = NO;
                }
            }
        }
        
        if (accept)
        {
            // We have a cache, and it's the right format.
            [self buildCachesFromDictionary:[cache objectForKey:kCacheKeyCaches]];
        }
        
        OOLogOutdentIf(kOOLogDataCacheFound);
    }
    else
    {
        // No cache
        OOLog(kOOLogDataCacheNotFound, @"%@", @"No data cache found, starting from scratch.");
    }
    
    // If loading failed, or there was a version or endianness conflict
    if (_caches == nil) _caches = [[NSMutableDictionary alloc] init];
    [self markClean];
}
 
 
- (void)write
{
    NSMutableDictionary     *newCache = nil;
    NSString                *ooliteVersion = nil;
    NSData                  *endianTag = nil;
    NSNumber                *formatVersion = nil;
    NSDictionary            *pListRep = nil;
    uint64_t                endianTagValue = kEndianTagValue;
    
    if (_caches == nil) return;
    if (_scheduledWrite != nil)  return;
    
#if PROFILE_WRITES
    OOProfilingStopwatch *stopwatch = [OOProfilingStopwatch stopwatch];
#endif
    
#if WRITE_ASYNC
    OOLog(@"dataCache.willWrite", @"%@", @"Scheduling data cache write.");
#else
    OOLog(@"dataCache.willWrite", @"%@", @"About to write cache.");
#endif
    
    ooliteVersion = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleVersion"];
    endianTag = [NSData dataWithBytes:&endianTagValue length:sizeof endianTagValue];
    formatVersion = [NSNumber numberWithUnsignedInt:kFormatVersionValue];
    
    pListRep = [self dictionaryOfCaches];
    if (ooliteVersion == nil || endianTag == nil || formatVersion == nil || pListRep == nil)
    {
        OOLog(@"dataCache.cantWrite", @"%@", @"Failed to write data cache -- prerequisites not fulfilled. This is an internal error, please report it.");
        return;
    }
    
    newCache = [NSMutableDictionary dictionaryWithCapacity:4];
    [newCache setObject:ooliteVersion forKey:kCacheKeyVersion];
    [newCache setObject:formatVersion forKey:kCacheKeyFormatVersion];
    [newCache setObject:endianTag forKey:kCacheKeyEndianTag];
    [newCache setObject:pListRep forKey:kCacheKeyCaches];
    
#if PROFILE_WRITES && !WRITE_ASYNC
    OOTimeDelta prepareT = [stopwatch reset];
#endif
    
#if WRITE_ASYNC
    NSDictionary *cacheData = newCache;
    _scheduledWrite = [[OOAsyncCacheWriter alloc] initWithCacheContents:cacheData];
    
#if PROFILE_WRITES
    OOTimeDelta endT = [stopwatch reset];
    OOLog(@"dataCache.profile", @"Time to prepare cache data: %g seconds.", endT);
#endif
    
    [[OOAsyncWorkManager sharedAsyncWorkManager] addTask:_scheduledWrite priority:kOOAsyncPriorityLow];
#else
#if PROFILE_WRITES
    OOLog(@"dataCache.profile", @"Time to prepare cache data: %g seconds.", prepareT);
#endif
    
    if ([self writeDict:newCache])
    {
        [self markClean];
        OOLog(kOOLogDataCacheWriteSuccess, @"%@", @"Wrote data cache.");
    }
    else
    {
        OOLog(kOOLogDataCacheWriteFailed, @"%@", @"Failed to write data cache.");
    }
#endif
}
 
 
- (void)clear
{
    [_caches release];
    _caches = nil;
}
 
 
- (BOOL)dirty
{
    return _dirty;
}
 
 
- (void)markClean
{
    _dirty = NO;
}
 
 
- (NSDictionary *)loadDict
{
    NSString            *path = nil;
    NSData              *data = nil;
    NSString            *errorString = nil;
    id                  contents = nil;
    
    path = [self cachePathCreatingIfNecessary:NO];
    if (path == nil) return nil;
    
    @try
    {
        data = [NSData dataWithContentsOfFile:path];
        if (data == nil)  return nil;
        
        contents = [NSPropertyListSerialization propertyListFromData:data
                                                    mutabilityOption:NSPropertyListImmutable
                                                              format:NULL
                                                    errorDescription:&errorString];
    }
    @catch (NSException *exception)
    {
        errorString = [exception reason];
        contents = nil;
    }
    
    if (errorString != nil)
    {
        OOLog(@"dataCache.badData", @"Could not read data cache: %@", errorString);
#if OOLITE_RELEASE_PLIST_ERROR_STRINGS
        [errorString release];
#endif
        return nil;
    }
    if (![contents isKindOfClass:[NSDictionary class]])  return nil;
    
    return contents;
}
 
 
- (BOOL)writeDict:(NSDictionary *)inDict
{
    NSString            *path = nil;
    NSData              *plist = nil;
    NSString            *errorDesc = nil;
    
    path = [self cachePathCreatingIfNecessary:YES];
    if (path == nil) return NO; 
    
#if PROFILE_WRITES
    OOProfilingStopwatch *stopwatch = [OOProfilingStopwatch stopwatch];
#endif
    
    plist = [NSPropertyListSerialization dataFromPropertyList:inDict format:CACHE_PLIST_FORMAT errorDescription:&errorDesc];
    if (plist == nil)
    {
#if OOLITE_RELEASE_PLIST_ERROR_STRINGS
        [errorDesc autorelease];
#endif
        OOLog(kOOLogDataCacheSerializationError, @"Could not convert data cache to property list data: %@", errorDesc);
        return NO;
    }
    
#if PROFILE_WRITES
    OOTimeDelta serializeT = [stopwatch reset];
#endif
    
    BOOL result = [plist writeToFile:path atomically:NO];
    
#if PROFILE_WRITES
    OOTimeDelta writeT = [stopwatch reset];
    
    OOLog(@"dataCache.profile", @"Time to serialize cache: %g seconds. Time to write data: %g seconds.", serializeT, writeT);
#endif
    
#if WRITE_ASYNC
    DESTROY(_scheduledWrite);
#endif
    return result;
}
 
 
- (void)buildCachesFromDictionary:(NSDictionary *)inDict
{
    NSEnumerator                *keyEnum = nil;
    id                          key = nil;
    id                          value = nil;
    NSMutableDictionary         *cache = nil;
    
    if (inDict == nil ) return;
    
    [_caches release];
    _caches = [[NSMutableDictionary alloc] initWithCapacity:[inDict count]];
    
    for (keyEnum = [inDict keyEnumerator]; (key = [keyEnum nextObject]); )
    {
        value = [inDict oo_dictionaryForKey:key];
        if (value != nil)
        {
            cache = [NSMutableDictionary dictionaryWithDictionary:value];
            if (cache != nil)
            {
                [_caches setObject:cache forKey:key];
            }
        }
    }
}
 
 
- (NSDictionary *)dictionaryOfCaches
{
    return [OODeepCopy(_caches) autorelease];
}
 
 
- (BOOL)directoryExists:(NSString *)inPath create:(BOOL)inCreate
{
    BOOL                exists, directory;
    NSFileManager       *fmgr =  [NSFileManager defaultManager];
    
    exists = [fmgr fileExistsAtPath:inPath isDirectory:&directory];
    
    if (exists && !directory)
    {
        OOLog(kOOLogDataCacheBuildPathError, @"Expected %@ to be a folder, but it is a file.", inPath);
        return NO;
    }
    if (!exists)
    {
        if (!inCreate) return NO;
        if (![fmgr oo_createDirectoryAtPath:inPath attributes:nil])
        {
            OOLog(kOOLogDataCacheBuildPathError, @"Could not create folder %@.", inPath);
            return NO;
        }
    }
    
    return YES;
}
 
 
#if OOLITE_MAC_OS_X
 
- (NSString *)cachePathCreatingIfNecessary:(BOOL)create
{
    NSString *cachePath = [self cacheDirectoryPathCreatingIfNecessary:create];
    return [cachePath stringByAppendingPathComponent:@"Data Cache.plist"];
}
 
#else
 
- (NSString *)cachePathCreatingIfNecessary:(BOOL)create
{
    NSString *cachePath = [self cacheDirectoryPathCreatingIfNecessary:create];
    return [cachePath stringByAppendingPathComponent:@"Oolite-cache.plist"];
}
 
#endif
 
@end
 
 
@implementation OOCacheManager (Singleton)
 
/*  Canonical singleton boilerplate.
    See Cocoa Fundamentals Guide: Creating a Singleton Instance.
    See also +sharedCache above.
    
    NOTE: assumes single-threaded access.
*/
 
+ (id)allocWithZone:(NSZone *)inZone
{
    if (sSingleton == nil)
    {
        sSingleton = [super allocWithZone:inZone];
        return sSingleton;
    }
    return nil;
}
 
 
- (id)copyWithZone:(NSZone *)inZone
{
    return self;
}
 
 
- (id)retain
{
    return self;
}
 
 
- (NSUInteger)retainCount
{
    return UINT_MAX;
}
 
 
- (void)release
{}
 
 
- (id)autorelease
{
    return self;
}
 
@end
 
 
#if WRITE_ASYNC
@implementation OOAsyncCacheWriter
 
- (id) initWithCacheContents:(NSDictionary *)cacheContents
{
    if ((self = [super init]))
    {
        _cacheContents = [cacheContents copy];
        if (_cacheContents == nil)
        {
            [self release];
            self = nil;
        }
    }
    
    return self;
}
 
 
- (void) dealloc
{
    DESTROY(_cacheContents);
    
    [super dealloc];
}
 
 
- (void) performAsyncTask
{
    if ([[OOCacheManager sharedCache] writeDict:_cacheContents])
    {
        OOLog(kOOLogDataCacheWriteSuccess, @"%@", @"Wrote data cache.");
    }
    else
    {
        OOLog(kOOLogDataCacheWriteFailed, @"%@", @"Failed to write data cache.");
    }
    DESTROY(_cacheContents);
}
 
 
- (void) completeAsyncTask
{
    // Don't need to do anything, but this needs to be here so we can wait on it.
}
 
@end
#endif  // WRITE_ASYNC