fixes #1102: implement reference-counted shared file cache vendor

gyp/platform-ios.gypi

@@ -22,6 +22,8 @@
         '../include/mbgl/ios/MGLMapView.h',
         '../include/mbgl/ios/MGLMapView+IBAdditions.h',
         '../platform/ios/MGLMapView.mm',
+        '../platform/ios/MGLFileCache.h',
+        '../platform/ios/MGLFileCache.mm',
         '../include/mbgl/ios/MGLAnnotation.h',
         '../include/mbgl/ios/MGLUserLocation.h',
         '../platform/ios/MGLUserLocation_Private.h',

platform/ios/MGLFileCache.h

@@ -0,0 +1,10 @@
+#import <Foundation/Foundation.h>
+
+#include <mbgl/storage/sqlite_cache.hpp>
+
+@interface MGLFileCache : NSObject
+
++ (mbgl::SQLiteCache *)obtainSharedCacheWithObject:(NSObject *)object;
++ (void)releaseSharedCacheForObject:(NSObject *)object;
+
+@end

platform/ios/MGLFileCache.mm

@@ -0,0 +1,83 @@
+#import "MGLFileCache.h"
+
+@interface MGLFileCache ()
+
+@property (nonatomic) MGLFileCache *sharedInstance;
+@property (nonatomic) mbgl::SQLiteCache *sharedCache;
+@property (nonatomic) NSHashTable *retainers;
+
+@end
+
+@implementation MGLFileCache
+
+const std::string &defaultCacheDatabasePath() {
+    static const std::string path = []() -> std::string {
+        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
+        if ([paths count] == 0) {
+            // Disable the cache if we don't have a location to write.
+            return "";
+        }
+
+        NSString *libraryDirectory = [paths objectAtIndex:0];
+        return [[libraryDirectory stringByAppendingPathComponent:@"cache.db"] UTF8String];
+    }();
+    return path;
+}
+
+- (instancetype)init {
+    self = [super init];
+    if (self) {
+        _retainers = [NSHashTable weakObjectsHashTable];
+    }
+    return self;
+}
+
++ (instancetype)sharedInstance {
+    static dispatch_once_t onceToken;
+    static MGLFileCache *_sharedInstance;
+    dispatch_once(&onceToken, ^{
+        _sharedInstance = [[self alloc] init];
+    });
+    return _sharedInstance;
+}
+
+- (void)teardown {
+    if (self.sharedCache) {
+        delete self.sharedCache;
+        self.sharedCache = nullptr;
+    }
+}
+
+- (void)dealloc {
+    [self.retainers removeAllObjects];
+    [self teardown];
+}
+
++ (mbgl::SQLiteCache *)obtainSharedCacheWithObject:(NSObject *)object {
+    return [[MGLFileCache sharedInstance] obtainSharedCacheWithObject:object];
+}
+
+- (mbgl::SQLiteCache *)obtainSharedCacheWithObject:(NSObject *)object {
+    assert([[NSThread currentThread] isMainThread]);
+    if (!self.sharedCache) {
+        self.sharedCache = new mbgl::SQLiteCache(defaultCacheDatabasePath());
+    }
+    [self.retainers addObject:object];
+    return self.sharedCache;
+}
+
++ (void)releaseSharedCacheForObject:(NSObject *)object {
+    return [[MGLFileCache sharedInstance] releaseSharedCacheForObject:object];
+}
+
+- (void)releaseSharedCacheForObject:(NSObject *)object {
+    assert([[NSThread currentThread] isMainThread]);
+    if ([self.retainers containsObject:object]) {
+        [self.retainers removeObject:object];
+    }
+    if ([self.retainers count] == 0) {
+        [self teardown];
+    }
+}
+
+@end

platform/ios/MGLMapView.mm

@@ -11,7 +11,6 @@
 #include <mbgl/platform/platform.hpp>
 #include <mbgl/platform/darwin/reachability.h>
 #include <mbgl/storage/default_file_source.hpp>
-#include <mbgl/storage/sqlite_cache.hpp>
 #include <mbgl/storage/network_status.hpp>
 #include <mbgl/util/geo.hpp>
 #include <mbgl/util/constants.hpp>
@@ -24,6 +23,7 @@
 #import "MGLAnnotation.h"
 #import "MGLUserLocationAnnotationView.h"
 #import "MGLUserLocation_Private.h"
+#import "MGLFileCache.h"
 
 #import "SMCalloutView.h"
 
@@ -33,21 +33,6 @@
 
 class MBGLView;
 
-// Returns the path to the default cache database on this system.
-const std::string &defaultCacheDatabase() {
-    static const std::string path = []() -> std::string {
-        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
-        if ([paths count] == 0) {
-            // Disable the cache if we don't have a location to write.
-            return "";
-        }
-
-        NSString *libraryDirectory = [paths objectAtIndex:0];
-        return [[libraryDirectory stringByAppendingPathComponent:@"cache.db"] UTF8String];
-    }();
-    return path;
-}
-
 static dispatch_once_t loadGLExtensions;
 
 NSString *const MGLDefaultStyleName = @"mapbox-streets";
@@ -101,7 +86,6 @@ static NSURL *MGLURLForBundledStyleNamed(NSString *styleName)
 {
     mbgl::Map *_mbglMap;
     MBGLView *_mbglView;
-    mbgl::SQLiteCache *_mbglFileCache;
     mbgl::DefaultFileSource *_mbglFileSource;
 
     BOOL _isTargetingInterfaceBuilder;
@@ -277,8 +261,7 @@ std::chrono::steady_clock::duration secondsAsDuration(float duration)
     // setup mbgl map
     //
     _mbglView = new MBGLView(self);
-    _mbglFileCache  = new mbgl::SQLiteCache(defaultCacheDatabase());
-    _mbglFileSource = new mbgl::DefaultFileSource(_mbglFileCache);
+    _mbglFileSource = new mbgl::DefaultFileSource([MGLFileCache obtainSharedCacheWithObject:self]);
 
     // Start paused on the IB canvas
     _mbglMap = new mbgl::Map(*_mbglView, *_mbglFileSource, mbgl::MapMode::Continuous, _isTargetingInterfaceBuilder);
@@ -424,6 +407,8 @@ std::chrono::steady_clock::duration secondsAsDuration(float duration)
         _mbglFileSource = nullptr;
     }
 
+    [MGLFileCache releaseSharedCacheForObject:self];
+
     if (_mbglView)
     {
         delete _mbglView;