RMAbstractWebMapSource.m
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//
// RMWebMapSource.m
//
// Copyright (c) 2009, Frank Schroeder, SharpMind GbR
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
#import "RMAbstractWebMapSource.h"
#import "RMTileCache.h"
@implementation RMAbstractWebMapSource
@synthesize retryCount, waitSeconds;
- (id)init
{
if (!(self = [super init]))
return nil;
self.retryCount = RMAbstractWebMapSourceDefaultRetryCount;
self.waitSeconds = RMAbstractWebMapSourceDefaultWaitSeconds;
return self;
}
- (NSURL *)URLForTile:(RMTile)tile
{
@throw [NSException exceptionWithName:@"RMAbstractMethodInvocation"
reason:@"URLForTile: invoked on AbstractMercatorWebSource. Override this method when instantiating abstract class."
userInfo:nil];
}
- (NSArray *)URLsForTile:(RMTile)tile
{
return [NSArray arrayWithObjects:[self URLForTile:tile], nil];
}
- (UIImage *)imageForTile:(RMTile)tile inCache:(RMTileCache *)tileCache
{
__block UIImage *image = nil;
tile = [[self mercatorToTileProjection] normaliseTile:tile];
image = [tileCache cachedImage:tile withCacheKey:[self uniqueTilecacheKey]];
if (image)
return image;
dispatch_async(dispatch_get_main_queue(), ^(void)
{
[[NSNotificationCenter defaultCenter] postNotificationName:RMTileRequested object:[NSNumber numberWithUnsignedLongLong:RMTileKey(tile)]];
});
[tileCache retain];
NSArray *URLs = [self URLsForTile:tile];
// fill up collection array with placeholders
//
NSMutableArray *tilesData = [NSMutableArray arrayWithCapacity:[URLs count]];
for (int p = 0; p < [URLs count]; ++p)
[tilesData addObject:[NSNull null]];
dispatch_group_t fetchGroup = dispatch_group_create();
for (int u = 0; u < [URLs count]; ++u)
{
NSURL *currentURL = [URLs objectAtIndex:u];
dispatch_group_async(fetchGroup, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void)
{
NSData *tileData = nil;
for (int try = 0; tileData == nil && try < self.retryCount; ++try)
{
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:currentURL];
[request setTimeoutInterval:(self.waitSeconds / (CGFloat)self.retryCount)];
tileData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
}
if (tileData)
{
@synchronized(self)
{
// safely put into collection array in proper order
//
[tilesData replaceObjectAtIndex:u withObject:tileData];
};
}
});
}
// wait for whole group of fetches (with retries) to finish, then clean up
//
dispatch_group_wait(fetchGroup, dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC * self.waitSeconds));
dispatch_release(fetchGroup);
// composite the collected images together
//
for (NSData *tileData in tilesData)
{
if (tileData && [tileData isKindOfClass:[NSData class]] && [tileData length])
{
if (image != nil)
{
UIGraphicsBeginImageContext(image.size);
[image drawAtPoint:CGPointMake(0,0)];
[[UIImage imageWithData:tileData] drawAtPoint:CGPointMake(0,0)];
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
else
{
image = [UIImage imageWithData:tileData];
}
}
}
if (image)
[tileCache addImage:image forTile:tile withCacheKey:[self uniqueTilecacheKey]];
[tileCache release];
dispatch_async(dispatch_get_main_queue(), ^(void)
{
[[NSNotificationCenter defaultCenter] postNotificationName:RMTileRetrieved object:[NSNumber numberWithUnsignedLongLong:RMTileKey(tile)]];
});
return image;
}
@end