ImageDownloadOperation.m
/* |
File: ImageDownloadOperation.m |
Contains: Downloads an image to a directory. |
Written by: DTS |
Copyright: Copyright (c) 2011-2013 Apple Inc. All Rights Reserved. |
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non-exclusive license, under Apple's copyrights in this |
original Apple software (the "Apple Software"), to use, |
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or logos of Apple Inc. may be used to endorse or promote |
products derived from the Apple Software without specific prior |
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by other works in which the Apple Software may be incorporated. |
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*/ |
#import "ImageDownloadOperation.h" |
#include <fcntl.h> |
#include <unistd.h> |
@interface ImageDownloadOperation () |
// Read/write versions of public properties |
@property (atomic, copy, readwrite) NSString * imageFilePath; |
@end |
@implementation ImageDownloadOperation |
@synthesize imagesDirPath = _imagesDirPath; |
@synthesize depth = _depth; |
@synthesize imageFilePath = _imageFilePath; |
- (id)initWithURL:(NSURL *)url imagesDirPath:(NSString *)imagesDirPath depth:(NSUInteger)depth |
// See comment in header. |
{ |
assert(imagesDirPath != nil); |
self = [super initWithURL:url]; |
if (self != nil) { |
self->_imagesDirPath = [imagesDirPath copy]; |
self->_depth = depth; |
} |
return self; |
} |
- (void)dealloc |
{ |
[self->_imageFilePath release]; |
[self->_imagesDirPath release]; |
[super dealloc]; |
} |
+ (NSString *)defaultExtensionToMIMEType:(NSString *)type |
// See comment in header. |
{ |
static NSDictionary * sTypeToExtensionMap; |
// This needs to be thread safe because the client could start multiple |
// download operations with different run loop threads and, if so, |
// +defaultExtensionToMIMEType: can get call by multiple threads simultaneously. |
@synchronized (self) { |
if (sTypeToExtensionMap == nil) { |
sTypeToExtensionMap = [@{ |
@"image/gif": @"gif", |
@"image/png": @"png", |
@"image/jpeg": @"jpg", |
} retain]; |
assert(sTypeToExtensionMap != nil); |
} |
} |
return (type == nil) ? nil : [sTypeToExtensionMap objectForKey:type]; |
} |
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response |
// An NSURLConnect delegate method. We override this to set up a |
// destination output stream for the incoming image data. |
{ |
[super connection:connection didReceiveResponse:response]; |
// If the response is an error, no need to do anything special here. |
// We only need to set up an output stream if we're successfully |
// getting the image. |
if (self.isStatusCodeAcceptable) { |
NSString * extension; |
NSString * prefix; |
assert(self.responseOutputStream == nil); |
// Create a unique file for the downloaded image. Start by getting an appropriate |
// extension. If we don't have one, that's bad. |
extension = [[self class] defaultExtensionToMIMEType:[self.lastResponse MIMEType]]; |
if (extension != nil) { |
NSString * fileName; |
NSString * filePath; |
int counter; |
int fd; |
// Next calculate the file name prefix and extension. |
fileName = [self.lastResponse suggestedFilename]; |
if (fileName == nil) { |
prefix = @"image"; |
assert(extension != nil); // that is, the default |
} else { |
if ([[fileName pathExtension] length] == 0) { |
prefix = fileName; |
assert(extension != nil); // that is, the default |
} else { |
prefix = [fileName stringByDeletingPathExtension]; |
extension = [fileName pathExtension]; |
} |
} |
assert(prefix != nil); |
assert(extension != nil); |
// Repeatedly try to create a new file with that info, adding a |
// unique number if we get a conflict. |
counter = 0; |
filePath = [self.imagesDirPath stringByAppendingPathComponent:[prefix stringByAppendingPathExtension:extension]]; |
do { |
int err; |
int junk; |
err = 0; |
fd = open([filePath UTF8String], O_CREAT | O_EXCL | O_RDWR, 0666); |
if (fd < 0) { |
err = errno; |
} else { |
junk = close(fd); |
assert(junk == 0); |
} |
if (err == 0) { |
self.imageFilePath = filePath; |
self.responseOutputStream = [NSOutputStream outputStreamToFileAtPath:filePath append:NO]; |
break; |
} else if (err == EEXIST) { |
counter += 1; |
if (counter > 500) { |
break; |
} |
filePath = [self.imagesDirPath stringByAppendingPathComponent:[[NSString stringWithFormat:@"%@-%d", prefix, counter] stringByAppendingPathExtension:extension]]; |
} else if (err == EINTR) { |
// do nothing |
} else { |
break; |
} |
} while (YES); |
} |
// If we've failed to create a valid file, redirect the output to the bit bucket. |
if (self.responseOutputStream == nil) { |
self.responseOutputStream = [NSOutputStream outputStreamToFileAtPath:@"/dev/null" append:NO]; |
} |
} |
} |
@end |
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