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I have two questions.

  1. How to create a NSFileHandle object with the FILE* instance?

  2. How to create a NSData object with the void* instance?

I am sorry there's little information without context.

Just refer to my recent question. Weird behavior of fopen on ios I cannot use the native fopen function to create or to write the content into a file.

As a result, I just want to use the api in the ios framework and wrap the code of fopen and fwrite and such staff. So I should convert the FILE* object into NSFileHandle or something that can manipulate the file. Also the content which is handled with void* should be converted to the data format that can be accepted in the ios framework. And I think NSData should be the choice.

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    Some more information? Context? Commented Apr 14, 2012 at 3:53
  • @TheDeveloper Sorry, I had updated the question. Commented Apr 14, 2012 at 3:58

2 Answers 2

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As for FILE* to NSFileHandle, I found this mailing list question that perfectly matches what you need. Relevant code:

FILE *fp; NSFileHandle *p; fp = fopen( "foo", "r"); p = [[[NSFileHandle alloc] initWithFileDescriptor:fileno( fp) closeOnDealloc:YES] autorelease];

And it comes with a lovely warning from the answerer:

Be careful not to read from fp, because stdio caches.

EDIT: As for void* to NSData, I think you want NSData's -initWithBytesNoCopy:Length:freeWhenDone:. See this related question on how to use it.

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I think this may be helpful. I will try first.
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You can just use FILE* like you do in C. For example...

- (id)initWithFileUrl:(NSURL *)url { if (self = [super init]) { NSFileManager *fileManager = [[NSFileManager alloc] init]; [fileManager createDirectoryAtPath:[[url path] stringByDeletingLastPathComponent] withIntermediateDirectories:YES attributes:nil error:0]; char const *path = [fileManager fileSystemRepresentationWithPath:url.path]; fp = fopen(path, "a"); if (!fp) { [NSException raise:@"Can't open file for recording: " format:@"%s", strerror(errno)]; } [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillResignActive:) name:UIApplicationWillResignActiveNotification object:[UIApplication sharedApplication]]; } return self; } - (void)writeBytes:(void const *)bytes length:(uint32_t)size { if (fp && fwrite(bytes, size, 1, fp) != 1) { [NSException raise:@"File Write Error" format:@"%s", strerror(errno)]; } } - (void)writeBytes:(void const *)bytes andSize:(uint32_t)size { if (!fp) return; if (fwrite(&size, sizeof size, 1, fp) != 1 || fwrite(bytes, size, 1, fp) != 1) { [NSException raise:@"File Write Error" format:@"%s", strerror(errno)]; } } - (void)writeInt32:(int32_t)value { [self writeBytes:&value length:sizeof value]; } - (void)writeInt64:(int64_t)value { [self writeBytes:&value length:sizeof value]; } - (void)writeData:(NSData *)data { [self writeBytes:data.bytes andSize:data.length]; } - (void)writeCGFloat:(CGFloat)value { [self writeBytes:&value length:sizeof value]; } - (void)writeCGPoint:(CGPoint)point { [self writeBytes:&point length:sizeof(point)]; }
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I had tried to solve my problem in this way. But when fwrite calls, it gave me an error log and said invalid sandbox. I don't know why.
I snipped this from a project of mine, and it's been working fine for a long time. I saw your other thread. Looks like maybe you were not using the proper method to create the file system string.

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