NSFileHandle fileHandleForWritingToURL example ios

fileHandleForWritingToURL :error:

Returns a file handle initialized for writing to the file, device, or named socket at the specified URL.

+ (id)fileHandleForWritingToURL:(NSURL *)url error:(NSError **)error

Parameters

url

The URL of the file, device, or named socket to access.

error

If an error occurs, upon return contains an NSError object that describes the problem. Pass NULL if you do not want error information.

Return Value of [NSFileHandle fileHandleForWritingToURL]

The initialized file handle object or nil if no file exists at url.

Discussion of [NSFileHandle fileHandleForWritingToURL]

The file pointer is set to the beginning of the file. The returned object responds only to writeData:.

When using this method to create a file handle object, the file handle owns its associated file descriptor and is responsible for closing it.

Example of [NSFileHandle fileHandleForWritingToURL]

static const NSUInteger BufferSize = 1024*1024;

@implementation ALAsset (Export)

- (BOOL) exportDataToURL: (NSURL*) fileURL error: (NSError**) error
{
    [[NSFileManager defaultManager] createFileAtPath:[fileURL path] contents:nil attributes:nil];
    NSFileHandle *handle = [NSFileHandle fileHandleForWritingToURL:fileURL error:error];
    if (!handle) {
        return NO;
    }

    ALAssetRepresentation *rep = [self defaultRepresentation];
    uint8_t *buffer = calloc(BufferSize, sizeof(*buffer));
    NSUInteger offset = 0, bytesRead = 0;

    do {
        @try {
            bytesRead = [rep getBytes:buffer fromOffset:offset length:BufferSize error:error];
            [handle writeData:[NSData dataWithBytesNoCopy:buffer length:bytesRead freeWhenDone:NO]];
            offset += bytesRead;
        } @catch (NSException *exception) {
            free(buffer);
            return NO;
        }
    } while (bytesRead > 0);

    free(buffer);
    return YES;
}