seek

问题 I am having problems appending data to a binary file. When i seek() to a location, then write() at that location and then read the whole file, i find that the data was not written at the location that i wanted. Instead, i find it right after every other data/text. My code file = open('myfile.dat', 'wb') file.write('This is a sample') file.close() file = open('myfile.dat', 'ab') file.seek(5) file.write(' text') file.close() file = open('myfile.dat', 'rb') print file.read() # -> This is a

问题 I'm trying to use C++ to write an entry in a specific place in a file so basicly I have ofstream ofs("file.dat", ios::binary | ios::app); ofs.seekp(220, ios::beg); ofs.write((char *)&i, sizeof(i)); But no matter what I do it always write at the end of the file. I suppose this is related to iso::app because according to the documentation app (append) Set the stream's position indicator to the end of the stream before each output operation But if I use ate or nothing it always erases the

问题 I am trying to pan and seek forwards and backwards in my AVPlayer. It is kind of working but the basic math of determining where the pan is translated to the length of the asset is wrong. Can any one offer assistance? - (void) handlePanGesture:(UIPanGestureRecognizer*)pan{ CGPoint translate = [pan translationInView:self.view]; CGFloat xCoord = translate.x; double diff = (xCoord); //NSLog(@"%F",diff); CMTime duration = self.avPlayer.currentItem.asset.duration; float seconds = CMTimeGetSeconds

问题 I'm using JWPlayer 5.4 and it's setup on the page using the javascript API. What I'd like to do is make it so that users can fastforward/rewing via the seek bar ONLY if they have already played that part of the video. So, if a user is watching the video for the first time they can't skip beyond the current position, however they can seek forward and back behind where the video played up until. I'm struggling with the API onTime events etc. to try and work out the Math to make this work. Does

问题 I find it difficult to express myself so I'll jump right into the code FileStream stream = new FileStream("//ignoreThis//demo.bin", FileMode.Append, FileAccess.Write, FileShare.Write)); BinaryWriter writer = new BinaryWriter(stream); writer.Write(myNum); writer.Write(myString); I can call this method several times and I know that every time I do so, it will add the new data at the end of the file 'demo.bin'. Now I'm trying to write a method where I can seek to my 3rd instance (I'm not sure if

问题 I am wondering if there is a simple way to get to the penultimate line of an open file. f.seek is giving me no end of trouble. I can easily get to the final line, but I can't figure out how to get to the line above that. 回答1: Assuming the file isn't too big and memory isn't a concern open('file.txt').readlines()[-2] 回答2: You can seek from the end of the file and count number of newlines encountered, as soon as you hit the second '\n' stop and call readline() : with open('foo.txt') as f: end

问题 First of all, I'm new to C#, so bear with me. I am making an application, that shows an .avi file in windows media player like this: private void button1_Click(object sender, EventArgs e) { axWindowsMediaPlayer1.URL = @"C:BlaBla\Family Guy\Season 10\S10E16.HDTV.x264-LOL.avi"; } I've found out that you cant fastforward or fastrewind in an .avi file, because it's not indexed. But using the WMP-slider of axWindowsMediaPlayer1, you can set the file to play at a specific point. For instance, start

问题 I have a big gzip file and I would like to read only parts of it using seek . About the use of seek on gzip files, this page says: The seek() position is relative to the uncompressed data, so the caller does not even need to know that the data file is compressed. Does this imply that seek has to read and decompress the data from the beginning of the file to the target position? 回答1: Yes. This is the code: elif self.mode == READ: if offset < self.offset: # for negative seek, rewind and do

问题 A hard disk system has the following parameters : Number of tracks = 500 Number of sectors/track = 100 Number of bytes /sector = 500 Time taken by the head to move from one track to adjacent track = 1 ms Rotation speed = 600 rpm. What is the average time taken for transferring 250 bytes from the disk ? Well I wanted to know How the average seek time is calculated ? My Approach Avg. time to transfer = Avg. seek time + Avg. rotational delay + Data transfer time Avg Seek Time given that : time

问题 If I have some file-like object and do the following: F = open('abc', 'r') ... loc = F.tell() F.seek(loc-10) What does seek do? Does is start at the beginning of the file and read loc-10 bytes? Or is it smart enough just to back up 10 bytes? 回答1: It is OS- and libc-specific. the file.seek() operation is delegated to the fseek(3) C call for actual OS-level files. 回答2: According to Python 2.7's docs: file.seek(offset[, whence]) Set the file’s current position, like stdio‘s fseek(). The whence