Re: FileWriter behavior between writes
On Wed, Aug 18, 2010 at 7:30 PM, Jonas Sicking wrote: > How is this noticeable from a webpage? I.e. why does the spec need to > say anything one way or another? > On Wednesday, August 18, 2010, Eric Uhrhane wrote: >> For >> example, what if script A has a FileWriter for "/foo.txt" and script B >> [using the FileSystem api] moves it elsewhere? If the file is closed, >> the next write from A may act as if the file was never there. If the >> file stayed open, on some systems the write would succeed, but the >> data would land at the file's new location. >> >> Similar issues come up when files are opened for reading, then written >> from another script, written from multiple scripts, etc. ~TJ
Re: FileWriter behavior between writes
On Wednesday, August 18, 2010, Eric Uhrhane wrote: > This just came up during implementation discussions, so I wanted to > share it with the list. > > The behavior of FileWriter in between writes isn't currently > specified. We haven't said anything about when the underlying file is > opened or closed. Does FileWriter.write() always do an > open-write-close, with the JS object effectively holding only a path > and offset, or could the implementation choose to keep the file open, > and have the effective offset come from the underlying file pointer? > > My take: we should act as if we're always doing an open-write-close, > for maximum portability. I believe that different operating systems > and file systems are likely to have varying behavior when there are > multiple simultaneous callers opening files at the same time. For > example, what if script A has a FileWriter for "/foo.txt" and script B > [using the FileSystem api] moves it elsewhere? If the file is closed, > the next write from A may act as if the file was never there. If the > file stayed open, on some systems the write would succeed, but the > data would land at the file's new location. > > Similar issues come up when files are opened for reading, then written > from another script, written from multiple scripts, etc. > > Specifying that each FileWriter.write() should be indistinguishable > from an open-write-close wouldn't remove all platform-specific > behavior, but it would certainly reduce the number of problem cases. > > Any thoughts? How is this noticeable from a webpage? I.e. why does the spec need to say anything one way or another? / Jonas
FileWriter behavior between writes
This just came up during implementation discussions, so I wanted to share it with the list. The behavior of FileWriter in between writes isn't currently specified. We haven't said anything about when the underlying file is opened or closed. Does FileWriter.write() always do an open-write-close, with the JS object effectively holding only a path and offset, or could the implementation choose to keep the file open, and have the effective offset come from the underlying file pointer? My take: we should act as if we're always doing an open-write-close, for maximum portability. I believe that different operating systems and file systems are likely to have varying behavior when there are multiple simultaneous callers opening files at the same time. For example, what if script A has a FileWriter for "/foo.txt" and script B [using the FileSystem api] moves it elsewhere? If the file is closed, the next write from A may act as if the file was never there. If the file stayed open, on some systems the write would succeed, but the data would land at the file's new location. Similar issues come up when files are opened for reading, then written from another script, written from multiple scripts, etc. Specifying that each FileWriter.write() should be indistinguishable from an open-write-close wouldn't remove all platform-specific behavior, but it would certainly reduce the number of problem cases. Any thoughts? Thanks, Eric Uhrhane er...@google.com
