Open FileDescriptor for reading and writing with a Channel
I have a FileDescriptor and would like to open it for reading and writing using a single channel. I can use streams like so to get one channel for reading, and one channel for writing, but I would prefer a single channel.
FileChannel in = new FileInputStream(fd).getChannel();
FileChannel out = new FileOutputStream(fd).getChannel();
java
asked Jul 26 '16 at 4:28
RedHatterRedHatter
81811228
add a comment |
I have a FileDescriptor and would like to open it for reading and writing using a single channel. I can use streams like so to get one channel for reading, and one channel for writing, but I would prefer a single channel.
FileChannel in = new FileInputStream(fd).getChannel();
FileChannel out = new FileOutputStream(fd).getChannel();
java
asked Jul 26 '16 at 4:28
RedHatterRedHatter
81811228
Why? Applications should not create their own file descriptors.
– user207421
Jul 26 '16 at 5:23
I'm implementing a VPNService on android, it provides me with the FileDescriptors.
– RedHatter
Jul 26 '16 at 5:32
add a comment |
I have a FileDescriptor and would like to open it for reading and writing using a single channel. I can use streams like so to get one channel for reading, and one channel for writing, but I would prefer a single channel.
FileChannel in = new FileInputStream(fd).getChannel();
FileChannel out = new FileOutputStream(fd).getChannel();
java
asked Jul 26 '16 at 4:28
RedHatterRedHatter
81811228
I have a FileDescriptor and would like to open it for reading and writing using a single channel. I can use streams like so to get one channel for reading, and one channel for writing, but I would prefer a single channel.
FileChannel in = new FileInputStream(fd).getChannel();
FileChannel out = new FileOutputStream(fd).getChannel();
java
java
asked Jul 26 '16 at 4:28
RedHatterRedHatter
81811228
asked Jul 26 '16 at 4:28
RedHatterRedHatter
81811228
asked Jul 26 '16 at 4:28
RedHatterRedHatter
81811228
asked Jul 26 '16 at 4:28
RedHatterRedHatter
81811228
asked Jul 26 '16 at 4:28
RedHatterRedHatter
81811228
81811228
Why? Applications should not create their own file descriptors.
– user207421
Jul 26 '16 at 5:23
I'm implementing a VPNService on android, it provides me with the FileDescriptors.
– RedHatter
Jul 26 '16 at 5:32
add a comment |
Why? Applications should not create their own file descriptors.
– user207421
Jul 26 '16 at 5:23
I'm implementing a VPNService on android, it provides me with the FileDescriptors.
– RedHatter
Jul 26 '16 at 5:32
Why? Applications should not create their own file descriptors.
– user207421
Jul 26 '16 at 5:23
Why? Applications should not create their own file descriptors.
– user207421
Jul 26 '16 at 5:23
I'm implementing a VPNService on android, it provides me with the FileDescriptors.
– RedHatter
Jul 26 '16 at 5:32
I'm implementing a VPNService on android, it provides me with the FileDescriptors.
– RedHatter
Jul 26 '16 at 5:32
add a comment |
1 Answer
1
active
oldest
votes
Been working with FileChannel recently, yes you can use 1 FileChannel for reading and writing as long as you use methods that do not modify the channel's position. In fact this is the only way you will have a consistent view of the file as write may be paged/cached by the OS that is yet to be "visible" from the other reader at least before flush.
This is excerpt from the Javadoc
File channels are safe for use by multiple concurrent threads. The
close method may be invoked at any time, as specified by the Channel
interface. Only one operation that involves the channel's position or
can change its file's size may be in progress at any given time;
attempts to initiate a second such operation while the first is still
in progress will block until the first operation completes. Other
operations, in particular those that take an explicit position, may
proceed concurrently; whether they in fact do so is dependent upon the
underlying implementation and is therefore unspecified.
I use single threaded write (that changes position) and multithreaded reads (that do not change position ie. read(ByteBuffer dst, long position))
Cheers
answered Nov 15 '18 at 8:29
ahasaniahasani
1
add a comment |
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Been working with FileChannel recently, yes you can use 1 FileChannel for reading and writing as long as you use methods that do not modify the channel's position. In fact this is the only way you will have a consistent view of the file as write may be paged/cached by the OS that is yet to be "visible" from the other reader at least before flush.
This is excerpt from the Javadoc
File channels are safe for use by multiple concurrent threads. The
close method may be invoked at any time, as specified by the Channel
interface. Only one operation that involves the channel's position or
can change its file's size may be in progress at any given time;
attempts to initiate a second such operation while the first is still
in progress will block until the first operation completes. Other
operations, in particular those that take an explicit position, may
proceed concurrently; whether they in fact do so is dependent upon the
underlying implementation and is therefore unspecified.
I use single threaded write (that changes position) and multithreaded reads (that do not change position ie. read(ByteBuffer dst, long position))
Cheers
answered Nov 15 '18 at 8:29
ahasaniahasani
1
add a comment |
Been working with FileChannel recently, yes you can use 1 FileChannel for reading and writing as long as you use methods that do not modify the channel's position. In fact this is the only way you will have a consistent view of the file as write may be paged/cached by the OS that is yet to be "visible" from the other reader at least before flush.
This is excerpt from the Javadoc
File channels are safe for use by multiple concurrent threads. The
close method may be invoked at any time, as specified by the Channel
interface. Only one operation that involves the channel's position or
can change its file's size may be in progress at any given time;
attempts to initiate a second such operation while the first is still
in progress will block until the first operation completes. Other
operations, in particular those that take an explicit position, may
proceed concurrently; whether they in fact do so is dependent upon the
underlying implementation and is therefore unspecified.
I use single threaded write (that changes position) and multithreaded reads (that do not change position ie. read(ByteBuffer dst, long position))
Cheers
answered Nov 15 '18 at 8:29
ahasaniahasani
1
add a comment |
Been working with FileChannel recently, yes you can use 1 FileChannel for reading and writing as long as you use methods that do not modify the channel's position. In fact this is the only way you will have a consistent view of the file as write may be paged/cached by the OS that is yet to be "visible" from the other reader at least before flush.
This is excerpt from the Javadoc
File channels are safe for use by multiple concurrent threads. The
close method may be invoked at any time, as specified by the Channel
interface. Only one operation that involves the channel's position or
can change its file's size may be in progress at any given time;
attempts to initiate a second such operation while the first is still
in progress will block until the first operation completes. Other
operations, in particular those that take an explicit position, may
proceed concurrently; whether they in fact do so is dependent upon the
underlying implementation and is therefore unspecified.
I use single threaded write (that changes position) and multithreaded reads (that do not change position ie. read(ByteBuffer dst, long position))
Cheers
answered Nov 15 '18 at 8:29
ahasaniahasani
1
Been working with FileChannel recently, yes you can use 1 FileChannel for reading and writing as long as you use methods that do not modify the channel's position. In fact this is the only way you will have a consistent view of the file as write may be paged/cached by the OS that is yet to be "visible" from the other reader at least before flush.
This is excerpt from the Javadoc
File channels are safe for use by multiple concurrent threads. The
close method may be invoked at any time, as specified by the Channel
interface. Only one operation that involves the channel's position or
can change its file's size may be in progress at any given time;
attempts to initiate a second such operation while the first is still
in progress will block until the first operation completes. Other
operations, in particular those that take an explicit position, may
proceed concurrently; whether they in fact do so is dependent upon the
underlying implementation and is therefore unspecified.
I use single threaded write (that changes position) and multithreaded reads (that do not change position ie. read(ByteBuffer dst, long position))
Cheers
answered Nov 15 '18 at 8:29
ahasaniahasani
1
answered Nov 15 '18 at 8:29
ahasaniahasani
1
answered Nov 15 '18 at 8:29
ahasaniahasani
1
answered Nov 15 '18 at 8:29
ahasaniahasani
1
1
add a comment |
add a comment |
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Why? Applications should not create their own file descriptors.
– user207421
Jul 26 '16 at 5:23
I'm implementing a VPNService on android, it provides me with the FileDescriptors.
– RedHatter
Jul 26 '16 at 5:32