www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - Tango file i/o

reply Jason House <jason.james.house gmail.com> writes:
I'm having trouble writing a unit test to check code that communicates via
standard in and standard out.  Attached to this post is my a reduced form
of my problems.  Can anyone tell me what's going wrong? (The assert in the
code fails)

"send" belongs to my test harness and can be changed easily
"receive" belongs to working console I/O code.
  In that code receive = new LineIterator!(char)(Cin.stream)
Mar 18 2008
parent reply torhu <no spam.invalid> writes:
Jason House wrote:

 I'm having trouble writing a unit test to check code that communicates via
 standard in and standard out.  Attached to this post is my a reduced form
 of my problems.  Can anyone tell me what's going wrong? (The assert in the
 code fails)


You need to rewind the file before starting to read after writing:

fakeConsole.seek(0);
Mar 18 2008
parent reply Jason House <jason.james.house gmail.com> writes:
torhu wrote:


 Jason House wrote:

 I'm having trouble writing a unit test to check code that communicates
 via
 standard in and standard out.  Attached to this post is my a reduced form
 of my problems.  Can anyone tell me what's going wrong? (The assert in
 the code fails)


 
 You need to rewind the file before starting to read after writing:
 
 fakeConsole.seek(0);


I interpret that to mean that writing to the file affects the read stream
and reading affects the write stream.  I need to decouple those because
reading and writing should be more or less independent of each other.

It sounds like if I open up a file twice, once for writing and once for
reading, that I can get independent access into the file.  The real test is
multi-threaded with reading and writing done asynchronously.  With
independent file classes, will EOF be a problem?  AKA, if a read occurs
when a write is in progress.
Mar 19 2008
parent reply Lars Ivar Igesund <larsivar igesund.net> writes:
Jason House wrote:


 torhu wrote:
 

 Jason House wrote:

 I'm having trouble writing a unit test to check code that communicates
 via
 standard in and standard out.  Attached to this post is my a reduced
 form
 of my problems.  Can anyone tell me what's going wrong? (The assert in
 the code fails)


 
 You need to rewind the file before starting to read after writing:
 
 fakeConsole.seek(0);


 
 I interpret that to mean that writing to the file affects the read stream
 and reading affects the write stream.  I need to decouple those because
 reading and writing should be more or less independent of each other.


Yes, because your TempFile is a Conduit that provides both the input and
output stream.


 
 It sounds like if I open up a file twice, once for writing and once for
 reading, that I can get independent access into the file.  


Yes.


 The real test 
 is
 multi-threaded with reading and writing done asynchronously.  With
 independent file classes, will EOF be a problem?  AKA, if a read occurs
 when a write is in progress.


You should lock your resources (files) while writing.

-- 
Lars Ivar Igesund
blog at http://larsivi.net
DSource, #d.tango & #D: larsivi
Dancing the Tango
Mar 19 2008
parent Jason House <jason.james.house gmail.com> writes:
Lars Ivar Igesund Wrote:


 Jason House wrote:
 Yes, because your TempFile is a Conduit that provides both the input and
 output stream.


One of these days, I'll try to figure out all the layers of abstraction int he
Tango I/O library...  Both what each piece means and why they (strange?) names
were chosen.



 The real test is
 multi-threaded with reading and writing done asynchronously.  With
 independent file classes, will EOF be a problem?  AKA, if a read occurs
 when a write is in progress.


 
 You should lock your resources (files) while writing.


What kind of locking mechanism are you talking about?  synchronized(obj)?  This
would work to ensure proper behavior when reading from temporary file like in
my unit test, but can't be done in a more general asynchronous case...  such as
when using pipes for communication, or the console.




 
 -- 
 Lars Ivar Igesund
 blog at http://larsivi.net
 DSource, #d.tango & #D: larsivi
 Dancing the Tango
Mar 19 2008