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digitalmars.D - readExact Problem

reply Charma <Motoko_Kusanagi web.de> writes:
hello,
I have following problem i can't solve for a whole day:
I got a file in which there are alternating 1 byte in which a name-lengh is
saved, then the name, then another byte with a name length and so on...
Now i got this piece of code:

scope uint t;
scope char VFSfile[][];
scope char[] temp;
for(int i=0;i<AmoundVFS;i++)
{
	index.readExact(&t, 1);
	writefln(t);
	index.readExact(VFSfile.ptr, t); // <-- error here "array bounds something
	index.readExact(VFSfile.ptr, t); // this way cauzes Error: not enough data in
stream, eventhough i have checked that t is correctly read and the file is big
enough
}

AmoundVFS is the amound of entries, index is the File which i loaded with
"File"...
now this aborts with the very first entry. what i want is, that the VFSfile has
all the names in an array in the end. in a way like this:
VFSfile[0] => "name1",
VFSfile[1] => "name2",
and so on...

anyone can help?!?
May 25 2007
next sibling parent reply Daniel Keep <daniel.keep.lists gmail.com> writes:
Charma wrote:

 hello,
 I have following problem i can't solve for a whole day:
 I got a file in which there are alternating 1 byte in which a name-lengh is
saved, then the name, then another byte with a name length and so on...
 Now i got this piece of code:
 
 scope uint t;


The "scope" there isn't going to do anything.


 scope char VFSfile[][];


Or there.


 scope char[] temp;


Or there.  "scope" only changes behaviour for class instances, nothing
else.  Although believe me, I wish it *did* work for arrays... man,
that'd be sweet.


 for(int i=0;i<AmoundVFS;i++)


I *could* say you should be using a size_t, or at least an unsigned
type, but that would just be me being pedantic.  Plus, I don't know what
type AmoundVFS is, and how this is being used, so I'll keep quiet :P


 {
 	index.readExact(&t, 1);


Didn't you say the name length was one byte?  So why are you reading
into a four-byte number?

  ubyte t;
  index.read(t);


 	writefln(t);
 	index.readExact(VFSfile.ptr, t); // <-- error here "array bounds something


Whoa, whoa, whoa.  Two things.  First of all, VFSfile.ptr is of type
char[]*: a pointer to an array of characters.  Secondly, you haven't
allocated any space for VFSfile yet, so there's nothing for readExact to
read into.

  VFSfile[i].length = t;
  index.readExact(VFSfile[i].ptr, t);

And you need this outside the loop somewhere:

  VFSfile.length = AmoundVFS;


 	index.readExact(VFSfile.ptr, t); // this way cauzes Error: not enough data in
stream, eventhough i have checked that t is correctly read and the file is big
enough


Why are you reading it twice?


 }


That's all the bugs I could see with it.  Hope this helps.

    -- Daniel

-- 
int getRandomNumber()
{
    return 4; // chosen by fair dice roll.
              // guaranteed to be random.
}

http://xkcd.com/

v2sw5+8Yhw5ln4+5pr6OFPma8u6+7Lw4Tm6+7l6+7D
i28a2Xs3MSr2e4/6+7t4TNSMb6HTOp5en5g6RAHCP  http://hackerkey.com/
May 25 2007
parent reply Charma <Motoko_Kusanagi web.de> writes:
Daniel Keep Wrote:


 
 
 Charma wrote:

 hello,
 I have following problem i can't solve for a whole day:
 I got a file in which there are alternating 1 byte in which a name-lengh is
saved, then the name, then another byte with a name length and so on...
 Now i got this piece of code:
 
 scope uint t;


 
 The "scope" there isn't going to do anything.
 

 scope char VFSfile[][];


 
 Or there.
 

 scope char[] temp;


 
 Or there.  "scope" only changes behaviour for class instances, nothing
 else.  Although believe me, I wish it *did* work for arrays... man,
 that'd be sweet.
 

 for(int i=0;i<AmoundVFS;i++)


 
 I *could* say you should be using a size_t, or at least an unsigned
 type, but that would just be me being pedantic.  Plus, I don't know what
 type AmoundVFS is, and how this is being used, so I'll keep quiet :P
 

 {
 	index.readExact(&t, 1);


 
 Didn't you say the name length was one byte?  So why are you reading
 into a four-byte number?
 
   ubyte t;
   index.read(t);
 

 	writefln(t);
 	index.readExact(VFSfile.ptr, t); // <-- error here "array bounds something


 
 Whoa, whoa, whoa.  Two things.  First of all, VFSfile.ptr is of type
 char[]*: a pointer to an array of characters.  Secondly, you haven't
 allocated any space for VFSfile yet, so there's nothing for readExact to
 read into.
 
   VFSfile[i].length = t;
   index.readExact(VFSfile[i].ptr, t);
 
 And you need this outside the loop somewhere:
 
   VFSfile.length = AmoundVFS;
 

 	index.readExact(VFSfile.ptr, t); // this way cauzes Error: not enough data in
stream, eventhough i have checked that t is correctly read and the file is big
enough


 
 Why are you reading it twice?
 

 }


 
 That's all the bugs I could see with it.  Hope this helps.
 
     -- Daniel
 
 -- 
 int getRandomNumber()
 {
     return 4; // chosen by fair dice roll.
               // guaranteed to be random.
 }
 
 http://xkcd.com/
 
 v2sw5+8Yhw5ln4+5pr6OFPma8u6+7Lw4Tm6+7l6+7D
 i28a2Xs3MSr2e4/6+7t4TNSMb6HTOp5en5g6RAHCP  http://hackerkey.com/





well... i know... i am newbie with D T_T sorry...
this is the way i wrote it now and it seams to work perfectly:

File index = new File(indexpath, FileMode.In);
byte AmoundVFS;
index.read(AmoundVFS);
byte t;
char[][] VFSfile;
VFSfile.length = AmoundVFS;
for(int i=0;i<AmoundVFS;i++)
{
	index.readExact(&t, 1);
	VFSfile[i].length = t;
	index.readExact(VFSfile[i].ptr, t);
}

AmoundVFS is saved in the very first byte of the file... i didn't mention it.
Why i used uint for t the last time was because i thought that this could be
the error since in Phobos it says that it want's a uint as parameter there...
I hope this code is good now. If there is anything to imporve, let me know!
thanks for the help!
May 25 2007
parent reply Daniel Keep <daniel.keep.lists gmail.com> writes:
Charma wrote:

 well... i know... i am newbie with D T_T sorry...


That's alright; we all have to start from somewhere.


 this is the way i wrote it now and it seams to work perfectly:
 
 File index = new File(indexpath, FileMode.In);
 byte AmoundVFS;
 index.read(AmoundVFS);
 byte t;


You should probably use ubyte's for AmoundVFS and t.  I don't imagine
you're going to have a negative number of entries, or negative length,
so you're restricting yourself to 127 entries/characters maximum.

Although, if you're conforming to an existing file format, best stick to
that :)


 char[][] VFSfile;
 VFSfile.length = AmoundVFS;
 for(int i=0;i<AmoundVFS;i++)
 {
 	index.readExact(&t, 1);
 	VFSfile[i].length = t;
 	index.readExact(VFSfile[i].ptr, t);
 }
 
 AmoundVFS is saved in the very first byte of the file... i didn't mention it.
Why i used uint for t the last time was because i thought that this could be
the error since in Phobos it says that it want's a uint as parameter there...
 I hope this code is good now. If there is anything to imporve, let me know!
thanks for the help!


The only other thing I can see is that index.readExact(&t,1) shouldn't
be necessary; you should be able to just use index.read(t), which does
basically the same thing, but is a bit cleaner.

	-- Daniel

-- 
int getRandomNumber()
{
    return 4; // chosen by fair dice roll.
              // guaranteed to be random.
}

http://xkcd.com/

v2sw5+8Yhw5ln4+5pr6OFPma8u6+7Lw4Tm6+7l6+7D
i28a2Xs3MSr2e4/6+7t4TNSMb6HTOp5en5g6RAHCP  http://hackerkey.com/
May 25 2007
parent Charma <Motoko_Kusanagi web.de> writes:
Daniel Keep Wrote:


 
 
 Charma wrote:

 well... i know... i am newbie with D T_T sorry...


 
 That's alright; we all have to start from somewhere.
 

 this is the way i wrote it now and it seams to work perfectly:
 
 File index = new File(indexpath, FileMode.In);
 byte AmoundVFS;
 index.read(AmoundVFS);
 byte t;


 
 You should probably use ubyte's for AmoundVFS and t.  I don't imagine
 you're going to have a negative number of entries, or negative length,
 so you're restricting yourself to 127 entries/characters maximum.
 
 Although, if you're conforming to an existing file format, best stick to
 that :)
 

 char[][] VFSfile;
 VFSfile.length = AmoundVFS;
 for(int i=0;i<AmoundVFS;i++)
 {
 	index.readExact(&t, 1);
 	VFSfile[i].length = t;
 	index.readExact(VFSfile[i].ptr, t);
 }
 
 AmoundVFS is saved in the very first byte of the file... i didn't mention it.
Why i used uint for t the last time was because i thought that this could be
the error since in Phobos it says that it want's a uint as parameter there...
 I hope this code is good now. If there is anything to imporve, let me know!
thanks for the help!


 
 The only other thing I can see is that index.readExact(&t,1) shouldn't
 be necessary; you should be able to just use index.read(t), which does
 basically the same thing, but is a bit cleaner.
 
 	-- Daniel
 
 -- 
 int getRandomNumber()
 {
     return 4; // chosen by fair dice roll.
               // guaranteed to be random.
 }
 
 http://xkcd.com/
 
 v2sw5+8Yhw5ln4+5pr6OFPma8u6+7Lw4Tm6+7l6+7D
 i28a2Xs3MSr2e4/6+7t4TNSMb6HTOp5en5g6RAHCP  http://hackerkey.com/



alright, fixed that too ^^;;
thanks for all!
May 25 2007
prev sibling parent "David B. Held" <dheld codelogicconsulting.com> writes:
Charma wrote:

 [...]
 anyone can help?!?


One thing that might help a lot is if you take advantage of the built-in 
unittest feature.  So as you are writing your code, when you are not 
entirely confident that you know how something works, just throw in a

unittest
{
    // write short test here
}

block and build with -unittest to see what D thinks of your code.  If 
you really want to get fancy, you should try Test-Driven Development, 
which requires that you write your tests first, and then work on your 
code until they pass.

Dave
May 25 2007