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C++ Language question

Posted on 1997-07-09
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Last Modified: 2008-03-06
I have been since recently in C++-programming after
several years of turbo pascal. Now I've encountered a
problem that I just can't seem to solve.
I used in tp the function blockread to read several bytes
at once in a memory block assigned by memalloc.

the class I use in c++ is that of ifstream to open the
file.
reserve x number of 16-bytes paragraphs with memalloc.

The thing I want to do is read n bytes in one time out of
the file opened by ifstream and place them in the buffer
assigned by memalloc.

someone knows how to solve this problem ?

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Question by:berox
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4 Comments
 
LVL 4

Expert Comment

by:AVaulin
ID: 1164599
Use FILE structure and fopen, fread and fclose functions instead ifstream class. This way is the easiest.
0
 

Author Comment

by:berox
ID: 1164600
still remains the question how can I put them in a buffer allocated by memalloc and (I forgot to put it in my former question)is there a function to read the memory locations reserved by memalloc (something like Mem[Seg:ofs] in TP), or is it just "pointer-work"
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LVL 4

Expert Comment

by:AVaulin
ID: 1164601
Example:

struct YourStuct
{
 int int1;
 floaf float1;
 char str[20];
}

void YourFunction( void )
{
 YourStuct* s;
 FILE* fp;

 s = new YourStuct [20];
 fp = fopen( "yourfile", "rb" );
 fread( s, sizeof(YourStuct), 20, fp );
 fclose( fp );

// do wht you want with s

 delete s;
}
0
 
LVL 1

Accepted Solution

by:
shappir earned 50 total points
ID: 1164602
Hi,

You can read a block directly from an ifstream.
First you probably want to open it in binary mode (using the ios::binary flag) as at appears from your question that you want to read the data as bytes not as text.
Use the get() member function to perform the acctual read operation:

char buffer[SIZE];
ifstream if("data.dat", ios::in | ios::binary);
if.get(buffer, sizeof(buffer));

Note:
1. If didn't check that the file was opened OK to make the code simpler.
2. No need to explicitly close the file -- the stream's destructor does that for you.
 

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