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Messing up stringstream

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Join Date: May 2008

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Clockowl

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Posting Whiz

Messing up stringstream

May 27th, 2009

Hey guys,

Below code isn't working as I expect it to do. I expect it to read all params when 6 are given, buuuuuuuuuuuut it only reads one, the rest remains zero. It does enter the case, but the stringstream buf seems empty. What am I doing wrong?

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;
 
#define SCREAM cout << "OMAGAWD" << endl
 
int main(int argc, char *argv[])
{
//    <src> <dest> [<offset> [<bytes, 0 = all> [<offset>]]
    //writes bytes bytes from src+offset to dest+offset
 
    size_t in_offset;
    size_t bytes;
    size_t out_offset;
 
    in_offset = bytes = out_offset = 0;
 
    stringstream buf;
 
    switch (argc)
    {
    case 6:
    SCREAM;
        buf.str(argv[5]);
        buf >> out_offset;
 
    case 5:
    SCREAM;
        buf.str(argv[4]);
        buf >> bytes;
 
    case 4:
    SCREAM;
        buf.str(argv[3]);
        buf >> in_offset;
 
    default:
        ifstream in(argv[1], ios::binary);
        ofstream out(argv[2], ios::binary);
        break;
    }
 
    cout << "Writing from " << argv[1] << " + " << in_offset <<  " to " << argv[2] << " + " << out_offset << " for " << bytes << " bytes" << endl;
 
    return 0;
}
#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;

#define SCREAM cout << "OMAGAWD" << endl

int main(int argc, char *argv[])
{
//    <src> <dest> [<offset> [<bytes, 0 = all> [<offset>]]
    //writes bytes bytes from src+offset to dest+offset

    size_t in_offset;
    size_t bytes;
    size_t out_offset;

    in_offset = bytes = out_offset = 0;

    stringstream buf;

    switch (argc)
    {
    case 6:
    SCREAM;
        buf.str(argv[5]);
        buf >> out_offset;

    case 5:
    SCREAM;
        buf.str(argv[4]);
        buf >> bytes;

    case 4:
    SCREAM;
        buf.str(argv[3]);
        buf >> in_offset;

    default:
        ifstream in(argv[1], ios::binary);
        ofstream out(argv[2], ios::binary);
        break;
    }

    cout << "Writing from " << argv[1] << " + " << in_offset <<  " to " << argv[2] << " + " << out_offset << " for " << bytes << " bytes" << endl;

    return 0;
}

Example params:

program.exe aap noot 1 2 3
example output:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
OMAGAWD
OMAGAWD
OMAGAWD
Writing from aap + 0 to noot + 3 for 0 bytes
OMAGAWD
OMAGAWD
OMAGAWD
Writing from aap + 0 to noot + 3 for 0 bytes

Thanks in advance,

Last edited by Clockowl; May 27th, 2009 at 6:08 pm.

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Narue

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Code Goddess

Re: Messing up stringstream

May 27th, 2009

The state of the stream and the contents of the buffer are separate. Even though you reset the buffer to a new string, the stream is still in an end-of-file state from the previous read.

You'll notice that out_offset is correctly set to 3 because the stream starts off in a good state when you create it. But the first time you read to the end of the initial buffer, the eofbit is set and changing the contents of the buffer won't make a difference.

Do a buf.clear(); to reset the stream state.

I'm here to prove you wrong.