Top: Streams: Examples

Example 1. This simple program creates a new file and writes a string to it.

#include <pstreams.h>

USING_PTYPES

int main() 
{
    // the outfile object is declared and constructed outside 
    // the try...catch clause, since the exception object
    // contains a reference to the stream that caused the error.
    // besides, stream constructors and destructors in PTypes 
    // never throw exceptions.
    outfile f(fname);

    f.set_bufsize(1024);             // the default value in this version is 8192

    try 
    {
        f.open();
        f.put("This is a test file.");
        f.close();
    }
    catch (estream* e) 
    {
        perr.putf("File error: %s\n", e->get_message());
        delete e;
    }
    return 0;
}

Example 2. This program reads a C source, extracts identifiers and builds a usage dictionary. It does not understand C comments and strings though, but can be easily improved to understand them too.

#include <ptypes.h>
#include <pstreams.h>

USING_PTYPES

const cset letters("_A-Za-z");
const cset digits("0-9");
const cset identchars = letters + digits;
const cset otherchars = !letters;

void main(int argc, char* argv[]) 
{
    strlist dic(SL_SORTED);

    infile f(argv[1]);

    try 
    {
        f.open();

        while (!f.get_eof()) 
        {
            char c = f.preview();

            // a C identifier begins with a letter
            if (c & letters)
            {
                // ... and may contain letters and digits
                string ident = f.token(identchars);
                int i;
                if (!search(dic, ident, i))
                    add(dic, ident, 0);
            }

            else
                // ignore everything else
                f.skiptoken(otherchars);
        }

    }

    catch (estream* e) 
    {
        pout.putf("Error: %s\n", e->get_message());
        delete e;
    }

    // now print the dictionary
    for (int i = 0; i < length(dic); i++)
        pout.putline(getstr(dic, i));
}

See also: iobase, instm, infile, outstm, outfile, Error handling