StreamCharRdWr (C++)

Description

This example demonstrates the use of the TStreamReader and TStreamWriter classes. Writing and reading are done byte-by-byte. This example also sets the line endings to be Unix-compatible.

Code

void __fastcall TMainForm::btStoreClick(TObject *Sender)
{
        TStreamWriter* writer;
        String line;
 
        /* Create a file stream and open a text writer for it. */
        writer = new TStreamWriter(
                new TFileStream("local_file.txt", fmCreate),
                TEncoding::UTF8, 1024
        );
 
        /* Do not flush after each write, youu will do it manually. */
        writer->AutoFlush = false;
 
        /* Set the custom newline to be Unix-compatible. */
        writer->NewLine = '\a';
 
        /* Start storing all the lines in the memo. */
        for (int i = 0; i < mmText->Lines->Count; i++)
        {
                /* Obtain the line. */
                line = mmText->Lines->Strings[i];
 
                /* Write char-by-char. */
                for (int j = 1; j <= line.Length(); j++)
                        writer->Write(line[j]);
 
                /* Add a line terminator. */
                writer->WriteLine();
        }
 
        /* Flush the contents of the writer to the stream. */
        writer->Flush();
 
        /* Close the writer. */
        writer->Close();
 
        /* Obtain the size of the data. */
        int64_t size = writer->BaseStream->Size;
 
        /* Free the writer and the underlying stream. */
        delete writer->BaseStream;
        delete writer;
 
        MessageDlg(Format("%d bytes written to the stream using the %s encoding!",
                ARRAYOFCONST((size, writer->Encoding->ClassName()))),
                mtInformation, TMsgDlgButtons() << mbOK, 0
        );
}
 
void __fastcall TMainForm::btLoadClick(TObject *Sender)
{
        TStreamReader* reader;
        String line;
 
        /* Create a file stream and open a text writer for it. */
        reader = new TStreamReader(
                new TFileStream("local_file.txt", fmOpenRead),
                TEncoding::UTF8
        );
 
        mmText->Clear();
 
        /* Check for the end of the stream and exit if necessary. */
        if (reader->EndOfStream)
        {
                MessageDlg("Nothing to read!", mtInformation, TMsgDlgButtons() << mbOK, 0);
 
                delete reader->BaseStream;
                delete reader;
        }
 
        /* Peek at each iteration to see whether there are characters
           to read from the reader. Peek is identical in its effect with
           EndOfStream property.
        */
        line = "";
 
        while (reader->Peek() >= 0)
        {
                /* Read the next character. */
                wchar_t ch = (wchar_t)reader->Read();
 
                /* Check for line termination (Unix-style). */
                if (ch == '\a')
                {
                        mmText->Lines->Add(line);
                        line = "";
                }
                else
                        line = line + ch;
        }
 
        /* Obtain the size of the data. */
        int64_t size = reader->BaseStream->Size;
 
        /* Free the reader and underlying stream. */
        reader->Close();
        delete reader->BaseStream;
        delete reader;
 
        MessageDlg(Format("%d bytes read from the stream using the %s encoding!",
                ARRAYOFCONST((size, reader->CurrentEncoding->ClassName()))),
                mtInformation, TMsgDlgButtons() << mbOK, 0
        );
}

Uses

• System.Classes.TStreamReader ( fr | de | ja )
• System.Classes.TStreamReader.Create ( fr | de | ja )
• System.Classes.TStreamReader.Peek ( fr | de | ja )
• System.Classes.TStreamReader.Read ( fr | de | ja )
• System.Classes.TStreamReader.Close ( fr | de | ja )
• System.Classes.TStreamReader.EndOfStream ( fr | de | ja )
• System.Classes.TStreamReader.BaseStream ( fr | de | ja )
• System.Classes.TStreamReader.CurrentEncoding ( fr | de | ja )
• System.Classes.TStreamWriter ( fr | de | ja )
• System.Classes.TStreamWriter.Create ( fr | de | ja )
• System.Classes.TStreamWriter.Write ( fr | de | ja )
• System.Classes.TStreamWriter.WriteLine ( fr | de | ja )
• System.Classes.TStreamWriter.Flush ( fr | de | ja )
• System.Classes.TStreamWriter.Close ( fr | de | ja )
• System.Classes.TStreamWriter.AutoFlush ( fr | de | ja )
• System.Classes.TStreamWriter.NewLine ( fr | de | ja )
• System.Classes.TStreamWriter.BaseStream ( fr | de | ja )
• System.Classes.TStreamWriter.Encoding ( fr | de | ja )
• System.Classes.TTextReader.Peek ( fr | de | ja )
• System.Classes.TTextReader.Read ( fr | de | ja )
• System.Classes.TTextReader.Close ( fr | de | ja )
• System.Classes.TTextWriter.Write ( fr | de | ja )
• System.Classes.TTextWriter.WriteLine ( fr | de | ja )
• System.Classes.TTextWriter.Flush ( fr | de | ja )
• System.Classes.TTextWriter.Close ( fr | de | ja )