import std.stdio;
import std.file;
import std.string;

// Reading files requires checking most calls for errors.
// This helper will streamline our error checks below.
void check(string msg)
{
    if (msg)
    {
        throw new Exception(msg);
    }
}

void main()
{
    // Perhaps the most basic file reading task is
    // slurping a file's entire contents into memory.
    string dat = readText("/tmp/dat");
    writeln(dat);

    // You'll often want more control over how and what
    // parts of a file are read. For these tasks, start
    // by opening a file to obtain a File object.
    auto f = File("/tmp/dat", "r");

    // Read some bytes from the beginning of the file.
    // Allow up to 5 to be read but also note how many
    // actually were read.
    char[5] b1;
    auto n1 = f.rawRead(b1);
    writefln("%d bytes: %s", n1.length, n1);

    // You can also seek to a known location in the file
    // and read from there.
    f.seek(6);
    char[2] b2;
    auto n2 = f.rawRead(b2);
    writefln("%d bytes @ %d: %s", n2.length, 6, n2);

    // The std.stdio package provides some functions that may
    // be helpful for file reading. For example, reads
    // like the ones above can be more robustly
    // implemented with readln.
    f.seek(0);
    string line = f.readln();
    writefln("Read line: %s", line.chomp());

    // There is no built-in rewind, but
    // seek(0) accomplishes this.
    f.seek(0);

    // The std.stdio package implements a buffered
    // reader that may be useful both for its efficiency
    // with many small reads and because of the additional
    // reading methods it provides.
    auto r4 = f.byLine();
    writefln("First line: %s", r4.front);

    // Close the file when you're done (usually this would
    // be scheduled immediately after opening with
    // scope(exit)).
    f.close();
}