Writing Files: Hare by Example

use bufio;
use crypto::random;
use encoding::hex;
use io;
use fmt;
use fs;
use os;
use strings;

export fn main() void = {
	// We create a brand new file in a temporary location. We also
	// specify appropriate permissions from the fs::mode enum.
	const handle = os::create("/tmp/writing-files.txt",
		fs::mode::USER_RW)!;

	const data: []u8 = strings::toutf8("hello\nhare\n");
	io::write(handle, data)!;

	const nonascii: []u8 = [2, 233, 10, 113, 13];
	io::write(handle, nonascii)!;

	// Set up read and write buffers, but since we're only writing
	// our read buffer is just an empty slice.
	let rbuf: []u8 = [];
	let wbuf: [os::BUFSZ]u8 = [0...];
	const buf = bufio::init(handle, rbuf, wbuf);

	// This will set the write buffer to an empty slice when we
	// flush all current writes to the underlying handle of the
	// buffer. In our case here, it is the file handle.
	bufio::setflush(&buf, []);

	// Generate a bunch of random bytes to write with.
	let rand: [100]u8 = [0...];
	random::buffer(rand[..]);

	io::write(&buf, rand[..])!;
	io::write(&buf, rand[..])!;
	io::write(&buf, rand[..])!;

	// Let's flush all those writes to the file. If we do not do
	// this and our program exits the data will be lost since it is
	// only in memory at this point.
	bufio::flush(&buf)!;

	// Let's close the file so we can open it and dump the contents.
	io::close(handle)!;

	const reader = os::open("/tmp/writing-files.txt")!;
	defer io::close(reader)!;

	// Set up our normal read buffer.
	let buf: [os::BUFSZ]u8 = [0...];

	// Force read to return the bytes written. We panic on error
	// with ! and ignore the EOF with ensuring we get a size back.
	const sz = io::read(reader, buf)! as size;

	fmt::println("Bytes read", sz)!;

	// We just dump the file contents as hex to see its contents.
	hex::dump(os::stdout, buf[..sz])!;
};

$ hare run writing-files.ha
4/4 tasks completed (100%)
Bytes read 316
00000000  68 65 6c 6c 6f 0a 68 61  72 65 0a 02 e9 0a 71 0d  |hello.hare....q.|
00000010  92 2a a9 e1 90 59 30 9e  d1 c2 27 80 1b be 3d 35  |.*...Y0...'...=5|
00000020  cf 5a 91 dc 71 4a e1 f8  3c 57 41 70 7c 27 bd 5e  |.Z..qJ..<WAp|'.^|
00000030  0e 47 96 cd 2c e5 48 13  b6 d8 09 dc 08 90 23 a3  |.G..,.H.......#.|
00000040  26 7a 65 f6 7c d3 0b f4  31 94 9b 66 9b c4 f3 29  |&ze.|...1..f...)|
00000050  73 37 6b 30 e2 f0 1f 12  d5 75 78 2a 74 82 91 0e  |s7k0.....ux*t...|
00000060  b1 51 ed af 3b 31 cd b2  d0 05 c7 aa 93 a8 ac b4  |.Q..;1..........|
00000070  35 75 ae d6 92 2a a9 e1  90 59 30 9e d1 c2 27 80  |5u...*...Y0...'.|
00000080  1b be 3d 35 cf 5a 91 dc  71 4a e1 f8 3c 57 41 70  |..=5.Z..qJ..<WAp|
00000090  7c 27 bd 5e 0e 47 96 cd  2c e5 48 13 b6 d8 09 dc  ||'.^.G..,.H.....|
000000a0  08 90 23 a3 26 7a 65 f6  7c d3 0b f4 31 94 9b 66  |..#.&ze.|...1..f|
000000b0  9b c4 f3 29 73 37 6b 30  e2 f0 1f 12 d5 75 78 2a  |...)s7k0.....ux*|
000000c0  74 82 91 0e b1 51 ed af  3b 31 cd b2 d0 05 c7 aa  |t....Q..;1......|
000000d0  93 a8 ac b4 35 75 ae d6  92 2a a9 e1 90 59 30 9e  |....5u...*...Y0.|
000000e0  d1 c2 27 80 1b be 3d 35  cf 5a 91 dc 71 4a e1 f8  |..'...=5.Z..qJ..|
000000f0  3c 57 41 70 7c 27 bd 5e  0e 47 96 cd 2c e5 48 13  |<WAp|'.^.G..,.H.|
00000100  b6 d8 09 dc 08 90 23 a3  26 7a 65 f6 7c d3 0b f4  |......#.&ze.|...|
00000110  31 94 9b 66 9b c4 f3 29  73 37 6b 30 e2 f0 1f 12  |1..f...)s7k0....|
00000120  d5 75 78 2a 74 82 91 0e  b1 51 ed af 3b 31 cd b2  |.ux*t....Q..;1..|
00000130  d0 05 c7 aa 93 a8 ac b4  35 75 ae d6              |........5u..|

Hare by Example: Writing Files