Zig test for std.io.StreamSource

stream_source_test.zig

const std = @import("std");
const expect = std.testing.expect;
const io = std.io;

fn copy(dst: *io.StreamSource, src: *io.StreamSource) !usize {
    const r = src.reader();
    const w = dst.writer();
    const BUFSIZE = 512;
    var buf: [BUFSIZE]u8 = undefined;
    var len: usize = BUFSIZE;
    var count: usize = 0;
    while (len == BUFSIZE) {
        len = try r.readAll(&buf);
        try w.writeAll(buf[0..len]);
        count += len;
    }
    return count;
}

fn buf2file(buf: []const u8, filename: []const u8) !usize {
    var f = io.StreamSource{ .file = try std.fs.cwd().createFile(filename, .{}) };
    defer f.file.close();
    var b = io.StreamSource{ .const_buffer = io.fixedBufferStream(buf) };
    return try copy(&f, &b);
}

fn file2buf(filename: []const u8, buf: []u8) !usize {
    var f = io.StreamSource{ .file = try std.fs.cwd().openFile(filename, .{}) };
    defer f.file.close();
    var b = io.StreamSource{ .buffer = io.fixedBufferStream(buf) };
    return try copy(&b, &f);
}

test {
    const str = "Alpha Bravo Charlie Delta Echo Foxtrot Golf Hotel India Juliett Kilo Lima Mike";
    const filename = "tmpfile";
    var buf: [str.len]u8 = undefined;
    try expect(str.len == try buf2file(str, filename));
    try expect(str.len == try file2buf(filename, &buf));
    try expect(std.mem.eql(u8, str, &buf));
}