1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85

// Copyright 2015 Axel Rasmussen
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::fmt;
use std::io;
use std::result;
use std::sync::Mutex;

/// The various `fmt::Write` implementations `bdrck_params` can use to e.g.
/// print out program help information. By default, `bdrck_params` uses Info.
/// This can be changed globally via `set_writer_impl`.
#[derive(Clone)]
pub enum WriterImpl {
    /// Print information to stdout.
    Stdout,
    /// Print information to stderr.
    Stderr,
    /// Log information using info!().
    Info,
    /// Silently discard any output information.
    Noop,
}

fn write_to_io_writer(writer: &mut io::Write, s: &str) -> result::Result<(), fmt::Error> {
    use std::fmt::Write;
    let mut buf = String::new();
    buf.write_str(s)?;
    writer.write_all(&buf.into_bytes()[..]).unwrap();
    Ok(())
}

lazy_static! {
    static ref WRITER_IMPL: Mutex<WriterImpl> = Mutex::new(WriterImpl::Info);
}

/// Change the writer implementation used by all `bdrck_params` functions.
pub fn set_writer_impl(i: WriterImpl) {
    let mut guard = match WRITER_IMPL.lock() {
        Ok(guard) => guard,
        Err(poisoned) => poisoned.into_inner(),
    };
    *guard = i;
}

/// This structure implements `fmt::Write` using one of various implementations
/// described by `WriterImpl`. This structure should generally not be
/// instantiated directly. Instead, callers should use `get_writer_impl`.
pub struct Writer {
    writer_impl: WriterImpl,
}

impl fmt::Write for Writer {
    fn write_str(&mut self, s: &str) -> result::Result<(), fmt::Error> {
        match self.writer_impl {
            WriterImpl::Stdout => write_to_io_writer(&mut io::stdout(), s),
            WriterImpl::Stderr => write_to_io_writer(&mut io::stderr(), s),
            WriterImpl::Info => {
                info!("{}", s);
                Ok(())
            },
            WriterImpl::Noop => Ok(()),
        }
    }
}

/// Return a structure which uses the current global `WriterImpl` to implement
/// `fmt::Write`.
pub fn get_writer_impl() -> Writer {
    let guard = match WRITER_IMPL.lock() {
        Ok(guard) => guard,
        Err(poisoned) => poisoned.into_inner(),
    };
    Writer { writer_impl: (*guard).clone() }
}