1use super::encoder::EncoderWriter;
2use crate::engine::Engine;
3use std::io;
4
5/// A `Write` implementation that base64-encodes data using the provided config and accumulates the
6/// resulting base64 utf8 `&str` in a [StrConsumer] implementation (typically `String`), which is
7/// then exposed via `into_inner()`.
8///
9/// # Examples
10///
11/// Buffer base64 in a new String:
12///
13/// ```
14/// use std::io::Write;
15/// use base64::engine::general_purpose;
16///
17/// let mut enc = base64::write::EncoderStringWriter::new(&general_purpose::STANDARD);
18///
19/// enc.write_all(b"asdf").unwrap();
20///
21/// // get the resulting String
22/// let b64_string = enc.into_inner();
23///
24/// assert_eq!("YXNkZg==", &b64_string);
25/// ```
26///
27/// Or, append to an existing `String`, which implements `StrConsumer`:
28///
29/// ```
30/// use std::io::Write;
31/// use base64::engine::general_purpose;
32///
33/// let mut buf = String::from("base64: ");
34///
35/// let mut enc = base64::write::EncoderStringWriter::from_consumer(
36/// &mut buf,
37/// &general_purpose::STANDARD);
38///
39/// enc.write_all(b"asdf").unwrap();
40///
41/// // release the &mut reference on buf
42/// let _ = enc.into_inner();
43///
44/// assert_eq!("base64: YXNkZg==", &buf);
45/// ```
46///
47/// # Panics
48///
49/// Calling `write()` (or related methods) or `finish()` after `finish()` has completed without
50/// error is invalid and will panic.
51///
52/// # Performance
53///
54/// Because it has to validate that the base64 is UTF-8, it is about 80% as fast as writing plain
55/// bytes to a `io::Write`.
56pub struct EncoderStringWriter<'e, E: Engine, S: StrConsumer> {
57 encoder: EncoderWriter<'e, E, Utf8SingleCodeUnitWriter<S>>,
58}
59
60impl<'e, E: Engine, S: StrConsumer> EncoderStringWriter<'e, E, S> {
61 /// Create a EncoderStringWriter that will append to the provided `StrConsumer`.
62 pub fn from_consumer(str_consumer: S, engine: &'e E) -> Self {
63 EncoderStringWriter {
64 encoder: EncoderWriter::new(delegate:Utf8SingleCodeUnitWriter { str_consumer }, engine),
65 }
66 }
67
68 /// Encode all remaining buffered data, including any trailing incomplete input triples and
69 /// associated padding.
70 ///
71 /// Returns the base64-encoded form of the accumulated written data.
72 pub fn into_inner(mut self) -> S {
73 self.encoder
74 .finish()
75 .expect(msg:"Writing to a consumer should never fail")
76 .str_consumer
77 }
78}
79
80impl<'e, E: Engine> EncoderStringWriter<'e, E, String> {
81 /// Create a EncoderStringWriter that will encode into a new `String` with the provided config.
82 pub fn new(engine: &'e E) -> Self {
83 EncoderStringWriter::from_consumer(str_consumer:String::new(), engine)
84 }
85}
86
87impl<'e, E: Engine, S: StrConsumer> io::Write for EncoderStringWriter<'e, E, S> {
88 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
89 self.encoder.write(buf)
90 }
91
92 fn flush(&mut self) -> io::Result<()> {
93 self.encoder.flush()
94 }
95}
96
97/// An abstraction around consuming `str`s produced by base64 encoding.
98pub trait StrConsumer {
99 /// Consume the base64 encoded data in `buf`
100 fn consume(&mut self, buf: &str);
101}
102
103/// As for io::Write, `StrConsumer` is implemented automatically for `&mut S`.
104impl<S: StrConsumer + ?Sized> StrConsumer for &mut S {
105 fn consume(&mut self, buf: &str) {
106 (**self).consume(buf);
107 }
108}
109
110/// Pushes the str onto the end of the String
111impl StrConsumer for String {
112 fn consume(&mut self, buf: &str) {
113 self.push_str(string:buf);
114 }
115}
116
117/// A `Write` that only can handle bytes that are valid single-byte UTF-8 code units.
118///
119/// This is safe because we only use it when writing base64, which is always valid UTF-8.
120struct Utf8SingleCodeUnitWriter<S: StrConsumer> {
121 str_consumer: S,
122}
123
124impl<S: StrConsumer> io::Write for Utf8SingleCodeUnitWriter<S> {
125 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
126 // Because we expect all input to be valid utf-8 individual bytes, we can encode any buffer
127 // length
128 let s: &str = std::str::from_utf8(buf).expect(msg:"Input must be valid UTF-8");
129
130 self.str_consumer.consume(buf:s);
131
132 Ok(buf.len())
133 }
134
135 fn flush(&mut self) -> io::Result<()> {
136 // no op
137 Ok(())
138 }
139}
140
141#[cfg(test)]
142mod tests {
143 use crate::{
144 engine::Engine, tests::random_engine, write::encoder_string_writer::EncoderStringWriter,
145 };
146 use rand::Rng;
147 use std::io::Write;
148
149 #[test]
150 fn every_possible_split_of_input() {
151 let mut rng = rand::thread_rng();
152 let mut orig_data = Vec::<u8>::new();
153 let mut normal_encoded = String::new();
154
155 let size = 5_000;
156
157 for i in 0..size {
158 orig_data.clear();
159 normal_encoded.clear();
160
161 for _ in 0..size {
162 orig_data.push(rng.gen());
163 }
164
165 let engine = random_engine(&mut rng);
166 engine.encode_string(&orig_data, &mut normal_encoded);
167
168 let mut stream_encoder = EncoderStringWriter::new(&engine);
169 // Write the first i bytes, then the rest
170 stream_encoder.write_all(&orig_data[0..i]).unwrap();
171 stream_encoder.write_all(&orig_data[i..]).unwrap();
172
173 let stream_encoded = stream_encoder.into_inner();
174
175 assert_eq!(normal_encoded, stream_encoded);
176 }
177 }
178}
179