cli: read data from stdin if no '-i' argument is given

This is especially useful for binary data, which may not survive in an argument
list (e.g. due to the presence of NUL bytes).

The 'encode' and 'decode' commands are now exact inverses of each other, so data
will roundtrip correctly, e.g.

    $ echo "hello world" | ./multibase encode | ./multibase decode

    hello world

    $ echo "hello world" | ./multibase encode | ./multibase decode | ./multibase encode

    z2yGEbwRFyhPZZckJm

    $ echo "hello world" | ./multibase encode

    z2yGEbwRFyhPZZckJm

Author: Warbo

cli/main.rs

@@ -20,24 +20,42 @@ enum Mode {
         /// The base to use for encoding.
         #[structopt(short = "b", long = "base", default_value = "base58btc")]
         base: StrBase,
-        /// The data need to be encoded.
+        /// The data to encode. Reads from stdin if not provided.
         #[structopt(short = "i", long = "input")]
-        input: String,
+        input: Option<String>,
     },
     #[structopt(name = "decode")]
     Decode {
-        /// The data need to be decoded.
+        /// The data to decode. Reads from stdin if not provided.
         #[structopt(short = "i", long = "input")]
-        input: String,
+        input: Option<String>,
     },
 }
 
 fn main() -> Result<()> {
     env_logger::init();
     let opts = Opts::from_args();
     match opts.mode {
-        Mode::Encode { base, input } => encode(base, input.as_bytes()),
-        Mode::Decode { input } => decode(&input),
+        Mode::Encode { base, input } => {
+            let input_bytes = if let Some(s) = input {
+                s.into_bytes()
+            } else {
+                let mut buf = Vec::new();
+                io::stdin().read_to_end(&mut buf)?;
+                buf
+            };
+            encode(base, &input_bytes)
+        }
+        Mode::Decode { input } => {
+            let input_str = if let Some(s) = input {
+                s
+            } else {
+                let mut buf = String::new();
+                io::stdin().read_to_string(&mut buf)?;
+                buf
+            };
+            decode(&input_str)
+        }
     }
 }