1 files changed, 94 insertions, 0 deletions
diff --git a/third_party/rust/leb128/src/bin/leb128-repl.rs b/third_party/rust/leb128/src/bin/leb128-repl.rs
new file mode 100644
index 0000000000..4f6c43e367
--- /dev/null
+++ b/third_party/rust/leb128/src/bin/leb128-repl.rs
@@ -0,0 +1,94 @@
+use leb128;
+
+use std::io::{self, BufRead, Write};
+use std::str;
+
+fn display(bytes: &[u8]) -> String {
+    let mut s = vec![];
+
+    // Base 10.
+    write!(&mut s, "{:?}\n", bytes).unwrap();
+
+    // Hex.
+    write!(&mut s, "[").unwrap();
+    for (i, b) in bytes.iter().enumerate() {
+        if i != 0 {
+            write!(&mut s, ", ").unwrap();
+        }
+        write!(&mut s, "{:0x}", b).unwrap();
+    }
+    writeln!(&mut s, "]").unwrap();
+
+    // Binary.
+    write!(&mut s, "[").unwrap();
+    for (i, b) in bytes.iter().enumerate() {
+        if i != 0 {
+            write!(&mut s, ", ").unwrap();
+        }
+        write!(&mut s, "{:08b}", b).unwrap();
+    }
+    writeln!(&mut s, "]").unwrap();
+
+    String::from_utf8(s).unwrap()
+}
+
+fn main() {
+    println!(
+        "
+LEB128 Read-Eval-Print-Loop!
+
+Converts numbers to signed and unsigned LEB128 and displays the results in
+base-10, hex, and binary.
+"
+    );
+
+    let mut stdin = io::BufReader::new(io::stdin());
+    let mut stdout = io::stdout();
+
+    let mut buf = vec![];
+
+    loop {
+        stdout.write_all(b"> ").expect("failed to write to stdout");
+        stdout.flush().expect("failed to flush stdout");
+
+        buf.clear();
+        let n = stdin
+            .read_until(b'\n', &mut buf)
+            .expect("failed to read line from stdin");
+        if n == 0 {
+            break;
+        }
+
+        let uleb = str::from_utf8(&buf)
+            .ok()
+            .and_then(|s| s.trim().parse().ok())
+            .and_then(|n: u64| {
+                let mut s = vec![];
+                leb128::write::unsigned(&mut s, n).ok()?;
+                Some(display(&s))
+            })
+            .unwrap_or_else(|| "error\n".into());
+        stdout
+            .write_all(b"# unsigned LEB128\n")
+            .and_then(|_| stdout.write_all(uleb.as_bytes()))
+            .and_then(|_| stdout.write_all(b"\n"))
+            .expect("failed to write to stdout");
+
+        let leb = str::from_utf8(&buf)
+            .ok()
+            .and_then(|s| s.trim().parse().ok())
+            .and_then(|n: i64| {
+                let mut s = vec![];
+                leb128::write::signed(&mut s, n).ok()?;
+                Some(display(&s))
+            })
+            .unwrap_or_else(|| "error\n".into());
+        stdout
+            .write_all(b"# signed LEB128\n")
+            .and_then(|_| stdout.write_all(leb.as_bytes()))
+            .and_then(|_| stdout.write_all(b"\n"))
+            .expect("failed to write to stdout");
+
+        stdout.flush().expect("failed to flush stdout");
+    }
+}