Restructure the native module

Consolidate all code into the src folder

native/src/base/misc.rs

@@ -0,0 +1,41 @@
+use std::cmp::min;
+use std::fmt;
+use std::fmt::Arguments;
+
+struct BufFmtWriter<'a> {
+    buf: &'a mut [u8],
+    used: usize,
+}
+
+impl<'a> BufFmtWriter<'a> {
+    fn new(buf: &'a mut [u8]) -> Self {
+        BufFmtWriter { buf, used: 0 }
+    }
+}
+
+impl<'a> fmt::Write for BufFmtWriter<'a> {
+    // The buffer should always be null terminated
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        if self.used >= self.buf.len() - 1 {
+            // Silent truncate
+            return Ok(());
+        }
+        let remain = &mut self.buf[self.used..];
+        let s_bytes = s.as_bytes();
+        let copied = min(s_bytes.len(), remain.len() - 1);
+        remain[..copied].copy_from_slice(&s_bytes[..copied]);
+        self.used += copied;
+        self.buf[self.used] = b'\0';
+        // Silent truncate
+        Ok(())
+    }
+}
+
+pub fn fmt_to_buf(buf: &mut [u8], args: Arguments) -> usize {
+    let mut w = BufFmtWriter::new(buf);
+    if let Ok(()) = fmt::write(&mut w, args) {
+        w.used
+    } else {
+        0
+    }
+}