abnf: a skeleton for an ABNF parser

1 files changed, 37 insertions, 0 deletions

diff --git a/grammar/src/abnf.rs b/grammar/src/abnf.rs
new file mode 100644
index 0000000..00bc0b2
--- /dev/null
+++ b/grammar/src/abnf.rs
@@ -0,0 +1,37 @@
+//! This file implements the function to read a grammar from a string,
+//! in the [augmented Backus Naur
+//! form][https://en.wikipedia.org/wiki/Augmented_Backus–Naur_form].
+//! See [RFC5234][https://www.rfc-editor.org/rfc/rfc5234] for its
+//! specifications.
+//!
+//! In fact, the rules of ABNF are considered to be too strict.  For
+//! example, only ASCII characters are allowed in the format, even
+//! within comments.  I think any character should be allowed within
+//! comments, so the implementation here does that.
+
+use super::*;
+
+/// The type of errors encountered during parsing a grammar in the
+/// ABNF format.  See the function [`abnf_to_grammar`] for the parsing
+/// function.
+#[derive(Debug, Clone, Copy)]
+pub enum Error {
+    /// Something invalid has occurred.
+    Invalid,
+}
+
+impl core::fmt::Display for Error {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Error::Invalid => write!(f, "invalid"),
+        }
+    }
+}
+
+#[allow(unused)]
+/// This function converts a string to a grammar.
+pub fn abnf_to_grammar(str: impl AsRef<str>) -> Result<Grammar, Error> {
+    let str = str.as_ref();
+
+    todo!()
+}