1 files changed, 83 insertions, 0 deletions
diff --git a/third_party/rust/unic-langid-impl/src/parser/mod.rs b/third_party/rust/unic-langid-impl/src/parser/mod.rs
new file mode 100644
index 0000000000..d750ebba98
--- /dev/null
+++ b/third_party/rust/unic-langid-impl/src/parser/mod.rs
@@ -0,0 +1,83 @@
+pub mod errors;
+
+use std::iter::Peekable;
+
+pub use self::errors::ParserError;
+use crate::subtags;
+use crate::LanguageIdentifier;
+
+pub fn parse_language_identifier_from_iter<'a>(
+    iter: &mut Peekable<impl Iterator<Item = &'a [u8]>>,
+    allow_extension: bool,
+) -> Result<LanguageIdentifier, ParserError> {
+    let language = if let Some(subtag) = iter.next() {
+        subtags::Language::from_bytes(subtag)?
+    } else {
+        subtags::Language::default()
+    };
+
+    let mut script = None;
+    let mut region = None;
+    let mut variants = vec![];
+
+    let mut position = 1;
+
+    while let Some(subtag) = iter.peek() {
+        if position == 1 {
+            if let Ok(s) = subtags::Script::from_bytes(subtag) {
+                script = Some(s);
+                position = 2;
+            } else if let Ok(s) = subtags::Region::from_bytes(subtag) {
+                region = Some(s);
+                position = 3;
+            } else if let Ok(v) = subtags::Variant::from_bytes(subtag) {
+                variants.push(v);
+                position = 3;
+            } else {
+                break;
+            }
+        } else if position == 2 {
+            if let Ok(s) = subtags::Region::from_bytes(subtag) {
+                region = Some(s);
+                position = 3;
+            } else if let Ok(v) = subtags::Variant::from_bytes(subtag) {
+                variants.push(v);
+                position = 3;
+            } else {
+                break;
+            }
+        } else {
+            // Variants
+            if let Ok(v) = subtags::Variant::from_bytes(subtag) {
+                variants.push(v);
+            } else {
+                break;
+            }
+        }
+        iter.next();
+    }
+
+    if !allow_extension && iter.peek().is_some() {
+        return Err(ParserError::InvalidSubtag);
+    }
+
+    let variants = if variants.is_empty() {
+        None
+    } else {
+        variants.sort_unstable();
+        variants.dedup();
+        Some(variants.into_boxed_slice())
+    };
+
+    Ok(LanguageIdentifier {
+        language,
+        script,
+        region,
+        variants,
+    })
+}
+
+pub fn parse_language_identifier(t: &[u8]) -> Result<LanguageIdentifier, ParserError> {
+    let mut iter = t.split(|c| *c == b'-' || *c == b'_').peekable();
+    parse_language_identifier_from_iter(&mut iter, false)
+}