1 files changed, 38 insertions, 0 deletions
diff --git a/third_party/rust/headers/src/util/csv.rs b/third_party/rust/headers/src/util/csv.rs
new file mode 100644
index 0000000000..2d0a8ed68d
--- /dev/null
+++ b/third_party/rust/headers/src/util/csv.rs
@@ -0,0 +1,38 @@
+use std::fmt;
+
+/// Reads a comma-delimited raw header into a Vec.
+pub(crate) fn from_comma_delimited<'i, I, T, E>(values: &mut I) -> Result<E, ::Error>
+where
+    I: Iterator<Item = &'i ::HeaderValue>,
+    T: ::std::str::FromStr,
+    E: ::std::iter::FromIterator<T>,
+{
+    values
+        .flat_map(|value| {
+            value.to_str().into_iter().flat_map(|string| {
+                string
+                    .split(',')
+                    .filter_map(|x| match x.trim() {
+                        "" => None,
+                        y => Some(y),
+                    })
+                    .map(|x| x.parse().map_err(|_| ::Error::invalid()))
+            })
+        })
+        .collect()
+}
+
+/// Format an array into a comma-delimited string.
+pub(crate) fn fmt_comma_delimited<T: fmt::Display>(
+    f: &mut fmt::Formatter,
+    mut iter: impl Iterator<Item = T>,
+) -> fmt::Result {
+    if let Some(part) = iter.next() {
+        fmt::Display::fmt(&part, f)?;
+    }
+    for part in iter {
+        f.write_str(", ")?;
+        fmt::Display::fmt(&part, f)?;
+    }
+    Ok(())
+}