1 files changed, 129 insertions, 0 deletions
diff --git a/third_party/rust/nom/src/bits/streaming.rs b/third_party/rust/nom/src/bits/streaming.rs
new file mode 100644
index 0000000000..e8adc1c0d4
--- /dev/null
+++ b/third_party/rust/nom/src/bits/streaming.rs
@@ -0,0 +1,129 @@
+//! Bit level parsers
+//!
+
+use crate::error::{ErrorKind, ParseError};
+use crate::internal::{Err, IResult, Needed};
+use crate::lib::std::ops::{AddAssign, Div, RangeFrom, Shl, Shr};
+use crate::traits::{InputIter, InputLength, Slice, ToUsize};
+
+/// Generates a parser taking `count` bits
+pub fn take<I, O, C, E: ParseError<(I, usize)>>(
+  count: C,
+) -> impl Fn((I, usize)) -> IResult<(I, usize), O, E>
+where
+  I: Slice<RangeFrom<usize>> + InputIter<Item = u8> + InputLength,
+  C: ToUsize,
+  O: From<u8> + AddAssign + Shl<usize, Output = O> + Shr<usize, Output = O>,
+{
+  let count = count.to_usize();
+  move |(input, bit_offset): (I, usize)| {
+    if count == 0 {
+      Ok(((input, bit_offset), 0u8.into()))
+    } else {
+      let cnt = (count + bit_offset).div(8);
+      if input.input_len() * 8 < count + bit_offset {
+        Err(Err::Incomplete(Needed::new(count as usize)))
+      } else {
+        let mut acc: O = 0_u8.into();
+        let mut offset: usize = bit_offset;
+        let mut remaining: usize = count;
+        let mut end_offset: usize = 0;
+
+        for byte in input.iter_elements().take(cnt + 1) {
+          if remaining == 0 {
+            break;
+          }
+          let val: O = if offset == 0 {
+            byte.into()
+          } else {
+            ((byte << offset) as u8 >> offset).into()
+          };
+
+          if remaining < 8 - offset {
+            acc += val >> (8 - offset - remaining);
+            end_offset = remaining + offset;
+            break;
+          } else {
+            acc += val << (remaining - (8 - offset));
+            remaining -= 8 - offset;
+            offset = 0;
+          }
+        }
+        Ok(((input.slice(cnt..), end_offset), acc))
+      }
+    }
+  }
+}
+
+/// Generates a parser taking `count` bits and comparing them to `pattern`
+pub fn tag<I, O, C, E: ParseError<(I, usize)>>(
+  pattern: O,
+  count: C,
+) -> impl Fn((I, usize)) -> IResult<(I, usize), O, E>
+where
+  I: Slice<RangeFrom<usize>> + InputIter<Item = u8> + InputLength + Clone,
+  C: ToUsize,
+  O: From<u8> + AddAssign + Shl<usize, Output = O> + Shr<usize, Output = O> + PartialEq,
+{
+  let count = count.to_usize();
+  move |input: (I, usize)| {
+    let inp = input.clone();
+
+    take(count)(input).and_then(|(i, o)| {
+      if pattern == o {
+        Ok((i, o))
+      } else {
+        Err(Err::Error(error_position!(inp, ErrorKind::TagBits)))
+      }
+    })
+  }
+}
+
+#[cfg(test)]
+mod test {
+  use super::*;
+
+  #[test]
+  fn test_take_0() {
+    let input = [].as_ref();
+    let count = 0usize;
+    assert_eq!(count, 0usize);
+    let offset = 0usize;
+
+    let result: crate::IResult<(&[u8], usize), usize> = take(count)((input, offset));
+
+    assert_eq!(result, Ok(((input, offset), 0)));
+  }
+
+  #[test]
+  fn test_tag_ok() {
+    let input = [0b00011111].as_ref();
+    let offset = 0usize;
+    let bits_to_take = 4usize;
+    let value_to_tag = 0b0001;
+
+    let result: crate::IResult<(&[u8], usize), usize> =
+      tag(value_to_tag, bits_to_take)((input, offset));
+
+    assert_eq!(result, Ok(((input, bits_to_take), value_to_tag)));
+  }
+
+  #[test]
+  fn test_tag_err() {
+    let input = [0b00011111].as_ref();
+    let offset = 0usize;
+    let bits_to_take = 4usize;
+    let value_to_tag = 0b1111;
+
+    let result: crate::IResult<(&[u8], usize), usize> =
+      tag(value_to_tag, bits_to_take)((input, offset));
+
+    assert_eq!(
+      result,
+      Err(crate::Err::Error(crate::error::Error {
+        input: (input, offset),
+        code: ErrorKind::TagBits
+      }))
+    );
+  }
+}