Bounds checks for bistream_restriction fields

Fixes #55

Cargo.toml

@@ -16,6 +16,7 @@ hex-slice = "0.1.4"
 memchr = "2.1.1"
 rfc6381-codec = "0.1"
 log = "0.4"
+lazy_static = "1.4"
 
 [dev-dependencies]
 hex-literal = "0.4.1"

src/lib.rs

@@ -3,6 +3,7 @@
 #![forbid(unsafe_code)]
 #![deny(rust_2018_idioms)]
 
+use crate::rbsp::BitReaderError;
 use std::fmt::Debug;
 
 pub mod annexb;
@@ -85,6 +86,45 @@ impl<T: Debug> Debug for ParamSetMap<T> {
     }
 }
 
+#[derive(Debug)]
+pub enum FieldErr {
+    TooLarge { value: u32, max_value: u32 },
+    TooSmall { value: u32, min_value: u32 },
+    BitReader(BitReaderError),
+}
+
+trait U32Field {
+    fn max(self, max_value: u32) -> Result<u32, FieldErr>;
+    fn min(self, min_value: u32) -> Result<u32, FieldErr>;
+}
+impl U32Field for Result<u32, BitReaderError> {
+    fn max(self, max_value: u32) -> Result<u32, FieldErr> {
+        match self {
+            Ok(value) => {
+                if value > max_value {
+                    Err(FieldErr::TooLarge { value, max_value })
+                } else {
+                    Ok(value)
+                }
+            }
+            Err(e) => Err(FieldErr::BitReader(e)),
+        }
+    }
+
+    fn min(self, min_value: u32) -> Result<u32, FieldErr> {
+        match self {
+            Ok(value) => {
+                if value < min_value {
+                    Err(FieldErr::TooSmall { value, min_value })
+                } else {
+                    Ok(value)
+                }
+            }
+            Err(e) => Err(FieldErr::BitReader(e)),
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     #[test]