fix some subbuffer end handling

src/readbuffer.rs

@@ -910,7 +910,8 @@ where
             bytes: self.bytes.clone(),
             bit_len,
             endianness: PhantomData,
-            slice: self.slice,
+            // SAFETY: we've done our bounds check above
+            slice: unsafe { self.slice.get_unchecked(0..bit_len.div_ceil(8)) },
         })
     }
 

src/readstream.rs

@@ -446,29 +446,9 @@ where
         let str = result.as_ref(output);
         let read = match byte_len {
             Some(len) => len * 8,
-            None => (str.len() + 1) * 8,
+            None => (str.len() + 1).min(max_length) * 8,
         };
 
-        // due to how sub buffer/streams work, the result string can be longer than the current stream
-        // (but not the top level buffer)
-        // thus we trim the resulting string to make sure it fits in the source stream
-        if read > self.bits_left() {
-            let mut target_length = str.len().min(max_length);
-            // find the closest char boundary
-            while !str.is_char_boundary(target_length) {
-                target_length -= 1;
-            }
-
-            let trimmed = match result {
-                MaybeBorrowed::Owned => {
-                    output.truncate(target_length);
-                    MaybeBorrowed::Owned
-                }
-                MaybeBorrowed::Borrowed(s) => MaybeBorrowed::Borrowed(&s[0..target_length]),
-            };
-            self.pos += target_length * 8;
-            return Ok(trimmed);
-        }
         self.pos += read;
         Ok(result)
     }

tests/read_tests.rs

@@ -3,7 +3,9 @@ use std::num::NonZeroU16;
 
 use maplit::hashmap;
 
-use bitbuffer::{BigEndian, BitError, BitRead, BitReadBuffer, BitReadStream, LittleEndian};
+use bitbuffer::{
+    BigEndian, BitError, BitRead, BitReadBuffer, BitReadStream, BitWriteStream, LittleEndian,
+};
 
 const BYTES: &[u8] = &[
     0b1011_0101,
@@ -519,3 +521,19 @@ fn test_invalid_utf8() {
 
     assert_eq!(stream.pos(), 6 * 8);
 }
+
+#[test]
+fn test_read_string_substream() {
+    let mut data = Vec::new();
+    {
+        let mut write = BitWriteStream::new(&mut data, LittleEndian);
+        write.write_int(3u32, 3).unwrap();
+        write.write_string("dummy content", None).unwrap();
+    }
+    let mut stream = BitReadStream::<LittleEndian>::from(data.as_slice());
+    let _ = stream.read_int::<u8>(3).unwrap();
+    let mut sub = stream.read_bits(5 * 8).unwrap();
+    let result = sub.read_string(None).unwrap();
+    assert_eq!("dummy", result);
+    assert_eq!(5 * 8, sub.pos());
+}