Fix bitreader look-ahead overflow

2 files changed, 30 insertions, 0 deletions

diff --git a/tests/tbitreader.nim b/tests/tbitreader.nim
index 8285f63..294f6c9 100644
--- a/tests/tbitreader.nim
+++ b/tests/tbitreader.nim
@@ -49,6 +49,29 @@ suite "bitreader":
     expect IOError: discard bitReader.readBits(16, uint16)
     check bitReader.atEnd()
 
+  test "readBits (look-ahead overflow)":
+    let stream = newStringStream()
+    defer: stream.close()
+    stream.write(0xAB'u8)
+    stream.setPosition(0)
+
+    let bitReader = stream.bitReader()
+    check bitReader.readBits(4, uint16) == 0x000B'u16
+    check bitReader.readBits(4, uint16) == 0x000A'u16
+    check bitReader.atEnd()
+
+  test "readBits (from buffer composition)":
+    let stream = newStringStream()
+    defer: stream.close()
+    stream.write(0xABCD'u16)
+    stream.setPosition(0)
+
+    let bitReader = stream.bitReader()
+    check bitReader.readBits(4, uint16) == 0x000D'u16
+    check bitReader.readBits(8, uint16) == 0x00BC'u16
+    check bitReader.readBits(4, uint16) == 0x000A'u16
+    check bitReader.atEnd()
+
   test "readSeq":
     let stream = newStringStream()
     defer: stream.close()
diff --git a/tests/tintegers.nim b/tests/tintegers.nim
index c77abec..956e4aa 100644
--- a/tests/tintegers.nim
+++ b/tests/tintegers.nim
@@ -27,6 +27,13 @@ suite "integers":
     check truncateToUint8(0x00FA'u16) == 0xFA'u8
     check truncateToUint8(0xFFFA'u16) == 0xFA'u8
 
+  test "leastSignificantBits":
+    check leastSignificantBits(0xFF'u8, 3) == 0b0000_0111'u8
+    check leastSignificantBits(0b0001_0101'u8, 3) == 0b0000_0101'u8
+    check leastSignificantBits(0xFF'u8, 10) == 0xFF'u8
+    check leastSignificantBits(0xFFFF'u16, 16) == 0xFFFF'u16
+    check leastSignificantBits(0xFFFF'u16, 8) == 0x00FF'u16
+
   test "chunks iterator":
     check toSeq(chunks(70, uint32)) == @[(0, 32), (1, 32), (2, 6)]
     check toSeq(chunks(32, uint16)) == @[(0, 16), (1, 16)]