Add 64-bit version of BitBuffer::ReadBits

Bug: webrtc:11933
Change-Id: Ie935192d2c81d7c24b83561711d59a7eff53db04
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/215966
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33997}

1 files changed, 32 insertions, 0 deletions

diff --git a/rtc_base/bit_buffer_unittest.cc b/rtc_base/bit_buffer_unittest.cc
index 656682c2ef..86c4f7fa5c 100644
--- a/rtc_base/bit_buffer_unittest.cc
+++ b/rtc_base/bit_buffer_unittest.cc
@@ -142,6 +142,38 @@ TEST(BitBufferTest, ReadBits) {
   EXPECT_FALSE(buffer.ReadBits(&val, 1));
 }
 
+TEST(BitBufferTest, ReadBits64) {
+  const uint8_t bytes[] = {0x4D, 0x32, 0xAB, 0x54, 0x00, 0xFF, 0xFE, 0x01,
+                           0xAB, 0xCD, 0xEF, 0x01, 0x23, 0x45, 0x67, 0x89};
+  BitBuffer buffer(bytes, 16);
+  uint64_t val;
+
+  // Peek and read first 33 bits.
+  EXPECT_TRUE(buffer.PeekBits(&val, 33));
+  EXPECT_EQ(0x4D32AB5400FFFE01ull >> (64 - 33), val);
+  val = 0;
+  EXPECT_TRUE(buffer.ReadBits(&val, 33));
+  EXPECT_EQ(0x4D32AB5400FFFE01ull >> (64 - 33), val);
+
+  // Peek and read next 31 bits.
+  constexpr uint64_t kMask31Bits = (1ull << 32) - 1;
+  EXPECT_TRUE(buffer.PeekBits(&val, 31));
+  EXPECT_EQ(0x4D32AB5400FFFE01ull & kMask31Bits, val);
+  val = 0;
+  EXPECT_TRUE(buffer.ReadBits(&val, 31));
+  EXPECT_EQ(0x4D32AB5400FFFE01ull & kMask31Bits, val);
+
+  // Peek and read remaining 64 bits.
+  EXPECT_TRUE(buffer.PeekBits(&val, 64));
+  EXPECT_EQ(0xABCDEF0123456789ull, val);
+  val = 0;
+  EXPECT_TRUE(buffer.ReadBits(&val, 64));
+  EXPECT_EQ(0xABCDEF0123456789ull, val);
+
+  // Nothing more to read.
+  EXPECT_FALSE(buffer.ReadBits(&val, 1));
+}
+
 TEST(BitBufferDeathTest, SetOffsetValues) {
   uint8_t bytes[4] = {0};
   BitBufferWriter buffer(bytes, 4);