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}
diff --git a/rtc_base/bit_buffer.cc b/rtc_base/bit_buffer.cc
index 540141f..222d30c 100644
--- a/rtc_base/bit_buffer.cc
+++ b/rtc_base/bit_buffer.cc
@@ -141,10 +141,48 @@
return true;
}
+bool BitBuffer::PeekBits(uint64_t* val, size_t bit_count) {
+ // TODO(nisse): Could allow bit_count == 0 and always return success. But
+ // current code reads one byte beyond end of buffer in the case that
+ // RemainingBitCount() == 0 and bit_count == 0.
+ RTC_DCHECK(bit_count > 0);
+ if (!val || bit_count > RemainingBitCount() || bit_count > 64) {
+ return false;
+ }
+ const uint8_t* bytes = bytes_ + byte_offset_;
+ size_t remaining_bits_in_current_byte = 8 - bit_offset_;
+ uint64_t bits = LowestBits(*bytes++, remaining_bits_in_current_byte);
+ // If we're reading fewer bits than what's left in the current byte, just
+ // return the portion of this byte that we need.
+ if (bit_count < remaining_bits_in_current_byte) {
+ *val = HighestBits(bits, bit_offset_ + bit_count);
+ return true;
+ }
+ // Otherwise, subtract what we've read from the bit count and read as many
+ // full bytes as we can into bits.
+ bit_count -= remaining_bits_in_current_byte;
+ while (bit_count >= 8) {
+ bits = (bits << 8) | *bytes++;
+ bit_count -= 8;
+ }
+ // Whatever we have left is smaller than a byte, so grab just the bits we need
+ // and shift them into the lowest bits.
+ if (bit_count > 0) {
+ bits <<= bit_count;
+ bits |= HighestBits(*bytes, bit_count);
+ }
+ *val = bits;
+ return true;
+}
+
bool BitBuffer::ReadBits(uint32_t* val, size_t bit_count) {
return PeekBits(val, bit_count) && ConsumeBits(bit_count);
}
+bool BitBuffer::ReadBits(uint64_t* val, size_t bit_count) {
+ return PeekBits(val, bit_count) && ConsumeBits(bit_count);
+}
+
bool BitBuffer::ConsumeBytes(size_t byte_count) {
return ConsumeBits(byte_count * 8);
}