Fixed bitstream reader

fraunhoferhhi · Oct 7, 2024 · cd7fab2 · cd7fab2
1 parent f2d83c2
commit cd7fab2
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Showing 2 changed files with 5 additions and 4 deletions.
diff --git a/source/Lib/CommonLib/BitStream.cpp b/source/Lib/CommonLib/BitStream.cpp
@@ -102,6 +102,7 @@ uint32_t InputBitstream::read (uint32_t uiNumberOfBits)
  m_numBitsRead += uiNumberOfBits;
 #endif
 
+ constexpr static uint64_t ONES = ~static_cast<uint64_t>( 0 ); // need to ensure 64 bits for the mask, because shift by 32 is UB for uin32_t
 
  /* NB, bits are extracted from the MSB of each byte. */
  uint32_t retval = 0;
@@ -111,7 +112,7 @@ uint32_t InputBitstream::read (uint32_t uiNumberOfBits)
  * n=3, len(H)=7: -VVV HHHH, shift_down=4, mask=0xf8
  */
  retval = static_cast<uint32_t>( m_held_bits >> ( m_num_held_bits - uiNumberOfBits ) );
- retval &= ~( ~0u << uiNumberOfBits );
+ retval &= ~( ONES << uiNumberOfBits );
  m_num_held_bits -= uiNumberOfBits;
 
  return retval;
@@ -127,7 +128,7 @@ uint32_t InputBitstream::read (uint32_t uiNumberOfBits)
  /* n=5, len(H)=3: ---- -VVV, mask=0x07, shift_up=5-3=2,
  * n=9, len(H)=3: ---- -VVV, mask=0x07, shift_up=9-3=6 */
  uiNumberOfBits -= m_num_held_bits;
- retval = static_cast<uint32_t>( m_held_bits ) & ~( ~0u << m_num_held_bits ); // we can cast to 32 bits, because the held bits are the rightmost bits
+ retval = static_cast<uint32_t>( m_held_bits ) & ~( ONES << m_num_held_bits ); // we can cast to 32 bits, because the held bits are the rightmost bits
  retval <<= uiNumberOfBits;
  }
 

diff --git a/source/Lib/DecoderLib/HLSyntaxReader.cpp b/source/Lib/DecoderLib/HLSyntaxReader.cpp
@@ -1194,11 +1194,11 @@ void HLSyntaxReader::parseVUI( VUI* pcVUI, unsigned vuiPayloadSize )
 void HLSyntaxReader::parseGeneralHrdParameters( GeneralHrdParams *hrd )
 {
  X_READ_CODE_NO_RANGE( num_units_in_tick, 32 );
- // CHECK( num_units_in_tick <= 0, "num_units_in_tick shall be greater than 0" ); // this breaks the testset (TEMPSCAL_B_Panasonic_7.bit) although specified in the spec
+ CHECK( num_units_in_tick <= 0, "num_units_in_tick shall be greater than 0" );
  hrd->setNumUnitsInTick( num_units_in_tick );
 
  X_READ_CODE_NO_RANGE( time_scale, 32 );
- // CHECK( time_scale <= 0, "The value of time_scale shall be greater than 0." ); // this breaks the testset (HRD_A_Fujitsu_3.bit & HRD_B_Fujitsu_2.bit) although specified in the spec
+ CHECK( time_scale <= 0, "The value of time_scale shall be greater than 0." );
  hrd->setTimeScale( time_scale );
 
  X_READ_FLAG( general_nal_hrd_params_present_flag );