GetBit

C++

long GetBit(
  BYTE *BitBuffer,                 // buffer that receives data
  long NumberOfBits,               // number of bits to read
  long FilePosition = -1           // position of data in file
);

BASIC

GetBit(
  BitBuffer As Variant,            // variant that receives data
  NumberOfBits As Long,            // number of bits to read
  FilePosition As Long = -1        // position of data in file
) As Long

Parameters

BitBuffer

C++

Pointer to variable that receives data.

BASIC

Variant that receives data.
Variant type must be compatible with Byte, Integer or Long data type; it must not be an array.
Variant can be uninitialized; in such case it is converted to Byte.

NumberOfBits

Number of bits to read. 1 to 8 bits can be read in one operation.
If this parameter is 0 no data is read and method only returns number of bits available in bit buffer.

FilePosition

Position in file to read data at.
If this parameter is -1 data is read at current file position.

Return Values

Remarks

Bits are buffered in special bit buffer which is one byte long and contains at most 8 bits to be accessed one by one. Bits are fetched from right to left - starting from least significant bit. If user requests more bits than are available in buffer, it is refilled with one complete byte read from file and file positon is moved forward by one byte. Such behaviour guarantees that other non-bit data read by user is always accessed on byte boundary regardless of number of bits present in bit buffer. Read and written bits are never mixed in bit buffer; if GetBit call is followed by PutBit, bit buffer is discarded before bits are written; if PutBit call is followed by GetBit, bit buffer is written to file before bits are read. Bit buffer is flushed whenever other non-bit data is read, file is repositioned, resized, closed or detached.

See Also