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Bit-level reads and writes for ArrayBuffers


BitBuffer provides two objects, BitView and BitStream. BitView is a wrapper for ArrayBuffers, similar to JavaScript's DataView, but with support for bit-level reads and writes. BitStream is a wrapper for a BitView used to help maintain your current buffer position, as well as to provide higher-level read / write operations such as for ASCII strings.



bb.buffer  // Underlying ArrayBuffer. 


BitView(buffer, optional byteOffset, optional byteLength)

Default constructor, takes in a single argument of an ArrayBuffer. Optional are the byteOffset and byteLength arguments to offset and truncate the view's representation of the buffer.

getBits(offset, bits, signed)

Reads bits number of bits starting at offset, twiddling the bits appropriately to return a proper 32-bit signed or unsigned value. NOTE: While JavaScript numbers are 64-bit floating-point values, we don't bother with anything other than the first 32 bits.

getInt8, getUint8, getInt16, getUint16, getInt32, getUint32(offset)

Shortcuts for getBits, setting the correct bits / signed values.


Gets 32 bits from offset, and coerces and returns as a proper float32 value.


Gets 64 bits from offset, and coerces and returns as a proper float64 value.

setBits(offset, value, bits)

Sets bits number of bits at offset.

setInt8, setUint8, setInt16, setUint16, setInt32, setUint32(offset)

Shortcuts for setBits, setting the correct bits count.


Coerces a float32 to uint32 and sets at offset.


Coerces a float64 to two uint32s and sets at offset.



bb.byteIndex  // Get current index in bytes. 
bb.byteIndex = 0;  // Set current index in bytes. 
bb.view  // Underlying BitView 



Default constructor, takes in a single argument of a BitView.

BitSteam(buffer, optional byteOffset, optional byteLength)

Shortcut constructor that initializes a new BitView(buffer, byteOffset, byteLength) for the stream to use.

readBits(bits, signed)

Returns bits numbers of bits from the view at the current index, updating the index.

writeBits(value, bits)

Sets bits numbers of bits from value in the view at the current index, updating the index.

readASCIIString(optional bytes)

Reads bytes from the underlying view at the current index until either bytes count is reached or a 0x00 terminator is reached.

writeASCIIString(string, optional bytes)

Writes a string followed by a NULL character to the underlying view starting at the current index. If the string is longer than bytes it will be truncated, and if it is shorter 0x00 will be written in its place.