evaluate functions in the BSON document scoped to the object deserialized.

cache evaluated functions for reuse.

use a crc32 code for caching, otherwise use the string of the function.

when deserializing a Long will fit it into a Number if it's smaller than 53 bits

when deserializing a Binary will return it as a node.js Buffer instance.

when deserializing will promote BSON values to their Node.js closest equivalent types.

allow to specify if there what fields we wish to return as unserialized raw buffer.

return BSON regular expressions as BSONRegExp instances.

allows the buffer to be larger than the parsed BSON object

Offset into buffer to begin reading document from