bitn.BitBin
- Super fast bitslicing.
- bitshift speed without bitwise complexity.
bitn.NBin (New!)
- the reverse bitn.BitBin
- Encodes values to bytes
Install
pip install bitnHelp(BitBin)
NAME
bitn
CLASSES
builtins.object
BitBin
NBin
class BitBin(builtins.object)
| bitn.Bitbin takes a byte string and
| converts it to a integer, a very large integer
| if needed. A 1500 bit integer is no problem.
| several methods are available for slicing off bits.
|
| Methods defined here:
|
| __init__(self, bites)
|
| as90k(self, num_bits)
| Returns num_bits
| of bits as 90k time
|
| asascii(self, num_bits)
| Returns num_bits
| as bytes decoded to ascii
|
| asflag(self, num_bits=1)
| Returns one bit as True or False
|
| ashex(self, num_bits)
| Returns the hex value
| of num_bits of bits
|
| asint(self, num_bits)
| Starting at self.idx of self.bits,
| slice off num_bits of bits.
|
| forward(self, num_bits)
| Advances the start point
| forward by num_bits
|
| negative_shift(self, num_bits)
| negative_shift is called instead of
| throwing a negative shift count error.
|
| ----------------------------------------------------------------------
class NBin(builtins.object)
| bitn.NBin is
| the reverse BitBin.
| Encodes data to integers
| and then bytes
|
| Methods defined here:
|
| __init__(self)
|
| add_90k(self, pts, bit_len=33)
| Converts 90k float timestamps
| to an int and appends it to nbits
| via self.add_int
|
| add_flag(self, flg)
| add_flag takes a boolean
| value and adds it as an integer
| to self.nbits via self.add_int
|
| add_hex(self, hex_str, bit_len)
| add_hex converts a
| hex encoded string to an int
| and appends it to self.nbits
| via self.add_int
|
| add_int(self, int_bits, bit_len)
| left shift nbits and append new_bits
|
| forward(self, num)
| Currently just an alias to reserve
|
| nbits2bites(self)
| nbits2bites converts
| the int self.nbits to bytes as self.bites
| and sets self.nbits and self.idx to 0
|
| reserve(self, num)
| reserve sets 'num' bits to 1
| and appends them to self.nbits
| via self.add_int
|
| ----------------------------------------------------------------------
I used to do this
from struct import unpack
sync,two_bytes,one_byte = unpack('>BHB', packet[:4])
tei = two_bytes >> 15
pusi = two_bytes >> 14 & 0x1
ts_priority = two_bytes >>13 & 0x1
pid = two_bytes & 0x1fff
scramble = one_byte >>6
afc = (one_byte & 48) >> 4
count = one_byte & 15Now I use bitn and do this
from bitn import BitBin
header= BitBin(packet[:4])
sync=header.asint(8)
tei=header.asflag(1)
pusi=header.asflag(1)
ts_priority=header.asflag(1)
pid=header.asint(13)
scramble=header.asint(2)
afc=header.asint(2)
count=header.asint(4)Example Usage
- Parse a SCTE 35 splice information section from a hex encoded string
>>> from bitn import BitBin
>>> bites= bytes.fromhex('FC302F000000000000FFFFF00506FEAEF17C4C0019021743554549480000077F9F0808000000002CA56C97110000C4876A2E')
>>> class Splice_Info_Section:
def __init__(self,bitbin):
self.table_id =bitbin.ashex(8)
self.section_syntax_indicator = bitbin.asflag(1)
self.private = bitbin.asflag(1)
self.reserved=bitbin.asint(2)
self.section_length = bitbin.asint(12)
self.protocol_version = bitbin.asint(8)
self.encrypted_packet = bitbin.asflag(1)
self.encryption_algorithm =bitbin.asint(6)
self.pts_adjustment = bitbin.as90k(33)
self.cw_index = bitbin.ashex(8)
self.tier = bitbin.ashex(12)
self.splice_command_length = bitbin.asint(12)
self.splice_command_type = bitbin.asint(8)
>>> bitbin=BitBin(bites)
>>> sps=Splice_Info_Section(bitbin)
>>> vars(sps)
{'table_id': '0xfc', 'section_syntax_indicator': False, 'private': False, 'reserved': 3, 'section_length': 47,
'protocol_version': 0, 'encrypted_packet': False, 'encryption_algorithm': 0, 'pts_adjustment': '0.000000',
'cw_index': '0xff', 'tier': '0xfff', 'splice_command_length': 5, 'splice_command_type': 6, 'descriptor_loop_length': 25}
>>> 
