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bitstreamio is a package for reading bits from a
connection or raw vector.
This package has no requirement that reads/write operations be byte aligned.
Reading/writing bits and unaligned bytes is useful for input/output with packed binary file formats e.g. h264-compressed video, mp3 audio etc.
In addition to reading individual bits, this package also provides for:
bs_write_bit(), bs_read_bit()bs_write_byte(), bs_read_byte()bs_write_uint(), bs_read_uint()bs_write_uint_exp_golomb(),
bs_read_uint_exp_golomb()bs_write_sint_exp_golomb(),
bs_read_sint_exp_golomb()bs_open(), bs_close()bs_is_aligned(), bs_align()bs_advance(), bs_peek()library(bitstreamio)
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Write bits to a raw vector
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bs <- bs_open(raw(), "w")
bs_write_bit(bs, c(TRUE , FALSE, FALSE, FALSE))
bs_write_byte(bs, c(0x01, 0x7f)) # write unaligned byte values
bs_write_bit(bs, c(FALSE, FALSE, FALSE, TRUE))
raw_vec <- bs_close(bs)
raw_vec
#> [1] 80 17 f1
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Read bits back from raw vector
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bs <- bs_open(raw_vec, mode = 'r')
bs_read_bit(bs, 4)
#> [1] TRUE FALSE FALSE FALSE
bs_read_byte(bs, 2) # unaligned byte read
#> [1] 01 7f
bs_read_bit(bs, 4)
#> [1] FALSE FALSE FALSE TRUE
bs_close(bs)filename <- tempfile()
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Write bits to a file
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
con <- file(filename, "wb")
bs <- bs_open(con, mode = 'w')
bs_write_bit(bs, c(TRUE , FALSE, FALSE, FALSE))
bs_write_byte(bs, c(1, 127))
bs_write_bit(bs, c(FALSE, FALSE, FALSE, TRUE))
bs_close(bs)
close(con)
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Read the bits back in
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
con <- file(filename, "rb")
bs <- bs_open(con, mode = 'r')
bs_read_bit(bs, 4)
#> [1] TRUE FALSE FALSE FALSE
bs_read_uint(bs, nbits = 8, n = 2)
#> [1] 1 127
bs_read_bit(bs, 4)
#> [1] FALSE FALSE FALSE TRUE
bs_close(bs)
close(con)library(bitstreamio)
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Write bits to a raw vector
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bs <- bs_open(raw(), "w")
bs_write_uint(bs, 0:7 , nbits = 3) # write 8 * 3-bit integers
bs_write_uint(bs, 10:15, nbits = 4) # write 6 * 4-bit integers
raw_vec <- bs_close(bs)
raw_vec
#> [1] 05 39 77 ab cd ef
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Read bits back from raw vector
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bs <- bs_open(raw_vec, mode = 'r')
bs_read_uint(bs, nbits = 3, n = 8)
#> [1] 0 1 2 3 4 5 6 7
bs_read_uint(bs, nbits = 4, n = 6)
#> [1] 10 11 12 13 14 15
bs_close(bs)Exponential-Golomb coding is a way of encoding integers to bit sequences. These bit sequences are often smaller than any standard integer type, and are often used to save space when packing data into a stream when the size of the integer is not known ahead of time.
# Converstion of unsigned integers to Exponential-Golomb coded bit sequences
uint_to_exp_golomb_bits(0)
#> [1] TRUE
uint_to_exp_golomb_bits(1)
#> [1] FALSE TRUE FALSE
uint_to_exp_golomb_bits(2)
#> [1] FALSE TRUE TRUE
uint_to_exp_golomb_bits(3)
#> [1] FALSE FALSE TRUE FALSE FALSE
# Converstion of signed integers to Exponential-Golomb coded bit sequences
sint_to_exp_golomb_bits(0)
#> [1] TRUE
sint_to_exp_golomb_bits(-1)
#> [1] FALSE TRUE TRUE
sint_to_exp_golomb_bits(-2)
#> [1] FALSE FALSE TRUE FALSE TRUE
sint_to_exp_golomb_bits(3)
#> [1] FALSE FALSE TRUE TRUE FALSElibrary(bitstreamio)
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Write bits to a raw vector
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bs <- bs_open(raw(), "w")
bs_write_uint_exp_golomb(bs, 0:9)
raw_vec <- bs_close(bs)
# 10 integers encoded into 6 bytes
raw_vec
#> [1] a6 42 98 e2 04 8a
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Read bits back from raw vector
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bs <- bs_open(raw_vec, mode = 'r')
bs_read_uint_exp_golomb(bs, 10)
#> [1] 0 1 2 3 4 5 6 7 8 9
bs_close(bs)These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.
Health stats visible at Monitor.