# Idiom #275 Binary digits to byte array

From the string s consisting of 8n binary digit characters ('0' or '1'), build the equivalent array a of n bytes.
Each chunk of 8 binary digits (2 possible values per digit) is decoded into one byte (256 possible values).

``````n = (len(s) - 1) // 8 + 1
a = bytearray(n)
for i in range(n):
b = int(s[i * 8:(i + 1) * 8], 2)
a[i] = b
``````
``````#include <string>
#include <vector>
using namespace std;``````
``````const size_t n = s.length() / 8;

vector<uint8_t> a(n);

for(size_t block = 0; block < n; block++)
{
uint8_t acc = 0;
const size_t start = block * 8;
for(size_t offset = start; offset < start + 8; offset++)
{
acc = (acc << 1) + (s[offset] - '0');
}

a[block] = acc;
}``````
``````using System;
using System.Linq;``````
``````var a = Enumerable.Range(0, s.Length / 8)
.Select(i => s.Substring(i * 8, 8).ToCharArray())
.Select(block => (byte)block.Aggregate(0, (acc, c) => (acc << 1) + (c - '0')))
.ToArray();``````
``````  subroutine to_s (s, a)
use iso_fortran_env, only: int8
character (len=*), intent(in) :: s
integer (kind=int8), allocatable, intent(out), dimension(:) :: a
allocate (a(len(s)/8))
end subroutine to_s``````
``import "strconv"``
``````n := len(s) / 8
a := make([]byte, n)
for i := range a {
b, err := strconv.ParseInt(s[i*8:i*8+8], 2, 0)
if err != nil {
log.Fatal(err)
}
a[i] = byte(b)
}``````
``````short[] a = new short[s.length() / 8];
for(int index1 = 0, index2 = 0; index1 < a.length; index1++, index2 += 8) {
a[index1] = Short.valueOf(s.substring(index2, index2 + 8), 2);
}``````
``````  Size := Length(S) div 8;
SetLength(a, Size);
for i := 0 to Size - 1 do
begin
SBin := '%' + Copy(S, 1+(i*8), 8);
Val(SBin, a[i], Err);
if (Err <> 0) then
RunError(106);
end;
``````
``````my \$s = '1000' . '0010' . '0101' . '1010';   # AZ

my @a;
for ( my \$i = 0; \$i < length \$s; \$i += 8) {
my @b = pack 'b8', substr(\$s, \$i, 8);
push @a, @b;
}
``````
``````a = s.scan(/[01]{8}/).map{|slice| slice.to_i(2).to_s(16).rjust(2, "0")}
``````
``````let a: Vec<u8> = s.as_bytes()
.chunks(8)
.map(|chunk| unsafe {
let chunk_str = std::str::from_utf8_unchecked(chunk);