break 128 bit sequence to bits - php

Question

i am trying to implement in php a parser which reads binary files of various sizes (e.g. $fsize). In these files there are repeating 16-byte sequences wich i want to process independently (one 16-byte sequence at a time). I have managed to read and isolate each such 16-byte sequence in the form of:
processing sample[2]...
Printing 16 sample bytes
$bit_sequence='10000000010111001000000001100111011010110110011110100110101000100111011100111111000100000000000010100011010010101001101111101000'
Array:
$bits=( [0] => 1 [1] => 0 [2] => 0 [3] => 0 [4] => 0 [5] => 0 [6] => 0 [7] => 0 [8] => 0 [9] => 1 [10] => 0 [11] => 1 [12] => 1 [13] => 1 [14] => 0 [15] => 0 [16] => 1 [17] => 0 [18] => 0 [19] => 0 [20] => 0 [21] => 0 [22] => 0 [23] => 0 [24] => 0 [25] => 1 [26] => 1 [27] => 0 [28] => 0 [29] => 1 [30] => 1 [31] => 1 [32] => 0 [33] => 1 [34] => 1 [35] => 0 [36] => 1 [37] => 0 [38] => 1 [39] => 1 [40] => 0 [41] => 1 [42] => 1 [43] => 0 [44] => 0 [45] => 1 [46] => 1 [47] => 1 [48] => 1 [49] => 0 [50] => 1 [51] => 0 [52] => 0 [53] => 1 [54] => 1 [55] => 0 [56] => 1 [57] => 0 [58] => 1 [59] => 0 [60] => 0 [61] => 0 [62] => 1 [63] => 0 [64] => 0 [65] => 1 [66] => 1 [67] => 1 [68] => 0 [69] => 1 [70] => 1 [71] => 1 [72] => 0 [73] => 0 [74] => 1 [75] => 1 [76] => 1 [77] => 1 [78] => 1 [79] => 1 [80] => 0 [81] => 0 [82] => 0 [83] => 1 [84] => 0 [85] => 0 [86] => 0 [87] => 0 [88] => 0 [89] => 0 [90] => 0 [91] => 0 [92] => 0 [93] => 0 [94] => 0 [95] => 0 [96] => 1 [97] => 0 [98] => 1 [99] => 0 [100] => 0 [101] => 0 [102] => 1 [103] => 1 [104] => 0 [105] => 1 [106] => 0 [107] => 0 [108] => 1 [109] => 0 [110] => 1 [111] => 0 [112] => 1 [113] => 0 [114] => 0 [115] => 1 [116] => 1 [117] => 0 [118] => 1 [119] => 1 [120] => 1 [121] => 1 [122] => 1 [123] => 0 [124] => 1 [125] => 0 [126] => 0 [127] => 0 )
I also have an array containing the variables to which i want to store the above information ...
Array:
$variables=( [0] => wide_avg_txon [1] => wide_avg [2] => wide_peak_rms [3] => wide_peak [4] => low_pw [5] => low_pp [6] => high_pw [7] => high_pp [8] => battery_voltage [9] => temperature_spr_flag [10] => temperature [11] => alarm_abat [12] => alarm_amem [13] => alarm_atmp [14] => alarm_alck [15] => alarm_prx [16] => alarm_arpb [17] => alarm_awrn [18] => alarm_aalr [19] => mask_mbat [20] => mask_mmem [21] => mask_mtmp [22] => mask_mlck [23] => mask_smx [24] => mask_mprb [25] => mask_mwrn [26] => mask_malr [27] => sample_rate [28] => avg_period [29] => months [30] => date_time )
My goal is to find a way to process the whole 128-bit sequence like an array with 128 elements and have the option to extract in such a way:
bits[0] -> store in variable $wide_avg_txon (boolean)
bits[1->15] -> store in variable $wide_avg (15-bit unsigned int)
bits[16] -> store in variable $wide_peak_rms (boolean)
bits[17->31] -> store in variable $wide_peak (15-bit unsigned int)
bits[32->39] -> store in variable $low_pw (8-bit unsigned int)
.... (and so on)
bits[112->127]-> store in variable $date_time (16-bit unsigned int)
i am quite new in php and in programming also...
I do not know if it is optimal solution ... but i have managed to store strings representing binary sequences of 1,8 or 16 bits to variables using code like this:
$wide_avg_txon = substr($bit_sequence,0,1);
//wide_avg_txon: 1
$wide_avg = '0'.substr($bit_sequence,1,15);
//wide_avg: 0000000001100000
$wide_peak_rms = substr($bit_sequence,16,1);
//wide_peak_rms: 1
$wide_peak = '0'.substr($bit_sequence,17,15);
//wide_peak: 0000000001100100
now i will need to process somehow these strings (representing binary numbers) numerically and convert to decimal numbers ...
Any suggestions to my posted solution would be useful and welcome...

Answer 1

In fact i managed to break the 128-bit sequence as desired using a quite dirty way:
$wide_avg = '0'.substr($bit_sequence,1,15);
$wide_avg_dec=bindec($wide_avg);
echo "wide_avg: " . $wide_avg . ", and as decimal: " . $wide_avg_dec . "";
and so on...

Answer 2

It seems you are just making an array from a string:
function getArrayFromString($string)
{
$length = strlen($string);
$ret = array();
for ($i = 0; $i < $length; $i++)
{
$ret[] = $string[$i];
}
}
However, it sounds like you are using the byte sequence like flags. This should be like what you need:
define("ADMIN_PRIV", 1); // 1<<1
define("DEV_PRIV", 4); // 1<<3
if ($byte & ADMIN_PRIV)
{
// this user is admin
}
however, PHP's integer is only 32-bits long (4 bytes), so that is the most that you can work with. So I would work on a per byte basis.