flexbase.php

<?php

class FlexBase {

  private $spec = array();
  private $bases = array();
  private $checksum = 1;
  private $num_digits;
  private $pretty = FALSE;
  private $base = 10;
  private $alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

  function __construct($spec) {
    if (func_num_args() > 1) {
      $spec = func_get_args();
    }
    foreach ($spec as $i => $s) {
      list($min, $max) = $s;
      $this->bases[$i] = $max - $min + 1;
      $this->spec[$i] = $min;
    }
    $this->update_digits();
  }

  private function update_digits() {
    $this->num_digits = strlen($this->max());
  }

  public function set_checksum($mod = 1) {
    if ($mod < 1) {
      return FALSE;
    }
    $this->checksum = $mod;
    $this->update_digits();
  }

  public function set_pretty($pretty = TRUE) {
    $this->pretty = !!$pretty;
  }

  public function set_base($base = 10) {
    if ($base < 2 || $base > 36) {
      return FALSE;
    }
    $this->base = $base;
    $this->update_digits();
    return TRUE;
  }

  public function set_alphabet($alphabet) {
    if (strlen($alphabet) < 2 || strlen($alphabet) > 36) {
      return FALSE;
    }
    $this->alphabet = $alphabet;
    $this->set_base(strlen($alphabet));
    return TRUE;
  }

  private function into_internal($data) {
    $value = 0;
    foreach ($this->spec as $i => $min) {
      $value *= $this->bases[$i];
      $d = $data[$i] ?? $min;
      $value += ($d - $min) % $this->bases[$i];
    }
    if ($this->checksum > 1) {
      $checksum = $value % $this->checksum;
      $value *= $this->checksum;
      $value += $checksum;
    }
    if ($this->base != 10) {
      $value = strtr(
        base_convert($value, 10, $this->base),
        "0123456789abcdefghijklmnopqrstuvwxyz",
        $this->alphabet
      );
    }
    return $value;
  }

  public function into($data) {
    if (func_num_args() != 1 && !is_array($data[0])) {
      $data = func_get_args();
    }
    $value = $this->into_internal($data);
    if ($this->pretty) {
      $value = str_pad("$value", $this->num_digits, $this->alphabet[0], STR_PAD_LEFT);
      $len = strlen($value);
      $seglen = intdiv($len, 3);
      $value = substr($value, 0, $seglen)
        . '-' . substr($value, $seglen, $len - 2 * $seglen)
        . '-' . substr($value, -$seglen);
    }
    return $value;
  }

  public function from($value) {
    if (is_string($value)) {
      $value = implode('', explode(' ', strtr($value, '_-', '  ')));
      for ($i = 0; $i < strlen($value); $i += 1) {
        if (strpos($this->alphabet, $value[$i]) === FALSE) {
          return FALSE;
        }
      }
      $value = strtr(
        $value,
        $this->alphabet,
        "0123456789abcdefghijklmnopqrstuvwxyz"
      );
      $value = ltrim($value, '0');
      if (empty($value)) {
        $value = 0;
      }
    }
    if ($this->base != 10) {
      $value = base_convert($value, $this->base, 10);
    }
    $data = array();
    $v = $value;
    $embedded_checksum = 0;
    if ($this->checksum > 1) {
      $v = intdiv($value, $this->checksum);
      $embedded_checksum = $value % $this->checksum;
      $calculated_checksum = $v % $this->checksum;
      if ($embedded_checksum != $calculated_checksum) {
        return FALSE;
      }
    }
    foreach (array_reverse($this->spec, TRUE) as $i => $min) {
      array_unshift($data, $min + ($v % $this->bases[$i]));
      $v = intdiv($v, $this->bases[$i]);
    }
    if ($v != 0) {
      return FALSE;
    }
    return $data;
  }

  public function max() {
    $data = array();
    foreach ($this->spec as $i => $min) {
      array_push($data, $this->bases[$i] + $min - 1);
    }
    return $this->into_internal($data);
  }

  public function num_digits() {
    return $this->num_digits;
  }

  public function num_components() {
    return count($this->spec);
  }
}

?>