<?php
/**
 * UTF8::to_unicode
 *
 * @package    Kohana
 * @author     Kohana Team
 * @copyright  (c) Kohana Team
 * @copyright  (c) 2005 Harry Fuecks
 * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt
 */
function _to_unicode($str)
{
	// Cached expected number of octets after the current octet until the beginning of the next UTF8 character sequence
	$m_state = 0;
	// Cached Unicode character
	$m_ucs4  = 0;
	// Cached expected number of octets in the current sequence
	$m_bytes = 1;

	$out = [];

	$len = strlen($str);

	for ($i = 0; $i < $len; $i++)
	{
		$in = ord($str[$i]);

		if ($m_state == 0)
		{
			// When m_state is zero we expect either a US-ASCII character or a multi-octet sequence.
			if (0 == (0x80 & $in))
			{
				// US-ASCII, pass straight through.
				$out[] = $in;
				$m_bytes = 1;
			}
			elseif (0xC0 == (0xE0 & $in))
			{
				// First octet of 2 octet sequence
				$m_ucs4 = $in;
				$m_ucs4 = ($m_ucs4 & 0x1F) << 6;
				$m_state = 1;
				$m_bytes = 2;
			}
			elseif (0xE0 == (0xF0 & $in))
			{
				// First octet of 3 octet sequence
				$m_ucs4 = $in;
				$m_ucs4 = ($m_ucs4 & 0x0F) << 12;
				$m_state = 2;
				$m_bytes = 3;
			}
			elseif (0xF0 == (0xF8 & $in))
			{
				// First octet of 4 octet sequence
				$m_ucs4 = $in;
				$m_ucs4 = ($m_ucs4 & 0x07) << 18;
				$m_state = 3;
				$m_bytes = 4;
			}
			elseif (0xF8 == (0xFC & $in))
			{
				/** First octet of 5 octet sequence.
				 *
				 * This is illegal because the encoded codepoint must be either
				 * (a) not the shortest form or
				 * (b) outside the Unicode range of 0-0x10FFFF.
				 * Rather than trying to resynchronize, we will carry on until the end
				 * of the sequence and let the later error handling code catch it.
				 **/
				$m_ucs4 = $in;
				$m_ucs4 = ($m_ucs4 & 0x03) << 24;
				$m_state = 4;
				$m_bytes = 5;
			}
			elseif (0xFC == (0xFE & $in))
			{
				// First octet of 6 octet sequence, see comments for 5 octet sequence.
				$m_ucs4 = $in;
				$m_ucs4 = ($m_ucs4 & 1) << 30;
				$m_state = 5;
				$m_bytes = 6;
			}
			else
			{
				// Current octet is neither in the US-ASCII range nor a legal first octet of a multi-octet sequence.
				trigger_error('UTF8::to_unicode: Illegal sequence identifier in UTF-8 at byte '.$i, E_USER_WARNING);
				return FALSE;
			}
		}
		else
		{
			// When m_state is non-zero, we expect a continuation of the multi-octet sequence
			if (0x80 == (0xC0 & $in))
			{
				// Legal continuation
				$shift = ($m_state - 1) * 6;
				$tmp = $in;
				$tmp = ($tmp & 0x0000003F) << $shift;
				$m_ucs4 |= $tmp;

				// End of the multi-octet sequence. mUcs4 now contains the final Unicode codepoint to be output
				if (0 == --$m_state)
				{
					// Check for illegal sequences and codepoints

					// From Unicode 3.1, non-shortest form is illegal
					if (((2 == $m_bytes) AND ($m_ucs4 < 0x0080)) OR
						((3 == $m_bytes) AND ($m_ucs4 < 0x0800)) OR
						((4 == $m_bytes) AND ($m_ucs4 < 0x10000)) OR
						(4 < $m_bytes) OR
						// From Unicode 3.2, surrogate characters are illegal
						(($m_ucs4 & 0xFFFFF800) == 0xD800) OR
						// Codepoints outside the Unicode range are illegal
						($m_ucs4 > 0x10FFFF))
					{
						trigger_error('UTF8::to_unicode: Illegal sequence or codepoint in UTF-8 at byte '.$i, E_USER_WARNING);
						return FALSE;
					}

					if (0xFEFF != $m_ucs4)
					{
						// BOM is legal but we don't want to output it
						$out[] = $m_ucs4;
					}

					// Initialize UTF-8 cache
					$m_state = 0;
					$m_ucs4  = 0;
					$m_bytes = 1;
				}
			}
			else
			{
				// ((0xC0 & (*in) != 0x80) AND (m_state != 0))
				// Incomplete multi-octet sequence
				throw new UTF8_Exception("UTF8::to_unicode: Incomplete multi-octet sequence in UTF-8 at byte ':byte'", [
					':byte' => $i,
				]);
			}
		}
	}

	return $out;
}
