1<?php
2
3namespace MediaWiki\Rest\HeaderParser;
4
5/**
6 * @internal
7 */
8class HeaderParserBase {
9	/**
10	 * @var string The input string being processed
11	 */
12	protected $input;
13
14	/**
15	 * @var int The position within $input
16	 */
17	protected $pos;
18
19	/**
20	 * @var int The length of $input
21	 */
22	protected $inputLength;
23
24	/**
25	 * Set the input, and derived convenience properties
26	 *
27	 * @param string $input
28	 */
29	protected function setInput( $input ) {
30		$this->input = $input;
31		$this->pos = 0;
32		$this->inputLength = strlen( $input );
33	}
34
35	/**
36	 * Consume a specified string, or throw an exception.
37	 *
38	 * @param string $s
39	 * @throws HeaderParserError
40	 */
41	protected function consumeString( $s ) {
42		if ( $this->pos >= $this->inputLength ) {
43			$this->error( "Expected \"$s\" but got end of string" );
44		}
45		if ( substr_compare( $this->input, $s, $this->pos, strlen( $s ) ) === 0 ) {
46			$this->pos += strlen( $s );
47		} else {
48			$this->error( "Expected \"$s\"" );
49		}
50	}
51
52	/**
53	 * Skip whitespace at the input position (OWS)
54	 */
55	protected function skipWhitespace() {
56		$this->pos += strspn( $this->input, " \t", $this->pos );
57	}
58
59	/**
60	 * Throw an exception to indicate a parse error
61	 *
62	 * @param string $message
63	 * @throws HeaderParserError
64	 */
65	protected function error( $message ) {
66		throw new HeaderParserError( "$message at {$this->pos}" );
67	}
68
69	/**
70	 * Consume a specified number of digits, or throw an exception
71	 *
72	 * @param int $numDigits
73	 * @return string
74	 * @throws HeaderParserError
75	 */
76	protected function consumeFixedDigits( $numDigits ) {
77		$digits = substr( $this->input, $this->pos, $numDigits );
78		if ( strlen( $digits ) !== $numDigits || !preg_match( '/^[0-9]*$/', $digits ) ) {
79			$this->error( "expected $numDigits digits" );
80		}
81		$this->pos += $numDigits;
82		return $digits;
83	}
84
85	/**
86	 * If the position is not at the end of the input string, raise an error,
87	 * complaining of trailing characters.
88	 *
89	 * @throws HeaderParserError
90	 */
91	protected function assertEnd() {
92		if ( $this->pos !== $this->inputLength ) {
93			$this->error( "trailing characters" );
94		}
95	}
96}
97