404-solution / includes / diagnostics / MeasuredBodyBytes.php

MeasuredBodyBytes.php in 404 Solution trunk, at includes/diagnostics/MeasuredBodyBytes.php

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1	<?php
2
3	if (!defined('ABSPATH')) {
4	exit;
5	}
6
7	/**
8	* A body-byte count somebody actually measured, and the name of who measured
9	* it.
10	*
11	* Both halves of the emitted-against-delivered comparison are byte counts, and
12	* both have to agree on one question before they can be compared at all: which
13	* reported values are real measurements and which are a refusal to answer. The
14	* rule and the vocabulary lived in two classes before this one existed --
15	* ABJ_404_Solution_ResponseBodyDeliveryEvidence for the emitted half and
16	* ABJ_404_Solution_DeliveredTableResponseSize for the delivered half -- as
17	* byte-identical copies, down to the same explanatory sentence. Two copies of
18	* the rule that decides whether a comparison is possible is one copy too many:
19	* if either had ever been "fixed" alone, the pair would have started comparing
20	* a measurement against a refusal and reporting the difference as a rewritten
21	* body, which is the exact false finding the comparison exists to avoid.
22	*
23	* Pure vocabulary and one pure rule. No I/O, no journal knowledge, no
24	* formatting.
25	*/
26	final class ABJ_404_Solution_MeasuredBodyBytes {
27
28	/** Nobody produced a usable count for this half of the comparison. */
29	const SOURCE_UNAVAILABLE = 'unavailable';
30
31	/**
32	* Delivered = Resource Timing `decodedBodySize`, the only octet count the
33	* browser measures on the wire rather than through the JSON parser.
34	*/
35	const SOURCE_RESOURCE_TIMING = 'resource_timing_decoded_body';
36
37	/** Emitted = the encoded JSON only. */
38	const SOURCE_ENCODE = 'json_encode';
39
40	/**
41	* Emitted = the encoded JSON plus the `stream` step's leading whitespace
42	* block, which is echoed outside json_encode() and so is absent from the
43	* encoded count.
44	*/
45	const SOURCE_ENCODE_PLUS_STREAM = 'json_encode_plus_stream_whitespace';
46
47	/**
48	* The count as a positive integer, or null when the reporter declined to
49	* give one.
50	*
51	* Zero and the client's own -1 sentinel are both unknown, not empty.
52	* Resource Timing reports 0 for an entry it will not disclose (an opaque
53	* or timing-restricted response) exactly as it would for a genuinely empty
54	* body, and nothing downstream can tell those apart. Calling either one
55	* "0 bytes" would invent a measurement out of a browser's refusal to
56	* answer, and a fabricated zero on either half of the comparison reads as
57	* the largest possible discrepancy.
58	*
59	* @param mixed $value Whatever the journal record carried.
60	*/
61	public static function disclosed($value): ?int {
62	return is_numeric($value) && (int)$value > 0 ? (int)$value : null;
63	}
64	}
65