ext.go RawHistoryFolder

1package xturbo
2
3// ExtInfo is a negotiated extension's wire opcode and event/error bases.
4type ExtInfo struct {
5	Present                       bool
6	Major, FirstEvent, FirstError uint8
7}
8
9// ExtTable is populated during setup. Fixed arrays avoid lookup allocations.
10// Reverse maps store ExtID+1 so the zero value means "none".
11type ExtTable struct {
12	info    [extCount]ExtInfo
13	byEvent [128]uint8
14	byError [256]uint8
15	byMajor [256]uint8
16}
17
18// Set records an extension's negotiated opcodes and fills the reverse maps
19// for the event and error codes the extension declares in the pinned XML.
20func (t *ExtTable) Set(id ExtID, major, firstEvent, firstError uint8) {
21	if id == ExtCore || id >= extCount {
22		return
23	}
24	tag := uint8(id) + 1
25	for i := range t.byEvent {
26		if t.byEvent[i] == tag {
27			t.byEvent[i] = 0
28		}
29	}
30	for i := range t.byError {
31		if t.byError[i] == tag {
32			t.byError[i] = 0
33		}
34		if t.byMajor[i] == tag {
35			t.byMajor[i] = 0
36		}
37	}
38	t.info[id] = ExtInfo{true, major, firstEvent, firstError}
39	if major != 0 {
40		t.byMajor[major] = tag
41	}
42	if firstEvent != 0 {
43		for i := 0; i < int(extEvents[id]) && int(firstEvent)+i < len(t.byEvent); i++ {
44			t.byEvent[int(firstEvent)+i] = tag
45		}
46	}
47	if firstError != 0 {
48		for i := 0; i < int(extErrors[id]) && int(firstError)+i < len(t.byError); i++ {
49			t.byError[int(firstError)+i] = tag
50		}
51	}
52}
53func (t *ExtTable) Info(id ExtID) ExtInfo {
54	if id >= extCount {
55		return ExtInfo{}
56	}
57	if id == ExtCore {
58		return ExtInfo{Present: true}
59	}
60	return t.info[id]
61}
62func (t *ExtTable) Major(id ExtID) uint8 { return t.Info(id).Major }
63
64// ByEvent maps an event code (raw[0]&0x7f) to its extension and the code
65// relative to the extension's first event.
66func (t *ExtTable) ByEvent(code uint8) (id ExtID, rel uint8, ok bool) {
67	if code >= 128 || t.byEvent[code] == 0 {
68		return ExtCore, 0, false
69	}
70	id = ExtID(t.byEvent[code] - 1)
71	return id, code - t.info[id].FirstEvent, true
72}
73
74// ByError maps a wire error code to its extension and relative error code.
75func (t *ExtTable) ByError(code uint8) (id ExtID, rel uint8, ok bool) {
76	if t.byError[code] == 0 {
77		return ExtCore, 0, false
78	}
79	id = ExtID(t.byError[code] - 1)
80	return id, code - t.info[id].FirstError, true
81}
82
83// ByMajor maps a major opcode to its extension.
84func (t *ExtTable) ByMajor(major uint8) (id ExtID, ok bool) {
85	if t.byMajor[major] == 0 {
86		return ExtCore, false
87	}
88	return ExtID(t.byMajor[major] - 1), true
89}