-
Notifications
You must be signed in to change notification settings - Fork 101
/
shared-channel.js
267 lines (213 loc) · 5.55 KB
/
shared-channel.js
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
let FINALIZED = 0xdeadbeef;
let WRITEABLE = 0;
let READABLE = 1;
export class Reader {
constructor(
buffer,
{ initialOffset = 4, useAtomics = true, stream = true, debug, name } = {}
) {
this.buffer = buffer;
this.atomicView = new Int32Array(buffer);
this.offset = initialOffset;
this.useAtomics = useAtomics;
this.stream = stream;
this.debug = debug;
this.name = name;
}
log(...args) {
if (this.debug) {
console.log(`[reader: ${this.name}]`, ...args);
}
}
waitWrite(name, timeout = null) {
if (this.useAtomics) {
this.log(`waiting for ${name}`);
while (Atomics.load(this.atomicView, 0) === WRITEABLE) {
if (timeout != null) {
if (
Atomics.wait(this.atomicView, 0, WRITEABLE, timeout) === 'timed-out'
) {
throw new Error('timeout');
}
}
Atomics.wait(this.atomicView, 0, WRITEABLE, 500);
}
this.log(`resumed for ${name}`);
} else {
if (this.atomicView[0] !== READABLE) {
throw new Error('`waitWrite` expected array to be readable');
}
}
}
flip() {
this.log('flip');
if (this.useAtomics) {
let prev = Atomics.compareExchange(
this.atomicView,
0,
READABLE,
WRITEABLE
);
if (prev !== READABLE) {
throw new Error('Read data out of sync! This is disastrous');
}
Atomics.notify(this.atomicView, 0);
} else {
this.atomicView[0] = WRITEABLE;
}
this.offset = 4;
}
done() {
this.waitWrite('done');
let dataView = new DataView(this.buffer, this.offset);
let done = dataView.getUint32(0) === FINALIZED;
if (done) {
this.log('done');
this.flip();
}
return done;
}
peek(fn) {
this.peekOffset = this.offset;
let res = fn();
this.offset = this.peekOffset;
this.peekOffset = null;
return res;
}
string(timeout) {
this.waitWrite('string', timeout);
let byteLength = this._int32();
let length = byteLength / 2;
let dataView = new DataView(this.buffer, this.offset, byteLength);
let chars = [];
for (let i = 0; i < length; i++) {
chars.push(dataView.getUint16(i * 2));
}
let str = String.fromCharCode.apply(null, chars);
this.log('string', str);
this.offset += byteLength;
if (this.peekOffset == null) {
this.flip();
}
return str;
}
_int32() {
let byteLength = 4;
let dataView = new DataView(this.buffer, this.offset);
let num = dataView.getInt32();
this.log('_int32', num);
this.offset += byteLength;
return num;
}
int32() {
this.waitWrite('int32');
let num = this._int32();
this.log('int32', num);
if (this.peekOffset == null) {
this.flip();
}
return num;
}
bytes() {
this.waitWrite('bytes');
let byteLength = this._int32();
let bytes = new ArrayBuffer(byteLength);
new Uint8Array(bytes).set(
new Uint8Array(this.buffer, this.offset, byteLength)
);
this.log('bytes', bytes);
this.offset += byteLength;
if (this.peekOffset == null) {
this.flip();
}
return bytes;
}
}
export class Writer {
constructor(
buffer,
{ initialOffset = 4, useAtomics = true, stream = true, debug, name } = {}
) {
this.buffer = buffer;
this.atomicView = new Int32Array(buffer);
this.offset = initialOffset;
this.useAtomics = useAtomics;
this.stream = stream;
this.debug = debug;
this.name = name;
if (this.useAtomics) {
// The buffer starts out as writeable
Atomics.store(this.atomicView, 0, WRITEABLE);
} else {
this.atomicView[0] = WRITEABLE;
}
}
log(...args) {
if (this.debug) {
console.log(`[writer: ${this.name}]`, ...args);
}
}
waitRead(name) {
if (this.useAtomics) {
this.log(`waiting for ${name}`);
// Switch to writable
// Atomics.store(this.atomicView, 0, 1);
let prev = Atomics.compareExchange(
this.atomicView,
0,
WRITEABLE,
READABLE
);
if (prev !== WRITEABLE) {
throw new Error(
'Wrote something into unwritable buffer! This is disastrous'
);
}
Atomics.notify(this.atomicView, 0);
while (Atomics.load(this.atomicView, 0) === READABLE) {
// console.log('waiting to be read...');
Atomics.wait(this.atomicView, 0, READABLE, 500);
}
this.log(`resumed for ${name}`);
} else {
this.atomicView[0] = READABLE;
}
this.offset = 4;
}
finalize() {
this.log('finalizing');
let dataView = new DataView(this.buffer, this.offset);
dataView.setUint32(0, FINALIZED);
this.waitRead('finalize');
}
string(str) {
this.log('string', str);
let byteLength = str.length * 2;
this._int32(byteLength);
let dataView = new DataView(this.buffer, this.offset, byteLength);
for (let i = 0; i < str.length; i++) {
dataView.setUint16(i * 2, str.charCodeAt(i));
}
this.offset += byteLength;
this.waitRead('string');
}
_int32(num) {
let byteLength = 4;
let dataView = new DataView(this.buffer, this.offset);
dataView.setInt32(0, num);
this.offset += byteLength;
}
int32(num) {
this.log('int32', num);
this._int32(num);
this.waitRead('int32');
}
bytes(buffer) {
this.log('bytes', buffer);
let byteLength = buffer.byteLength;
this._int32(byteLength);
new Uint8Array(this.buffer, this.offset).set(new Uint8Array(buffer));
this.offset += byteLength;
this.waitRead('bytes');
}
}