a collection of lightweight TypeScript packages for AT Protocol, the protocol powering Bluesky
atproto
bluesky
typescript
npm
feat(varint): unroll varint encode/decode
+93
-7
+5
.changeset/silent-plants-cut.md
+5
.changeset/silent-plants-cut.md
+88
-7
packages/utilities/varint/lib/index.ts
+88
-7
packages/utilities/varint/lib/index.ts
···
27
27
28
28
const start = offset;
29
29
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+
if (num < N1) {
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+
buf[offset] = num;
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+
return 1;
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+
}
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+
35
+
if (num < N2) {
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buf[offset] = (num & REST) | MSB;
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buf[offset + 1] = num >>> 7;
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return 2;
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}
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+
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if (num < N3) {
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buf[offset] = (num & REST) | MSB;
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buf[offset + 1] = ((num >>> 7) & REST) | MSB;
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buf[offset + 2] = num >>> 14;
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return 3;
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}
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+
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+
if (num < N4) {
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+
buf[offset] = (num & REST) | MSB;
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buf[offset + 1] = ((num >>> 7) & REST) | MSB;
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buf[offset + 2] = ((num >>> 14) & REST) | MSB;
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buf[offset + 3] = num >>> 21;
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return 4;
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+
}
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+
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if (num < INT) {
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buf[offset] = (num & REST) | MSB;
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buf[offset + 1] = ((num >>> 7) & REST) | MSB;
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buf[offset + 2] = ((num >>> 14) & REST) | MSB;
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buf[offset + 3] = ((num >>> 21) & REST) | MSB;
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buf[offset + 4] = num >>> 28;
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return 5;
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}
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+
30
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while (num >= INT) {
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buf[offset++] = (num & 0xff) | MSB;
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num /= 128;
···
48
83
* @returns A tuple containing the resulting number, and the amount of bytes read
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*/
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export const decode = (buf: Uint8Array | number[], offset = 0): [num: number, read: number] => {
51
-
// deno-lint-ignore prefer-const
52
-
let l = buf.length;
86
+
const l = buf.length;
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let counter = offset;
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+
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+
if (counter >= l) {
90
+
throw new RangeError('could not decode varint');
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}
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+
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+
let b = buf[counter++];
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+
let res = b & REST;
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if (b < MSB) {
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return [res, 1];
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+
}
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+
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+
if (counter >= l) {
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+
throw new RangeError('could not decode varint');
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}
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+
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b = buf[counter++];
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res |= (b & REST) << 7;
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if (b < MSB) {
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return [res, 2];
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}
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+
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+
if (counter >= l) {
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throw new RangeError('could not decode varint');
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}
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+
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b = buf[counter++];
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res |= (b & REST) << 14;
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+
if (b < MSB) {
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return [res, 3];
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}
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+
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+
if (counter >= l) {
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throw new RangeError('could not decode varint');
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}
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+
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b = buf[counter++];
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res |= (b & REST) << 21;
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if (b < MSB) {
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return [res, 4];
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+
}
53
128
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-
let res = 0;
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-
let shift = 0;
56
-
let counter = offset;
57
-
let b: number;
129
+
if (counter >= l) {
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+
throw new RangeError('could not decode varint');
131
+
}
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+
133
+
b = buf[counter++];
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+
res += (b & REST) * N4;
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+
if (b < MSB) {
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return [res, 5];
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+
}
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+
let shift = 35;
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140
do {
60
141
if (counter >= l) {
61
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throw new RangeError('could not decode varint');
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143
}
63
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b = buf[counter++];
65
-
res += shift < 28 ? (b & REST) << shift : (b & REST) * Math.pow(2, shift);
146
+
res += (b & REST) * 2 ** shift;
66
147
shift += 7;
67
148
} while (b >= MSB);
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149