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perf: improve hexToBase64 #3178

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merged 5 commits into from
Aug 22, 2022
Merged

perf: improve hexToBase64 #3178

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6b2d939
perf: improve hexToBase64
seemk Aug 18, 2022
b542105
chore: update changelog
seemk Aug 18, 2022
2d17e04
Merge branch 'main' into improve-hex-to-base64-perf
dyladan Aug 22, 2022
95966fa
perf: hexToBase64: use preallocated buffer
seemk Aug 22, 2022
13471d7
test: add a test for longer hex strings
seemk Aug 22, 2022
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -8,6 +8,7 @@ All notable changes to this project will be documented in this file.

### :rocket: (Enhancement)

* perf(opentelemetry-core): improve hexToBase64 performance [#3178](https://github.com/open-telemetry/opentelemetry-js/pull/3178)
* feat(sdk-trace-base): move Sampler declaration into sdk-trace-base [#3088](https://github.com/open-telemetry/opentelemetry-js/pull/3088) @legendecas
* fix(grpc-instrumentation): added grpc attributes in instrumentation [#3127](https://github.com/open-telemetry/opentelemetry-js/pull/3127) @andrewzenkov
* feat: support latest `@opentelemetry/api` [#3177](https://github.com/open-telemetry/opentelemetry-js/pull/3177) @dyladan
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30 changes: 23 additions & 7 deletions packages/opentelemetry-core/src/platform/node/hex-to-base64.ts
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Expand Up @@ -13,14 +13,30 @@
* See the License for the specific language governing permissions and
* limitations under the License.
*/
function intValue(charCode: number): number {
// 0-9
if (charCode >= 48 && charCode <= 57) {
return charCode - 48;
}

// a-f
if (charCode >= 97 && charCode <= 102) {
return charCode - 87;
}

// A-F
return charCode - 55;
}

export function hexToBase64(hexStr: string): string {
const hexStrLen = hexStr.length;
let hexAsciiCharsStr = '';
for (let i = 0; i < hexStrLen; i += 2) {
const hexPair = hexStr.substring(i, i + 2);
const hexVal = parseInt(hexPair, 16);
hexAsciiCharsStr += String.fromCharCode(hexVal);
const buf = Buffer.alloc(hexStr.length / 2);
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The alloc is probably the most expensive part of this function at this point. Preallocating common lengths likely results in a significant speedup

const buf8 = Buffer.alloc(8)
const buf16 = Buffer.alloc(16)

function hexToBase64(hexStr) {
    let buf;
    if (hexStr.length === 16) buf = buf8;
    else if (hexStr.length === 32) buf = buf16;
    else buf = Buffer.alloc(hexStr.length / 2);

    let offset = 0;

    for (let i = 0; i < hexStr.length; i += 2) {
        const hi = intValue(hexStr.charCodeAt(i));
        const lo = intValue(hexStr.charCodeAt(i + 1));
        buf.writeUInt8((hi << 4) | lo, offset++);
    }

    return buf.toString('base64');
}

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That's a good point, added in 95966fa

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I used node-microbenchmark and the speedup is definitely real

Iterations: 375
  +-------------------------+--------------------+----------------------+-----------+
  | Name                    | nano seconds       | milli seconds        | Slower by |
  +-------------------------+--------------------+----------------------+-----------+
  | testHexToBase64Prealloc | 8349.088           | 0.008349088          | fastest   |
  | testHexToBase64         | 12648.157333333333 | 0.012648157333333333 | 1x        |
  +-------------------------+--------------------+----------------------+-----------+

let offset = 0;

for (let i = 0; i < hexStr.length; i += 2) {
const hi = intValue(hexStr.charCodeAt(i));
const lo = intValue(hexStr.charCodeAt(i + 1));
buf.writeUInt8((hi << 4) | lo, offset++);
}

return Buffer.from(hexAsciiCharsStr, 'ascii').toString('base64');
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return buf.toString('base64');
}
6 changes: 4 additions & 2 deletions packages/opentelemetry-core/test/platform/hex-to-base64.test.ts
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Expand Up @@ -20,8 +20,10 @@ import { hexToBase64 } from '../../src/platform';
describe('hexToBase64', () => {
it('convert hex to base64', () => {
const id1 = '7deb739e02e44ef2';
const id2 = '46cef837b919a16ff26e608c8cf42c80';
const id2 = '12abc034d567e89ff26e608c8cf42c80';
const id3 = id2.toUpperCase();
assert.strictEqual(hexToBase64(id1), 'fetzngLkTvI=');
assert.strictEqual(hexToBase64(id2), 'Rs74N7kZoW/ybmCMjPQsgA==');
assert.strictEqual(hexToBase64(id2), 'EqvANNVn6J/ybmCMjPQsgA==');
assert.strictEqual(hexToBase64(id3), 'EqvANNVn6J/ybmCMjPQsgA==');
});
});