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| # @jridgewell/sourcemap-codec | |
| Encode/decode the `mappings` property of a [sourcemap](https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit). | |
| ## Why? | |
| Sourcemaps are difficult to generate and manipulate, because the `mappings` property – the part that actually links the generated code back to the original source – is encoded using an obscure method called [Variable-length quantity](https://en.wikipedia.org/wiki/Variable-length_quantity). On top of that, each segment in the mapping contains offsets rather than absolute indices, which means that you can't look at a segment in isolation – you have to understand the whole sourcemap. | |
| This package makes the process slightly easier. | |
| ## Installation | |
| ```bash | |
| npm install @jridgewell/sourcemap-codec | |
| ``` | |
| ## Usage | |
| ```js | |
| import { encode, decode } from '@jridgewell/sourcemap-codec'; | |
| var decoded = decode( ';EAEEA,EAAE,EAAC,CAAE;ECQY,UACC' ); | |
| assert.deepEqual( decoded, [ | |
| // the first line (of the generated code) has no mappings, | |
| // as shown by the starting semi-colon (which separates lines) | |
| [], | |
| // the second line contains four (comma-separated) segments | |
| [ | |
| // segments are encoded as you'd expect: | |
| // [ generatedCodeColumn, sourceIndex, sourceCodeLine, sourceCodeColumn, nameIndex ] | |
| // i.e. the first segment begins at column 2, and maps back to the second column | |
| // of the second line (both zero-based) of the 0th source, and uses the 0th | |
| // name in the `map.names` array | |
| [ 2, 0, 2, 2, 0 ], | |
| // the remaining segments are 4-length rather than 5-length, | |
| // because they don't map a name | |
| [ 4, 0, 2, 4 ], | |
| [ 6, 0, 2, 5 ], | |
| [ 7, 0, 2, 7 ] | |
| ], | |
| // the final line contains two segments | |
| [ | |
| [ 2, 1, 10, 19 ], | |
| [ 12, 1, 11, 20 ] | |
| ] | |
| ]); | |
| var encoded = encode( decoded ); | |
| assert.equal( encoded, ';EAEEA,EAAE,EAAC,CAAE;ECQY,UACC' ); | |
| ``` | |
| ## Benchmarks | |
| ``` | |
| node v18.0.0 | |
| amp.js.map - 45120 segments | |
| Decode Memory Usage: | |
| @jridgewell/sourcemap-codec 5479160 bytes | |
| sourcemap-codec 5659336 bytes | |
| source-map-0.6.1 17144440 bytes | |
| source-map-0.8.0 6867424 bytes | |
| Smallest memory usage is @jridgewell/sourcemap-codec | |
| Decode speed: | |
| decode: @jridgewell/sourcemap-codec x 502 ops/sec ±1.03% (90 runs sampled) | |
| decode: sourcemap-codec x 445 ops/sec ±0.97% (92 runs sampled) | |
| decode: source-map-0.6.1 x 36.01 ops/sec ±1.64% (49 runs sampled) | |
| decode: source-map-0.8.0 x 367 ops/sec ±0.04% (95 runs sampled) | |
| Fastest is decode: @jridgewell/sourcemap-codec | |
| Encode Memory Usage: | |
| @jridgewell/sourcemap-codec 1261620 bytes | |
| sourcemap-codec 9119248 bytes | |
| source-map-0.6.1 8968560 bytes | |
| source-map-0.8.0 8952952 bytes | |
| Smallest memory usage is @jridgewell/sourcemap-codec | |
| Encode speed: | |
| encode: @jridgewell/sourcemap-codec x 738 ops/sec ±0.42% (98 runs sampled) | |
| encode: sourcemap-codec x 238 ops/sec ±0.73% (88 runs sampled) | |
| encode: source-map-0.6.1 x 162 ops/sec ±0.43% (84 runs sampled) | |
| encode: source-map-0.8.0 x 191 ops/sec ±0.34% (90 runs sampled) | |
| Fastest is encode: @jridgewell/sourcemap-codec | |
| *** | |
| babel.min.js.map - 347793 segments | |
| Decode Memory Usage: | |
| @jridgewell/sourcemap-codec 35338184 bytes | |
| sourcemap-codec 35922736 bytes | |
| source-map-0.6.1 62366360 bytes | |
| source-map-0.8.0 44337416 bytes | |
| Smallest memory usage is @jridgewell/sourcemap-codec | |
| Decode speed: | |
| decode: @jridgewell/sourcemap-codec x 40.35 ops/sec ±4.47% (54 runs sampled) | |
| decode: sourcemap-codec x 36.76 ops/sec ±3.67% (51 runs sampled) | |
| decode: source-map-0.6.1 x 4.44 ops/sec ±2.15% (16 runs sampled) | |
| decode: source-map-0.8.0 x 59.35 ops/sec ±0.05% (78 runs sampled) | |
| Fastest is decode: source-map-0.8.0 | |
| Encode Memory Usage: | |
| @jridgewell/sourcemap-codec 7212604 bytes | |
| sourcemap-codec 21421456 bytes | |
| source-map-0.6.1 25286888 bytes | |
| source-map-0.8.0 25498744 bytes | |
| Smallest memory usage is @jridgewell/sourcemap-codec | |
| Encode speed: | |
| encode: @jridgewell/sourcemap-codec x 112 ops/sec ±0.13% (84 runs sampled) | |
| encode: sourcemap-codec x 30.23 ops/sec ±2.76% (53 runs sampled) | |
| encode: source-map-0.6.1 x 19.43 ops/sec ±3.70% (37 runs sampled) | |
| encode: source-map-0.8.0 x 19.40 ops/sec ±3.26% (37 runs sampled) | |
| Fastest is encode: @jridgewell/sourcemap-codec | |
| *** | |
| preact.js.map - 1992 segments | |
| Decode Memory Usage: | |
| @jridgewell/sourcemap-codec 500272 bytes | |
| sourcemap-codec 516864 bytes | |
| source-map-0.6.1 1596672 bytes | |
| source-map-0.8.0 517272 bytes | |
| Smallest memory usage is @jridgewell/sourcemap-codec | |
| Decode speed: | |
| decode: @jridgewell/sourcemap-codec x 16,137 ops/sec ±0.17% (99 runs sampled) | |
| decode: sourcemap-codec x 12,139 ops/sec ±0.13% (99 runs sampled) | |
| decode: source-map-0.6.1 x 1,264 ops/sec ±0.12% (100 runs sampled) | |
| decode: source-map-0.8.0 x 9,894 ops/sec ±0.08% (101 runs sampled) | |
| Fastest is decode: @jridgewell/sourcemap-codec | |
| Encode Memory Usage: | |
| @jridgewell/sourcemap-codec 321026 bytes | |
| sourcemap-codec 830832 bytes | |
| source-map-0.6.1 586608 bytes | |
| source-map-0.8.0 586680 bytes | |
| Smallest memory usage is @jridgewell/sourcemap-codec | |
| Encode speed: | |
| encode: @jridgewell/sourcemap-codec x 19,876 ops/sec ±0.78% (95 runs sampled) | |
| encode: sourcemap-codec x 6,983 ops/sec ±0.15% (100 runs sampled) | |
| encode: source-map-0.6.1 x 5,070 ops/sec ±0.12% (102 runs sampled) | |
| encode: source-map-0.8.0 x 5,641 ops/sec ±0.17% (100 runs sampled) | |
| Fastest is encode: @jridgewell/sourcemap-codec | |
| *** | |
| react.js.map - 5726 segments | |
| Decode Memory Usage: | |
| @jridgewell/sourcemap-codec 734848 bytes | |
| sourcemap-codec 954200 bytes | |
| source-map-0.6.1 2276432 bytes | |
| source-map-0.8.0 955488 bytes | |
| Smallest memory usage is @jridgewell/sourcemap-codec | |
| Decode speed: | |
| decode: @jridgewell/sourcemap-codec x 5,723 ops/sec ±0.12% (98 runs sampled) | |
| decode: sourcemap-codec x 4,555 ops/sec ±0.09% (101 runs sampled) | |
| decode: source-map-0.6.1 x 437 ops/sec ±0.11% (93 runs sampled) | |
| decode: source-map-0.8.0 x 3,441 ops/sec ±0.15% (100 runs sampled) | |
| Fastest is decode: @jridgewell/sourcemap-codec | |
| Encode Memory Usage: | |
| @jridgewell/sourcemap-codec 638672 bytes | |
| sourcemap-codec 1109840 bytes | |
| source-map-0.6.1 1321224 bytes | |
| source-map-0.8.0 1324448 bytes | |
| Smallest memory usage is @jridgewell/sourcemap-codec | |
| Encode speed: | |
| encode: @jridgewell/sourcemap-codec x 6,801 ops/sec ±0.48% (98 runs sampled) | |
| encode: sourcemap-codec x 2,533 ops/sec ±0.13% (101 runs sampled) | |
| encode: source-map-0.6.1 x 2,248 ops/sec ±0.08% (100 runs sampled) | |
| encode: source-map-0.8.0 x 2,303 ops/sec ±0.15% (100 runs sampled) | |
| Fastest is encode: @jridgewell/sourcemap-codec | |
| ``` | |
| # License | |
| MIT | |