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We just released a new package: spatie/sourcemaps-lookup It resolves JS stack frames against source maps. Flare uses it in its frame resolver. It's 99% faster and uses 91% less memory on a 6 MB map. Took me a couple of steps to get there... 🧵

First win: lazy parsing + binary search. A source map is a list of lines, each with mappings sorted by column. The old approach decoded every line upfront, all 110K of them. By only decoding the line you ask for and halving the search space, it's only ~17 steps instead of 3000.

The biggest win: PHP's lesser-known (un)pack function lets you store data as raw bytes instead of PHP objects. Each mapping is 5 ints. As an object that's ±200 bytes, but as 5 int32s in a packed string it's only 20 bytes. That's 10x less memory used!