perf(ast/estree): pre-allocate CodeBuffer for JSON output

[overlookmotel]

ESTree serialization pre-allocate capacity in CodeBuffer for JSON, based on an heuristic ratio of source text length to JSON length, to avoid the buffer having to grow during serialization.

[overlookmotel]

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• perf(ast/estree): pre-allocate CodeBuffer for JSON output #9340 👈 (View in Graphite)
• perf(ast/estree): ESTree serializer use CodeBuffer #9331
• refactor(estree): make itoa dependency optional #9338
• feat(data_structures): add CodeBuffer::print_bytes_iter_unchecked method #9337
• refactor(data_structures): add debug assertion to CodeBuffer::peek_nth_char_back and improve safety docs #9336
• refactor(data_structures): CodeBuffer::print_str use Vec::extend_from_slice #9332 : 1 other dependent PR (#9335 )
• main

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[codspeed-hq]

CodSpeed Performance Report

Merging #9340 will improve performances by 24.38%

_{Comparing 02-24-perf_ast_estree_pre-allocate_codebuffer_for_json_output (b179153) with 02-23-perf_ast_estree_estree_serializer_use_codebuffer_ (2c8281a)}

Summary

⚡ 1 improvements
✅ 32 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	estree[checker.ts]	152 ms	122.2 ms	+24.38%

[overlookmotel]

Now we're talking!

To be fair, this effect is only so pronounced because the file we're benchmarking - checker.ts - is so large that it generates about 3 MB of JSON. If the buffer has to grow, copying a chunk of memory that large is really expensive. The effect would be much smaller on average size files.