fs: add a fast-path for readFileSync utf-8

[anonrig]

This pull request improves the performance of fs.readFileSync for UTF-8 encoding.

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/1346

 confidence improvement accuracy (*) (**) (***) fs/readFileSync.js n=600 path='existing' encoding='undefined' -2.98 % ±3.46% ±4.61% ±6.00% fs/readFileSync.js n=600 path='existing' encoding='utf8' *** 72.60 % ±6.46% ±8.64% ±11.32% fs/readFileSync.js n=600 path='non-existing' encoding='undefined' -1.16 % ±2.29% ±3.05% ±3.97% fs/readFileSync.js n=600 path='non-existing' encoding='utf8' 2.02 % ±3.05% ±4.06% ±5.28% Be aware that when doing many comparisons the risk of a false-positive result increases. In this case, there are 4 comparisons, you can thus expect the following amount of false-positive results: 0.20 false positives, when considering a 5% risk acceptance (*, **, ***), 0.04 false positives, when considering a 1% risk acceptance (**, ***), 0.00 false positives, when considering a 0.1% risk acceptance (***) 

[anonrig]

@santigimeno@bnoordhuis One of the tests failing and throwing ESPIPE: invalid seek, undefined error. Can you point me towards the faulty lines?

Stack trace

AssertionError [ERR_ASSERTION]: ifError got unwanted exception: Command failed: cat /Users/yagiz/Developer/node/test/.tmp.0/readfilesync_pipe_large_test.txt | "/Users/yagiz/Developer/node/out/Release/node" "/Users/yagiz/Developer/node/test/parallel/test-fs-readfilesync-pipe-large.js" child node:internal/fs/utils:351 throw err; ^ Error: ESPIPE: invalid seek, undefined at readFileSyncUtf8 (node:internal/fs/read-file/utf8:19:3) at Object.readFileSync (node:fs:467:12) at Object.<anonymous> (/Users/yagiz/Developer/node/test/parallel/test-fs-readfilesync-pipe-large.js:14:27) at Module._compile (node:internal/modules/cjs/loader:1233:14) at Module._extensions..js (node:internal/modules/cjs/loader:1287:10) at Module.load (node:internal/modules/cjs/loader:1091:32) at Module._load (node:internal/modules/cjs/loader:938:12) at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:83:12) at node:internal/main/run_main_module:23:47{errno: -29, code: 'ESPIPE' } Node.js v21.0.0-pre at ChildProcess.exithandler (node:child_process:419:12) at ChildProcess.emit (node:events:512:28) at maybeClose (node:internal/child_process:1105:16) at Socket.<anonymous> (node:internal/child_process:457:11) at Socket.emit (node:events:512:28) at Pipe.<anonymous> (node:net:334:12){generatedMessage: false, code: 'ERR_ASSERTION', actual: Error: Command failed: cat /Users/yagiz/Developer/node/test/.tmp.0/readfilesync_pipe_large_test.txt | "/Users/yagiz/Developer/node/out/Release/node" "/Users/yagiz/Developer/node/test/parallel/test-fs-readfilesync-pipe-large.js" child node:internal/fs/utils:351 throw err; ^ Error: ESPIPE: invalid seek, undefined at readFileSyncUtf8 (node:internal/fs/read-file/utf8:19:3) at Object.readFileSync (node:fs:467:12) at Object.<anonymous> (/Users/yagiz/Developer/node/test/parallel/test-fs-readfilesync-pipe-large.js:14:27) at Module._compile (node:internal/modules/cjs/loader:1233:14) at Module._extensions..js (node:internal/modules/cjs/loader:1287:10) at Module.load (node:internal/modules/cjs/loader:1091:32) at Module._load (node:internal/modules/cjs/loader:938:12) at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:83:12) at node:internal/main/run_main_module:23:47{errno: -29, code: 'ESPIPE' } Node.js v21.0.0-pre at ChildProcess.exithandler (node:child_process:419:12) at ChildProcess.emit (node:events:512:28) at maybeClose (node:internal/child_process:1105:16) at Socket.<anonymous> (node:internal/child_process:457:11) at Socket.emit (node:events:512:28) at Pipe.<anonymous> (node:net:334:12){code: 1, killed: false, signal: null, cmd: 'cat /Users/yagiz/Developer/node/test/.tmp.0/readfilesync_pipe_large_test.txt | "/Users/yagiz/Developer/node/out/Release/node" "/Users/yagiz/Developer/node/test/parallel/test-fs-readfilesync-pipe-large.js" child' }, expected: null, operator: 'ifError' } Node.js v21.0.0-pre 

[mcollina]

great work!

[mcollina]

lgtm

I would recommend a CITGM run anyway

[anonrig]

Is this PR worth having a notable-change label? I believe informing & sharing with the users might be a good thing. Please, remove it, if you think it's unnecessary. cc @nodejs/performance

[github-actions]

The notable-changePRs with changes that should be highlighted in changelogs. label has been added by @anonrig.

Please suggest a text for the release notes if you'd like to include a more detailed summary, then proceed to update the PR description with the text or a link to the notable change suggested text comment.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/52637/