src: consolidate C++ ReadFileSync/WriteFileSync utilities

[joyeecheung]

This patch moves ReadFileSync and WriteFileSync from src/util.cc to src/node_file_utils.cc, consolidates the implementation to reuse code, and adds a few more enhancements:

For ReadFileSync:

• Use fstat-based pre-allocation to minimize buffer resizing and repeated reads for bigger files.
• Handle various potential overflows in size conversions.
• Handle fallback for 0-byte special files.

For WriteFileSync:

• Handle potential partial writes for big enough files and support non-seekable files (with -1 as offset).
• Handle 0-byte writes correctly.

In both cases, this now avoids hard aborts and return error code for the caller to handle as much as possible, except std::vector<char> ReadFileSync(FILE* fp) which is part of the embedder API.

This patch uses the new ReadFileSync to address a TODO in node_sea.bin.cc.

Some numbers from --build-sea (note that most of the time is spent on parsing the executable and building the SEA, but even so there's a measurable difference just from the file I/O because the binary is ~120MB).

$ hyperfine "out/Release/node --build-sea sea-config.json" "./node_main --build-sea sea-config.json" --warmup 5
Benchmark 1: out/Release/node --build-sea sea-config.json
  Time (mean ± σ):      1.696 s ±  0.040 s    [User: 1.509 s, System: 0.173 s]
  Range (min … max):    1.651 s …  1.756 s    10 runs

Benchmark 2: ./node_main --build-sea sea-config.json
  Time (mean ± σ):      1.730 s ±  0.030 s    [User: 1.530 s, System: 0.183 s]
  Range (min … max):    1.681 s …  1.787 s    10 runs

Summary
  out/Release/node --build-sea sea-config.json ran
    1.02 ± 0.03 times faster than ./node_main --build-sea sea-config.json

[nodejs-github-bot]

Review requested:

• @nodejs/gyp
• @nodejs/single-executable

[joyeecheung]

cc @nodejs/cpp-reviewers

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/71186/

[codecov]

Codecov Report

❌ Patch coverage is 60.95890% with 57 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.73%. Comparing base (8e41b8d) to head (0ae8c1a).
⚠️ Report is 19 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_file_utils.cc	60.41%	34 Missing and 23 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61662      +/-   ##
==========================================
- Coverage   89.74%   89.73%   -0.02%     
==========================================
  Files         674      675       +1     
  Lines      204348   204444      +96     
  Branches    39271    39288      +17     
==========================================
+ Hits       183396   183452      +56     
- Misses      13262    13280      +18     
- Partials     7690     7712      +22     

Files with missing lines	Coverage Δ
src/node_internals.h	82.35% <ø> (ø)
src/node_sea_bin.cc	41.51% <100.00%> (-0.22%)	⬇️
src/util.cc	87.44% <ø> (+1.34%)	⬆️
src/util.h	90.09% <ø> (ø)
src/node_file_utils.cc	60.41% <60.41%> (ø)

... and 33 files with indirect coverage changes

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[Qard]

LGTM. A few small code quality improvement ideas, but I'm fine landing as-is. These are just minor suggestions to simplify things slightly. 🙂

[Qard]

Took me a moment to understand the connection between these and the outer loop. Perhaps a clearer version might simply be:

Suggested change

	while (idx < iovs.size() && iovs[idx].len == 0) {
	idx++;
	}
	if (idx >= iovs.size()) { // No non-empty buffers left.
	break;
	}
	if (iovs[idx].len == 0) {
	idx++;
	continue;
	}

[Qard]

Could merge those to:

Suggested change

	if (req.result < 0) { // Error during write.
	int err = req.result;
	uv_fs_req_cleanup(&req);
	uv_fs_close(nullptr, &req, fd, nullptr);
	uv_fs_req_cleanup(&req);
	return err;
	}
	if (req.result == 0) { // Should not happen unless the file system is full.
	uv_fs_req_cleanup(&req);
	uv_fs_close(nullptr, &req, fd, nullptr);
	uv_fs_req_cleanup(&req);
	return UV_EIO;
	}
	if (req.result <= 0) { // Error during write.
	// UV_EIO should not happen unless the file system is full.
	int err = req.result < 0 ? req.result : UV_EIO;
	uv_fs_req_cleanup(&req);
	uv_fs_close(nullptr, &req, fd, nullptr);
	uv_fs_req_cleanup(&req);
	return err;
	}