src: consolidate C++ ReadFileSync/WriteFileSync utilities #61662

joyeecheung · 2026-02-03T20:19:17Z

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

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.

nodejs-github-bot · 2026-02-03T20:19:22Z

Review requested:

@nodejs/gyp
@nodejs/single-executable

joyeecheung · 2026-02-03T20:26:48Z

cc @nodejs/cpp-reviewers

nodejs-github-bot · 2026-02-03T20:56:23Z

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

codecov · 2026-02-03T22:04:51Z

Codecov Report

❌ Patch coverage is 62.85714% with 52 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.72%. Comparing base (8e41b8d) to head (48ed3ef).
⚠️ Report is 42 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_file_utils.cc	62.31%	30 Missing and 22 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61662      +/-   ##
==========================================
- Coverage   89.74%   89.72%   -0.03%     
==========================================
  Files         674      675       +1     
  Lines      204348   204472     +124     
  Branches    39271    39290      +19     
==========================================
+ Hits       183396   183460      +64     
- Misses      13262    13303      +41     
- Partials     7690     7709      +19

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	`62.31% <62.31%> (ø)`

... and 35 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. 🙂

src/node_file_utils.cc

Co-authored-by: Stephen Belanger <admin@stephenbelanger.com>

joyeecheung · 2026-02-05T01:11:48Z

Thanks for the suggestion. @Qard @RafaelGSS Can you take a look again?

nodejs-github-bot · 2026-02-05T02:12:45Z

CI: https://ci.nodejs.org/job/node-test-pull-request/71197/

nodejs-github-bot · 2026-02-05T13:16:42Z

CI: https://ci.nodejs.org/job/node-test-pull-request/71203/

nodejs-github-bot · 2026-02-07T00:45:41Z

CI: https://ci.nodejs.org/job/node-test-pull-request/71225/

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. PR-URL: #61662 Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com> Reviewed-By: Stephen Belanger <admin@stephenbelanger.com> Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: James M Snell <jasnell@gmail.com>

nodejs-github-bot · 2026-02-07T02:38:59Z

Landed in 9bc369f...3ab9dd8

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. PR-URL: #61662 Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com> Reviewed-By: Stephen Belanger <admin@stephenbelanger.com> Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: James M Snell <jasnell@gmail.com>

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fixup! src: consolidate C++ ReadFileSync/WriteFileSync utilities

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Co-authored-by: Stephen Belanger <admin@stephenbelanger.com>

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