[vim/vim] JSON control escapes use costly numeric formatting (PR #21381)
mattn
JSON encoding currently formats each ASCII control character without a short escape through vim_snprintf_safelen(). Generate the two hexadecimal digits of \u00xx directly, preserving the encoded output. Add coverage for all control escapes mixed with multibyte text across buffer growth, for both json_encode() and js_encode().
Before/after measurements for 1,000 calls to json_encode() on a 4,096-byte string (median of five runs, GCC -O2; baseline 1b405bb705, patched 0e6b0ddfb5):
| Input | Before | After | Time reduction |
|---|---|---|---|
Control characters: repeat("\x01", 4096) |
392.821 ms | 27.634 ms | 93.0% |
Mixed text: repeat(repeat('a', 63) .. "\x1b", 64) |
11.603 ms | 6.563 ms | 43.4% |
Plain ASCII: repeat('a', 4096) |
5.840 ms | 5.819 ms | 0.4% (essentially unchanged) |
These are focused microbenchmarks; baseline and patched binaries were alternated between runs and were not CPU-pinned.
Validation: make -C src -j4 completed without compiler warnings, all eight tests in test_json.vim passed, and git diff --check passed.
You can view, comment on, or merge this pull request online at:
https://github.com/vim/vim/pull/21381
Commit Summary
- 0e6b0dd patch 9.2.NNNN: JSON control escapes use costly numeric formatting
File Changes
(2 files)
- M src/json.c (9)
- M src/testdir/test_json.vim (11)
Patch Links:
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Christian Brabandt
chrisbra left a comment (vim/vim#21381)thanks
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