mirror of
https://github.com/nlohmann/json.git
synced 2026-10-15 02:37:13 +00:00
Niels Lohmann
c391abccb1
Parsing from a FILE* reads one character at a time with std::fgetc, which locks and unlocks the FILE object for every character. file_input_adapter now locks the file once when it is created and unlocks it when it is destroyed - also when parsing throws - and reads with the unlocked stdio functions in between: flockfile/getc_unlocked/funlockfile with glibc, Apple, Android, and the BSDs, and _lock_file/_fgetc_nolock/_unlock_file with the Microsoft C runtime. Other C libraries keep std::fgetc. The lock is recursive, so fread() in the binary readers and stdio calls of a SAX handler or parser callback on the same thread keep working. On an Apple M1 Max, parsing from a FILE* is 2.9 to 4.0 times as fast (twitter.json 14.3 -> 4.1 ms, citm_catalog.json 35.4 -> 8.8 ms); with glibc, whose locking is cheaper, 1.1 to 1.3 times. The values and the position of the file after parsing are unchanged. Other threads that use the same FILE object now wait until parsing is done instead of interleaving their reads with the parser's. JSON_DISABLE_UNLOCKED_FILE_IO restores std::fgetc, for programs in which a SAX handler waits for another thread that uses the same FILE. The new tests check from a second thread that the lock is released after success and after a parse error, and run again with the macro. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Documentation
Generate documentation
Note on documentation: The source files contain links to the online documentation at https://json.nlohmann.me.
This URL provides the most recent documentation and also applies to previous versions. Documentation for deprecated
functions is not removed; instead, it is marked as deprecated.
If you want to view the documentation for a specific tag or commit hash, you can generate it locally as follows (example
using tag v3.12.0):
git clone https://github.com/nlohmann/json.git
cd json
git checkout v3.12.0
make install_venv serve -C docs/mkdocs
Open http://127.0.0.1:8000/ in your browser. Replace any URL in the source code that points to
https://json.nlohmann.me with http://127.0.0.1:8000 to view the documentation for the selected tag or commit hash.