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Niels Lohmann
6c3ab966d3
* CBOR reader: read runs of scalar array elements in one loop When a definite-length CBOR array opens and the input is contiguous, read the integers, floats, booleans, and nulls that follow in a tight loop instead of going through parse_cbor_internal's container logic and parse_cbor_value's dispatch for every element. The loop stops at any other kind of value and when fewer than 9 bytes are left; those values are read by the general path exactly as before. Non-contiguous inputs are not affected (tag dispatch on the bulk-scan capability). Also pass a member empty string as the number source to number_float instead of constructing a std::string for every float. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * CBOR reader: address review of the scalar-run reader - parse_cbor_scalar_run: set the size explicitly in every case that reads a value, instead of relying on a default that every other case overwrites. - Remove cbor_scalar_follows(): parse_cbor_scalar_run already returns on the same conditions, and without the pre-check SAX canada needs another 8.5 % fewer instructions with GCC 13 (0.915 against the previous version), with no row more than 0.5 % worse (Mac and GCC). - Restore the comment on why parse_cbor_internal copies the container frame. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * CBOR reader: enter the scalar run only when a scalar follows An array of containers or strings called the out-of-line run start once per array only to leave it at once; on nested data (arrays of objects) that call made reading slower than before the run reader. enter_cbor_array now tests the first byte and the remaining length inline and calls the run only for a scalar, so the run's loop condition moves to the end (do-while). Signed-off-by: Niels Lohmann <mail@nlohmann.me> * CBOR reader: mark the initial accepted in the scalar run as a false-positive dead store ci_infer reports DEAD_STORE for 'bool accepted = true;' in parse_cbor_scalar_run because every case assigns accepted before it is read. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * CBOR reader: drop the scalar pre-check before the run enter_cbor_array calls the run directly again, and parse_cbor_scalar_run tests the remaining count and length at the top of a while loop; its own switch already leaves on any value that is not a scalar. The MessagePack reader is built the same way. Instructions per repetition, new/old: clang SAX canada 0.983, read canada 0.993; GCC 13 read canada 0.997, the other rows at most 1.004. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * CBOR reader: say why the initial accepted in the scalar run stays Infer's DEAD_STORE report is right, not a false positive: every case that reaches the read assigns accepted. The initializer is kept for clang-tidy's cppcoreguidelines-init-variables. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * CBOR reader: give the scalar run the bulk tag instead of a wrapper parse_cbor_scalar_run takes the bulk-scan tag itself and is the function that is kept out of line, so the one-line parse_cbor_array_start wrapper goes, as the UBJSON typed run already does. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * CBOR reader: start the scalar run's accepted at false Infer ignores dead stores of 0 (--liveness-ignored-constant defaults to "0"), and false is 0 to it, so the suppression and its comment go. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * CBOR reader: let the scalar run find its array itself parse_cbor_scalar_run reads container_stack.back() in its bulk version, so the caller no longer evaluates it for input that is not contiguous. Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>