The parser records where the integer digits, the fraction digits, and the
exponent of a float token are. For doubles with at most 19 digits, the
value is now read from that layout: the digits eight at a time, without
scanning the token, and rounded with Clinger's fast path where both
operands are exact, else with the Eisel-Lemire algorithm (which needs no
fallback for up to 19 digits). Both round correctly, so the values are
those of parse(); other tokens and types keep the library's conversion.
get<double>(), materialize(), dump(), and comparisons use it. Traversing
canada.json (111,000 floats, every number converted): 0.53 -> 0.86 GB/s.
Tests add tokens around the limits (19 and 20 digits, 2^53, 10^22) to the
bit-for-bit comparison with parse().
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The public classes of the zero-copy view (#5295), in the new header
<nlohmann/json_view.hpp>:
- basic_json_document<BasicJsonType>: parse (borrowing contiguous byte
inputs, owning rvalue strings, streams, and other inputs), parse_copy,
accept, read, root, is_discarded, source, owns_source, node_count,
memory_usage, shrink_to_fit
- basic_json_view<BasicJsonType>: type and the is_* queries, size, empty,
materialize (the value parse() would produce, built by the same SAX
handler), source_offset
- the aliases json_document, json_view, ordered_json_document, and
ordered_json_view
A parse error throws the exception basic_json::parse would throw for the
same input: the library parser is run on the failing input, so messages,
positions, and exception ids are the same. Inputs of 4 GiB or more are
rejected with out_of_range.416.
The single header single_include/nlohmann/json_view.hpp keeps including
json.hpp; make amalgamate, check-amalgamation, include.zip, and release
handle it.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
