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Niels Lohmann
60107eda3f
* Read ND-arrays of half floats and enforce the char limit in ND-arrays BJData N-dimensional arrays with element type 'h' (float16) failed to read with a misleading parse_error.112, because the reader's dtype name table lacked 'h'. It now maps to "half", the JData name. The writer still does not pack "half"; such an object is written as a plain object and reads back equal. BJData limits 'C' (char) to 0..127 in Draft 2 and Draft 3, and the 1-D reader enforces this, but ND-arrays with _ArrayType_ "char" wrote values up to 255 as 'C' elements and read them back without a check. The writer now only packs values in 0..127 (others fall back to a plain object that round-trips), and the reader rejects 'C' elements above 127 with parse_error.113 like the 1-D reader. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: correct and complete the BJData documentation Verify the BJData chapter against the library and the Draft 2/3/4 specifications and fix what did not match: - bjdata.md: correct the list of unused markers (N, not Z), the ND-array example (3x2, not 2x3), the conditions under which an object is packed as an ND-array (exactly three keys, row vectors, float-only elements for single/double, char 0..127, byte only in Draft 3), the binary table row and notes (which flag/draft combinations write [$B), the "$" type restriction (Draft 3, Z is excluded too), the H marker in the deserialization table, and the claim of a complete deserialization mapping. Document the supported drafts, that Draft 4 (SoA containers, extension type E) and column-major ND-arrays are rejected, ND-arrays of half floats, duplicate object keys, and link the Draft 3 specifications instead of master. - Add an API page for basic_json::bjdata_version_t with an example, and link it from the nav, the API index and to_bjdata. - Update binary_formats/index.md and binary_values.md, which still claimed that BJData has no binary type, and fix a wrong byte comment there. - Document parse_error.115 and the out_of_range.408 cases for from_bjdata, the precise other_error.502 condition for to_bjdata, and reword the note on truncated unsigned integers in exceptions.md (only ND-array elements were truncated before 3.13.0). Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Regenerate single_include and apply astyle Result of make amalgamate (including make pretty) for the preceding changes. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Address review of the BJData documentation The $ type restriction exists since Draft 2 (Draft 3 added B), $ requires a count, ND char above 127 is rejected on read, and the new API page is listed in alphabetical order in the nav. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: format tables, use the Oxford comma Reformat the tables changed by this PR (BJData serialization and deserialization mappings, completeness and binary-value tables) so all rows are aligned, and add the Oxford comma to lists of three or more items in the added text. Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me>
4.2 KiB
4.2 KiB
Binary Formats
Though JSON is a ubiquitous data format, it is not a very compact format suitable for data exchange, for instance, over a network. Hence, the library supports
- BJData (Binary JData),
- BON8 (Binary Object Notation 8),
- BSON (Binary JSON),
- CBOR (Concise Binary Object Representation),
- MessagePack, and
- UBJSON (Universal Binary JSON)
to efficiently encode JSON values to byte vectors and to decode such vectors.
Comparison
Completeness
| Format | Serialization | Deserialization |
|---|---|---|
| BJData | complete | incomplete: no column-major ND-arrays, no Draft 4 SoA/extension types |
| BON8 | incomplete: no unsigned integers above int64 | complete |
| BSON | incomplete: top-level value must be an object | incomplete, but all JSON types are supported |
| CBOR | complete | incomplete, but all JSON types are supported |
| MessagePack | complete | incomplete, but all JSON types are supported |
| UBJSON | complete | complete |
Binary values
| Format | Binary values | Binary subtypes |
|---|---|---|
| BJData | supported (Draft 3 only) | not supported |
| BON8 | not supported | not supported |
| BSON | supported | supported |
| CBOR | supported | supported |
| MessagePack | supported | supported |
| UBJSON | not supported | not supported |
See binary values for more information.
Sizes
| Format | canada.json | twitter.json | citm_catalog.json | jeopardy.json |
|---|---|---|---|---|
| BJData | 53.2 % | 91.1 % | 78.1 % | 96.6 % |
| BJData (size) | 58.6 % | 92.1 % | 86.7 % | 97.4 % |
| BJData (size+type) | 58.6 % | 92.1 % | 86.5 % | 97.4 % |
| BON8 | 50.5 % | 83.8 % | 63.5 % | 87.5 % |
| BSON | 85.8 % | 95.2 % | 95.8 % | 106.7 % |
| CBOR | 50.5 % | 86.3 % | 68.4 % | 88.0 % |
| MessagePack | 50.5 % | 86.0 % | 68.5 % | 87.9 % |
| UBJSON | 53.2 % | 91.3 % | 78.2 % | 96.6 % |
| UBJSON (size) | 58.6 % | 92.3 % | 86.8 % | 97.4 % |
| UBJSON (size+type) | 55.9 % | 92.3 % | 85.0 % | 95.0 % |
Sizes compared to minified JSON value; the smallest size per file is printed in bold.
See also
- Binary values - binary values and subtypes
- to_cbor / from_cbor, to_msgpack / from_msgpack, to_bson / from_bson, to_ubjson / from_ubjson, to_bjdata / from_bjdata, to_bon8 / from_bon8 - the conversion functions
- Parsing untrusted input
- SAX interface - decode binary formats without building a value