# nlohmann::basic_json::sax_parse ```cpp // (1) template static bool sax_parse(InputType&& i, SAX* sax, input_format_t format = input_format_t::json, const bool strict = true, const bool ignore_comments = false, const bool ignore_trailing_commas = false); // (2) template static bool sax_parse(IteratorType first, IteratorType last, SAX* sax, input_format_t format = input_format_t::json, const bool strict = true, const bool ignore_comments = false, const bool ignore_trailing_commas = false); ``` Read from input and generate SAX events 1. Read from a compatible input. 2. Read from a pair of character iterators The value_type of the iterator must be an integral type with a size of 1, 2, or 4 bytes, which will be interpreted respectively as UTF-8, UTF-16, and UTF-32. The SAX event lister must follow the interface of [`json_sax`](../json_sax/index.md). ## Template parameters `InputType` : A compatible input, for instance: - an `std::istream` object - a `FILE` pointer - a C-style array of characters - a pointer to a null-terminated string of single byte characters - an object `obj` for which `begin(obj)` and `end(obj)` produces a valid pair of iterators. `IteratorType` : Description `SAX` : Description ## Parameters `i` (in) : Input to parse from `sax` (in) : SAX event listener (must not be null) `format` (in) : the format to parse (JSON, CBOR, MessagePack, or UBJSON) (optional, `input_format_t::json` by default), see [`input_format_t`](input_format_t.md) for more information `strict` (in) : whether the input has to be consumed completely (optional, `#!cpp true` by default) `ignore_comments` (in) : whether comments should be ignored and treated like whitespace (`#!cpp true`) or yield a parse error (`#!cpp false`); (optional, `#!cpp false` by default) `ignore_trailing_commas` (in) : whether trailing commas in arrays or objects should be ignored and treated like whitespace (`#!cpp true`) or yield a parse error (`#!cpp false`); (optional, `#!cpp false` by default) `first` (in) : iterator to the start of a character range `last` (in) : iterator to the end of a character range ## Return value return value of the last processed SAX event ## Exception safety Strong guarantee: if an exception is thrown, there are no changes in the JSON value. ## Exceptions - Throws [`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101) in case of an unexpected token, or empty input like a null `FILE*` or `char*` pointer. - Throws [`parse_error.102`](../../home/exceptions.md#jsonexceptionparse_error102) if `to_unicode` fails or surrogate error. - Throws [`parse_error.103`](../../home/exceptions.md#jsonexceptionparse_error103) if `to_unicode` fails. - Throws [`other_error.502`](../../home/exceptions.md#jsonexceptionother_error502) if `sax` is a null pointer. ## Complexity Linear in the length of the input. The parser is a predictive LL(1) parser. The complexity can be higher if the SAX consumer `sax` has a super-linear complexity. ## Notes A UTF-8 byte order mark is silently ignored. ## Examples ??? example The example below demonstrates the `sax_parse()` function reading from string and processing the events with a user-defined SAX event consumer. ```cpp --8<-- "examples/sax_parse.cpp" ``` Output: ```json --8<-- "examples/sax_parse.output" ``` ## Version history - Added in version 3.2.0. - Ignoring comments via `ignore_comments` added in version 3.9.0. - Added `ignore_trailing_commas` in version 3.12.1. - Added `json.exception.other_error.502` exception in version 3.12.1. !!! warning "Deprecation" Overload (2) replaces calls to `sax_parse` with a pair of iterators as their first parameter which has been deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like `#!cpp sax_parse({ptr, ptr+len});` with `#!cpp sax_parse(ptr, ptr+len);`.