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api/basic_json/sax_parse.md

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+# <small>nlohmann::basic_json::</small>sax_parse
+
+```cpp
+// (1)
+template <typename InputType, typename SAX>
+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<class IteratorType, class SAX>
+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`
+:   a compatible iterator type for overload (2); a pair of character iterators whose `value_type` is an integral type
+    with a size of 1, 2, or 4 bytes (interpreted respectively as UTF-8, UTF-16, and UTF-32)
+
+`SAX`
+:   a class fulfilling the SAX event listener interface; see [`json_sax`](../json_sax/index.md)
+
+## 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.
+
+## 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"
+    ```
+
+## See also
+
+- [parse](parse.md) - deserialize from a compatible input
+- [accept](accept.md) - check if the input is valid JSON
+
+## 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.x.
+
+!!! 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);`.