mirror of
https://github.com/simdjson/simdjson
synced 2026-06-08 17:27:07 +00:00
Daniel Lemire
79 lines
2.5 KiB
C++
79 lines
2.5 KiB
C++
/**
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* @file compile_time_json.h
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* @brief Compile-time JSON parsing using C++26 reflection with
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* std::meta::substitute()
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*/
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#ifndef SIMDJSON_GENERIC_COMPILE_TIME_JSON_H
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#define SIMDJSON_GENERIC_COMPILE_TIME_JSON_H
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#if SIMDJSON_STATIC_REFLECTION
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#include <algorithm>
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#include <array>
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#include <charconv>
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#include <cstdint>
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#include <expected>
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#include <meta>
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#include <string>
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#include <string_view>
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#include <vector>
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namespace simdjson {
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namespace compile_time {
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/**
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* @brief Compile-time JSON parser. This function parses the provided JSON
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* string at compile time and returns a custom struct type representing the JSON
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* object.
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*
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* We have a few limitations which trigger compile-time errors if violated:
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* - Only JSON objects and arrays are supported at the top level (no primitives).
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* We will lift this limitation in the future.
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* - Strings are represented using the const char * in UTF-8, but they must not
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* contain embedded nulls. We would prefer to represent them as std::string or
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* std::string_view, and hope to do so in the future.
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* - Heterogeneous arrays are not supported yet. E.g., you need to have arrays of
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* all integers, or all strings, all floats, all compatible objects, etc.
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* For example, the following is accepted:
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* [
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* { "name": "Alice", "age": 30 },
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* { "name": "Bob", "age": 25 },
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* { "name": "Charlie", "age": 35 }
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* ]
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* but the following is not:
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* [
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* { "name": "Alice", "age": 30 },
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* "Just a string",
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* 42,
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* { "name": "Charlie", "age": 35 }
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* ]
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*
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* We may support heterogeneous arrays in the future with std::variant types.
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* - We parse the first JSON document encountered in the string. Trailing
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* characters are ignored. Thus if your JSON begins with {"a":1}, everything
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* after the closing } is ignored. This limitation will be lifted in the future,
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* reporting an error.
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*
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* These limitations are safe in the sense that they result in compile-time errors.
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* Thus you will not get truncated strings or imprecise floats silently.
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*
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* This function is subject to change in the future.
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*/
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template <constevalutil::fixed_string json_str> consteval auto parse_json();
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} // namespace compile_time
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inline namespace literals {
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template <simdjson::constevalutil::fixed_string str>
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consteval auto operator ""_json() {
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return simdjson::compile_time::parse_json<str>();
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}
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} // namespace literals
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} // namespace simdjson
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#endif // SIMDJSON_STATIC_REFLECTION
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#endif // SIMDJSON_GENERIC_COMPILE_TIME_JSON_H
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