simdjson-simdjson/include/simdjson/generic/builder/json_string_builder.h

#ifndef SIMDJSON_GENERIC_STRING_BUILDER_H

#ifndef SIMDJSON_CONDITIONAL_INCLUDE
#define SIMDJSON_GENERIC_STRING_BUILDER_H
#include "simdjson/generic/implementation_simdjson_result_base.h"
#endif // SIMDJSON_CONDITIONAL_INCLUDE

namespace simdjson {


#if SIMDJSON_SUPPORTS_CONCEPTS

namespace SIMDJSON_IMPLEMENTATION {
namespace builder {
  class string_builder;
}}

template <typename T, typename = void>
struct has_custom_serialization : std::false_type {};

inline constexpr struct serialize_tag {
  template <typename T>
  constexpr void operator()(SIMDJSON_IMPLEMENTATION::builder::string_builder& b, T&& obj) const{
    return tag_invoke(*this, b, std::forward<T>(obj));
  }


} serialize{};
template <typename T>
struct has_custom_serialization<T, std::void_t<
    decltype(tag_invoke(serialize, std::declval<SIMDJSON_IMPLEMENTATION::builder::string_builder&>(), std::declval<T&>()))
>> : std::true_type {};

template <typename T>
constexpr bool require_custom_serialization = has_custom_serialization<T>::value;
#else
struct has_custom_serialization : std::false_type {};
#endif // SIMDJSON_SUPPORTS_CONCEPTS

namespace SIMDJSON_IMPLEMENTATION {
namespace builder {
/**
 * A builder for JSON strings representing documents. This is a low-level
 * builder that is not meant to be used directly by end-users. Though it
 * supports atomic types (Booleans, strings), it does not support composed
 * types (arrays and objects).
 *
 * Ultimately, this class can support kernel-specific optimizations. E.g.,
 * it may make use of SIMD instructions to escape strings faster.
 */
class string_builder {
public:
  simdjson_inline string_builder(size_t initial_capacity = DEFAULT_INITIAL_CAPACITY);

  static constexpr size_t DEFAULT_INITIAL_CAPACITY = 1024;

  /**
   * Append number (includes Booleans). Booleans are mapped to the strings
   * false and true. Numbers are converted to strings abiding by the JSON standard.
   * Floating-point numbers are converted to the shortest string that 'correctly'
   * represents the number.
   */
  template<typename number_type,
    typename = typename std::enable_if<std::is_arithmetic<number_type>::value>::type>
  simdjson_inline void append(number_type v) noexcept;

  /**
   * Append character c.
   */
  simdjson_inline void append(char c)  noexcept;

  /**
   * Append the string 'null'.
   */
  simdjson_inline void append_null()  noexcept;

  /**
   * Clear the content.
   */
  simdjson_inline void clear()  noexcept;

  /**
   * Append the std::string_view, after escaping it.
   * There is no UTF-8 validation.
   */
  simdjson_inline void escape_and_append(std::string_view input)  noexcept;

  /**
   * Append the std::string_view surrounded by double quotes, after escaping it.
   * There is no UTF-8 validation.
   */
  simdjson_inline void escape_and_append_with_quotes(std::string_view input)  noexcept;
#if SIMDJSON_SUPPORTS_CONCEPTS
  template<constevalutil::fixed_string key>
  simdjson_inline void escape_and_append_with_quotes()  noexcept;
#endif
  /**
   * Append the character surrounded by double quotes, after escaping it.
   * There is no UTF-8 validation.
   */
  simdjson_inline void escape_and_append_with_quotes(char input)  noexcept;

  /**
   * Append the character surrounded by double quotes, after escaping it.
   * There is no UTF-8 validation.
   */
   simdjson_inline void escape_and_append_with_quotes(const char* input)  noexcept;

  /**
   * Append the C string directly, without escaping.
   * There is no UTF-8 validation.
   */
  simdjson_inline void append_raw(const char *c)  noexcept;

  /**
   * Append "{" to the buffer.
   */
  simdjson_inline void start_object()  noexcept;

  /**
   * Append "}" to the buffer.
   */
  simdjson_inline void end_object()  noexcept;

  /**
   * Append "[" to the buffer.
   */
  simdjson_inline void start_array()  noexcept;

  /**
   * Append "]" to the buffer.
   */
  simdjson_inline void end_array()  noexcept;

  /**
   * Append "," to the buffer.
   */
  simdjson_inline void append_comma()  noexcept;

  /**
   * Append ":" to the buffer.
   */
  simdjson_inline void append_colon()  noexcept;

  /**
   * Append a key-value pair to the buffer.
   * The key is escaped and surrounded by double quotes.
   * The value is escaped if it is a string.
   */
  template<typename key_type, typename value_type>
  simdjson_inline void append_key_value(key_type key, value_type value) noexcept;
#if SIMDJSON_SUPPORTS_CONCEPTS
  template<constevalutil::fixed_string key, typename value_type>
  simdjson_inline void append_key_value(value_type value) noexcept;

  // Support for optional types (std::optional, etc.)
  template <concepts::optional_type T>
  requires(!require_custom_serialization<T>)
  simdjson_inline void append(const T &opt);

  template <typename T>
  requires(require_custom_serialization<T>)
  simdjson_inline void append(T &&val);

  // Support for string-like types
  template <typename T>
  requires(std::is_convertible<T, std::string_view>::value ||
  std::is_same<T, const char*>::value )
  simdjson_inline void append(const T &value);
#endif
#if SIMDJSON_SUPPORTS_RANGES && SIMDJSON_SUPPORTS_CONCEPTS
  // Support for range-based appending (std::ranges::view, etc.)
  template <std::ranges::range R>
requires (!std::is_convertible<R, std::string_view>::value && !concepts::optional_type<R> && !require_custom_serialization<R>)
  simdjson_inline void append(const R &range) noexcept;
#endif
  /**
   * Append the std::string_view directly, without escaping.
   * There is no UTF-8 validation.
   */
  simdjson_inline void append_raw(std::string_view input)  noexcept;

  /**
   * Append len characters from str.
   * There is no UTF-8 validation.
   */
  simdjson_inline void append_raw(const char *str, size_t len) noexcept;

  /**
   * Append exactly N characters from str. The length is a template parameter
   * so the compiler can fully inline the memcpy with a compile-time-constant
   * size, avoiding the libc call. Used for compile-time-constant keys in the
   * reflection struct atom.
   */
  template <size_t N>
  simdjson_inline void append_raw_n(const char *str) noexcept;
#if SIMDJSON_EXCEPTIONS
  /**
   * Creates an std::string from the written JSON buffer.
   * Throws if memory allocation failed
   *
   * The result may not be valid UTF-8 if some of your content was not valid UTF-8.
   * Use validate_unicode() to check the content if needed.
   */
  simdjson_inline operator std::string() const noexcept(false);

  /**
   * Creates an std::string_view from the written JSON buffer.
   * Throws if memory allocation failed.
   *
   * The result may not be valid UTF-8 if some of your content was not valid UTF-8.
   * Use validate_unicode() to check the content if needed.
   */
  simdjson_inline operator std::string_view() const noexcept(false) simdjson_lifetime_bound;
#endif

  /**
   * Returns a view on the written JSON buffer. Returns an error
   * if memory allocation failed.
   *
   * The result may not be valid UTF-8 if some of your content was not valid UTF-8.
   * Use validate_unicode() to check the content.
   */
  simdjson_inline simdjson_result<std::string_view> view() const noexcept;

  /**
   * Appends the null character to the buffer and returns
   * a pointer to the beginning of the written JSON buffer.
   * Returns an error if memory allocation failed.
   * The result is null-terminated.
   *
   * The result may not be valid UTF-8 if some of your content was not valid UTF-8.
   * Use validate_unicode() to check the content.
   */
  simdjson_inline simdjson_result<const char *> c_str() noexcept;

  /**
   * Return true if the content is valid UTF-8.
   */
  simdjson_inline bool validate_unicode() const noexcept;

  /**
   * Returns the current size of the written JSON buffer.
   * If an error occurred, returns 0.
   */
  simdjson_inline size_t size() const noexcept;

  // ============================================================
  // Internal hooks for the position-as-local writer in json_builder.h.
  // These exist so the reflection atom code can hold buffer pointer,
  // position and capacity in registers across long write chains rather
  // than reloading them after every char* write (strict aliasing
  // forces those reloads when accessed via members of *this). User
  // code should NOT call these directly.
  // ============================================================
  simdjson_inline char *unsafe_data() noexcept { return buffer.get(); }
  simdjson_inline size_t unsafe_position() const noexcept { return position; }
  simdjson_inline size_t unsafe_capacity() const noexcept { return capacity; }
  simdjson_inline void unsafe_set_position(size_t p) noexcept { position = p; }
  /// Make capacity available for at least `n` more bytes after the current
  /// position. Returns false if the allocation failed.
  simdjson_inline bool unsafe_grow(size_t needed_total_capacity) noexcept {
    grow_buffer(needed_total_capacity);
    return is_valid;
  }
  simdjson_inline bool unsafe_is_valid() const noexcept { return is_valid; }

private:
  /**
   * Returns true if we can write at least upcoming_bytes bytes.
   * The underlying buffer is reallocated if needed. It is designed
   * to be called before writing to the buffer. It should be fast.
   */
  simdjson_inline bool capacity_check(size_t upcoming_bytes);

  /**
   * Grow the buffer to at least desired_capacity bytes.
   * If the allocation fails, is_valid is set to false. We expect
   * that this function would not be repeatedly called.
   */
  inline void grow_buffer(size_t desired_capacity);

  /**
   * We use this helper function to make sure that is_valid is kept consistent.
   */
  simdjson_inline void set_valid(bool valid) noexcept;

  std::unique_ptr<char[]> buffer{};
  size_t position{0};
  size_t capacity{0};
  bool is_valid{true};
};



}
}


#if !SIMDJSON_STATIC_REFLECTION
// fallback implementation until we have static reflection
template <class Z>
simdjson_warn_unused simdjson_result<std::string> to_json(const Z &z, size_t initial_capacity = simdjson::SIMDJSON_IMPLEMENTATION::builder::string_builder::DEFAULT_INITIAL_CAPACITY) {
  simdjson::SIMDJSON_IMPLEMENTATION::builder::string_builder b(initial_capacity);
  b.append(z);
  std::string_view s;
  auto e = b.view().get(s);
  if(e) { return e; }
  return std::string(s);
}
template <class Z>
simdjson_warn_unused error_code to_json(const Z &z, std::string &s, size_t initial_capacity = simdjson::SIMDJSON_IMPLEMENTATION::builder::string_builder::DEFAULT_INITIAL_CAPACITY) {
  simdjson::SIMDJSON_IMPLEMENTATION::builder::string_builder b(initial_capacity);
  b.append(z);
  std::string_view sv;
  auto e = b.view().get(sv);
  if(e) { return e; }
  s.assign(sv.data(), sv.size());
  return simdjson::SUCCESS;
}
#endif

#if SIMDJSON_SUPPORTS_CONCEPTS
#endif // SIMDJSON_SUPPORTS_CONCEPTS

} // namespace simdjson

#endif // SIMDJSON_GENERIC_STRING_BUILDER_H