mirror of
https://github.com/nlohmann/json.git
synced 2026-09-30 22:15:19 +00:00
1ab017bbfe
Internal parts of the zero-copy view (#5295), under detail/view and not included by json.hpp, so that users of json.hpp compile nothing of it: - macro_scope.hpp/macro_unscope.hpp: the few macros the view needs, under its own prefix (json.hpp undefines its own at its end); the throw macro honors JSON_NOEXCEPTION and JSON_THROW_USER like JSON_THROW - string_ref.hpp: std::string_view from C++17 on, else a small stand-in - node.hpp: the 16-byte node of the index; its kinds are value_t values (checked by a static_assert) - document_data.hpp: the storage of a parsed document (node array, decode arena, owned input) - scan.hpp: string and digit scanning with unrolled checks at fixed offsets (after yyjson) and the library's SWAR and UTF-8 checks, independent of the byte order Signed-off-by: Niels Lohmann <mail@nlohmann.me>
129 lines
3.8 KiB
C++
129 lines
3.8 KiB
C++
// __ _____ _____ _____
|
|
// __| | __| | | | JSON for Modern C++
|
|
// | | |__ | | | | | | version 3.12.0
|
|
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
|
|
//
|
|
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
|
|
// SPDX-License-Identifier: MIT
|
|
|
|
#pragma once
|
|
|
|
#include <cstddef> // size_t
|
|
#include <cstring> // memcpy
|
|
#include <new> // operator new, placement new
|
|
#include <string> // string
|
|
|
|
#include <nlohmann/json.hpp>
|
|
#include <nlohmann/detail/view/macro_scope.hpp>
|
|
#include <nlohmann/detail/view/node.hpp>
|
|
|
|
NLOHMANN_JSON_NAMESPACE_BEGIN
|
|
namespace detail
|
|
{
|
|
namespace view
|
|
{
|
|
|
|
/// storage of a parsed document; heap-allocated (header and an initial node
|
|
/// array in one block) so that views survive moves of the owning document
|
|
struct document_data
|
|
{
|
|
const char* src = nullptr;
|
|
std::size_t size = 0;
|
|
node* tape = nullptr;
|
|
std::size_t tape_size = 0;
|
|
std::size_t tape_cap = 0;
|
|
node* inline_tape = nullptr; ///< node array allocated together with this header
|
|
std::size_t inline_cap = 0;
|
|
std::string arena{}; ///< decoded strings that contained escapes
|
|
std::string owned{}; ///< owned copy of the input, if any
|
|
const char* base[4] = {nullptr, nullptr, nullptr, nullptr}; ///< string bases: source, arena (indexed by flags & node_flags::storage)
|
|
bool discarded = true;
|
|
|
|
/// one allocation for the header and room for `nodes` nodes; large
|
|
/// documents get a separate node array instead (so it can be trimmed)
|
|
static document_data* create(std::size_t nodes)
|
|
{
|
|
nodes = nodes <= 256 ? nodes : 0;
|
|
void* mem = ::operator new (sizeof(document_data) + (nodes * sizeof(node)));
|
|
auto* d = new (mem) document_data();
|
|
d->inline_tape = static_cast<node*>(static_cast<void*>(static_cast<char*>(mem) + sizeof(document_data))); // (aligned: sizeof is a multiple of the alignment)
|
|
d->inline_cap = nodes;
|
|
d->tape = d->inline_tape;
|
|
d->tape_cap = nodes;
|
|
return d;
|
|
}
|
|
|
|
struct deleter
|
|
{
|
|
void operator()(document_data* d) const noexcept
|
|
{
|
|
d->~document_data();
|
|
::operator delete (d);
|
|
}
|
|
};
|
|
|
|
document_data() noexcept = default;
|
|
document_data(const document_data&) = delete;
|
|
document_data(document_data&&) = delete;
|
|
document_data& operator=(const document_data&) = delete;
|
|
document_data& operator=(document_data&&) = delete;
|
|
~document_data()
|
|
{
|
|
release();
|
|
}
|
|
|
|
void release() noexcept
|
|
{
|
|
if (tape != inline_tape)
|
|
{
|
|
::operator delete (tape);
|
|
}
|
|
tape = inline_tape;
|
|
tape_cap = inline_cap;
|
|
}
|
|
|
|
/// make room for n nodes; keeps the first tape_size nodes
|
|
void reserve(std::size_t n)
|
|
{
|
|
if (n <= tape_cap)
|
|
{
|
|
return;
|
|
}
|
|
node* fresh = static_cast<node*>(::operator new (n * sizeof(node)));
|
|
if (tape_size != 0)
|
|
{
|
|
std::memcpy(fresh, tape, tape_size * sizeof(node));
|
|
}
|
|
release();
|
|
tape = fresh;
|
|
tape_cap = n;
|
|
}
|
|
|
|
const char* str(const node& n) const noexcept
|
|
{
|
|
return base[n.flags & node_flags::storage] + n.off;
|
|
}
|
|
|
|
/// the node after n's subtree (containers span `next` nodes, scalars one)
|
|
static NLOHMANN_VIEW_ALWAYS_INLINE const node* after(const node* n) noexcept
|
|
{
|
|
return n + (is_container(*n) ? n->next : 1u);
|
|
}
|
|
|
|
/// first element (array) or first key (object) of a container
|
|
static NLOHMANN_VIEW_ALWAYS_INLINE const node* first_child(const node* n) noexcept
|
|
{
|
|
return n + 1;
|
|
}
|
|
|
|
/// end of the elements of a container
|
|
static NLOHMANN_VIEW_ALWAYS_INLINE const node* child_end(const node* n) noexcept
|
|
{
|
|
return n + n->next;
|
|
}
|
|
};
|
|
|
|
} // namespace view
|
|
} // namespace detail
|
|
NLOHMANN_JSON_NAMESPACE_END
|