mirror of
https://github.com/nlohmann/json.git
synced 2026-10-27 16:28:57 +00:00
Niels Lohmann
4c130c33d9
With JSON_DIAGNOSTIC_POSITIONS, materialize() now gives every value the start_pos()/end_pos() that basic_json::parse() would give it, so exceptions about materialized values name the same bytes (#5864). - json_sax_dom_parser takes the lexer type as a defaulted template parameter; materialize() passes position_source, which reports the positions it derives from the index. diagnostic_positions treats npos as "no position" and keeps ranges all-or-nothing. - Strings with escapes keep the offset of their opening quote plus one in `next` (only with the macro); materialize() scans from there to the closing quote. The end of an array or object is found by scanning from the end of its last element over whitespace, comments and a trailing comma. - In editable documents, values written by edits, arrays and objects whose elements changed, and containers whose last element has no position get none. Images keep the flag is_new, and load() checks that `next` of a string is within the text. Nothing changes on the parse path without the macro. The view's own exceptions still carry no byte range, so the tests that compare them with those of materialized values skip it under the macro, as they skip the path under JSON_DIAGNOSTICS. Signed-off-by: Niels Lohmann <mail@nlohmann.me>
411 lines
14 KiB
C++
411 lines
14 KiB
C++
// __ _____ _____ _____
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// __| | __| | | | JSON for Modern C++
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// | | |__ | | | | | | version 3.12.0
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// |_____|_____|_____|_|___| https://github.com/nlohmann/json
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//
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// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
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// SPDX-License-Identifier: MIT
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#pragma once
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#include <array> // array
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#include <cstddef> // size_t
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#include <cstdint> // int64_t, uint8_t
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#include <string> // string
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#include <vector> // vector
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#include <nlohmann/json.hpp>
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#include <nlohmann/detail/view/document_data.hpp>
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#include <nlohmann/detail/view/macro_scope.hpp>
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#include <nlohmann/detail/view/node.hpp>
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#include <nlohmann/detail/view/number.hpp>
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NLOHMANN_JSON_NAMESPACE_BEGIN
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namespace detail
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{
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namespace view
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{
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#if JSON_DIAGNOSTIC_POSITIONS
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/*!
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@brief the source positions of the values materialize() replays
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Stands in for the lexer of json_sax_dom_parser, which reads the positions of
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the values it stores from these three functions (diagnostic_positions). npos
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is a value without a source position.
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*/
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struct position_source
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{
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/// the token, of which diagnostic_positions only reads the length
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struct token
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{
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std::size_t length;
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std::size_t size() const noexcept
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{
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return length;
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}
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};
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std::size_t start = std::string::npos; ///< the first byte of the next value
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std::size_t end = std::string::npos; ///< one past the next value (start_object/start_array: one past the bracket)
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std::size_t get_chars_read_total() const noexcept
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{
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return end;
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}
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std::size_t get_token_start_position() const noexcept
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{
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return start;
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}
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token get_string() const noexcept
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{
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return token{end - start};
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}
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/// the range [first, last), or none if either is npos
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void set(std::size_t first, std::size_t last) noexcept
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{
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const bool known = first != std::string::npos && last != std::string::npos;
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start = known ? first : std::string::npos;
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end = known ? last : std::string::npos;
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}
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/// one past the closing quote of the string whose opening quote is at
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/// src[quote], or npos (the scan is bounded by size, as images can be
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/// loaded without a check)
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static std::size_t string_end(const char* src, std::size_t size, std::size_t quote) noexcept
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{
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for (std::size_t i = quote + 1; i < size; ++i)
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{
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if (src[i] == '\\')
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{
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++i;
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}
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else if (src[i] == '"')
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{
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return i + 1;
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}
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}
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return std::string::npos;
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}
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/// one past the closing bracket of the array or object whose last element
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/// ends at src[pos] (or whose opening bracket is at src[pos - 1]), or npos;
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/// in between, there can only be whitespace, comments, and a trailing comma
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/// (the source was validated when it was parsed)
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static std::size_t container_end(const char* src, std::size_t size, std::size_t pos) noexcept
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{
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while (pos < size)
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{
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switch (src[pos])
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{
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case ' ':
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case '\t':
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case '\n':
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case '\r':
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case ',':
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++pos;
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break;
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case ']':
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case '}':
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return pos + 1;
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case '/':
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if (pos + 1 < size && src[pos + 1] == '/')
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{
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pos += 2;
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while (pos < size && src[pos] != '\n' && src[pos] != '\r')
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{
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++pos;
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}
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break;
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}
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if (pos + 1 < size && src[pos + 1] == '*')
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{
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pos += 2;
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while (pos < size && !(src[pos] == '*' && pos + 1 < size && src[pos + 1] == '/'))
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{
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++pos;
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}
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pos += 2;
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break;
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}
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return std::string::npos;
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default:
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return std::string::npos;
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}
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}
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return std::string::npos;
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}
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/// the range of the scalar n of document d
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void set_scalar(const document_data& d, const node& n) noexcept
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{
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const std::size_t size = d.size;
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const std::size_t off = n.off;
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std::size_t first = std::string::npos;
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std::size_t last = std::string::npos;
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if ((n.flags & node_flags::is_new) == 0)
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{
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switch (static_cast<value_t>(n.kind))
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{
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case value_t::string:
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if ((n.flags & node_flags::storage) == 0)
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{
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// off is the first byte after the opening quote
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if (off != 0)
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{
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first = off - 1;
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last = off + std::size_t{n.len} + 1;
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}
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}
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else if ((n.flags & node_flags::storage) == node_flags::escaped && n.next != 0)
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{
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// next is the offset of the opening quote plus one
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first = n.next - 1;
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last = string_end(d.base[0], size, first);
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}
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break;
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case value_t::number_integer:
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case value_t::number_unsigned:
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case value_t::number_float:
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if ((n.flags & node_flags::storage) == 0)
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{
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first = off;
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last = off + number_length(n);
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}
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break;
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case value_t::boolean:
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first = off;
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last = off + ((n.flags & node_flags::is_true) != 0 ? 4u : 5u);
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break;
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case value_t::null:
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first = off;
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last = off + 4u;
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break;
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case value_t::object:
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case value_t::array:
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case value_t::binary:
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case value_t::discarded:
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default:
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break;
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}
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}
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// (a crafted image can point past the text)
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set(first, last != std::string::npos && last <= size ? last : std::string::npos);
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}
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};
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#endif
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/*!
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@brief the basic_json value of the subtree at n
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The subtree is replayed into the SAX handler that parse() uses to build its
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values, so the result is the value parse() would produce: duplicate keys keep
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the last value, and with JSON_DIAGNOSTICS the parent pointers are set. It is
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iterative, so the nesting depth is limited by memory only, as for parse().
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With JSON_DIAGNOSTIC_POSITIONS, the values get their source positions as with
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parse(): position_source stands in for the lexer. Values written by edits have
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none (npos), and neither has an array or object whose elements changed, or
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whose last element has none (the end of its closing bracket is found by
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scanning from the end of the last element).
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*/
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template<typename BasicJsonType, bool Editable>
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BasicJsonType materialize(const document_data& d, const node* n)
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{
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using string_t = typename BasicJsonType::string_t;
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#if JSON_DIAGNOSTIC_POSITIONS
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using sax_t = json_sax_dom_parser<BasicJsonType, iterator_input_adapter<const char*>, true, position_source>;
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#else
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using sax_t = json_sax_dom_parser<BasicJsonType, iterator_input_adapter<const char*>, true>;
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#endif
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using nav = navigation<Editable>;
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// the open containers: their next element (or key of the next member),
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// their end, and whether they are objects; for the first 16 levels on the
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// stack, else sized once from the document's deepest nesting (for a
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// subtree an upper bound)
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struct frame
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{
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const node* pos;
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const node* end;
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bool object;
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#if JSON_DIAGNOSTIC_POSITIONS
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std::size_t start; ///< the opening bracket (npos: unknown)
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std::size_t last_end; ///< the end of the last element read (npos: unknown)
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#endif
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};
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#if !JSON_DIAGNOSTIC_POSITIONS
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// a scalar needs neither the handler nor the stack of open containers
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// (with positions, it goes through the handler, which sets them)
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switch (static_cast<value_t>(n->kind))
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{
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case value_t::string:
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return BasicJsonType(string_t(d.str(*n), n->len));
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case value_t::number_integer:
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return BasicJsonType(static_cast<typename BasicJsonType::number_integer_t>(static_cast<std::int64_t>(integer_bits(*n))));
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case value_t::number_unsigned:
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return BasicJsonType(static_cast<typename BasicJsonType::number_unsigned_t>(integer_bits(*n)));
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case value_t::number_float:
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return BasicJsonType(float_value<typename BasicJsonType::number_float_t>(d, *n));
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case value_t::boolean:
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return BasicJsonType((n->flags & node_flags::is_true) != 0);
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case value_t::null:
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return BasicJsonType(nullptr);
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case value_t::object:
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case value_t::array:
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case value_t::binary:
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case value_t::discarded:
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default:
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break;
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}
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#endif
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BasicJsonType result;
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#if JSON_DIAGNOSTIC_POSITIONS
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position_source positions;
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sax_t sax(result, true, &positions);
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#else
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sax_t sax(result, true);
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#endif
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const string_t no_token {};
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// (shallow subtrees on the stack: a call for a small value then allocates only for the value)
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std::array<frame, 16> shallow; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): filled as containers open
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std::vector<frame> deep{};
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frame* open = shallow.data();
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std::size_t capacity = shallow.size();
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if (d.max_depth > capacity)
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{
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deep.resize(d.max_depth);
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open = deep.data();
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capacity = deep.size();
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}
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std::size_t depth = 0;
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for (;;)
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{
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#if JSON_DIAGNOSTIC_POSITIONS
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if (!is_container(*n))
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{
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positions.set_scalar(d, *n);
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if (depth != 0)
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{
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open[depth - 1].last_end = positions.end;
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}
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}
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#endif
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// false positive: n comes from nav::value(), which never returns null for a valid index
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// @infer-ignore NULLPTR_DEREFERENCE
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switch (static_cast<value_t>(n->kind))
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{
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case value_t::object:
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case value_t::array:
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{
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const bool object = n->kind == node_kind::object;
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#if JSON_DIAGNOSTIC_POSITIONS
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// (moved containers are also new)
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const std::size_t start = (n->flags & node_flags::is_new) == 0 && n->off < d.size ? std::size_t{n->off} :
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std::string::npos;
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positions.set(start, start + 1);
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#endif
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if (object)
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{
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sax.start_object(n->len);
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}
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else
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{
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sax.start_array(n->len);
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}
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if (NLOHMANN_VIEW_UNLIKELY(depth == capacity))
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{
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// (deeper than the recorded nesting, e.g. after edits)
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deep.assign(open, open + depth);
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deep.resize(depth * 2);
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open = deep.data();
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capacity = deep.size();
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}
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#if JSON_DIAGNOSTIC_POSITIONS
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// (until an element is read, the container's own bracket is the last thing read)
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open[depth++] = frame{nav::first(d, n), nav::end(d, n), object, start, positions.end};
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break;
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#else
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open[depth++] = frame {nav::first(d, n), nav::end(d, n), object};
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break;
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#endif
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}
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case value_t::string:
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{
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string_t s(d.str(*n), n->len);
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sax.string(s);
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break;
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}
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case value_t::number_integer:
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sax.number_integer(static_cast<typename BasicJsonType::number_integer_t>(static_cast<std::int64_t>(integer_bits(*n))));
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break;
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case value_t::number_unsigned:
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sax.number_unsigned(static_cast<typename BasicJsonType::number_unsigned_t>(integer_bits(*n)));
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break;
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case value_t::number_float:
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sax.number_float(float_value<typename BasicJsonType::number_float_t>(d, *n), no_token);
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break;
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case value_t::boolean:
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sax.boolean((n->flags & node_flags::is_true) != 0);
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break;
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case value_t::null:
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case value_t::binary:
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case value_t::discarded:
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default:
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// false positive: the parser's frame stack points into its own storage (never null)
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// @infer-ignore NULLPTR_DEREFERENCE
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sax.null();
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break;
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}
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// the next value: close finished containers, then read the key
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for (;;)
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{
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if (depth == 0)
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{
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return result;
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}
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frame& f = open[depth - 1];
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if (f.pos == f.end)
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{
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#if JSON_DIAGNOSTIC_POSITIONS
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const std::size_t end = f.start == std::string::npos || f.last_end == std::string::npos ? std::string::npos : position_source::container_end(d.base[0], d.size, f.last_end);
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// (an end of npos clears the start, see diagnostic_positions)
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positions.set(end == std::string::npos ? end : end - 1, end);
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if (depth > 1)
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{
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open[depth - 2].last_end = end;
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}
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#endif
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if (f.object)
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{
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sax.end_object();
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}
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else
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{
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sax.end_array();
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}
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--depth;
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continue;
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}
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const node* entry = f.pos;
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if (f.object)
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{
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string_t key(d.str(*entry), entry->len);
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sax.key(key);
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++entry;
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}
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n = nav::value(entry);
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f.pos = document_data::after(entry);
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break;
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}
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}
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}
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} // namespace view
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} // namespace detail
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NLOHMANN_JSON_NAMESPACE_END
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