Files
json/docs/mkdocs/docs/examples/basic_json_document__load.cpp
T
Niels Lohmann 330fbead59 Document clang-tidy exclusions, drop unneeded ones, and clean up doc examples (#5909)
* Document clang-tidy exclusions and drop unneeded ones

Re-enable every excluded check in a run of clang-tidy 22 over all tests
and remove the seven that never fire (cert-err58-cpp,
clang-analyzer-webkit.NoUncountedMemberChecker,
cppcoreguidelines-virtual-class-destructor, google-readability-function-size,
hicpp-function-size, hicpp-no-assembler, readability-function-size).

Document the reason for every remaining exclusion at the top of the file.

Exclude in advance the checks that only exist in clang-tidy 23 and are
noise here (bugprone-signed-bitwise, *-explicit-constructor,
readability-trailing-comma, modernize-use-string-view), plus
modernize-use-integer-sign-comparison, which needs C++20 std::cmp_less
and flags deliberate casts.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix clang-tidy findings in documentation examples and replace redundant aliases

Apply clang-tidy fixes to the documentation examples:
- performance-avoid-endl: std::endl -> '\n'
- readability-qualified-auto: auto -> auto* / const auto*
- performance-for-range-copy: copy -> const reference
- google-readability-casting: C-style cast -> static_cast

Replace redundant aliases (readability-redundant-qualified-alias) such as
"using json = nlohmann::json;" with "using nlohmann::json;" in the
documentation, README, examples, tests, and benchmarks. Aliases at class
scope and aliases of other types (with_base_class_t etc.) are kept.

No changes to the library or its public API. All changed examples were
compiled and run; their output matches the stored .output files (except
max_size and meta, which depend on the platform and compiler).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Format doc examples with the pinned astyle

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-25 12:07:51 +01:00

53 lines
2.0 KiB
C++

#include <cstdint>
#include <iostream>
#include <string>
#include <vector>
#include <nlohmann/json_view.hpp>
using nlohmann::json;
using nlohmann::json_document;
using image_check = json_document::image_check;
int main()
{
std::cout << std::boolalpha;
// the image of a parsed document -- as if read back from a cache file or
// received from another process running the same build of the library
const std::string text = R"({"name": "cache", "note": "caf\u00e9", "replicas": ["db2", "db3"]})";
const json_document parsed = json_document::parse(text);
const std::vector<std::uint8_t> image = parsed.save();
// (1)/(2) load() needs no parsing, yet dumps exactly what parsing did
const json_document borrowed = json_document::load(image);
std::cout << (borrowed.root().dump() == parsed.root().dump()) << '\n';
std::cout << borrowed.owns_source() << '\n'; // borrowed: still points into `image`
// (3) load(std::move(image)) keeps the vector instead of copying it
std::vector<std::uint8_t> to_move = image;
const json_document owned = json_document::load(std::move(to_move));
std::cout << owned.owns_source() << '\n';
// a damaged image -- the last byte of the decoded string "note" holds
// (an escape sequence, so it was unescaped into the document's own
// buffer), flipped, as storage or transport corruption might do
std::vector<std::uint8_t> damaged = image;
damaged[damaged.size() - 2] = 0xFF;
// image_check::full inspects strings and numbers, so it catches the damage
try
{
static_cast<void>(json_document::load(damaged, image_check::full));
}
catch (const json::parse_error& e)
{
std::cout << e.id << '\n';
}
// image_check::bounds only checks structure and bounds, so a cache the
// process already trusts loads without the extra scan -- reading a value
// the damage did not touch is still safe
const json_document trusted = json_document::load(damaged, image_check::bounds);
std::cout << trusted.root()["name"].get<std::string>() << '\n';
}