Niels Lohmann
9856da2561
- API pages for get, get_to, get_string, number_token, and value of basic_json_view; JSON pointer overloads of operator[], at, and contains; links both ways with the basic_json pages - the feature page describes which conversions copy nothing - the examples show when the view helps: strings without copies, numbers exactly as written, and paths into a large text Signed-off-by: Niels Lohmann <mail@nlohmann.me>
32 lines
1.4 KiB
C++
32 lines
1.4 KiB
C++
#include <iostream>
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#include <nlohmann/json_view.hpp>
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#include <string>
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using json_document = nlohmann::json_document;
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using json_view = nlohmann::json_view;
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int main()
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{
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// a "large response" stand-in: only the "id" field is ever read out of it
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const std::string text =
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R"({"id": "8f14e45f-ceea-467e-bb92-963f5e3c7a08", "note": "created via API\n", "payload": "..."})";
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const json_document doc = json_document::parse(text);
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const json_view response = doc.root();
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const json_view::string_view_t id = response["id"].get_string();
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std::cout << id << '\n';
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// no std::string was allocated for "id": its bytes still live inside
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// the original buffer, so id's data lies inside [text.data(),
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// text.data() + text.size())
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const bool id_in_source = id.data() >= text.data() && id.data() + id.size() <= text.data() + text.size();
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std::cout << std::boolalpha << id_in_source << '\n';
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// "note" contains an escape sequence ('\n'), so it was decoded once
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// into the document's own buffer -- get_string() still avoids a copy
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// into a new std::string, but the bytes no longer live inside "text"
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const json_view::string_view_t note = response["note"].get_string();
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const bool note_in_source = note.data() >= text.data() && note.data() + note.size() <= text.data() + text.size();
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std::cout << std::boolalpha << note_in_source << '\n';
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}
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