boost/json/parser.hpp
// // Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com) // // Distributed under the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) // // Official repository: https://github.com/boostorg/json // #ifndef BOOST_JSON_PARSER_HPP #define BOOST_JSON_PARSER_HPP #include <boost/json/detail/config.hpp> #include <boost/json/basic_parser.hpp> #include <boost/json/storage_ptr.hpp> #include <boost/json/value.hpp> #include <boost/json/detail/handler.hpp> #include <type_traits> #include <cstddef> BOOST_JSON_NS_BEGIN //---------------------------------------------------------- /** A DOM parser for JSON contained in a single buffer. This class is used to parse a JSON contained in a single character buffer, into a @ref value container. @par Usage To use the parser first construct it, then optionally call @ref reset to specify a @ref storage_ptr to use for the resulting @ref value. Then call @ref write to parse a character buffer containing a complete JSON. If the parse is successful, call @ref release to take ownership of the value: @code parser p; // construct a parser size_t n = p.write( "[1,2,3]" ); // parse a complete JSON assert( n == 7 ); // all characters consumed value jv = p.release(); // take ownership of the value @endcode @par Extra Data When the character buffer provided as input contains additional data that is not part of the complete JSON, an error is returned. The @ref write_some function is an alternative which allows the parse to finish early, without consuming all the characters in the buffer. This allows parsing of a buffer containing multiple individual JSONs or containing different protocol data: @code parser p; // construct a parser size_t n = p.write_some( "[1,2,3] null" ); // parse a complete JSON assert( n == 8 ); // only some characters consumed value jv = p.release(); // take ownership of the value @endcode @par Temporary Storage The parser may dynamically allocate temporary storage as needed to accommodate the nesting level of the JSON being parsed. Temporary storage is first obtained from an optional, caller-owned buffer specified upon construction. When that is exhausted, the next allocation uses the @ref memory_resource passed to the constructor; if no such argument is specified, the default memory resource is used. Temporary storage is freed only when the parser is destroyed; The performance of parsing multiple JSONs may be improved by reusing the same parser instance. \n It is important to note that the @ref memory_resource supplied upon construction is used for temporary storage only, and not for allocating the elements which make up the parsed value. That other memory resource is optionally supplied in each call to @ref reset. @par Duplicate Keys If there are object elements with duplicate keys; that is, if multiple elements in an object have keys that compare equal, only the last equivalent element will be inserted. @par Non-Standard JSON The @ref parse_options structure optionally provided upon construction is used to customize some parameters of the parser, including which non-standard JSON extensions should be allowed. A default-constructed parse options allows only standard JSON. @par Thread Safety Distinct instances may be accessed concurrently. Non-const member functions of a shared instance may not be called concurrently with any other member functions of that instance. @see @ref parse, @ref parse_options, @ref stream_parser. */ class parser { basic_parser<detail::handler> p_; public: /// Copy constructor (deleted) parser( parser const&) = delete; /// Copy assignment (deleted) parser& operator=( parser const&) = delete; /** Destructor. All dynamically allocated memory, including any incomplete parsing results, is freed. @par Complexity Linear in the size of partial results @par Exception Safety No-throw guarantee. */ ~parser() = default; /** Constructor. This constructs a new parser which first uses the caller-owned storage pointed to by `buffer` for temporary storage, falling back to the memory resource `sp` if needed. The parser will use the specified parsing options. \n The parsed value will use the default memory resource for storage. To use a different resource, call @ref reset after construction. @par Complexity Constant. @par Exception Safety No-throw guarantee. @param sp The memory resource to use for temporary storage after `buffer` is exhausted. @param opt The parsing options to use. @param buffer A pointer to valid memory of at least `size` bytes for the parser to use for temporary storage. Ownership is not transferred, the caller is responsible for ensuring the lifetime of the memory pointed to by `buffer` extends until the parser is destroyed. @param size The number of valid bytes in `buffer`. */ BOOST_JSON_DECL parser( storage_ptr sp, parse_options const& opt, unsigned char* buffer, std::size_t size) noexcept; /** Constructor. This constructs a new parser which uses the default memory resource for temporary storage, and accepts only strict JSON. \n The parsed value will use the default memory resource for storage. To use a different resource, call @ref reset after construction. @par Complexity Constant. @par Exception Safety No-throw guarantee. */ parser() noexcept : parser({}, {}) { } /** Constructor. This constructs a new parser which uses the specified memory resource for temporary storage, and is configured to use the specified parsing options. \n The parsed value will use the default memory resource for storage. To use a different resource, call @ref reset after construction. @par Complexity Constant. @par Exception Safety No-throw guarantee. @param sp The memory resource to use for temporary storage. @param opt The parsing options to use. */ BOOST_JSON_DECL parser( storage_ptr sp, parse_options const& opt) noexcept; /** Constructor. This constructs a new parser which uses the specified memory resource for temporary storage, and accepts only strict JSON. \n The parsed value will use the default memory resource for storage. To use a different resource, call @ref reset after construction. @par Complexity Constant. @par Exception Safety No-throw guarantee. @param sp The memory resource to use for temporary storage. */ explicit parser(storage_ptr sp) noexcept : parser(std::move(sp), {}) { } /** Constructor. This constructs a new parser which first uses the caller-owned storage `buffer` for temporary storage, falling back to the memory resource `sp` if needed. The parser will use the specified parsing options. \n The parsed value will use the default memory resource for storage. To use a different resource, call @ref reset after construction. @par Complexity Constant. @par Exception Safety No-throw guarantee. @param sp The memory resource to use for temporary storage after `buffer` is exhausted. @param opt The parsing options to use. @param buffer A buffer for the parser to use for temporary storage. Ownership is not transferred, the caller is responsible for ensuring the lifetime of `buffer` extends until the parser is destroyed. */ template<std::size_t N> parser( storage_ptr sp, parse_options const& opt, unsigned char(&buffer)[N]) noexcept : parser(std::move(sp), opt, &buffer[0], N) { } #if defined(__cpp_lib_byte) || defined(BOOST_JSON_DOCS) /** Constructor. This constructs a new parser which first uses the caller-owned storage pointed to by `buffer` for temporary storage, falling back to the memory resource `sp` if needed. The parser will use the specified parsing options. \n The parsed value will use the default memory resource for storage. To use a different resource, call @ref reset after construction. @par Complexity Constant. @par Exception Safety No-throw guarantee. @param sp The memory resource to use for temporary storage after `buffer` is exhausted. @param opt The parsing options to use. @param buffer A pointer to valid memory of at least `size` bytes for the parser to use for temporary storage. Ownership is not transferred, the caller is responsible for ensuring the lifetime of the memory pointed to by `buffer` extends until the parser is destroyed. @param size The number of valid bytes in `buffer`. */ parser( storage_ptr sp, parse_options const& opt, std::byte* buffer, std::size_t size) noexcept : parser(sp, opt, reinterpret_cast< unsigned char*>(buffer), size) { } /** Constructor. This constructs a new parser which first uses the caller-owned storage `buffer` for temporary storage, falling back to the memory resource `sp` if needed. The parser will use the specified parsing options. \n The parsed value will use the default memory resource for storage. To use a different resource, call @ref reset after construction. @par Complexity Constant. @par Exception Safety No-throw guarantee. @param sp The memory resource to use for temporary storage after `buffer` is exhausted. @param opt The parsing options to use. @param buffer A buffer for the parser to use for temporary storage. Ownership is not transferred, the caller is responsible for ensuring the lifetime of `buffer` extends until the parser is destroyed. */ template<std::size_t N> parser( storage_ptr sp, parse_options const& opt, std::byte(&buffer)[N]) noexcept : parser(std::move(sp), opt, &buffer[0], N) { } #endif #ifndef BOOST_JSON_DOCS // Safety net for accidental buffer overflows template<std::size_t N> parser( storage_ptr sp, parse_options const& opt, unsigned char(&buffer)[N], std::size_t n) noexcept : parser(std::move(sp), opt, &buffer[0], n) { // If this goes off, check your parameters // closely, chances are you passed an array // thinking it was a pointer. BOOST_ASSERT(n <= N); } #ifdef __cpp_lib_byte // Safety net for accidental buffer overflows template<std::size_t N> parser( storage_ptr sp, parse_options const& opt, std::byte(&buffer)[N], std::size_t n) noexcept : parser(std::move(sp), opt, &buffer[0], n) { // If this goes off, check your parameters // closely, chances are you passed an array // thinking it was a pointer. BOOST_ASSERT(n <= N); } #endif #endif /** Reset the parser for a new JSON. This function is used to reset the parser to prepare it for parsing a new complete JSON. Any previous partial results are destroyed. @par Complexity Constant or linear in the size of any previous partial parsing results. @par Exception Safety No-throw guarantee. @param sp A pointer to the @ref memory_resource to use for the resulting @ref value. The parser will acquire shared ownership. */ BOOST_JSON_DECL void reset(storage_ptr sp = {}) noexcept; /** Parse a buffer containing a complete JSON. This function parses a complete JSON contained in the specified character buffer. Additional characters past the end of the complete JSON are ignored. The function returns the actual number of characters parsed, which may be less than the size of the input. This allows parsing of a buffer containing multiple individual JSONs or containing different protocol data: @par Example @code parser p; // construct a parser size_t n = p.write_some( "[1,2,3] null" ); // parse a complete JSON assert( n == 8 ); // only some characters consumed value jv = p.release(); // take ownership of the value @endcode @par Complexity Linear in `size`. @par Exception Safety Basic guarantee. Calls to `memory_resource::allocate` may throw. Upon error or exception, subsequent calls will fail until @ref reset is called to parse a new JSON. @return The number of characters consumed from the buffer. @param data A pointer to a buffer of `size` characters to parse. @param size The number of characters pointed to by `data`. @param ec Set to the error, if any occurred. */ /** @{ */ BOOST_JSON_DECL std::size_t write_some( char const* data, std::size_t size, error_code& ec); BOOST_JSON_DECL std::size_t write_some( char const* data, std::size_t size, std::error_code& ec); /** @} */ /** Parse a buffer containing a complete JSON. This function parses a complete JSON contained in the specified character buffer. Additional characters past the end of the complete JSON are ignored. The function returns the actual number of characters parsed, which may be less than the size of the input. This allows parsing of a buffer containing multiple individual JSONs or containing different protocol data: @par Example @code parser p; // construct a parser size_t n = p.write_some( "[1,2,3] null" ); // parse a complete JSON assert( n == 8 ); // only some characters consumed value jv = p.release(); // take ownership of the value @endcode @par Complexity Linear in `size`. @par Exception Safety Basic guarantee. Calls to `memory_resource::allocate` may throw. Upon error or exception, subsequent calls will fail until @ref reset is called to parse a new JSON. @return The number of characters consumed from the buffer. @param data A pointer to a buffer of `size` characters to parse. @param size The number of characters pointed to by `data`. @throw system_error Thrown on error. */ BOOST_JSON_DECL std::size_t write_some( char const* data, std::size_t size); /** Parse a buffer containing a complete JSON. This function parses a complete JSON contained in the specified character buffer. Additional characters past the end of the complete JSON are ignored. The function returns the actual number of characters parsed, which may be less than the size of the input. This allows parsing of a buffer containing multiple individual JSONs or containing different protocol data: @par Example @code parser p; // construct a parser size_t n = p.write_some( "[1,2,3] null" ); // parse a complete JSON assert( n == 8 ); // only some characters consumed value jv = p.release(); // take ownership of the value @endcode @par Complexity Linear in `size`. @par Exception Safety Basic guarantee. Calls to `memory_resource::allocate` may throw. Upon error or exception, subsequent calls will fail until @ref reset is called to parse a new JSON. @return The number of characters consumed from the buffer. @param s The character string to parse. @param ec Set to the error, if any occurred. */ /** @{ */ std::size_t write_some( string_view s, error_code& ec) { return write_some( s.data(), s.size(), ec); } std::size_t write_some( string_view s, std::error_code& ec) { return write_some( s.data(), s.size(), ec); } /** @} */ /** Parse a buffer containing a complete JSON. This function parses a complete JSON contained in the specified character buffer. Additional characters past the end of the complete JSON are ignored. The function returns the actual number of characters parsed, which may be less than the size of the input. This allows parsing of a buffer containing multiple individual JSONs or containing different protocol data: @par Example @code parser p; // construct a parser size_t n = p.write_some( "[1,2,3] null" ); // parse a complete JSON assert( n == 8 ); // only some characters consumed value jv = p.release(); // take ownership of the value @endcode @par Complexity Linear in `size`. @par Exception Safety Basic guarantee. Calls to `memory_resource::allocate` may throw. Upon error or exception, subsequent calls will fail until @ref reset is called to parse a new JSON. @return The number of characters consumed from the buffer. @param s The character string to parse. @throw system_error Thrown on error. */ std::size_t write_some( string_view s) { return write_some( s.data(), s.size()); } /** Parse a buffer containing a complete JSON. This function parses a complete JSON contained in the specified character buffer. The entire buffer must be consumed; if there are additional characters past the end of the complete JSON, the parse fails and an error is returned. @par Example @code parser p; // construct a parser size_t n = p.write( "[1,2,3]" ); // parse a complete JSON assert( n == 7 ); // all characters consumed value jv = p.release(); // take ownership of the value @endcode @par Complexity Linear in `size`. @par Exception Safety Basic guarantee. Calls to `memory_resource::allocate` may throw. Upon error or exception, subsequent calls will fail until @ref reset is called to parse a new JSON. @return The number of characters consumed from the buffer. @param data A pointer to a buffer of `size` characters to parse. @param size The number of characters pointed to by `data`. @param ec Set to the error, if any occurred. */ /** @{ */ BOOST_JSON_DECL std::size_t write( char const* data, std::size_t size, error_code& ec); BOOST_JSON_DECL std::size_t write( char const* data, std::size_t size, std::error_code& ec); /** @} */ /** Parse a buffer containing a complete JSON. This function parses a complete JSON contained in the specified character buffer. The entire buffer must be consumed; if there are additional characters past the end of the complete JSON, the parse fails and an error is returned. @par Example @code parser p; // construct a parser size_t n = p.write( "[1,2,3]" ); // parse a complete JSON assert( n == 7 ); // all characters consumed value jv = p.release(); // take ownership of the value @endcode @par Complexity Linear in `size`. @par Exception Safety Basic guarantee. Calls to `memory_resource::allocate` may throw. Upon error or exception, subsequent calls will fail until @ref reset is called to parse a new JSON. @return The number of characters consumed from the buffer. @param data A pointer to a buffer of `size` characters to parse. @param size The number of characters pointed to by `data`. @throw system_error Thrown on error. */ BOOST_JSON_DECL std::size_t write( char const* data, std::size_t size); /** Parse a buffer containing a complete JSON. This function parses a complete JSON contained in the specified character buffer. The entire buffer must be consumed; if there are additional characters past the end of the complete JSON, the parse fails and an error is returned. @par Example @code parser p; // construct a parser size_t n = p.write( "[1,2,3]" ); // parse a complete JSON assert( n == 7 ); // all characters consumed value jv = p.release(); // take ownership of the value @endcode @par Complexity Linear in `size`. @par Exception Safety Basic guarantee. Calls to `memory_resource::allocate` may throw. Upon error or exception, subsequent calls will fail until @ref reset is called to parse a new JSON. @return The number of characters consumed from the buffer. @param s The character string to parse. @param ec Set to the error, if any occurred. */ /** @{ */ std::size_t write( string_view s, error_code& ec) { return write( s.data(), s.size(), ec); } std::size_t write( string_view s, std::error_code& ec) { return write( s.data(), s.size(), ec); } /** @} */ /** Parse a buffer containing a complete JSON. This function parses a complete JSON contained in the specified character buffer. The entire buffer must be consumed; if there are additional characters past the end of the complete JSON, the parse fails and an error is returned. @par Example @code parser p; // construct a parser size_t n = p.write( "[1,2,3]" ); // parse a complete JSON assert( n == 7 ); // all characters consumed value jv = p.release(); // take ownership of the value @endcode @par Complexity Linear in `size`. @par Exception Safety Basic guarantee. Calls to `memory_resource::allocate` may throw. Upon error or exception, subsequent calls will fail until @ref reset is called to parse a new JSON. @return The number of characters consumed from the buffer. @param s The character string to parse. @throw system_error Thrown on error. */ std::size_t write( string_view s) { return write( s.data(), s.size()); } /** Return the parsed JSON as a @ref value. This returns the parsed value, or throws an exception if the parsing is incomplete or failed. It is necessary to call @ref reset after calling this function in order to parse another JSON. @par Complexity Constant. @return The parsed value. Ownership of this value is transferred to the caller. @throw system_error Thrown on failure. */ BOOST_JSON_DECL value release(); }; BOOST_JSON_NS_END #endif