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Diffstat (limited to 'libbutl/json/parser.hxx')
| -rw-r--r-- | libbutl/json/parser.hxx | 408 |
1 files changed, 408 insertions, 0 deletions
diff --git a/libbutl/json/parser.hxx b/libbutl/json/parser.hxx new file mode 100644 index 0000000..241ca46 --- /dev/null +++ b/libbutl/json/parser.hxx @@ -0,0 +1,408 @@ +#pragma once + +#ifdef BUILD2_BOOTSTRAP +# error JSON parser not available during bootstrap +#endif + +#include <iosfwd> +#include <string> +#include <cstddef> // size_t +#include <cstdint> // uint64_t +#include <utility> // pair +#include <exception> // exception_ptr +#include <stdexcept> // invalid_argument + +#include <libbutl/optional.hxx> // butl::optional is std::optional or similar. + +#include <libbutl/json/event.hxx> + +#include <libbutl/json/pdjson.h> // Implementation details. + +#include <libbutl/export.hxx> + +namespace butl +{ + // Using the RFC8259 terminology: JSON (input) text, JSON value, object + // member. + // + namespace json + { + class invalid_json_input: public std::invalid_argument + { + public: + std::string name; + std::uint64_t line; + std::uint64_t column; + std::uint64_t position; + + invalid_json_input (std::string name, + std::uint64_t line, + std::uint64_t column, + std::uint64_t position, + const std::string& description); + + invalid_json_input (std::string name, + std::uint64_t line, + std::uint64_t column, + std::uint64_t position, + const char* description); + }; + + class LIBBUTL_SYMEXPORT parser + { + public: + const char* input_name; + + // Construction. + // + + // Parse JSON input text from std::istream. + // + // The name argument is used to identify the input being parsed. Note + // that the stream, name, and separators are kept as references so they + // must outlive the parser instance. + // + // If stream exceptions are enabled then the std::ios_base::failure + // exception is used to report input/output errors (badbit and failbit). + // Otherwise, those are reported as the invalid_json_input exception. + // + // If multi_value is true, enable the multi-value mode in which case the + // input stream may contain multiple JSON values (more precisely, zero + // or more). If false (the default), parsing will fail unless there is + // exactly one JSON value in the input stream. + // + // If multi_value is true, the separators argument specifies the + // required separator characters between JSON values. At least one of + // them must be present between every pair of JSON values (in addition + // to any number of JSON whitespaces). No separators are required after + // the last JSON value (but any found will be skipped). + // + // Specifically, if it is NULL, then no separation is required (that is, + // both `{...}{...}` and `{...} {...}` would be valid). If it is empty, + // then at least one JSON whitespace is required. And if it is non- + // empty, then at least one of its characters must be present (for + // example, "\n\t" would require at least one newline or TAB character + // between JSON values). + // + // Note that a separator need not be valid JSON whitespace: any + // character is acceptable (though it probably shouldn't be an object, + // array, or string delimiter and should not occur within a non-self- + // delimited top-level value, such as `true`, `false`, `null`, or a + // number). All instances of required separators before and after a + // value are skipped. Therefore JSON Text Sequences (RFC 7464; AKA + // Record Separator-delimited JSON), which requires the RS (0x1E) + // character before each value, can be handled as well. + // + parser (std::istream&, + const std::string& name, + bool multi_value = false, + const char* separators = nullptr) noexcept; + + parser (std::istream&, + const char* name, + bool multi_value = false, + const char* separators = nullptr) noexcept; + + parser (std::istream&, + std::string&&, + bool = false, + const char* = nullptr) = delete; + + // Parse a memory buffer that contains the entire JSON input text. + // + // The name argument is used to identify the input being parsed. Note + // that the buffer, name, and separators are kept as references so they + // must outlive the parser instance. + // + parser (const void* text, + std::size_t size, + const std::string& name, + bool multi_value = false, + const char* separators = nullptr) noexcept; + + parser (const void* text, + std::size_t size, + const char* name, + bool multi_value = false, + const char* separators = nullptr) noexcept; + + parser (const void*, + std::size_t, + std::string&&, + bool = false, + const char* = nullptr) = delete; + + // Similar to the above but parse a string. + // + parser (const std::string& text, + const std::string& name, + bool multi_value = false, + const char* separators = nullptr) noexcept; + + parser (const std::string& text, + const char* name, + bool multi_value = false, + const char* separators = nullptr) noexcept; + + parser (const std::string&, + std::string&&, + bool = false, + const char* = nullptr) = delete; + + // Similar to the above but parse a C-string. + // + parser (const char* text, + const std::string& name, + bool multi_value = false, + const char* separators = nullptr) noexcept; + + parser (const char* text, + const char* name, + bool multi_value = false, + const char* separators = nullptr) noexcept; + + parser (const char*, + std::string&&, + bool = false, + const char* = nullptr) = delete; + + parser (parser&&) = delete; + parser (const parser&) = delete; + + parser& operator= (parser&&) = delete; + parser& operator= (const parser&) = delete; + + // Return the next event or nullopt if end of input is reached. + // + // In the single-value parsing mode (default) the parsing code could + // look like this: + // + // while (optional<event> e = p.next ()) + // { + // switch (*e) + // { + // // ... + // } + // } + // + // In the multi-value mode the parser additionally returns nullopt after + // every JSON value parsed (so there will be two nullopt's after the + // last JSON value, the second indicating the end of input). + // + // One way to perform multi-value parsing is with the help of the peek() + // function (see below): + // + // while (p.peek ()) + // { + // while (optional<event> e = p.next ()) + // { + // switch (*e) + // { + // //... + // } + // } + // } + // + // Note that while the single-value mode will always parse exactly one + // value, the multi-value mode will accept zero values in which case a + // single nullopt is returned. + // + optional<event> + next (); + + // The range-based for loop support. + // + // In the single-value parsing mode (default) the parsing code could + // look like this: + // + // for (event e: p) + // { + // switch (e) + // { + // //... + // } + // } + // + // And in the multi-value mode (see next() for more information) like + // this: + // + // while (p.peek ()) + // { + // for (event e: p) + // { + // switch (e) + // { + // //... + // } + // } + // } + // + // Note that generally, the iterator interface doesn't make much sense + // for the parser so for now we have an implementation that is just + // enough for the range-based for. + // + struct iterator; + + iterator begin () {return iterator (this, next ());} + iterator end () {return iterator (nullptr, nullopt);} + + // Return the next event without considering it parsed. In other words, + // after this call, any subsequent calls to peek() and the next call to + // next() (if any) will all return the same event. + // + // Note that the name, value, and line corresponding to the peeked event + // are not accessible with name(), value() and line(); these functions + // will still return values corresponding to the most recent call to + // next(). The peeked values, however, can be accessed in the raw form + // using data(). + // + optional<event> + peek (); + + // Event data. + // + + // Return the object member name. + // + const std::string& + name (); + + // Any value (string, number, boolean, and null) can be retrieved as a + // string. Calling this function after any non-value events is illegal. + // + // Note that the value is returned as a non-const string reference and + // you are allowed to move the value out of it. However, this should not + // be done unnecessarily or in cases where the small string optimization + // is likely since the string's buffer is reused to store subsequent + // values. + // + std::string& + value (); + + // Convert the value to an integer, floating point, or bool. Throw + // invalid_json_input if the conversion is impossible without a loss. + // + template <typename T> + T + value () const; + + // Return the value or object member name in the raw form. + // + // Calling this function on non-value/name events is legal in which case + // NULL is returned. Note also that the returned data corresponds to the + // most recent event, whether peeked or parsed. + // + std::pair<const char*, std::size_t> + data () const {return std::make_pair (raw_s_, raw_n_);} + + // Return the line number (1-based) corresponding to the most recently + // parsed event or 0 if nothing has been parsed yet. + // + std::uint64_t + line () const noexcept; + + // Return the column number (1-based) corresponding to the beginning of + // the most recently parsed event or 0 if nothing has been parsed yet. + // + std::uint64_t + column () const noexcept; + + // Return the position (byte offset) pointing immediately after the most + // recently parsed event or 0 if nothing has been parsed yet. + // + std::uint64_t + position () const noexcept; + + // Implementation details. + // + public: + struct iterator + { + using value_type = event; + + explicit + iterator (parser* p = nullptr, optional<event> e = nullopt) + : p_ (p), e_ (e) {} + + event operator* () const {return *e_;} + iterator& operator++ () {e_ = p_->next (); return *this;} + + // Comparison only makes sense when comparing to end (eof). + // + bool operator== (iterator y) const {return !e_ && !y.e_;} + bool operator!= (iterator y) const {return !(*this == y);} + + private: + parser* p_; + optional<event> e_; + }; + + struct stream + { + std::istream* is; + optional<std::exception_ptr> exception; + }; + + [[noreturn]] void + throw_invalid_value (const char* type, const char*, std::size_t) const; + + ~parser (); + + private: + // Functionality shared by next() and peek(). + // + json_type + next_impl (); + + // Translate the event produced by the most recent call to next_impl(). + // + // Note that the underlying parser state determines whether name or + // value is returned when translating JSON_STRING. + // + optional<event> + translate (json_type) const noexcept; + + // Cache state (name/value) produced by the most recent call to + // next_impl(). + // + void + cache_parsed_data (); + + // Cache the location numbers as determined by the most recent call to + // next_impl(). + // + void + cache_parsed_location () noexcept; + + // Return true if this is a value event (string, number, boolean, or + // null). + // + static bool + value_event (optional<event>) noexcept; + + stream stream_; + + bool multi_value_; + const char* separators_; + + // The *_p_ members indicate whether the value is present (cached). + // Note: not using optional not to reallocate the string's buffer. + // + std::string name_; bool name_p_ = false; + std::string value_; bool value_p_ = false; + std::uint64_t line_, column_, position_; bool location_p_ = false; + + optional<json_type> parsed_; // Current parsed event if any. + optional<json_type> peeked_; // Current peeked event if any. + + ::json_stream impl_[1]; + + // Cached raw value. + // + const char* raw_s_; + std::size_t raw_n_; + }; + } +} + +#include <libbutl/json/parser.ixx> |