From 3a0743db9726b65b8c2fd3d12ed772076680650c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Th=C3=A9o=20DELRIEU?= Date: Mon, 14 Aug 2017 16:54:16 +0200 Subject: [PATCH] add detail/parsing/lexer.hpp --- Makefile | 3 +- src/detail/parsing/lexer.hpp | 1273 ++++++++++++++++++++++++++++++++++ src/json.hpp | 1259 +-------------------------------- 3 files changed, 1279 insertions(+), 1256 deletions(-) create mode 100644 src/detail/parsing/lexer.hpp diff --git a/Makefile b/Makefile index 9a3060af8..aacaa00fe 100644 --- a/Makefile +++ b/Makefile @@ -10,7 +10,8 @@ SRCS = ${SRCDIR}/json.hpp \ ${SRCDIR}/detail/value_t.hpp \ ${SRCDIR}/detail/conversions/from_json.hpp \ ${SRCDIR}/detail/conversions/to_json.hpp \ - ${SRCDIR}/detail/parsing/input_adapters.hpp + ${SRCDIR}/detail/parsing/input_adapters.hpp \ + ${SRCDIR}/detail/parsing/lexer.hpp diff --git a/src/detail/parsing/lexer.hpp b/src/detail/parsing/lexer.hpp new file mode 100644 index 000000000..b1232db07 --- /dev/null +++ b/src/detail/parsing/lexer.hpp @@ -0,0 +1,1273 @@ +#ifndef NLOHMANN_JSON_DETAIL_PARSING_LEXER_HPP +#define NLOHMANN_JSON_DETAIL_PARSING_LEXER_HPP + +#include +#include +#include + +#include "detail/macro_scope.hpp" +#include "detail/parsing/input_adapters.hpp" + +namespace nlohmann +{ +namespace detail +{ +/////////// +// lexer // +/////////// + +/*! +@brief lexical analysis + +This class organizes the lexical analysis during JSON deserialization. +*/ +template +class lexer +{ + using number_integer_t = typename BasicJsonType::number_integer_t; + using number_unsigned_t = typename BasicJsonType::number_unsigned_t; + using number_float_t = typename BasicJsonType::number_float_t; + + public: + /// token types for the parser + enum class token_type + { + uninitialized, ///< indicating the scanner is uninitialized + literal_true, ///< the `true` literal + literal_false, ///< the `false` literal + literal_null, ///< the `null` literal + value_string, ///< a string -- use get_string() for actual value + value_unsigned, ///< an unsigned integer -- use get_number_unsigned() for actual value + value_integer, ///< a signed integer -- use get_number_integer() for actual value + value_float, ///< an floating point number -- use get_number_float() for actual value + begin_array, ///< the character for array begin `[` + begin_object, ///< the character for object begin `{` + end_array, ///< the character for array end `]` + end_object, ///< the character for object end `}` + name_separator, ///< the name separator `:` + value_separator, ///< the value separator `,` + parse_error, ///< indicating a parse error + end_of_input, ///< indicating the end of the input buffer + literal_or_value ///< a literal or the begin of a value (only for diagnostics) + }; + + /// return name of values of type token_type (only used for errors) + static const char* token_type_name(const token_type t) noexcept + { + switch (t) + { + case token_type::uninitialized: + return ""; + case token_type::literal_true: + return "true literal"; + case token_type::literal_false: + return "false literal"; + case token_type::literal_null: + return "null literal"; + case token_type::value_string: + return "string literal"; + case lexer::token_type::value_unsigned: + case lexer::token_type::value_integer: + case lexer::token_type::value_float: + return "number literal"; + case token_type::begin_array: + return "'['"; + case token_type::begin_object: + return "'{'"; + case token_type::end_array: + return "']'"; + case token_type::end_object: + return "'}'"; + case token_type::name_separator: + return "':'"; + case token_type::value_separator: + return "','"; + case token_type::parse_error: + return ""; + case token_type::end_of_input: + return "end of input"; + case token_type::literal_or_value: + return "'[', '{', or a literal"; + default: // catch non-enum values + return "unknown token"; // LCOV_EXCL_LINE + } + } + + explicit lexer(detail::input_adapter_t adapter) + : ia(std::move(adapter)), decimal_point_char(get_decimal_point()) {} + + // delete because of pointer members + lexer(const lexer&) = delete; + lexer& operator=(lexer&) = delete; + + private: + ///////////////////// + // locales + ///////////////////// + + /// return the locale-dependent decimal point + static char get_decimal_point() noexcept + { + const auto loc = localeconv(); + assert(loc != nullptr); + return (loc->decimal_point == nullptr) ? '.' : *(loc->decimal_point); + } + + ///////////////////// + // scan functions + ///////////////////// + + /*! + @brief get codepoint from 4 hex characters following `\u` + + For input "\u c1 c2 c3 c4" the codepoint is: + (c1 * 0x1000) + (c2 * 0x0100) + (c3 * 0x0010) + c4 + = (c1 << 12) + (c2 << 8) + (c3 << 4) + (c4 << 0) + + Furthermore, the possible characters '0'..'9', 'A'..'F', and 'a'..'f' + must be converted to the integers 0x0..0x9, 0xA..0xF, 0xA..0xF, resp. The + conversion is done by subtracting the offset (0x30, 0x37, and 0x57) + between the ASCII value of the character and the desired integer value. + + @return codepoint (0x0000..0xFFFF) or -1 in case of an error (e.g. EOF or + non-hex character) + */ + int get_codepoint() + { + // this function only makes sense after reading `\u` + assert(current == 'u'); + int codepoint = 0; + + const auto factors = { 12, 8, 4, 0 }; + for (const auto factor : factors) + { + get(); + + if (current >= '0' and current <= '9') + { + codepoint += ((current - 0x30) << factor); + } + else if (current >= 'A' and current <= 'F') + { + codepoint += ((current - 0x37) << factor); + } + else if (current >= 'a' and current <= 'f') + { + codepoint += ((current - 0x57) << factor); + } + else + { + return -1; + } + } + + assert(0x0000 <= codepoint and codepoint <= 0xFFFF); + return codepoint; + } + + /*! + @brief check if the next byte(s) are inside a given range + + Adds the current byte and, for each passed range, reads a new byte and + checks if it is inside the range. If a violation was detected, set up an + error message and return false. Otherwise, return true. + + @param[in] ranges list of integers; interpreted as list of pairs of + inclusive lower and upper bound, respectively + + @pre The passed list @a ranges must have 2, 4, or 6 elements; that is, + 1, 2, or 3 pairs. This precondition is enforced by an assertion. + + @return true if and only if no range violation was detected + */ + bool next_byte_in_range(std::initializer_list ranges) + { + assert(ranges.size() == 2 or ranges.size() == 4 or ranges.size() == 6); + add(current); + + for (auto range = ranges.begin(); range != ranges.end(); ++range) + { + get(); + if (JSON_LIKELY(*range <= current and current <= *(++range))) + { + add(current); + } + else + { + error_message = "invalid string: ill-formed UTF-8 byte"; + return false; + } + } + + return true; + } + + /*! + @brief scan a string literal + + This function scans a string according to Sect. 7 of RFC 7159. While + scanning, bytes are escaped and copied into buffer yytext. Then the function + returns successfully, yytext is *not* null-terminated (as it may contain \0 + bytes), and yytext.size() is the number of bytes in the string. + + @return token_type::value_string if string could be successfully scanned, + token_type::parse_error otherwise + + @note In case of errors, variable error_message contains a textual + description. + */ + token_type scan_string() + { + // reset yytext (ignore opening quote) + reset(); + + // we entered the function by reading an open quote + assert(current == '\"'); + + while (true) + { + // get next character + switch (get()) + { + // end of file while parsing string + case std::char_traits::eof(): + { + error_message = "invalid string: missing closing quote"; + return token_type::parse_error; + } + + // closing quote + case '\"': + { + return token_type::value_string; + } + + // escapes + case '\\': + { + switch (get()) + { + // quotation mark + case '\"': + add('\"'); + break; + // reverse solidus + case '\\': + add('\\'); + break; + // solidus + case '/': + add('/'); + break; + // backspace + case 'b': + add('\b'); + break; + // form feed + case 'f': + add('\f'); + break; + // line feed + case 'n': + add('\n'); + break; + // carriage return + case 'r': + add('\r'); + break; + // tab + case 't': + add('\t'); + break; + + // unicode escapes + case 'u': + { + const int codepoint1 = get_codepoint(); + int codepoint = codepoint1; // start with codepoint1 + + if (JSON_UNLIKELY(codepoint1 == -1)) + { + error_message = "invalid string: '\\u' must be followed by 4 hex digits"; + return token_type::parse_error; + } + + // check if code point is a high surrogate + if (0xD800 <= codepoint1 and codepoint1 <= 0xDBFF) + { + // expect next \uxxxx entry + if (JSON_LIKELY(get() == '\\' and get() == 'u')) + { + const int codepoint2 = get_codepoint(); + + if (JSON_UNLIKELY(codepoint2 == -1)) + { + error_message = "invalid string: '\\u' must be followed by 4 hex digits"; + return token_type::parse_error; + } + + // check if codepoint2 is a low surrogate + if (JSON_LIKELY(0xDC00 <= codepoint2 and codepoint2 <= 0xDFFF)) + { + // overwrite codepoint + codepoint = + // high surrogate occupies the most significant 22 bits + (codepoint1 << 10) + // low surrogate occupies the least significant 15 bits + + codepoint2 + // there is still the 0xD800, 0xDC00 and 0x10000 noise + // in the result so we have to subtract with: + // (0xD800 << 10) + DC00 - 0x10000 = 0x35FDC00 + - 0x35FDC00; + } + else + { + error_message = "invalid string: surrogate U+DC00..U+DFFF must be followed by U+DC00..U+DFFF"; + return token_type::parse_error; + } + } + else + { + error_message = "invalid string: surrogate U+DC00..U+DFFF must be followed by U+DC00..U+DFFF"; + return token_type::parse_error; + } + } + else + { + if (JSON_UNLIKELY(0xDC00 <= codepoint1 and codepoint1 <= 0xDFFF)) + { + error_message = "invalid string: surrogate U+DC00..U+DFFF must follow U+D800..U+DBFF"; + return token_type::parse_error; + } + } + + // result of the above calculation yields a proper codepoint + assert(0x00 <= codepoint and codepoint <= 0x10FFFF); + + // translate codepoint into bytes + if (codepoint < 0x80) + { + // 1-byte characters: 0xxxxxxx (ASCII) + add(codepoint); + } + else if (codepoint <= 0x7FF) + { + // 2-byte characters: 110xxxxx 10xxxxxx + add(0xC0 | (codepoint >> 6)); + add(0x80 | (codepoint & 0x3F)); + } + else if (codepoint <= 0xFFFF) + { + // 3-byte characters: 1110xxxx 10xxxxxx 10xxxxxx + add(0xE0 | (codepoint >> 12)); + add(0x80 | ((codepoint >> 6) & 0x3F)); + add(0x80 | (codepoint & 0x3F)); + } + else + { + // 4-byte characters: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx + add(0xF0 | (codepoint >> 18)); + add(0x80 | ((codepoint >> 12) & 0x3F)); + add(0x80 | ((codepoint >> 6) & 0x3F)); + add(0x80 | (codepoint & 0x3F)); + } + + break; + } + + // other characters after escape + default: + error_message = "invalid string: forbidden character after backslash"; + return token_type::parse_error; + } + + break; + } + + // invalid control characters + case 0x00: + case 0x01: + case 0x02: + case 0x03: + case 0x04: + case 0x05: + case 0x06: + case 0x07: + case 0x08: + case 0x09: + case 0x0A: + case 0x0B: + case 0x0C: + case 0x0D: + case 0x0E: + case 0x0F: + case 0x10: + case 0x11: + case 0x12: + case 0x13: + case 0x14: + case 0x15: + case 0x16: + case 0x17: + case 0x18: + case 0x19: + case 0x1A: + case 0x1B: + case 0x1C: + case 0x1D: + case 0x1E: + case 0x1F: + { + error_message = "invalid string: control character must be escaped"; + return token_type::parse_error; + } + + // U+0020..U+007F (except U+0022 (quote) and U+005C (backspace)) + case 0x20: + case 0x21: + case 0x23: + case 0x24: + case 0x25: + case 0x26: + case 0x27: + case 0x28: + case 0x29: + case 0x2A: + case 0x2B: + case 0x2C: + case 0x2D: + case 0x2E: + case 0x2F: + case 0x30: + case 0x31: + case 0x32: + case 0x33: + case 0x34: + case 0x35: + case 0x36: + case 0x37: + case 0x38: + case 0x39: + case 0x3A: + case 0x3B: + case 0x3C: + case 0x3D: + case 0x3E: + case 0x3F: + case 0x40: + case 0x41: + case 0x42: + case 0x43: + case 0x44: + case 0x45: + case 0x46: + case 0x47: + case 0x48: + case 0x49: + case 0x4A: + case 0x4B: + case 0x4C: + case 0x4D: + case 0x4E: + case 0x4F: + case 0x50: + case 0x51: + case 0x52: + case 0x53: + case 0x54: + case 0x55: + case 0x56: + case 0x57: + case 0x58: + case 0x59: + case 0x5A: + case 0x5B: + case 0x5D: + case 0x5E: + case 0x5F: + case 0x60: + case 0x61: + case 0x62: + case 0x63: + case 0x64: + case 0x65: + case 0x66: + case 0x67: + case 0x68: + case 0x69: + case 0x6A: + case 0x6B: + case 0x6C: + case 0x6D: + case 0x6E: + case 0x6F: + case 0x70: + case 0x71: + case 0x72: + case 0x73: + case 0x74: + case 0x75: + case 0x76: + case 0x77: + case 0x78: + case 0x79: + case 0x7A: + case 0x7B: + case 0x7C: + case 0x7D: + case 0x7E: + case 0x7F: + { + add(current); + break; + } + + // U+0080..U+07FF: bytes C2..DF 80..BF + case 0xC2: + case 0xC3: + case 0xC4: + case 0xC5: + case 0xC6: + case 0xC7: + case 0xC8: + case 0xC9: + case 0xCA: + case 0xCB: + case 0xCC: + case 0xCD: + case 0xCE: + case 0xCF: + case 0xD0: + case 0xD1: + case 0xD2: + case 0xD3: + case 0xD4: + case 0xD5: + case 0xD6: + case 0xD7: + case 0xD8: + case 0xD9: + case 0xDA: + case 0xDB: + case 0xDC: + case 0xDD: + case 0xDE: + case 0xDF: + { + if (JSON_UNLIKELY(not next_byte_in_range({0x80, 0xBF}))) + { + return token_type::parse_error; + } + break; + } + + // U+0800..U+0FFF: bytes E0 A0..BF 80..BF + case 0xE0: + { + if (JSON_UNLIKELY(not (next_byte_in_range({0xA0, 0xBF, 0x80, 0xBF})))) + { + return token_type::parse_error; + } + break; + } + + // U+1000..U+CFFF: bytes E1..EC 80..BF 80..BF + // U+E000..U+FFFF: bytes EE..EF 80..BF 80..BF + case 0xE1: + case 0xE2: + case 0xE3: + case 0xE4: + case 0xE5: + case 0xE6: + case 0xE7: + case 0xE8: + case 0xE9: + case 0xEA: + case 0xEB: + case 0xEC: + case 0xEE: + case 0xEF: + { + if (JSON_UNLIKELY(not (next_byte_in_range({0x80, 0xBF, 0x80, 0xBF})))) + { + return token_type::parse_error; + } + break; + } + + // U+D000..U+D7FF: bytes ED 80..9F 80..BF + case 0xED: + { + if (JSON_UNLIKELY(not (next_byte_in_range({0x80, 0x9F, 0x80, 0xBF})))) + { + return token_type::parse_error; + } + break; + } + + // U+10000..U+3FFFF F0 90..BF 80..BF 80..BF + case 0xF0: + { + if (JSON_UNLIKELY(not (next_byte_in_range({0x90, 0xBF, 0x80, 0xBF, 0x80, 0xBF})))) + { + return token_type::parse_error; + } + break; + } + + // U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF + case 0xF1: + case 0xF2: + case 0xF3: + { + if (JSON_UNLIKELY(not (next_byte_in_range({0x80, 0xBF, 0x80, 0xBF, 0x80, 0xBF})))) + { + return token_type::parse_error; + } + break; + } + + // U+100000..U+10FFFF F4 80..8F 80..BF 80..BF + case 0xF4: + { + if (JSON_UNLIKELY(not (next_byte_in_range({0x80, 0x8F, 0x80, 0xBF, 0x80, 0xBF})))) + { + return token_type::parse_error; + } + break; + } + + // remaining bytes (80..C1 and F5..FF) are ill-formed + default: + { + error_message = "invalid string: ill-formed UTF-8 byte"; + return token_type::parse_error; + } + } + } + } + + static void strtof(float& f, const char* str, char** endptr) noexcept + { + f = std::strtof(str, endptr); + } + + static void strtof(double& f, const char* str, char** endptr) noexcept + { + f = std::strtod(str, endptr); + } + + static void strtof(long double& f, const char* str, char** endptr) noexcept + { + f = std::strtold(str, endptr); + } + + /*! + @brief scan a number literal + + This function scans a string according to Sect. 6 of RFC 7159. + + The function is realized with a deterministic finite state machine derived + from the grammar described in RFC 7159. Starting in state "init", the + input is read and used to determined the next state. Only state "done" + accepts the number. State "error" is a trap state to model errors. In the + table below, "anything" means any character but the ones listed before. + + state | 0 | 1-9 | e E | + | - | . | anything + ---------|----------|----------|----------|---------|---------|----------|----------- + init | zero | any1 | [error] | [error] | minus | [error] | [error] + minus | zero | any1 | [error] | [error] | [error] | [error] | [error] + zero | done | done | exponent | done | done | decimal1 | done + any1 | any1 | any1 | exponent | done | done | decimal1 | done + decimal1 | decimal2 | [error] | [error] | [error] | [error] | [error] | [error] + decimal2 | decimal2 | decimal2 | exponent | done | done | done | done + exponent | any2 | any2 | [error] | sign | sign | [error] | [error] + sign | any2 | any2 | [error] | [error] | [error] | [error] | [error] + any2 | any2 | any2 | done | done | done | done | done + + The state machine is realized with one label per state (prefixed with + "scan_number_") and `goto` statements between them. The state machine + contains cycles, but any cycle can be left when EOF is read. Therefore, + the function is guaranteed to terminate. + + During scanning, the read bytes are stored in yytext. This string is + then converted to a signed integer, an unsigned integer, or a + floating-point number. + + @return token_type::value_unsigned, token_type::value_integer, or + token_type::value_float if number could be successfully scanned, + token_type::parse_error otherwise + + @note The scanner is independent of the current locale. Internally, the + locale's decimal point is used instead of `.` to work with the + locale-dependent converters. + */ + token_type scan_number() + { + // reset yytext to store the number's bytes + reset(); + + // the type of the parsed number; initially set to unsigned; will be + // changed if minus sign, decimal point or exponent is read + token_type number_type = token_type::value_unsigned; + + // state (init): we just found out we need to scan a number + switch (current) + { + case '-': + { + add(current); + goto scan_number_minus; + } + + case '0': + { + add(current); + goto scan_number_zero; + } + + case '1': + case '2': + case '3': + case '4': + case '5': + case '6': + case '7': + case '8': + case '9': + { + add(current); + goto scan_number_any1; + } + + default: + { + // all other characters are rejected outside scan_number() + assert(false); // LCOV_EXCL_LINE + } + } + +scan_number_minus: + // state: we just parsed a leading minus sign + number_type = token_type::value_integer; + switch (get()) + { + case '0': + { + add(current); + goto scan_number_zero; + } + + case '1': + case '2': + case '3': + case '4': + case '5': + case '6': + case '7': + case '8': + case '9': + { + add(current); + goto scan_number_any1; + } + + default: + { + error_message = "invalid number; expected digit after '-'"; + return token_type::parse_error; + } + } + +scan_number_zero: + // state: we just parse a zero (maybe with a leading minus sign) + switch (get()) + { + case '.': + { + add(decimal_point_char); + goto scan_number_decimal1; + } + + case 'e': + case 'E': + { + add(current); + goto scan_number_exponent; + } + + default: + goto scan_number_done; + } + +scan_number_any1: + // state: we just parsed a number 0-9 (maybe with a leading minus sign) + switch (get()) + { + case '0': + case '1': + case '2': + case '3': + case '4': + case '5': + case '6': + case '7': + case '8': + case '9': + { + add(current); + goto scan_number_any1; + } + + case '.': + { + add(decimal_point_char); + goto scan_number_decimal1; + } + + case 'e': + case 'E': + { + add(current); + goto scan_number_exponent; + } + + default: + goto scan_number_done; + } + +scan_number_decimal1: + // state: we just parsed a decimal point + number_type = token_type::value_float; + switch (get()) + { + case '0': + case '1': + case '2': + case '3': + case '4': + case '5': + case '6': + case '7': + case '8': + case '9': + { + add(current); + goto scan_number_decimal2; + } + + default: + { + error_message = "invalid number; expected digit after '.'"; + return token_type::parse_error; + } + } + +scan_number_decimal2: + // we just parsed at least one number after a decimal point + switch (get()) + { + case '0': + case '1': + case '2': + case '3': + case '4': + case '5': + case '6': + case '7': + case '8': + case '9': + { + add(current); + goto scan_number_decimal2; + } + + case 'e': + case 'E': + { + add(current); + goto scan_number_exponent; + } + + default: + goto scan_number_done; + } + +scan_number_exponent: + // we just parsed an exponent + number_type = token_type::value_float; + switch (get()) + { + case '+': + case '-': + { + add(current); + goto scan_number_sign; + } + + case '0': + case '1': + case '2': + case '3': + case '4': + case '5': + case '6': + case '7': + case '8': + case '9': + { + add(current); + goto scan_number_any2; + } + + default: + { + error_message = + "invalid number; expected '+', '-', or digit after exponent"; + return token_type::parse_error; + } + } + +scan_number_sign: + // we just parsed an exponent sign + switch (get()) + { + case '0': + case '1': + case '2': + case '3': + case '4': + case '5': + case '6': + case '7': + case '8': + case '9': + { + add(current); + goto scan_number_any2; + } + + default: + { + error_message = "invalid number; expected digit after exponent sign"; + return token_type::parse_error; + } + } + +scan_number_any2: + // we just parsed a number after the exponent or exponent sign + switch (get()) + { + case '0': + case '1': + case '2': + case '3': + case '4': + case '5': + case '6': + case '7': + case '8': + case '9': + { + add(current); + goto scan_number_any2; + } + + default: + goto scan_number_done; + } + +scan_number_done: + // unget the character after the number (we only read it to know that + // we are done scanning a number) + unget(); + + char* endptr = nullptr; + errno = 0; + + // try to parse integers first and fall back to floats + if (number_type == token_type::value_unsigned) + { + const auto x = std::strtoull(yytext.data(), &endptr, 10); + + // we checked the number format before + assert(endptr == yytext.data() + yytext.size()); + + if (errno == 0) + { + value_unsigned = static_cast(x); + if (value_unsigned == x) + { + return token_type::value_unsigned; + } + } + } + else if (number_type == token_type::value_integer) + { + const auto x = std::strtoll(yytext.data(), &endptr, 10); + + // we checked the number format before + assert(endptr == yytext.data() + yytext.size()); + + if (errno == 0) + { + value_integer = static_cast(x); + if (value_integer == x) + { + return token_type::value_integer; + } + } + } + + // this code is reached if we parse a floating-point number or if an + // integer conversion above failed + strtof(value_float, yytext.data(), &endptr); + + // we checked the number format before + assert(endptr == yytext.data() + yytext.size()); + + return token_type::value_float; + } + + /*! + @param[in] literal_text the literal text to expect + @param[in] length the length of the passed literal text + @param[in] return_type the token type to return on success + */ + token_type scan_literal(const char* literal_text, const std::size_t length, + token_type return_type) + { + assert(current == literal_text[0]); + for (std::size_t i = 1; i < length; ++i) + { + if (JSON_UNLIKELY(get() != literal_text[i])) + { + error_message = "invalid literal"; + return token_type::parse_error; + } + } + return return_type; + } + + ///////////////////// + // input management + ///////////////////// + + /// reset yytext; current character is beginning of token + void reset() noexcept + { + yytext.clear(); + token_string.clear(); + token_string.push_back(std::char_traits::to_char_type(current)); + } + + /* + @brief get next character from the input + + This function provides the interface to the used input adapter. It does + not throw in case the input reached EOF, but returns a + `std::char_traits::eof()` in that case. Stores the scanned characters + for use in error messages. + + @return character read from the input + */ + std::char_traits::int_type get() + { + ++chars_read; + current = ia->get_character(); + if (JSON_LIKELY(current != std::char_traits::eof())) + { + token_string.push_back(std::char_traits::to_char_type(current)); + } + return current; + } + + /// unget current character (return it again on next get) + void unget() + { + --chars_read; + if (JSON_LIKELY(current != std::char_traits::eof())) + { + ia->unget_character(); + assert(token_string.size() != 0); + token_string.pop_back(); + } + } + + /// add a character to yytext + void add(int c) + { + yytext.push_back(std::char_traits::to_char_type(c)); + } + + public: + ///////////////////// + // value getters + ///////////////////// + + /// return integer value + constexpr number_integer_t get_number_integer() const noexcept + { + return value_integer; + } + + /// return unsigned integer value + constexpr number_unsigned_t get_number_unsigned() const noexcept + { + return value_unsigned; + } + + /// return floating-point value + constexpr number_float_t get_number_float() const noexcept + { + return value_float; + } + + /// return current string value (implicitly resets the token; useful only once) + std::string move_string() + { + return std::move(yytext); + } + + ///////////////////// + // diagnostics + ///////////////////// + + /// return position of last read token + constexpr std::size_t get_position() const noexcept + { + return chars_read; + } + + /// return the last read token (for errors only). Will never contain EOF + /// (an arbitrary value that is not a valid char value, often -1), because + /// 255 may legitimately occur. May contain NUL, which should be escaped. + std::string get_token_string() const + { + // escape control characters + std::string result; + for (const auto c : token_string) + { + if ('\x00' <= c and c <= '\x1F') + { + // escape control characters + std::stringstream ss; + ss << "(c) << ">"; + result += ss.str(); + } + else + { + // add character as is + result.push_back(c); + } + } + + return result; + } + + /// return syntax error message + constexpr const char* get_error_message() const noexcept + { + return error_message; + } + + ///////////////////// + // actual scanner + ///////////////////// + + token_type scan() + { + // read next character and ignore whitespace + do + { + get(); + } + while (current == ' ' or current == '\t' or current == '\n' or current == '\r'); + + switch (current) + { + // structural characters + case '[': + return token_type::begin_array; + case ']': + return token_type::end_array; + case '{': + return token_type::begin_object; + case '}': + return token_type::end_object; + case ':': + return token_type::name_separator; + case ',': + return token_type::value_separator; + + // literals + case 't': + return scan_literal("true", 4, token_type::literal_true); + case 'f': + return scan_literal("false", 5, token_type::literal_false); + case 'n': + return scan_literal("null", 4, token_type::literal_null); + + // string + case '\"': + return scan_string(); + + // number + case '-': + case '0': + case '1': + case '2': + case '3': + case '4': + case '5': + case '6': + case '7': + case '8': + case '9': + return scan_number(); + + // end of input (the null byte is needed when parsing from + // string literals) + case '\0': + case std::char_traits::eof(): + return token_type::end_of_input; + + // error + default: + error_message = "invalid literal"; + return token_type::parse_error; + } + } + + private: + /// input adapter + detail::input_adapter_t ia = nullptr; + + /// the current character + std::char_traits::int_type current = std::char_traits::eof(); + + /// the number of characters read + std::size_t chars_read = 0; + + /// raw input token string (for error messages) + std::vector token_string {}; + + /// buffer for variable-length tokens (numbers, strings) + std::string yytext {}; + + /// a description of occurred lexer errors + const char* error_message = ""; + + // number values + number_integer_t value_integer = 0; + number_unsigned_t value_unsigned = 0; + number_float_t value_float = 0; + + /// the decimal point + const char decimal_point_char = '.'; +}; +} +} + +#endif diff --git a/src/json.hpp b/src/json.hpp index f3fea0b88..d93ba3163 100644 --- a/src/json.hpp +++ b/src/json.hpp @@ -58,6 +58,7 @@ SOFTWARE. #include "detail/conversions/from_json.hpp" #include "detail/conversions/to_json.hpp" #include "detail/parsing/input_adapters.hpp" +#include "detail/parsing/lexer.hpp" /*! @brief namespace for Niels Lohmann @@ -68,1261 +69,9 @@ namespace nlohmann { namespace detail { -////////////////////// -// lexer and parser // -////////////////////// - -/*! -@brief lexical analysis - -This class organizes the lexical analysis during JSON deserialization. -*/ -template -class lexer -{ - using number_integer_t = typename BasicJsonType::number_integer_t; - using number_unsigned_t = typename BasicJsonType::number_unsigned_t; - using number_float_t = typename BasicJsonType::number_float_t; - - public: - /// token types for the parser - enum class token_type - { - uninitialized, ///< indicating the scanner is uninitialized - literal_true, ///< the `true` literal - literal_false, ///< the `false` literal - literal_null, ///< the `null` literal - value_string, ///< a string -- use get_string() for actual value - value_unsigned, ///< an unsigned integer -- use get_number_unsigned() for actual value - value_integer, ///< a signed integer -- use get_number_integer() for actual value - value_float, ///< an floating point number -- use get_number_float() for actual value - begin_array, ///< the character for array begin `[` - begin_object, ///< the character for object begin `{` - end_array, ///< the character for array end `]` - end_object, ///< the character for object end `}` - name_separator, ///< the name separator `:` - value_separator, ///< the value separator `,` - parse_error, ///< indicating a parse error - end_of_input, ///< indicating the end of the input buffer - literal_or_value ///< a literal or the begin of a value (only for diagnostics) - }; - - /// return name of values of type token_type (only used for errors) - static const char* token_type_name(const token_type t) noexcept - { - switch (t) - { - case token_type::uninitialized: - return ""; - case token_type::literal_true: - return "true literal"; - case token_type::literal_false: - return "false literal"; - case token_type::literal_null: - return "null literal"; - case token_type::value_string: - return "string literal"; - case lexer::token_type::value_unsigned: - case lexer::token_type::value_integer: - case lexer::token_type::value_float: - return "number literal"; - case token_type::begin_array: - return "'['"; - case token_type::begin_object: - return "'{'"; - case token_type::end_array: - return "']'"; - case token_type::end_object: - return "'}'"; - case token_type::name_separator: - return "':'"; - case token_type::value_separator: - return "','"; - case token_type::parse_error: - return ""; - case token_type::end_of_input: - return "end of input"; - case token_type::literal_or_value: - return "'[', '{', or a literal"; - default: // catch non-enum values - return "unknown token"; // LCOV_EXCL_LINE - } - } - - explicit lexer(detail::input_adapter_t adapter) - : ia(std::move(adapter)), decimal_point_char(get_decimal_point()) {} - - // delete because of pointer members - lexer(const lexer&) = delete; - lexer& operator=(lexer&) = delete; - - private: - ///////////////////// - // locales - ///////////////////// - - /// return the locale-dependent decimal point - static char get_decimal_point() noexcept - { - const auto loc = localeconv(); - assert(loc != nullptr); - return (loc->decimal_point == nullptr) ? '.' : *(loc->decimal_point); - } - - ///////////////////// - // scan functions - ///////////////////// - - /*! - @brief get codepoint from 4 hex characters following `\u` - - For input "\u c1 c2 c3 c4" the codepoint is: - (c1 * 0x1000) + (c2 * 0x0100) + (c3 * 0x0010) + c4 - = (c1 << 12) + (c2 << 8) + (c3 << 4) + (c4 << 0) - - Furthermore, the possible characters '0'..'9', 'A'..'F', and 'a'..'f' - must be converted to the integers 0x0..0x9, 0xA..0xF, 0xA..0xF, resp. The - conversion is done by subtracting the offset (0x30, 0x37, and 0x57) - between the ASCII value of the character and the desired integer value. - - @return codepoint (0x0000..0xFFFF) or -1 in case of an error (e.g. EOF or - non-hex character) - */ - int get_codepoint() - { - // this function only makes sense after reading `\u` - assert(current == 'u'); - int codepoint = 0; - - const auto factors = { 12, 8, 4, 0 }; - for (const auto factor : factors) - { - get(); - - if (current >= '0' and current <= '9') - { - codepoint += ((current - 0x30) << factor); - } - else if (current >= 'A' and current <= 'F') - { - codepoint += ((current - 0x37) << factor); - } - else if (current >= 'a' and current <= 'f') - { - codepoint += ((current - 0x57) << factor); - } - else - { - return -1; - } - } - - assert(0x0000 <= codepoint and codepoint <= 0xFFFF); - return codepoint; - } - - /*! - @brief check if the next byte(s) are inside a given range - - Adds the current byte and, for each passed range, reads a new byte and - checks if it is inside the range. If a violation was detected, set up an - error message and return false. Otherwise, return true. - - @param[in] ranges list of integers; interpreted as list of pairs of - inclusive lower and upper bound, respectively - - @pre The passed list @a ranges must have 2, 4, or 6 elements; that is, - 1, 2, or 3 pairs. This precondition is enforced by an assertion. - - @return true if and only if no range violation was detected - */ - bool next_byte_in_range(std::initializer_list ranges) - { - assert(ranges.size() == 2 or ranges.size() == 4 or ranges.size() == 6); - add(current); - - for (auto range = ranges.begin(); range != ranges.end(); ++range) - { - get(); - if (JSON_LIKELY(*range <= current and current <= *(++range))) - { - add(current); - } - else - { - error_message = "invalid string: ill-formed UTF-8 byte"; - return false; - } - } - - return true; - } - - /*! - @brief scan a string literal - - This function scans a string according to Sect. 7 of RFC 7159. While - scanning, bytes are escaped and copied into buffer yytext. Then the function - returns successfully, yytext is *not* null-terminated (as it may contain \0 - bytes), and yytext.size() is the number of bytes in the string. - - @return token_type::value_string if string could be successfully scanned, - token_type::parse_error otherwise - - @note In case of errors, variable error_message contains a textual - description. - */ - token_type scan_string() - { - // reset yytext (ignore opening quote) - reset(); - - // we entered the function by reading an open quote - assert(current == '\"'); - - while (true) - { - // get next character - switch (get()) - { - // end of file while parsing string - case std::char_traits::eof(): - { - error_message = "invalid string: missing closing quote"; - return token_type::parse_error; - } - - // closing quote - case '\"': - { - return token_type::value_string; - } - - // escapes - case '\\': - { - switch (get()) - { - // quotation mark - case '\"': - add('\"'); - break; - // reverse solidus - case '\\': - add('\\'); - break; - // solidus - case '/': - add('/'); - break; - // backspace - case 'b': - add('\b'); - break; - // form feed - case 'f': - add('\f'); - break; - // line feed - case 'n': - add('\n'); - break; - // carriage return - case 'r': - add('\r'); - break; - // tab - case 't': - add('\t'); - break; - - // unicode escapes - case 'u': - { - const int codepoint1 = get_codepoint(); - int codepoint = codepoint1; // start with codepoint1 - - if (JSON_UNLIKELY(codepoint1 == -1)) - { - error_message = "invalid string: '\\u' must be followed by 4 hex digits"; - return token_type::parse_error; - } - - // check if code point is a high surrogate - if (0xD800 <= codepoint1 and codepoint1 <= 0xDBFF) - { - // expect next \uxxxx entry - if (JSON_LIKELY(get() == '\\' and get() == 'u')) - { - const int codepoint2 = get_codepoint(); - - if (JSON_UNLIKELY(codepoint2 == -1)) - { - error_message = "invalid string: '\\u' must be followed by 4 hex digits"; - return token_type::parse_error; - } - - // check if codepoint2 is a low surrogate - if (JSON_LIKELY(0xDC00 <= codepoint2 and codepoint2 <= 0xDFFF)) - { - // overwrite codepoint - codepoint = - // high surrogate occupies the most significant 22 bits - (codepoint1 << 10) - // low surrogate occupies the least significant 15 bits - + codepoint2 - // there is still the 0xD800, 0xDC00 and 0x10000 noise - // in the result so we have to subtract with: - // (0xD800 << 10) + DC00 - 0x10000 = 0x35FDC00 - - 0x35FDC00; - } - else - { - error_message = "invalid string: surrogate U+DC00..U+DFFF must be followed by U+DC00..U+DFFF"; - return token_type::parse_error; - } - } - else - { - error_message = "invalid string: surrogate U+DC00..U+DFFF must be followed by U+DC00..U+DFFF"; - return token_type::parse_error; - } - } - else - { - if (JSON_UNLIKELY(0xDC00 <= codepoint1 and codepoint1 <= 0xDFFF)) - { - error_message = "invalid string: surrogate U+DC00..U+DFFF must follow U+D800..U+DBFF"; - return token_type::parse_error; - } - } - - // result of the above calculation yields a proper codepoint - assert(0x00 <= codepoint and codepoint <= 0x10FFFF); - - // translate codepoint into bytes - if (codepoint < 0x80) - { - // 1-byte characters: 0xxxxxxx (ASCII) - add(codepoint); - } - else if (codepoint <= 0x7FF) - { - // 2-byte characters: 110xxxxx 10xxxxxx - add(0xC0 | (codepoint >> 6)); - add(0x80 | (codepoint & 0x3F)); - } - else if (codepoint <= 0xFFFF) - { - // 3-byte characters: 1110xxxx 10xxxxxx 10xxxxxx - add(0xE0 | (codepoint >> 12)); - add(0x80 | ((codepoint >> 6) & 0x3F)); - add(0x80 | (codepoint & 0x3F)); - } - else - { - // 4-byte characters: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx - add(0xF0 | (codepoint >> 18)); - add(0x80 | ((codepoint >> 12) & 0x3F)); - add(0x80 | ((codepoint >> 6) & 0x3F)); - add(0x80 | (codepoint & 0x3F)); - } - - break; - } - - // other characters after escape - default: - error_message = "invalid string: forbidden character after backslash"; - return token_type::parse_error; - } - - break; - } - - // invalid control characters - case 0x00: - case 0x01: - case 0x02: - case 0x03: - case 0x04: - case 0x05: - case 0x06: - case 0x07: - case 0x08: - case 0x09: - case 0x0A: - case 0x0B: - case 0x0C: - case 0x0D: - case 0x0E: - case 0x0F: - case 0x10: - case 0x11: - case 0x12: - case 0x13: - case 0x14: - case 0x15: - case 0x16: - case 0x17: - case 0x18: - case 0x19: - case 0x1A: - case 0x1B: - case 0x1C: - case 0x1D: - case 0x1E: - case 0x1F: - { - error_message = "invalid string: control character must be escaped"; - return token_type::parse_error; - } - - // U+0020..U+007F (except U+0022 (quote) and U+005C (backspace)) - case 0x20: - case 0x21: - case 0x23: - case 0x24: - case 0x25: - case 0x26: - case 0x27: - case 0x28: - case 0x29: - case 0x2A: - case 0x2B: - case 0x2C: - case 0x2D: - case 0x2E: - case 0x2F: - case 0x30: - case 0x31: - case 0x32: - case 0x33: - case 0x34: - case 0x35: - case 0x36: - case 0x37: - case 0x38: - case 0x39: - case 0x3A: - case 0x3B: - case 0x3C: - case 0x3D: - case 0x3E: - case 0x3F: - case 0x40: - case 0x41: - case 0x42: - case 0x43: - case 0x44: - case 0x45: - case 0x46: - case 0x47: - case 0x48: - case 0x49: - case 0x4A: - case 0x4B: - case 0x4C: - case 0x4D: - case 0x4E: - case 0x4F: - case 0x50: - case 0x51: - case 0x52: - case 0x53: - case 0x54: - case 0x55: - case 0x56: - case 0x57: - case 0x58: - case 0x59: - case 0x5A: - case 0x5B: - case 0x5D: - case 0x5E: - case 0x5F: - case 0x60: - case 0x61: - case 0x62: - case 0x63: - case 0x64: - case 0x65: - case 0x66: - case 0x67: - case 0x68: - case 0x69: - case 0x6A: - case 0x6B: - case 0x6C: - case 0x6D: - case 0x6E: - case 0x6F: - case 0x70: - case 0x71: - case 0x72: - case 0x73: - case 0x74: - case 0x75: - case 0x76: - case 0x77: - case 0x78: - case 0x79: - case 0x7A: - case 0x7B: - case 0x7C: - case 0x7D: - case 0x7E: - case 0x7F: - { - add(current); - break; - } - - // U+0080..U+07FF: bytes C2..DF 80..BF - case 0xC2: - case 0xC3: - case 0xC4: - case 0xC5: - case 0xC6: - case 0xC7: - case 0xC8: - case 0xC9: - case 0xCA: - case 0xCB: - case 0xCC: - case 0xCD: - case 0xCE: - case 0xCF: - case 0xD0: - case 0xD1: - case 0xD2: - case 0xD3: - case 0xD4: - case 0xD5: - case 0xD6: - case 0xD7: - case 0xD8: - case 0xD9: - case 0xDA: - case 0xDB: - case 0xDC: - case 0xDD: - case 0xDE: - case 0xDF: - { - if (JSON_UNLIKELY(not next_byte_in_range({0x80, 0xBF}))) - { - return token_type::parse_error; - } - break; - } - - // U+0800..U+0FFF: bytes E0 A0..BF 80..BF - case 0xE0: - { - if (JSON_UNLIKELY(not (next_byte_in_range({0xA0, 0xBF, 0x80, 0xBF})))) - { - return token_type::parse_error; - } - break; - } - - // U+1000..U+CFFF: bytes E1..EC 80..BF 80..BF - // U+E000..U+FFFF: bytes EE..EF 80..BF 80..BF - case 0xE1: - case 0xE2: - case 0xE3: - case 0xE4: - case 0xE5: - case 0xE6: - case 0xE7: - case 0xE8: - case 0xE9: - case 0xEA: - case 0xEB: - case 0xEC: - case 0xEE: - case 0xEF: - { - if (JSON_UNLIKELY(not (next_byte_in_range({0x80, 0xBF, 0x80, 0xBF})))) - { - return token_type::parse_error; - } - break; - } - - // U+D000..U+D7FF: bytes ED 80..9F 80..BF - case 0xED: - { - if (JSON_UNLIKELY(not (next_byte_in_range({0x80, 0x9F, 0x80, 0xBF})))) - { - return token_type::parse_error; - } - break; - } - - // U+10000..U+3FFFF F0 90..BF 80..BF 80..BF - case 0xF0: - { - if (JSON_UNLIKELY(not (next_byte_in_range({0x90, 0xBF, 0x80, 0xBF, 0x80, 0xBF})))) - { - return token_type::parse_error; - } - break; - } - - // U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF - case 0xF1: - case 0xF2: - case 0xF3: - { - if (JSON_UNLIKELY(not (next_byte_in_range({0x80, 0xBF, 0x80, 0xBF, 0x80, 0xBF})))) - { - return token_type::parse_error; - } - break; - } - - // U+100000..U+10FFFF F4 80..8F 80..BF 80..BF - case 0xF4: - { - if (JSON_UNLIKELY(not (next_byte_in_range({0x80, 0x8F, 0x80, 0xBF, 0x80, 0xBF})))) - { - return token_type::parse_error; - } - break; - } - - // remaining bytes (80..C1 and F5..FF) are ill-formed - default: - { - error_message = "invalid string: ill-formed UTF-8 byte"; - return token_type::parse_error; - } - } - } - } - - static void strtof(float& f, const char* str, char** endptr) noexcept - { - f = std::strtof(str, endptr); - } - - static void strtof(double& f, const char* str, char** endptr) noexcept - { - f = std::strtod(str, endptr); - } - - static void strtof(long double& f, const char* str, char** endptr) noexcept - { - f = std::strtold(str, endptr); - } - - /*! - @brief scan a number literal - - This function scans a string according to Sect. 6 of RFC 7159. - - The function is realized with a deterministic finite state machine derived - from the grammar described in RFC 7159. Starting in state "init", the - input is read and used to determined the next state. Only state "done" - accepts the number. State "error" is a trap state to model errors. In the - table below, "anything" means any character but the ones listed before. - - state | 0 | 1-9 | e E | + | - | . | anything - ---------|----------|----------|----------|---------|---------|----------|----------- - init | zero | any1 | [error] | [error] | minus | [error] | [error] - minus | zero | any1 | [error] | [error] | [error] | [error] | [error] - zero | done | done | exponent | done | done | decimal1 | done - any1 | any1 | any1 | exponent | done | done | decimal1 | done - decimal1 | decimal2 | [error] | [error] | [error] | [error] | [error] | [error] - decimal2 | decimal2 | decimal2 | exponent | done | done | done | done - exponent | any2 | any2 | [error] | sign | sign | [error] | [error] - sign | any2 | any2 | [error] | [error] | [error] | [error] | [error] - any2 | any2 | any2 | done | done | done | done | done - - The state machine is realized with one label per state (prefixed with - "scan_number_") and `goto` statements between them. The state machine - contains cycles, but any cycle can be left when EOF is read. Therefore, - the function is guaranteed to terminate. - - During scanning, the read bytes are stored in yytext. This string is - then converted to a signed integer, an unsigned integer, or a - floating-point number. - - @return token_type::value_unsigned, token_type::value_integer, or - token_type::value_float if number could be successfully scanned, - token_type::parse_error otherwise - - @note The scanner is independent of the current locale. Internally, the - locale's decimal point is used instead of `.` to work with the - locale-dependent converters. - */ - token_type scan_number() - { - // reset yytext to store the number's bytes - reset(); - - // the type of the parsed number; initially set to unsigned; will be - // changed if minus sign, decimal point or exponent is read - token_type number_type = token_type::value_unsigned; - - // state (init): we just found out we need to scan a number - switch (current) - { - case '-': - { - add(current); - goto scan_number_minus; - } - - case '0': - { - add(current); - goto scan_number_zero; - } - - case '1': - case '2': - case '3': - case '4': - case '5': - case '6': - case '7': - case '8': - case '9': - { - add(current); - goto scan_number_any1; - } - - default: - { - // all other characters are rejected outside scan_number() - assert(false); // LCOV_EXCL_LINE - } - } - -scan_number_minus: - // state: we just parsed a leading minus sign - number_type = token_type::value_integer; - switch (get()) - { - case '0': - { - add(current); - goto scan_number_zero; - } - - case '1': - case '2': - case '3': - case '4': - case '5': - case '6': - case '7': - case '8': - case '9': - { - add(current); - goto scan_number_any1; - } - - default: - { - error_message = "invalid number; expected digit after '-'"; - return token_type::parse_error; - } - } - -scan_number_zero: - // state: we just parse a zero (maybe with a leading minus sign) - switch (get()) - { - case '.': - { - add(decimal_point_char); - goto scan_number_decimal1; - } - - case 'e': - case 'E': - { - add(current); - goto scan_number_exponent; - } - - default: - goto scan_number_done; - } - -scan_number_any1: - // state: we just parsed a number 0-9 (maybe with a leading minus sign) - switch (get()) - { - case '0': - case '1': - case '2': - case '3': - case '4': - case '5': - case '6': - case '7': - case '8': - case '9': - { - add(current); - goto scan_number_any1; - } - - case '.': - { - add(decimal_point_char); - goto scan_number_decimal1; - } - - case 'e': - case 'E': - { - add(current); - goto scan_number_exponent; - } - - default: - goto scan_number_done; - } - -scan_number_decimal1: - // state: we just parsed a decimal point - number_type = token_type::value_float; - switch (get()) - { - case '0': - case '1': - case '2': - case '3': - case '4': - case '5': - case '6': - case '7': - case '8': - case '9': - { - add(current); - goto scan_number_decimal2; - } - - default: - { - error_message = "invalid number; expected digit after '.'"; - return token_type::parse_error; - } - } - -scan_number_decimal2: - // we just parsed at least one number after a decimal point - switch (get()) - { - case '0': - case '1': - case '2': - case '3': - case '4': - case '5': - case '6': - case '7': - case '8': - case '9': - { - add(current); - goto scan_number_decimal2; - } - - case 'e': - case 'E': - { - add(current); - goto scan_number_exponent; - } - - default: - goto scan_number_done; - } - -scan_number_exponent: - // we just parsed an exponent - number_type = token_type::value_float; - switch (get()) - { - case '+': - case '-': - { - add(current); - goto scan_number_sign; - } - - case '0': - case '1': - case '2': - case '3': - case '4': - case '5': - case '6': - case '7': - case '8': - case '9': - { - add(current); - goto scan_number_any2; - } - - default: - { - error_message = - "invalid number; expected '+', '-', or digit after exponent"; - return token_type::parse_error; - } - } - -scan_number_sign: - // we just parsed an exponent sign - switch (get()) - { - case '0': - case '1': - case '2': - case '3': - case '4': - case '5': - case '6': - case '7': - case '8': - case '9': - { - add(current); - goto scan_number_any2; - } - - default: - { - error_message = "invalid number; expected digit after exponent sign"; - return token_type::parse_error; - } - } - -scan_number_any2: - // we just parsed a number after the exponent or exponent sign - switch (get()) - { - case '0': - case '1': - case '2': - case '3': - case '4': - case '5': - case '6': - case '7': - case '8': - case '9': - { - add(current); - goto scan_number_any2; - } - - default: - goto scan_number_done; - } - -scan_number_done: - // unget the character after the number (we only read it to know that - // we are done scanning a number) - unget(); - - char* endptr = nullptr; - errno = 0; - - // try to parse integers first and fall back to floats - if (number_type == token_type::value_unsigned) - { - const auto x = std::strtoull(yytext.data(), &endptr, 10); - - // we checked the number format before - assert(endptr == yytext.data() + yytext.size()); - - if (errno == 0) - { - value_unsigned = static_cast(x); - if (value_unsigned == x) - { - return token_type::value_unsigned; - } - } - } - else if (number_type == token_type::value_integer) - { - const auto x = std::strtoll(yytext.data(), &endptr, 10); - - // we checked the number format before - assert(endptr == yytext.data() + yytext.size()); - - if (errno == 0) - { - value_integer = static_cast(x); - if (value_integer == x) - { - return token_type::value_integer; - } - } - } - - // this code is reached if we parse a floating-point number or if an - // integer conversion above failed - strtof(value_float, yytext.data(), &endptr); - - // we checked the number format before - assert(endptr == yytext.data() + yytext.size()); - - return token_type::value_float; - } - - /*! - @param[in] literal_text the literal text to expect - @param[in] length the length of the passed literal text - @param[in] return_type the token type to return on success - */ - token_type scan_literal(const char* literal_text, const std::size_t length, - token_type return_type) - { - assert(current == literal_text[0]); - for (std::size_t i = 1; i < length; ++i) - { - if (JSON_UNLIKELY(get() != literal_text[i])) - { - error_message = "invalid literal"; - return token_type::parse_error; - } - } - return return_type; - } - - ///////////////////// - // input management - ///////////////////// - - /// reset yytext; current character is beginning of token - void reset() noexcept - { - yytext.clear(); - token_string.clear(); - token_string.push_back(std::char_traits::to_char_type(current)); - } - - /* - @brief get next character from the input - - This function provides the interface to the used input adapter. It does - not throw in case the input reached EOF, but returns a - `std::char_traits::eof()` in that case. Stores the scanned characters - for use in error messages. - - @return character read from the input - */ - std::char_traits::int_type get() - { - ++chars_read; - current = ia->get_character(); - if (JSON_LIKELY(current != std::char_traits::eof())) - { - token_string.push_back(std::char_traits::to_char_type(current)); - } - return current; - } - - /// unget current character (return it again on next get) - void unget() - { - --chars_read; - if (JSON_LIKELY(current != std::char_traits::eof())) - { - ia->unget_character(); - assert(token_string.size() != 0); - token_string.pop_back(); - } - } - - /// add a character to yytext - void add(int c) - { - yytext.push_back(std::char_traits::to_char_type(c)); - } - - public: - ///////////////////// - // value getters - ///////////////////// - - /// return integer value - constexpr number_integer_t get_number_integer() const noexcept - { - return value_integer; - } - - /// return unsigned integer value - constexpr number_unsigned_t get_number_unsigned() const noexcept - { - return value_unsigned; - } - - /// return floating-point value - constexpr number_float_t get_number_float() const noexcept - { - return value_float; - } - - /// return current string value (implicitly resets the token; useful only once) - std::string move_string() - { - return std::move(yytext); - } - - ///////////////////// - // diagnostics - ///////////////////// - - /// return position of last read token - constexpr std::size_t get_position() const noexcept - { - return chars_read; - } - - /// return the last read token (for errors only). Will never contain EOF - /// (an arbitrary value that is not a valid char value, often -1), because - /// 255 may legitimately occur. May contain NUL, which should be escaped. - std::string get_token_string() const - { - // escape control characters - std::string result; - for (const auto c : token_string) - { - if ('\x00' <= c and c <= '\x1F') - { - // escape control characters - std::stringstream ss; - ss << "(c) << ">"; - result += ss.str(); - } - else - { - // add character as is - result.push_back(c); - } - } - - return result; - } - - /// return syntax error message - constexpr const char* get_error_message() const noexcept - { - return error_message; - } - - ///////////////////// - // actual scanner - ///////////////////// - - token_type scan() - { - // read next character and ignore whitespace - do - { - get(); - } - while (current == ' ' or current == '\t' or current == '\n' or current == '\r'); - - switch (current) - { - // structural characters - case '[': - return token_type::begin_array; - case ']': - return token_type::end_array; - case '{': - return token_type::begin_object; - case '}': - return token_type::end_object; - case ':': - return token_type::name_separator; - case ',': - return token_type::value_separator; - - // literals - case 't': - return scan_literal("true", 4, token_type::literal_true); - case 'f': - return scan_literal("false", 5, token_type::literal_false); - case 'n': - return scan_literal("null", 4, token_type::literal_null); - - // string - case '\"': - return scan_string(); - - // number - case '-': - case '0': - case '1': - case '2': - case '3': - case '4': - case '5': - case '6': - case '7': - case '8': - case '9': - return scan_number(); - - // end of input (the null byte is needed when parsing from - // string literals) - case '\0': - case std::char_traits::eof(): - return token_type::end_of_input; - - // error - default: - error_message = "invalid literal"; - return token_type::parse_error; - } - } - - private: - /// input adapter - detail::input_adapter_t ia = nullptr; - - /// the current character - std::char_traits::int_type current = std::char_traits::eof(); - - /// the number of characters read - std::size_t chars_read = 0; - - /// raw input token string (for error messages) - std::vector token_string {}; - - /// buffer for variable-length tokens (numbers, strings) - std::string yytext {}; - - /// a description of occurred lexer errors - const char* error_message = ""; - - // number values - number_integer_t value_integer = 0; - number_unsigned_t value_unsigned = 0; - number_float_t value_float = 0; - - /// the decimal point - const char decimal_point_char = '.'; -}; +//////////// +// parser // +//////////// /*! @brief syntax analysis -- GitLab