template<typename BasicJsonType, typename InputAdapterType>
class nlohmann::detail::lexer< BasicJsonType, InputAdapterType >
lexical analysis
This class organizes the lexical analysis during JSON deserialization.
Definition at line 6638 of file json.hpp.
template<typename BasicJsonType , typename InputAdapterType >
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.
- Returns
- codepoint (0x0000..0xFFFF) or -1 in case of an error (e.g. EOF or non-hex character)
Definition at line 6696 of file json.hpp.
template<typename BasicJsonType , typename InputAdapterType >
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.
Definition at line 7975 of file json.hpp.
template<typename BasicJsonType , typename InputAdapterType >
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.
- Parameters
-
| [in] | ranges | list of integers; interpreted as list of pairs of inclusive lower and upper bound, respectively |
- Precondition
- The passed list ranges must have 2, 4, or 6 elements; that is, 1, 2, or 3 pairs. This precondition is enforced by an assertion.
- Returns
- true if and only if no range violation was detected
Definition at line 6744 of file json.hpp.
template<typename BasicJsonType , typename InputAdapterType >
scan a number literal
This function scans a string according to Sect. 6 of RFC 8259.
The function is realized with a deterministic finite state machine derived from the grammar described in RFC 8259. 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 | decimal2 | [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 token_buffer. This string is then converted to a signed integer, an unsigned integer, or a floating-point number.
- Returns
- 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.
Definition at line 7496 of file json.hpp.
template<typename BasicJsonType , typename InputAdapterType >
scan a string literal
This function scans a string according to Sect. 7 of RFC 8259. While scanning, bytes are escaped and copied into buffer token_buffer. Then the function returns successfully, token_buffer is not null-terminated (as it may contain \0 bytes), and token_buffer.size() is the number of bytes in the string.
- Returns
- 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.
Definition at line 6781 of file json.hpp.
template<typename BasicJsonType , typename InputAdapterType >
unget current character (read it again on next get)
We implement unget by setting variable next_unget to true. The input is not changed - we just simulate ungetting by modifying chars_read_total, chars_read_current_line, and token_string. The next call to get() will behave as if the unget character is read again.
Definition at line 7901 of file json.hpp.
Inheritance diagram for nlohmann::detail::lexer< BasicJsonType, InputAdapterType >:
1.10.0