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2334cd85a2
Similar to decimal floating point parsing the current strtod hex float parsing gives a lot of incorrect results. We can use a similar technique as with decimal parsing however hex floats are much simpler as we don't need to scale with a power of 5. For hex floats we just provide the parse_first_hexfloat API as there is currently no need for a parse_hexfloat_completely API. Again the accepted input for parse_first_hexfloat is very lenient and any validation should be done before calling this method.
85 lines
3.6 KiB
C++
85 lines
3.6 KiB
C++
/*
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* Copyright (c) 2022, David Tuin <davidot@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#ifdef KERNEL
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# error This file should not be included in the KERNEL as it deals with doubles \
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and there is no guraantee does not do any floating point computations.
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#endif
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#include <AK/StringView.h>
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namespace AK {
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static constexpr char floating_point_decimal_separator = '.';
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enum class FloatingPointError {
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None,
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NoOrInvalidInput,
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OutOfRange,
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RoundedDownToZero
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};
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template<FloatingPoint T>
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struct FloatingPointParseResults {
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char const* end_ptr { nullptr };
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FloatingPointError error = FloatingPointError::None;
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T value {};
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[[nodiscard]] bool parsed_value() const
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{
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// All other errors do indicate out of range but did produce a valid value.
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return error != FloatingPointError::NoOrInvalidInput;
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}
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};
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/// This function finds the first floating point within [start, end). The accepted format is
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/// intentionally as lenient as possible. If your format is stricter you must validate it
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/// first. The format accepts:
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/// - An optional sign, both + and - are supported
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/// - 0 or more decimal digits, with leading zeros allowed [1]
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/// - A decimal point '.', which can have no digits after it
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/// - 0 or more decimal digits, unless the first digits [1] doesn't have any digits,
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/// then this must have at least one
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/// - An exponent 'e' or 'E' followed by an optional sign '+' or '-' and at least one digit
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/// This function additionally detects out of range values which have been rounded to
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/// [-]infinity or 0 and gives the next character to read after the floating point.
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template<FloatingPoint T = double>
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FloatingPointParseResults<T> parse_first_floating_point(char const* start, char const* end);
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/// This function finds the first floating point starting at start up to the first '\0'.
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/// The format is identical to parse_first_floating_point above.
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template<FloatingPoint T = double>
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FloatingPointParseResults<T> parse_first_floating_point_until_zero_character(char const* start);
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/// This function will return either a floating point, or an empty optional if the given StringView
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/// does not a floating point or contains more characters beyond the floating point. For the format
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/// check the comment on parse_first_floating_point.
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template<FloatingPoint T = double>
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Optional<T> parse_floating_point_completely(char const* start, char const* end);
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/// This function finds the first floating point as a hex float within [start, end).
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/// The accepted format is intentionally as lenient as possible. If your format is
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/// stricter you must validate it first. The format accepts:
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/// - An optional sign, both + and - are supported
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/// - Optionally either 0x or OX
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/// - 0 or more hexadecimal digits, with leading zeros allowed [1]
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/// - A decimal point '.', which can have no digits after it
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/// - 0 or more hexadecimal digits, unless the first digits [1] doesn't have any digits,
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/// then this must have at least one
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/// - An exponent 'p' or 'P' followed by an optional sign '+' or '-' and at least one decimal digit
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/// NOTE: The exponent is _not_ hexadecimal and gives powers of 2 not 16.
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/// This function additionally detects out of range values which have been rounded to
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/// [-]infinity or 0 and gives the next character to read after the floating point.
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template<FloatingPoint T = double>
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FloatingPointParseResults<T> parse_first_hexfloat_until_zero_character(char const* start);
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}
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using AK::parse_first_floating_point;
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using AK::parse_first_hexfloat_until_zero_character;
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using AK::parse_floating_point_completely;
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