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charconv.hpp
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#ifndef _C4_CHARCONV_HPP_
#define _C4_CHARCONV_HPP_
/** @file charconv.hpp Lightweight generic type-safe wrappers for
* converting individual values to/from strings.
*/
#include "c4/language.hpp"
#include <inttypes.h>
#include <type_traits>
#include <climits>
#include <limits>
#include <utility>
#include "c4/config.hpp"
#include "c4/substr.hpp"
#include "c4/std/std_fwd.hpp"
#include "c4/memory_util.hpp"
#include "c4/szconv.hpp"
#ifndef C4CORE_NO_FAST_FLOAT
# if (C4_CPP >= 17)
# if defined(_MSC_VER)
# if (C4_MSVC_VERSION >= C4_MSVC_VERSION_2019) // VS2017 and lower do not have these macros
# include <charconv>
# define C4CORE_HAVE_STD_TOCHARS 1
# define C4CORE_HAVE_STD_FROMCHARS 0 // prefer fast_float with MSVC
# define C4CORE_HAVE_FAST_FLOAT 1
# else
# define C4CORE_HAVE_STD_TOCHARS 0
# define C4CORE_HAVE_STD_FROMCHARS 0
# define C4CORE_HAVE_FAST_FLOAT 1
# endif
# else
# if __has_include(<charconv>)
# include <charconv>
# if defined(__cpp_lib_to_chars)
# define C4CORE_HAVE_STD_TOCHARS 1
# define C4CORE_HAVE_STD_FROMCHARS 0 // glibc uses fast_float internally
# define C4CORE_HAVE_FAST_FLOAT 1
# else
# define C4CORE_HAVE_STD_TOCHARS 0
# define C4CORE_HAVE_STD_FROMCHARS 0
# define C4CORE_HAVE_FAST_FLOAT 1
# endif
# else
# define C4CORE_HAVE_STD_TOCHARS 0
# define C4CORE_HAVE_STD_FROMCHARS 0
# define C4CORE_HAVE_FAST_FLOAT 1
# endif
# endif
# else
# define C4CORE_HAVE_STD_TOCHARS 0
# define C4CORE_HAVE_STD_FROMCHARS 0
# define C4CORE_HAVE_FAST_FLOAT 1
# endif
# if C4CORE_HAVE_FAST_FLOAT
# include "c4/ext/fast_float.hpp"
# endif
#elif (C4_CPP >= 17)
# define C4CORE_HAVE_FAST_FLOAT 0
# if defined(_MSC_VER)
# if (C4_MSVC_VERSION >= C4_MSVC_VERSION_2019) // VS2017 and lower do not have these macros
# include <charconv>
# define C4CORE_HAVE_STD_TOCHARS 1
# define C4CORE_HAVE_STD_FROMCHARS 1
# else
# define C4CORE_HAVE_STD_TOCHARS 0
# define C4CORE_HAVE_STD_FROMCHARS 0
# endif
# else
# if __has_include(<charconv>)
# include <charconv>
# if defined(__cpp_lib_to_chars)
# define C4CORE_HAVE_STD_TOCHARS 1
# define C4CORE_HAVE_STD_FROMCHARS 1 // glibc uses fast_float internally
# else
# define C4CORE_HAVE_STD_TOCHARS 0
# define C4CORE_HAVE_STD_FROMCHARS 0
# endif
# else
# define C4CORE_HAVE_STD_TOCHARS 0
# define C4CORE_HAVE_STD_FROMCHARS 0
# endif
# endif
#else
# define C4CORE_HAVE_STD_TOCHARS 0
# define C4CORE_HAVE_STD_FROMCHARS 0
# define C4CORE_HAVE_FAST_FLOAT 0
#endif
#if !C4CORE_HAVE_STD_FROMCHARS
#include <cstdio>
#endif
#if defined(_MSC_VER) && !defined(__clang__)
# pragma warning(push)
# pragma warning(disable: 4996) // snprintf/scanf: this function or variable may be unsafe
# if C4_MSVC_VERSION != C4_MSVC_VERSION_2017
# pragma warning(disable: 4800) //'int': forcing value to bool 'true' or 'false' (performance warning)
# endif
#elif defined(__clang__)
# pragma clang diagnostic push
# pragma clang diagnostic ignored "-Wtautological-constant-out-of-range-compare"
# pragma clang diagnostic ignored "-Wformat-nonliteral"
# pragma clang diagnostic ignored "-Wdouble-promotion" // implicit conversion increases floating-point precision
# pragma clang diagnostic ignored "-Wold-style-cast"
#elif defined(__GNUC__)
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wformat-nonliteral"
# pragma GCC diagnostic ignored "-Wdouble-promotion" // implicit conversion increases floating-point precision
# pragma GCC diagnostic ignored "-Wuseless-cast"
# pragma GCC diagnostic ignored "-Wold-style-cast"
#endif
#if defined(__clang__)
#define C4_NO_UBSAN_IOVRFLW __attribute__((no_sanitize("signed-integer-overflow")))
#elif defined(__GNUC__)
#if __GNUC__ > 7
#define C4_NO_UBSAN_IOVRFLW __attribute__((no_sanitize("signed-integer-overflow")))
#else
#define C4_NO_UBSAN_IOVRFLW
#endif
#else
#define C4_NO_UBSAN_IOVRFLW
#endif
// NOLINTBEGIN(hicpp-signed-bitwise)
namespace c4 {
/** @defgroup doc_charconv Charconv utilities
*
* Lightweight, very fast generic type-safe wrappers for converting
* individual values to/from strings. These are the main generic
* functions:
* - @ref doc_to_chars and its alias @ref xtoa(): implemented by calling @ref itoa() / @ref utoa() / @ref ftoa() / @ref dtoa() (or generically @ref xtoa())
* - @ref doc_from_chars and its alias @ref atox(): implemented by calling @ref atoi() / @ref atou() / @ref atof() / @ref atod() (or generically @ref atox())
* - @ref to_chars_sub()
* - @ref from_chars_first()
* - @ref xtoa() and @ref atox() are implemented in terms of @ref write_dec() / @ref read_dec() et al (see @ref doc_write / @ref doc_read())
*
* And also some modest brag is in order: these functions are really
* fast: faster even than C++17 `std::to_chars()` and
* `std::to_chars()`, and many dozens of times faster than the
* iostream abominations.
*
* For example, here are some benchmark comparisons for @ref
* doc_from_chars (link leads to the main project README, where these
* results are shown more systematically).
*
* <table>
* <caption id="atox-i64-results">atox,int64_t</caption>
* <tr><th>g++12, linux <th>Visual Studio 2019
* <tr><td> \image html linux-x86_64-gxx12.1-Release-c4core-bm-charconv-atox-mega_bytes_per_second-i64.png <td> \image html windows-x86_64-vs2019-Release-c4core-bm-charconv-atox-mega_bytes_per_second-i64.png
* </table>
*
* <table>
* <caption id="xtoa-i64-results">xtoa,int64_t</caption>
* <tr><th>g++12, linux <th>Visual Studio 2019
* <tr><td> \image html linux-x86_64-gxx12.1-Release-c4core-bm-charconv-xtoa-mega_bytes_per_second-i64.png <td> \image html windows-x86_64-vs2019-Release-c4core-bm-charconv-xtoa-mega_bytes_per_second-i64.png
* </table>
*
* To parse floating point, c4core uses
* [fastfloat](https://github.com/fastfloat/fast_float), which is
* extremely fast, by an even larger factor:
*
* <table>
* <caption id="atox-float-results">atox,float</caption>
* <tr><th>g++12, linux <th>Visual Studio 2019
* <tr><td> \image html linux-x86_64-gxx12.1-Release-c4core-bm-charconv-atof-mega_bytes_per_second-float.png <td> \image html windows-x86_64-vs2019-Release-c4core-bm-charconv-atof-mega_bytes_per_second-float.png
* </table>
*
* @{
*/
#if C4CORE_HAVE_STD_TOCHARS
/** @warning Use only the symbol. Do not rely on the type or naked value of this enum. */
typedef enum : std::underlying_type<std::chars_format>::type {
/** print the real number in floating point format (like %f) */
FTOA_FLOAT = static_cast<std::underlying_type<std::chars_format>::type>(std::chars_format::fixed),
/** print the real number in scientific format (like %e) */
FTOA_SCIENT = static_cast<std::underlying_type<std::chars_format>::type>(std::chars_format::scientific),
/** print the real number in flexible format (like %g) */
FTOA_FLEX = static_cast<std::underlying_type<std::chars_format>::type>(std::chars_format::general),
/** print the real number in hexadecimal format (like %a) */
FTOA_HEXA = static_cast<std::underlying_type<std::chars_format>::type>(std::chars_format::hex),
} RealFormat_e;
#else
/** @warning Use only the symbol. Do not rely on the type or naked value of this enum. */
typedef enum : char {
/** print the real number in floating point format (like %f) */
FTOA_FLOAT = 'f',
/** print the real number in scientific format (like %e) */
FTOA_SCIENT = 'e',
/** print the real number in flexible format (like %g) */
FTOA_FLEX = 'g',
/** print the real number in hexadecimal format (like %a) */
FTOA_HEXA = 'a',
} RealFormat_e;
#endif
/** @cond dev */
/** in some platforms, int,unsigned int
* are not any of int8_t...int64_t and
* long,unsigned long are not any of uint8_t...uint64_t */
template<class T>
struct is_fixed_length
{
enum : bool {
/** true if T is one of the fixed length signed types */
value_i = (std::is_integral<T>::value
&& (std::is_same<T, int8_t>::value
|| std::is_same<T, int16_t>::value
|| std::is_same<T, int32_t>::value
|| std::is_same<T, int64_t>::value)),
/** true if T is one of the fixed length unsigned types */
value_u = (std::is_integral<T>::value
&& (std::is_same<T, uint8_t>::value
|| std::is_same<T, uint16_t>::value
|| std::is_same<T, uint32_t>::value
|| std::is_same<T, uint64_t>::value)),
/** true if T is one of the fixed length signed or unsigned types */
value = value_i || value_u
};
};
/** @endcond */
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
#if defined(_MSC_VER) && !defined(__clang__)
# pragma warning(push)
#elif defined(__clang__)
# pragma clang diagnostic push
#elif defined(__GNUC__)
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wconversion"
# if __GNUC__ >= 6
# pragma GCC diagnostic ignored "-Wnull-dereference"
# endif
#endif
/** @cond dev */
namespace detail {
/* python command to get the values below:
def dec(v):
return str(v)
for bits in (8, 16, 32, 64):
imin, imax, umax = (-(1 << (bits - 1))), (1 << (bits - 1)) - 1, (1 << bits) - 1
for vname, v in (("imin", imin), ("imax", imax), ("umax", umax)):
for f in (bin, oct, dec, hex):
print(f"{bits}b: {vname}={v} {f.__name__}: len={len(f(v)):2d}: {v} {f(v)}")
*/
// do not use the type as the template argument because in some
// platforms long!=int32 and long!=int64. Just use the numbytes
// which is more generic and spares lengthy SFINAE code.
template<size_t num_bytes, bool is_signed> struct charconv_digits_;
template<class T> using charconv_digits = charconv_digits_<sizeof(T), std::is_signed<T>::value>;
template<> struct charconv_digits_<1u, true> // int8_t
{
enum : size_t {
maxdigits_bin = 1 + 2 + 8, // -128==-0b10000000
maxdigits_oct = 1 + 2 + 3, // -128==-0o200
maxdigits_dec = 1 + 3, // -128
maxdigits_hex = 1 + 2 + 2, // -128==-0x80
maxdigits_bin_nopfx = 8, // -128==-0b10000000
maxdigits_oct_nopfx = 3, // -128==-0o200
maxdigits_dec_nopfx = 3, // -128
maxdigits_hex_nopfx = 2, // -128==-0x80
};
// min values without sign!
static constexpr csubstr min_value_dec() noexcept { return csubstr("128"); }
static constexpr csubstr min_value_hex() noexcept { return csubstr("80"); }
static constexpr csubstr min_value_oct() noexcept { return csubstr("200"); }
static constexpr csubstr min_value_bin() noexcept { return csubstr("10000000"); }
static constexpr csubstr max_value_dec() noexcept { return csubstr("127"); }
static constexpr bool is_oct_overflow(csubstr str) noexcept { return !((str.len < 3) || (str.len == 3 && str[0] <= '1')); }
};
template<> struct charconv_digits_<1u, false> // uint8_t
{
enum : size_t {
maxdigits_bin = 2 + 8, // 255 0b11111111
maxdigits_oct = 2 + 3, // 255 0o377
maxdigits_dec = 3, // 255
maxdigits_hex = 2 + 2, // 255 0xff
maxdigits_bin_nopfx = 8, // 255 0b11111111
maxdigits_oct_nopfx = 3, // 255 0o377
maxdigits_dec_nopfx = 3, // 255
maxdigits_hex_nopfx = 2, // 255 0xff
};
static constexpr csubstr max_value_dec() noexcept { return csubstr("255"); }
static constexpr bool is_oct_overflow(csubstr str) noexcept { return !((str.len < 3) || (str.len == 3 && str[0] <= '3')); }
};
template<> struct charconv_digits_<2u, true> // int16_t
{
enum : size_t {
maxdigits_bin = 1 + 2 + 16, // -32768 -0b1000000000000000
maxdigits_oct = 1 + 2 + 6, // -32768 -0o100000
maxdigits_dec = 1 + 5, // -32768 -32768
maxdigits_hex = 1 + 2 + 4, // -32768 -0x8000
maxdigits_bin_nopfx = 16, // -32768 -0b1000000000000000
maxdigits_oct_nopfx = 6, // -32768 -0o100000
maxdigits_dec_nopfx = 5, // -32768 -32768
maxdigits_hex_nopfx = 4, // -32768 -0x8000
};
// min values without sign!
static constexpr csubstr min_value_dec() noexcept { return csubstr("32768"); }
static constexpr csubstr min_value_hex() noexcept { return csubstr("8000"); }
static constexpr csubstr min_value_oct() noexcept { return csubstr("100000"); }
static constexpr csubstr min_value_bin() noexcept { return csubstr("1000000000000000"); }
static constexpr csubstr max_value_dec() noexcept { return csubstr("32767"); }
static constexpr bool is_oct_overflow(csubstr str) noexcept { return !((str.len < 6)); }
};
template<> struct charconv_digits_<2u, false> // uint16_t
{
enum : size_t {
maxdigits_bin = 2 + 16, // 65535 0b1111111111111111
maxdigits_oct = 2 + 6, // 65535 0o177777
maxdigits_dec = 6, // 65535 65535
maxdigits_hex = 2 + 4, // 65535 0xffff
maxdigits_bin_nopfx = 16, // 65535 0b1111111111111111
maxdigits_oct_nopfx = 6, // 65535 0o177777
maxdigits_dec_nopfx = 6, // 65535 65535
maxdigits_hex_nopfx = 4, // 65535 0xffff
};
static constexpr csubstr max_value_dec() noexcept { return csubstr("65535"); }
static constexpr bool is_oct_overflow(csubstr str) noexcept { return !((str.len < 6) || (str.len == 6 && str[0] <= '1')); }
};
template<> struct charconv_digits_<4u, true> // int32_t
{
enum : size_t {
maxdigits_bin = 1 + 2 + 32, // len=35: -2147483648 -0b10000000000000000000000000000000
maxdigits_oct = 1 + 2 + 11, // len=14: -2147483648 -0o20000000000
maxdigits_dec = 1 + 10, // len=11: -2147483648 -2147483648
maxdigits_hex = 1 + 2 + 8, // len=11: -2147483648 -0x80000000
maxdigits_bin_nopfx = 32, // len=35: -2147483648 -0b10000000000000000000000000000000
maxdigits_oct_nopfx = 11, // len=14: -2147483648 -0o20000000000
maxdigits_dec_nopfx = 10, // len=11: -2147483648 -2147483648
maxdigits_hex_nopfx = 8, // len=11: -2147483648 -0x80000000
};
// min values without sign!
static constexpr csubstr min_value_dec() noexcept { return csubstr("2147483648"); }
static constexpr csubstr min_value_hex() noexcept { return csubstr("80000000"); }
static constexpr csubstr min_value_oct() noexcept { return csubstr("20000000000"); }
static constexpr csubstr min_value_bin() noexcept { return csubstr("10000000000000000000000000000000"); }
static constexpr csubstr max_value_dec() noexcept { return csubstr("2147483647"); }
static constexpr bool is_oct_overflow(csubstr str) noexcept { return !((str.len < 11) || (str.len == 11 && str[0] <= '1')); }
};
template<> struct charconv_digits_<4u, false> // uint32_t
{
enum : size_t {
maxdigits_bin = 2 + 32, // len=34: 4294967295 0b11111111111111111111111111111111
maxdigits_oct = 2 + 11, // len=13: 4294967295 0o37777777777
maxdigits_dec = 10, // len=10: 4294967295 4294967295
maxdigits_hex = 2 + 8, // len=10: 4294967295 0xffffffff
maxdigits_bin_nopfx = 32, // len=34: 4294967295 0b11111111111111111111111111111111
maxdigits_oct_nopfx = 11, // len=13: 4294967295 0o37777777777
maxdigits_dec_nopfx = 10, // len=10: 4294967295 4294967295
maxdigits_hex_nopfx = 8, // len=10: 4294967295 0xffffffff
};
static constexpr csubstr max_value_dec() noexcept { return csubstr("4294967295"); }
static constexpr bool is_oct_overflow(csubstr str) noexcept { return !((str.len < 11) || (str.len == 11 && str[0] <= '3')); }
};
template<> struct charconv_digits_<8u, true> // int64_t
{
enum : size_t {
maxdigits_bin = 1 + 2 + 64, // len=67: -9223372036854775808 -0b1000000000000000000000000000000000000000000000000000000000000000
maxdigits_oct = 1 + 2 + 22, // len=25: -9223372036854775808 -0o1000000000000000000000
maxdigits_dec = 1 + 19, // len=20: -9223372036854775808 -9223372036854775808
maxdigits_hex = 1 + 2 + 16, // len=19: -9223372036854775808 -0x8000000000000000
maxdigits_bin_nopfx = 64, // len=67: -9223372036854775808 -0b1000000000000000000000000000000000000000000000000000000000000000
maxdigits_oct_nopfx = 22, // len=25: -9223372036854775808 -0o1000000000000000000000
maxdigits_dec_nopfx = 19, // len=20: -9223372036854775808 -9223372036854775808
maxdigits_hex_nopfx = 16, // len=19: -9223372036854775808 -0x8000000000000000
};
static constexpr csubstr min_value_dec() noexcept { return csubstr("9223372036854775808"); }
static constexpr csubstr min_value_hex() noexcept { return csubstr("8000000000000000"); }
static constexpr csubstr min_value_oct() noexcept { return csubstr("1000000000000000000000"); }
static constexpr csubstr min_value_bin() noexcept { return csubstr("1000000000000000000000000000000000000000000000000000000000000000"); }
static constexpr csubstr max_value_dec() noexcept { return csubstr("9223372036854775807"); }
static constexpr bool is_oct_overflow(csubstr str) noexcept { return !((str.len < 22)); }
};
template<> struct charconv_digits_<8u, false> // uint64_t
{
enum : size_t {
maxdigits_bin = 2 + 64, // len=66: 18446744073709551615 0b1111111111111111111111111111111111111111111111111111111111111111
maxdigits_oct = 2 + 22, // len=24: 18446744073709551615 0o1777777777777777777777
maxdigits_dec = 20, // len=20: 18446744073709551615 18446744073709551615
maxdigits_hex = 2 + 16, // len=18: 18446744073709551615 0xffffffffffffffff
maxdigits_bin_nopfx = 64, // len=66: 18446744073709551615 0b1111111111111111111111111111111111111111111111111111111111111111
maxdigits_oct_nopfx = 22, // len=24: 18446744073709551615 0o1777777777777777777777
maxdigits_dec_nopfx = 20, // len=20: 18446744073709551615 18446744073709551615
maxdigits_hex_nopfx = 16, // len=18: 18446744073709551615 0xffffffffffffffff
};
static constexpr csubstr max_value_dec() noexcept { return csubstr("18446744073709551615"); }
static constexpr bool is_oct_overflow(csubstr str) noexcept { return !((str.len < 22) || (str.len == 22 && str[0] <= '1')); }
};
} // namespace detail
// Helper macros, undefined below
#define _c4append(c) { if(C4_LIKELY(pos < buf.len)) { buf.str[pos++] = static_cast<char>(c); } else { ++pos; } }
#define _c4appendhex(i) { if(C4_LIKELY(pos < buf.len)) { buf.str[pos++] = hexchars[i]; } else { ++pos; } }
/** @endcond */
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
/** @defgroup doc_digits Get number of digits
*
* @note At first sight this code may look heavily branchy and
* therefore inefficient. However, measurements revealed this to be
* the fastest among the alternatives.
*
* @see https://github.com/biojppm/c4core/pull/77
*
* @{
*/
/** decimal digits for 8 bit integers */
template<class T>
C4_CONSTEXPR14 C4_ALWAYS_INLINE
auto digits_dec(T v) noexcept
-> typename std::enable_if<sizeof(T) == 1u, unsigned>::type
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
return ((v >= 100) ? 3u : ((v >= 10) ? 2u : 1u));
}
/** decimal digits for 16 bit integers */
template<class T>
C4_CONSTEXPR14 C4_ALWAYS_INLINE
auto digits_dec(T v) noexcept
-> typename std::enable_if<sizeof(T) == 2u, unsigned>::type
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
return ((v >= 10000) ? 5u : (v >= 1000) ? 4u : (v >= 100) ? 3u : (v >= 10) ? 2u : 1u);
}
/** decimal digits for 32 bit integers */
template<class T>
C4_CONSTEXPR14 C4_ALWAYS_INLINE
auto digits_dec(T v) noexcept
-> typename std::enable_if<sizeof(T) == 4u, unsigned>::type
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
return ((v >= 1000000000) ? 10u : (v >= 100000000) ? 9u : (v >= 10000000) ? 8u :
(v >= 1000000) ? 7u : (v >= 100000) ? 6u : (v >= 10000) ? 5u :
(v >= 1000) ? 4u : (v >= 100) ? 3u : (v >= 10) ? 2u : 1u);
}
/** decimal digits for 64 bit integers */
template<class T>
C4_CONSTEXPR14 C4_ALWAYS_INLINE
auto digits_dec(T v) noexcept
-> typename std::enable_if<sizeof(T) == 8u, unsigned>::type
{
// thanks @fargies!!!
// https://github.com/biojppm/c4core/pull/77#issuecomment-1063753568
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
if(v >= 1000000000) // 10
{
if(v >= 100000000000000) // 15 [15-20] range
{
if(v >= 100000000000000000) // 18 (15 + (20 - 15) / 2)
{
if((typename std::make_unsigned<T>::type)v >= 10000000000000000000u) // 20
return 20u;
else
return (v >= 1000000000000000000) ? 19u : 18u;
}
else if(v >= 10000000000000000) // 17
return 17u;
else
return(v >= 1000000000000000) ? 16u : 15u;
}
else if(v >= 1000000000000) // 13
return (v >= 10000000000000) ? 14u : 13u;
else if(v >= 100000000000) // 12
return 12;
else
return(v >= 10000000000) ? 11u : 10u;
}
else if(v >= 10000) // 5 [5-9] range
{
if(v >= 10000000) // 8
return (v >= 100000000) ? 9u : 8u;
else if(v >= 1000000) // 7
return 7;
else
return (v >= 100000) ? 6u : 5u;
}
else if(v >= 100)
return (v >= 1000) ? 4u : 3u;
else
return (v >= 10) ? 2u : 1u;
}
/** return the number of digits required to encode an hexadecimal number. */
template<class T>
C4_CONSTEXPR14 C4_ALWAYS_INLINE unsigned digits_hex(T v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
return v ? 1u + (msb((typename std::make_unsigned<T>::type)v) >> 2u) : 1u;
}
/** return the number of digits required to encode a binary number. */
template<class T>
C4_CONSTEXPR14 C4_ALWAYS_INLINE unsigned digits_bin(T v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
return v ? 1u + msb((typename std::make_unsigned<T>::type)v) : 1u;
}
/** return the number of digits required to encode an octal number. */
template<class T>
C4_CONSTEXPR14 C4_ALWAYS_INLINE unsigned digits_oct(T v_) noexcept
{
// TODO: is there a better way?
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v_ >= 0);
using U = typename std::conditional<sizeof(T) <= sizeof(unsigned),
unsigned,
typename std::make_unsigned<T>::type>::type;
U v = (U) v_; // safe because we require v_ >= 0 // NOLINT
uint32_t __n = 1;
enum : U {
__b2 = 64u,
__b3 = 64u * 8u,
__b4 = 64u * 8u * 8u,
};
while(true)
{
if(v < 8u)
return __n;
else if(v < __b2)
return __n + 1;
else if(v < __b3)
return __n + 2;
else if(v < __b4)
return __n + 3;
v /= (U) __b4;
__n += 4;
}
}
/** @} */
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
/** @cond dev */
namespace detail {
C4_INLINE_CONSTEXPR const char hexchars[] = "0123456789abcdef";
C4_INLINE_CONSTEXPR const char digits0099[] =
"0001020304050607080910111213141516171819"
"2021222324252627282930313233343536373839"
"4041424344454647484950515253545556575859"
"6061626364656667686970717273747576777879"
"8081828384858687888990919293949596979899";
} // namespace detail
/** @endcond */
C4_SUPPRESS_WARNING_GCC_PUSH
C4_SUPPRESS_WARNING_GCC("-Warray-bounds") // gcc has false positives here
#if (defined(__GNUC__) && (__GNUC__ >= 7))
C4_SUPPRESS_WARNING_GCC("-Wstringop-overflow") // gcc has false positives here
#endif
/** @defgroup doc_write_unchecked Write with known number of digits
*
* Writes a value without checking the buffer length with regards to
* the required number of digits to encode the value. It is the
* responsibility of the caller to ensure that the provided number of
* digits is enough to write the given value. Notwithstanding the
* name, assertions are liberally performed, so this code is safe.
*
* @{ */
template<class T>
C4_HOT C4_ALWAYS_INLINE
void write_dec_unchecked(substr buf, T v, unsigned digits_v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
C4_ASSERT(buf.len >= digits_v);
C4_XASSERT(digits_v == digits_dec(v));
// in bm_xtoa: checkoncelog_singlediv_write2
while(v >= T(100))
{
T quo = v;
quo /= T(100);
const auto num = (v - quo * T(100)) << 1u; // NOLINT
v = quo;
buf.str[--digits_v] = detail::digits0099[num + 1];
buf.str[--digits_v] = detail::digits0099[num];
}
if(v >= T(10))
{
C4_ASSERT(digits_v == 2);
const auto num = v << 1u;
buf.str[1] = detail::digits0099[num + 1];
buf.str[0] = detail::digits0099[num];
}
else
{
C4_ASSERT(digits_v == 1);
buf.str[0] = (char)('0' + v);
}
}
template<class T>
C4_HOT C4_ALWAYS_INLINE
void write_hex_unchecked(substr buf, T v, unsigned digits_v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
C4_ASSERT(buf.len >= digits_v);
C4_XASSERT(digits_v == digits_hex(v));
do {
buf.str[--digits_v] = detail::hexchars[v & T(15)];
v >>= 4;
} while(v);
C4_ASSERT(digits_v == 0);
}
template<class T>
C4_HOT C4_ALWAYS_INLINE
void write_oct_unchecked(substr buf, T v, unsigned digits_v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
C4_ASSERT(buf.len >= digits_v);
C4_XASSERT(digits_v == digits_oct(v));
do {
buf.str[--digits_v] = (char)('0' + (v & T(7)));
v >>= 3;
} while(v);
C4_ASSERT(digits_v == 0);
}
template<class T>
C4_HOT C4_ALWAYS_INLINE
void write_bin_unchecked(substr buf, T v, unsigned digits_v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
C4_ASSERT(buf.len >= digits_v);
C4_XASSERT(digits_v == digits_bin(v));
do {
buf.str[--digits_v] = (char)('0' + (v & T(1)));
v >>= 1;
} while(v);
C4_ASSERT(digits_v == 0);
}
/** @} */ // write_unchecked
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
/** @defgroup doc_write Write a value
*
* Writes a value without checking the buffer length
* decimal number -- but asserting.
*
* @{ */
/** write an integer to a string in decimal format. This is the
* lowest level (and the fastest) function to do this task.
* @note does not accept negative numbers
* @note the resulting string is NOT zero-terminated.
* @note it is ok to call this with an empty or too-small buffer;
* no writes will occur, and the required size will be returned
* @return the number of characters required for the buffer. */
template<class T>
C4_ALWAYS_INLINE size_t write_dec(substr buf, T v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
unsigned digits = digits_dec(v);
if(C4_LIKELY(buf.len >= digits))
write_dec_unchecked(buf, v, digits);
return digits;
}
/** write an integer to a string in hexadecimal format. This is the
* lowest level (and the fastest) function to do this task.
* @note does not accept negative numbers
* @note does not prefix with 0x
* @note the resulting string is NOT zero-terminated.
* @note it is ok to call this with an empty or too-small buffer;
* no writes will occur, and the required size will be returned
* @return the number of characters required for the buffer. */
template<class T>
C4_ALWAYS_INLINE size_t write_hex(substr buf, T v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
unsigned digits = digits_hex(v);
if(C4_LIKELY(buf.len >= digits))
write_hex_unchecked(buf, v, digits);
return digits;
}
/** write an integer to a string in octal format. This is the
* lowest level (and the fastest) function to do this task.
* @note does not accept negative numbers
* @note does not prefix with 0o
* @note the resulting string is NOT zero-terminated.
* @note it is ok to call this with an empty or too-small buffer;
* no writes will occur, and the required size will be returned
* @return the number of characters required for the buffer. */
template<class T>
C4_ALWAYS_INLINE size_t write_oct(substr buf, T v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
unsigned digits = digits_oct(v);
if(C4_LIKELY(buf.len >= digits))
write_oct_unchecked(buf, v, digits);
return digits;
}
/** write an integer to a string in binary format. This is the
* lowest level (and the fastest) function to do this task.
* @note does not accept negative numbers
* @note does not prefix with 0b
* @note the resulting string is NOT zero-terminated.
* @note it is ok to call this with an empty or too-small buffer;
* no writes will occur, and the required size will be returned
* @return the number of characters required for the buffer. */
template<class T>
C4_ALWAYS_INLINE size_t write_bin(substr buf, T v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
C4_ASSERT(v >= 0);
unsigned digits = digits_bin(v);
C4_ASSERT(digits > 0);
if(C4_LIKELY(buf.len >= digits))
write_bin_unchecked(buf, v, digits);
return digits;
}
/** @cond dev */
namespace detail {
template<class U> using NumberWriter = size_t (*)(substr, U);
template<class T, NumberWriter<T> writer>
size_t write_num_digits(substr buf, T v, size_t num_digits) noexcept
{
C4_STATIC_ASSERT(std::is_integral<T>::value);
const size_t ret = writer(buf, v);
if(ret >= num_digits)
return ret;
else if(ret >= buf.len || num_digits > buf.len)
return num_digits;
C4_ASSERT(num_digits >= ret);
const size_t delta = static_cast<size_t>(num_digits - ret); // NOLINT
C4_ASSERT(ret + delta <= buf.len);
if(ret)
memmove(buf.str + delta, buf.str, ret);
if(delta)
memset(buf.str, '0', delta);
return num_digits;
}
} // namespace detail
/** @endcond */
/** same as c4::write_dec(), but pad with zeroes on the left
* such that the resulting string is @p num_digits wide.
* If the given number is requires more than num_digits, then the number prevails. */
template<class T>
C4_ALWAYS_INLINE size_t write_dec(substr buf, T val, size_t num_digits) noexcept
{
return detail::write_num_digits<T, &write_dec<T>>(buf, val, num_digits);
}
/** same as c4::write_hex(), but pad with zeroes on the left
* such that the resulting string is @p num_digits wide.
* If the given number is requires more than num_digits, then the number prevails. */
template<class T>
C4_ALWAYS_INLINE size_t write_hex(substr buf, T val, size_t num_digits) noexcept
{
return detail::write_num_digits<T, &write_hex<T>>(buf, val, num_digits);
}
/** same as c4::write_bin(), but pad with zeroes on the left
* such that the resulting string is @p num_digits wide.
* If the given number is requires more than num_digits, then the number prevails. */
template<class T>
C4_ALWAYS_INLINE size_t write_bin(substr buf, T val, size_t num_digits) noexcept
{
return detail::write_num_digits<T, &write_bin<T>>(buf, val, num_digits);
}
/** same as c4::write_oct(), but pad with zeroes on the left
* such that the resulting string is @p num_digits wide.
* If the given number is requires more than num_digits, then the number prevails. */
template<class T>
C4_ALWAYS_INLINE size_t write_oct(substr buf, T val, size_t num_digits) noexcept
{
return detail::write_num_digits<T, &write_oct<T>>(buf, val, num_digits);
}
/** @} */ // write
C4_SUPPRESS_WARNING_GCC_POP
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
C4_SUPPRESS_WARNING_MSVC_PUSH
C4_SUPPRESS_WARNING_MSVC(4365) // '=': conversion from 'int' to 'I', signed/unsigned mismatch
/** @defgroup doc_read Read a value
*
* @{ */
/** read a decimal integer from a string. This is the
* lowest level (and the fastest) function to do this task.
* @note does not accept negative numbers
* @note The string must be trimmed. Whitespace is not accepted.
* @note the string must not be empty
* @note there is no check for overflow; the value wraps around
* in a way similar to the standard C/C++ overflow behavior.
* For example, `read_dec<int8_t>("128", &val)` returns true
* and val will be set to 0 because 127 is the max i8 value.
* @see overflows<T>() to find out if a number string overflows a type range
* @return true if the conversion was successful (no overflow check) */
template<class I>
C4_NO_UBSAN_IOVRFLW
C4_ALWAYS_INLINE bool read_dec(csubstr s, I *C4_RESTRICT v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<I>::value);
C4_ASSERT(!s.empty());
*v = 0;
for(char c : s)
{
if(C4_UNLIKELY(c < '0' || c > '9'))
return false;
*v = (*v) * I(10) + (I(c) - I('0'));
}
return true;
}
/** read an hexadecimal integer from a string. This is the
* lowest level (and the fastest) function to do this task.
* @note does not accept negative numbers
* @note does not accept leading 0x or 0X
* @note the string must not be empty
* @note the string must be trimmed. Whitespace is not accepted.
* @note there is no check for overflow; the value wraps around
* in a way similar to the standard C/C++ overflow behavior.
* For example, `read_hex<int8_t>("80", &val)` returns true
* and val will be set to 0 because 7f is the max i8 value.
* @see overflows<T>() to find out if a number string overflows a type range
* @return true if the conversion was successful (no overflow check) */
template<class I>
C4_NO_UBSAN_IOVRFLW
C4_ALWAYS_INLINE bool read_hex(csubstr s, I *C4_RESTRICT v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<I>::value);
C4_ASSERT(!s.empty());
*v = 0;
for(char c : s)
{
I cv;
if(c >= '0' && c <= '9')
cv = I(c) - I('0');
else if(c >= 'a' && c <= 'f')
cv = I(10) + (I(c) - I('a'));
else if(c >= 'A' && c <= 'F')
cv = I(10) + (I(c) - I('A'));
else
return false;
*v = (*v) * I(16) + cv;
}
return true;
}
/** read a binary integer from a string. This is the
* lowest level (and the fastest) function to do this task.
* @note does not accept negative numbers
* @note does not accept leading 0b or 0B
* @note the string must not be empty
* @note the string must be trimmed. Whitespace is not accepted.
* @note there is no check for overflow; the value wraps around
* in a way similar to the standard C/C++ overflow behavior.
* For example, `read_bin<int8_t>("10000000", &val)` returns true
* and val will be set to 0 because 1111111 is the max i8 value.
* @see overflows<T>() to find out if a number string overflows a type range
* @return true if the conversion was successful (no overflow check) */
template<class I>
C4_NO_UBSAN_IOVRFLW
C4_ALWAYS_INLINE bool read_bin(csubstr s, I *C4_RESTRICT v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<I>::value);
C4_ASSERT(!s.empty());
*v = 0;
for(char c : s)
{
*v <<= 1;
if(c == '1')
*v |= 1;
else if(c != '0')
return false;
}
return true;
}
/** read an octal integer from a string. This is the
* lowest level (and the fastest) function to do this task.
* @note does not accept negative numbers
* @note does not accept leading 0o or 0O
* @note the string must not be empty
* @note the string must be trimmed. Whitespace is not accepted.
* @note there is no check for overflow; the value wraps around
* in a way similar to the standard C/C++ overflow behavior.
* For example, `read_oct<int8_t>("200", &val)` returns true
* and val will be set to 0 because 177 is the max i8 value.
* @see overflows<T>() to find out if a number string overflows a type range
* @return true if the conversion was successful (no overflow check) */
template<class I>
C4_NO_UBSAN_IOVRFLW
C4_ALWAYS_INLINE bool read_oct(csubstr s, I *C4_RESTRICT v) noexcept
{
C4_STATIC_ASSERT(std::is_integral<I>::value);
C4_ASSERT(!s.empty());
*v = 0;
for(char c : s)
{
if(C4_UNLIKELY(c < '0' || c > '7'))
return false;
*v = (*v) * I(8) + (I(c) - I('0'));
}
return true;
}
/** @} */
C4_SUPPRESS_WARNING_MSVC_POP
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
C4_SUPPRESS_WARNING_GCC_WITH_PUSH("-Wswitch-default")
/** @cond dev */
namespace detail {
inline size_t _itoa2buf(substr buf, size_t pos, csubstr val) noexcept
{
C4_ASSERT(pos < buf.len);
C4_ASSERT(pos + val.len <= buf.len);
C4_ASSERT(val.len > 0);
memcpy(buf.str + pos, val.str, val.len);
return pos + val.len;
}
inline size_t _itoa2bufwithdigits(substr buf, size_t pos, size_t num_digits, csubstr val) noexcept
{
num_digits = num_digits > val.len ? num_digits - val.len : 0;
C4_ASSERT(num_digits + val.len <= buf.len);
for(size_t i = 0; i < num_digits; ++i)
_c4append('0');
return detail::_itoa2buf(buf, pos, val);
}
template<class I>
C4_NO_INLINE size_t _itoadec2buf(substr buf) noexcept
{