gecko-dev/mfbt/TextUtils.h
Jeff Walden c55625cdec Bug 1467336 - Implement mozilla::IsAscii to detect pure ASCII characters. r=froydnj
--HG--
extra : rebase_source : 1f6de2745234766d676178bdeafb9b82e48e51b5
2018-06-07 02:17:10 -07:00

152 lines
3.8 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* Character/text operations. */
#ifndef mozilla_TextUtils_h
#define mozilla_TextUtils_h
#include "mozilla/Assertions.h"
#include "mozilla/TypeTraits.h"
namespace mozilla {
namespace detail {
template<typename Char>
class MakeUnsignedChar
: public MakeUnsigned<Char>
{};
template<>
class MakeUnsignedChar<char16_t>
{
public:
using Type = char16_t;
};
template<>
class MakeUnsignedChar<char32_t>
{
public:
using Type = char32_t;
};
} // namespace detail
/** Returns true iff |aChar| is ASCII, i.e. in the range [0, 0x80). */
template<typename Char>
constexpr bool
IsAscii(Char aChar)
{
using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
auto uc = static_cast<UnsignedChar>(aChar);
return uc < 0x80;
}
/**
* Returns true iff |aChar| matches [a-z].
*
* This function is basically what you thought islower was, except its behavior
* doesn't depend on the user's current locale.
*/
template<typename Char>
constexpr bool
IsAsciiLowercaseAlpha(Char aChar)
{
using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
auto uc = static_cast<UnsignedChar>(aChar);
return 'a' <= uc && uc <= 'z';
}
/**
* Returns true iff |aChar| matches [A-Z].
*
* This function is basically what you thought isupper was, except its behavior
* doesn't depend on the user's current locale.
*/
template<typename Char>
constexpr bool
IsAsciiUppercaseAlpha(Char aChar)
{
using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
auto uc = static_cast<UnsignedChar>(aChar);
return 'A' <= uc && uc <= 'Z';
}
/**
* Returns true iff |aChar| matches [a-zA-Z].
*
* This function is basically what you thought isalpha was, except its behavior
* doesn't depend on the user's current locale.
*/
template<typename Char>
constexpr bool
IsAsciiAlpha(Char aChar)
{
return IsAsciiLowercaseAlpha(aChar) || IsAsciiUppercaseAlpha(aChar);
}
/**
* Returns true iff |aChar| matches [0-9].
*
* This function is basically what you thought isdigit was, except its behavior
* doesn't depend on the user's current locale.
*/
template<typename Char>
constexpr bool
IsAsciiDigit(Char aChar)
{
using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
auto uc = static_cast<UnsignedChar>(aChar);
return '0' <= uc && uc <= '9';
}
/**
* Returns true iff |aChar| matches [a-zA-Z0-9].
*
* This function is basically what you thought isalnum was, except its behavior
* doesn't depend on the user's current locale.
*/
template<typename Char>
constexpr bool
IsAsciiAlphanumeric(Char aChar)
{
return IsAsciiDigit(aChar) || IsAsciiAlpha(aChar);
}
/**
* Converts an ASCII alphanumeric digit [0-9a-zA-Z] to number as if in base-36.
* (This function therefore works for decimal, hexadecimal, etc.).
*/
template<typename Char>
uint8_t
AsciiAlphanumericToNumber(Char aChar)
{
using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
auto uc = static_cast<UnsignedChar>(aChar);
if ('0' <= uc && uc <= '9') {
return uc - '0';
}
if ('A' <= uc && uc <= 'Z') {
return uc - 'A' + 10;
}
// Ideally this function would be constexpr, but unfortunately gcc at least as
// of 6.4 forbids non-constexpr function calls in unevaluated constexpr
// function calls. See bug 1453456. So for now, just assert and leave the
// entire function non-constexpr.
MOZ_ASSERT('a' <= uc && uc <= 'z',
"non-ASCII alphanumeric character can't be converted to number");
return uc - 'a' + 10;
}
} // namespace mozilla
#endif /* mozilla_TextUtils_h */