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[Imgtool] Changing imgtool::simple_charconverter::from_utf8() to not perform an O(n) lookup whenever locating a character

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This commit is contained in:
Nathan Woods 2017-01-05 21:02:45 -05:00
parent 46ddd46f25
commit e38b9b63ba
2 changed files with 35 additions and 37 deletions
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62
src/tools/imgtool/charconv.cpp
View file

@ -36,6 +36,29 @@ void imgtool::charconverter::to_utf8(std::ostream &dest, const std::string &src)
}
//-------------------------------------------------
// simple_charconverter::simple_charconverter
//-------------------------------------------------
imgtool::simple_charconverter::simple_charconverter(const char32_t lowpage[0x80], const char32_t highpage[0x80], unicode_normalization_form norm)
: m_norm(norm), m_lowpage(lowpage), m_highpage(highpage)
{
// build the reverse lookup table
for (int i = 0; i < 256; i++)
{
const char32_t *page = i >= 128 ? m_highpage : m_lowpage;
char32_t unicode_char = page ? page[i % 128] : i;
m_reverse_lookup.emplace_back(unicode_char, (char)i);
}
// and sort it
std::sort(m_reverse_lookup.begin(), m_reverse_lookup.end(), [](const std::pair<char32_t, char> &a, const std::pair<char32_t, char> &b)
{
return b.first > a.first;
});
}
//-------------------------------------------------
// from_utf8
//-------------------------------------------------
@ -58,39 +81,16 @@ void imgtool::simple_charconverter::from_utf8(std::ostream &dest, const char *sr
}
iter += rc;
// look in all pages
const char32_t *pages[2];
pages[0] = m_lowpage;
pages[1] = m_highpage;
bool found = false;
for (int i = 0; !found && i < ARRAY_LENGTH(pages); i++)
// do the reverse lookup
auto lookup = std::lower_bound(m_reverse_lookup.begin(), m_reverse_lookup.end(), ch, [](const std::pair<char32_t, char> &a, const char32_t &b)
{
if (pages[i] == nullptr)
{
// null page; perhaps we can just emit this
if (ch >= i * 0x80 && (ch < (i + 1) * 0x80))
{
dest << (char)ch;
found = true;
}
}
else
{
// non-null page; perform a lookup
// if we have a page, perform the lookup
const util::contiguous_sequence_wrapper<const char32_t> lookup(pages[i], 0x80);
auto lookup_iter = std::find(lookup.begin(), lookup.end(), ch);
if (lookup_iter != lookup.end())
{
// and emit the result
dest << (char)((i * 0x80) + (lookup_iter - lookup.begin()));
found = true;
}
}
}
if (!found)
return a.first < b;
});
if (lookup == m_reverse_lookup.end())
throw charconverter_exception();
// and output the results
dest << lookup->second;
}
}

10
src/tools/imgtool/charconv.h
View file

@ -52,20 +52,18 @@ namespace imgtool
class simple_charconverter : public charconverter
{
public:
constexpr simple_charconverter(const char32_t highpage[0x80], unicode_normalization_form norm = unicode_normalization_form::C)
: m_norm(norm), m_lowpage(nullptr), m_highpage(highpage)
simple_charconverter(const char32_t highpage[0x80], unicode_normalization_form norm = unicode_normalization_form::C)
: simple_charconverter(nullptr, highpage, norm)
{
}
constexpr simple_charconverter(const char32_t lowpage[0x80], const char32_t highpage[0x80], unicode_normalization_form norm = unicode_normalization_form::C)
: m_norm(norm), m_lowpage(lowpage), m_highpage(highpage)
{
}
simple_charconverter(const char32_t lowpage[0x80], const char32_t highpage[0x80], unicode_normalization_form norm = unicode_normalization_form::C);
virtual void from_utf8(std::ostream &dest, const char *src, size_t src_length) const override;
virtual void to_utf8(std::ostream &dest, const char *src, size_t src_length) const override;
private:
std::vector<std::pair<char32_t, char> > m_reverse_lookup;
unicode_normalization_form m_norm;
const char32_t *m_lowpage;
const char32_t *m_highpage;