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Implements Zero-Copy String Views onto Contiguous Memory, resolves #3265.

Browse Source 
- http://www.boost.org/doc/libs/1_61_0/libs/utility/doc/html/string_ref.html
- http://en.cppreference.com/w/cpp/string/basic_string_view
This commit is contained in:
Daniel J. Hofmann
2016-12-15 18:27:09 +01:00
parent b1f1c26703
commit c277b95f03
13 changed files with 219 additions and 144 deletions
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src/util/name_table.cpp
+26 -26
View File
@@ -1,9 +1,10 @@
#include "util/name_table.hpp"
#include "storage/io.hpp"
#include "util/exception.hpp"
#include "util/log.hpp"
#include <algorithm>
#include <fstream>
#include <iterator>
#include <limits>
#include <boost/filesystem/fstream.hpp>
@@ -18,11 +19,9 @@ NameTable::NameTable(const std::string &filename)
storage::io::FileReader name_stream_file_reader(filename,
storage::io::FileReader::HasNoFingerprint);
// name_stream >> m_name_table;
m_name_table.ReadARangeTable(name_stream_file_reader);
unsigned number_of_chars = name_stream_file_reader.ReadElementCount32();
const auto number_of_chars = name_stream_file_reader.ReadElementCount32();
m_names_char_list.resize(number_of_chars + 1); //+1 gives sentinel element
m_names_char_list.back() = 0;
@@ -37,58 +36,59 @@ NameTable::NameTable(const std::string &filename)
}
}
std::string NameTable::GetNameForID(const unsigned name_id) const
StringView NameTable::GetNameForID(const NameID id) const
{
if (std::numeric_limits<unsigned>::max() == name_id)
if (std::numeric_limits<NameID>::max() == id)
{
return "";
return {};
}
auto range = m_name_table.GetRange(name_id);
std::string result;
result.reserve(range.size());
if (range.begin() != range.end())
auto range = m_name_table.GetRange(id);
if (range.begin() == range.end())
{
result.resize(range.back() - range.front() + 1);
std::copy(m_names_char_list.begin() + range.front(),
m_names_char_list.begin() + range.back() + 1,
result.begin());
return {};
}
return result;
auto first = begin(m_names_char_list) + range.front();
auto last = begin(m_names_char_list) + range.back() + 1;
const std::size_t len = last - first;
return StringView{&*first, len};
}
std::string NameTable::GetRefForID(const unsigned name_id) const
StringView NameTable::GetRefForID(const NameID id) const
{
// Way string data is stored in blocks based on `name_id` as follows:
// Way string data is stored in blocks based on `id` as follows:
//
// | name | destination | pronunciation | ref |
// ^ ^
// [range)
// ^ name_id + 3
// ^ id + 3
//
// `name_id + offset` gives us the range of chars.
// `id + offset` gives us the range of chars.
//
// Offset 0 is name, 1 is destination, 2 is pronunciation, 3 is ref.
// See datafacades and extractor callbacks for details.
const constexpr auto OFFSET_REF = 3u;
return GetNameForID(name_id + OFFSET_REF);
return GetNameForID(id + OFFSET_REF);
}
std::string NameTable::GetPronunciationForID(const unsigned name_id) const
StringView NameTable::GetPronunciationForID(const NameID id) const
{
// Way string data is stored in blocks based on `name_id` as follows:
// Way string data is stored in blocks based on `id` as follows:
//
// | name | destination | pronunciation | ref |
// ^ ^
// [range)
// ^ name_id + 2
// ^ id + 2
//
// `name_id + offset` gives us the range of chars.
// `id + offset` gives us the range of chars.
//
// Offset 0 is name, 1 is destination, 2 is pronunciation, 3 is ref.
// See datafacades and extractor callbacks for details.
const constexpr auto OFFSET_PRONUNCIATION = 2u;
return GetNameForID(name_id + OFFSET_PRONUNCIATION);
return GetNameForID(id + OFFSET_PRONUNCIATION);
}
} // namespace util