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Use murmur3 to explicitly hash the font index keys

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This significantly improves performance by avoiding the need to
construct std::strings of the things to be hashed, eliminating a bunch
of memory allocations and copies.
This commit is contained in:
Thomas Goyne 2015-12-26 12:27:44 -08:00
parent 879661a379
commit 3b13260ca1
2 changed files with 39 additions and 8 deletions
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2
src/font_file_lister.h
View file

@ -42,7 +42,7 @@ struct CollectionResult {
#ifdef _WIN32
class GdiFontFileLister {
std::unordered_multimap<std::string, agi::fs::path> index;
std::unordered_multimap<uint32_t, agi::fs::path> index;
agi::scoped_holder<HDC> dc;
std::string buffer;

45
src/font_file_lister_gdi.cpp
View file

@ -25,6 +25,38 @@
#include <boost/scope_exit.hpp>
namespace {
uint32_t murmur3(const char *data, uint32_t len) {
static const uint32_t c1 = 0xcc9e2d51;
static const uint32_t c2 = 0x1b873593;
static const uint32_t r1 = 15;
static const uint32_t r2 = 13;
static const uint32_t m = 5;
static const uint32_t n = 0xe6546b64;
uint32_t hash = 0;
const int nblocks = len / 4;
auto blocks = reinterpret_cast<const uint32_t *>(data);
for (uint32_t i = 0; i * 4 < len; ++i) {
uint32_t k = blocks[i];
k *= c1;
k = _rotl(k, r1);
k *= c2;
hash ^= k;
hash = _rotl(hash, r2) * m + n;
}
hash ^= len;
hash ^= hash >> 16;
hash *= 0x85ebca6b;
hash ^= hash >> 13;
hash *= 0xc2b2ae35;
hash ^= hash >> 16;
return hash;
}
std::vector<agi::fs::path> get_installed_fonts() {
static const auto fonts_key_name = L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Fonts";
@ -57,18 +89,17 @@ std::vector<agi::fs::path> get_installed_fonts() {
return files;
}
using font_index = std::unordered_multimap<std::string, agi::fs::path>;
using font_index = std::unordered_multimap<uint32_t, agi::fs::path>;
font_index index_fonts() {
font_index hash_to_path;
auto fonts = get_installed_fonts();
std::unique_ptr<char[]> buffer(new char[1024]);
for (auto const& path : fonts) {
auto stream = agi::io::Open(path, true);
std::string data(1024, '\0');
stream->read(&data[0], data.size());
data.resize(stream->tellg());
hash_to_path.emplace(std::move(data), path);
stream->read(&buffer[0], 1024);
auto hash = murmur3(&buffer[0], stream->tellg());
hash_to_path.emplace(hash, path);
}
return hash_to_path;
}
@ -158,7 +189,7 @@ CollectionResult GdiFontFileLister::GetFontPaths(std::string const& facename, in
get_font_data(buffer, dc);
auto range = index.equal_range(buffer.substr(0, 1024));
auto range = index.equal_range(murmur3(buffer.c_str(), std::min(buffer.size(), 1024U)));
if (range.first == range.second)
return ret; // could instead write to a temp dir