mirror of https://github.com/ksherlock/mpw.git
99 lines
2.0 KiB
C++
99 lines
2.0 KiB
C++
#include "intern.h"
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#include <unordered_map>
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#include <cstring>
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namespace {
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std::unordered_multimap<unsigned, std::string *> InternTable;
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std::string EmptyString;
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unsigned int DJBHash(const char* begin, size_t length)
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{
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unsigned int hash = 5381;
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for(size_t i = 0; i < length; ++i)
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{
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hash = ((hash << 5) + hash) + (begin[i]);
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}
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return hash;
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}
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}
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namespace Intern {
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const std::string *String(std::string &&str)
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{
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size_t size = str.size();
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if (!size) return &EmptyString;
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unsigned hash = DJBHash(str.data(), size);
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auto range = InternTable.equal_range(hash);
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auto iter = range.first;
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auto endit = range.second;
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for( ; iter != endit; ++iter)
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{
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// hash matches, make sure the string does.
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const std::string *s = iter->second;
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if (s->size() == size && std::memcmp(s->data(), str.data(), size) == 0)
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return s;
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}
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// insert it. I suppose this could throw, in which case a string would leak.
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std::string *s = new std::string(std::move(str));
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InternTable.emplace(std::make_pair(hash, s));
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return s;
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}
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const std::string *String(const char *begin, size_t size)
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{
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if (!size) return &EmptyString;
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unsigned hash = DJBHash(begin, size);
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auto range = InternTable.equal_range(hash);
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auto iter = range.first;
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auto endit = range.second;
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for( ; iter != endit; ++iter)
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{
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// hash matches, make sure the string does.
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const std::string *s = iter->second;
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if (s->size() == size && std::memcmp(s->data(), begin, size) == 0)
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return s;
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}
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// insert it. I suppose this could throw, in which case a string would leak.
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std::string *s = new std::string(begin, size);
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InternTable.emplace(std::make_pair(hash, s));
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return s;
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}
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const std::string *String(const char *begin, const char *end)
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{
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return String(begin, end - begin);
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}
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const std::string *String(const char *cp)
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{
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if (!cp || !*cp) return &EmptyString;
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return String(cp, strlen(cp));
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}
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const std::string *String(const std::string &s)
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{
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return String(s.data(), s.size());
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}
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}
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