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#pragma once
#include "opaque_trie_iterator.h"
#include <util/generic/ptr.h>
namespace NCompactTrie {
// Iterates over possible first symbols in a trie.
// Allows one to get the symbol and the subtrie starting from it.
template <class TTrie>
class TFirstSymbolIterator {
public:
using TSymbol = typename TTrie::TSymbol;
using TData = typename TTrie::TData;
void SetTrie(const TTrie& trie, const ILeafSkipper& skipper) {
Trie = trie;
Impl.Reset(new TOpaqueTrieIterator(
TOpaqueTrie(Trie.Data().AsCharPtr(), Trie.Data().Size(), skipper),
nullptr,
false,
sizeof(TSymbol)));
if (Impl->MeasureKey<TSymbol>() == 0) {
MakeStep();
}
}
const TTrie& GetTrie() const {
return Trie;
}
bool AtEnd() const {
return *Impl == TOpaqueTrieIterator(Impl->GetTrie(), nullptr, true, sizeof(TSymbol));
}
TSymbol GetKey() const {
return Impl->GetKey<TSymbol>()[0];
}
TTrie GetTails() const {
const TNode& node = Impl->GetNode();
const size_t forwardOffset = node.GetForwardOffset();
const char* emptyValue = node.IsFinal() ? Trie.Data().AsCharPtr() + node.GetLeafOffset() : nullptr;
if (forwardOffset) {
const char* start = Trie.Data().AsCharPtr() + forwardOffset;
TBlob body = TBlob::NoCopy(start, Trie.Data().Size() - forwardOffset);
return TTrie(body, emptyValue, Trie.GetPacker());
} else {
return TTrie(emptyValue);
}
}
void MakeStep() {
Impl->Forward();
}
private:
TTrie Trie;
TCopyPtr<TOpaqueTrieIterator> Impl;
};
}
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