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194 lines (164 loc) · 6.88 KB
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#pragma once
#include <util/generic/string.h>
#include <util/generic/typetraits.h>
#include <util/string/cast.h>
#include "cast.h"
/*
* Default implementation of AppendToString uses a temporary TString object which is inefficient. You can overload it
* for your type to speed up string joins. If you already have an Out() or operator<<() implementation you can simply
* do the following:
*
* inline void AppendToString(TString& dst, const TMyType& t) {
* TStringOutput o(dst);
* o << t;
* }
*
* Unfortunately we can't do this by default because for some types ToString() is defined while Out() is not.
* For standard types (strings of all kinds and arithmetic types) we don't use a temporary TString in AppendToString().
*/
template <typename T>
inline std::enable_if_t<!std::is_arithmetic<std::remove_cv_t<T>>::value, void>
AppendToString(TString& dst, const T& t) {
dst.AppendNoAlias(ToString(t));
}
template <typename T>
inline std::enable_if_t<std::is_arithmetic<std::remove_cv_t<T>>::value, void>
AppendToString(TString& dst, const T& t) {
char buf[512];
dst.append(buf, ToString<std::remove_cv_t<T>>(t, buf, sizeof(buf)));
}
inline void AppendToString(TString& dst, const char* t) {
dst.append(t);
}
inline void AppendToString(TString& dst, const TStringBuf t) {
dst.append(t);
}
namespace NPrivate {
template <typename T>
inline size_t GetLength(const T&) {
// By default don't pre-allocate space when joining and appending non-string types.
// This code can be extended by estimating stringified length for specific types (e.g. 10 for ui32).
return 0;
}
template <>
inline size_t GetLength(const TString& s) {
return s.length();
}
template <>
inline size_t GetLength(const TStringBuf& s) {
return s.length();
}
template <>
inline size_t GetLength(const char* const& s) {
return (s ? TCharTraits<char>::length(s) : 0);
}
inline size_t GetAppendLength(const TStringBuf /*delim*/) {
return 0;
}
template <typename TFirst, typename... TRest>
size_t GetAppendLength(const TStringBuf delim, const TFirst& f, const TRest&... r) {
return delim.length() + ::NPrivate::GetLength(f) + ::NPrivate::GetAppendLength(delim, r...);
}
}
inline void AppendJoinNoReserve(TString&, const TStringBuf) {
}
template <typename TFirst, typename... TRest>
inline void AppendJoinNoReserve(TString& dst, const TStringBuf delim, const TFirst& f, const TRest&... r) {
AppendToString(dst, delim);
AppendToString(dst, f);
AppendJoinNoReserve(dst, delim, r...);
}
template <typename... TValues>
inline void AppendJoin(TString& dst, const TStringBuf delim, const TValues&... values) {
const size_t appendLength = ::NPrivate::GetAppendLength(delim, values...);
if (appendLength > 0) {
dst.reserve(dst.length() + appendLength);
}
AppendJoinNoReserve(dst, delim, values...);
}
template <typename TFirst, typename... TRest>
inline TString Join(const TStringBuf delim, const TFirst& f, const TRest&... r) {
TString ret = ToString(f);
AppendJoin(ret, delim, r...);
return ret;
}
// Note that char delimeter @cdelim will be printed as single char string,
// but any char value @v will be printed as corresponding numeric code.
// For example, Join('a', 'a', 'a') will print "97a97" (see unit-test).
template <typename... TValues>
inline TString Join(char cdelim, const TValues&... v) {
return Join(TStringBuf(&cdelim, 1), v...);
}
template <typename TIter>
inline TString JoinRange(const TStringBuf delim, const TIter beg, const TIter end) {
TString out;
if (beg != end) {
size_t total = ::NPrivate::GetLength(*beg);
for (TIter pos = beg; ++pos != end;) {
total += delim.length() + ::NPrivate::GetLength(*pos);
}
if (total > 0) {
out.reserve(total);
}
AppendToString(out, *beg);
for (TIter pos = beg; ++pos != end;) {
AppendJoinNoReserve(out, delim, *pos);
}
}
return out;
}
template <typename TContainer>
TString JoinSeq(const TStringBuf delim, const TContainer& data) {
using std::begin;
using std::end;
return JoinRange(delim, begin(data), end(data));
}
/** \brief Functor for streaming iterative objects from TIterB e to TIterE b, separated with delim.
* Difference from JoinSeq, JoinRange, Join is the lack of TString object - all depends on operator<< for the type and
* realization of IOutputStream
*/
template<class TIterB, class TIterE>
struct TRangeJoiner{
friend constexpr IOutputStream& operator<<(IOutputStream& stream, const TRangeJoiner<TIterB, TIterE>& rangeJoiner) {
if(rangeJoiner.b != rangeJoiner.e) {
stream << *rangeJoiner.b;
for(auto it = std::next(rangeJoiner.b); it != rangeJoiner.e; ++it)
stream << rangeJoiner.delim << *it;
}
return stream;
}
constexpr TRangeJoiner(TStringBuf delim, TIterB && b, TIterE && e) : delim(delim), b(std::forward<TIterB>(b)), e(std::forward<TIterE>(e)) {}
private:
const TStringBuf delim;
const TIterB b;
const TIterE e;
};
template<class TIterB, class TIterE = TIterB> constexpr auto MakeRangeJoiner(TStringBuf delim, TIterB && b, TIterE && e) {
return TRangeJoiner<TIterB, TIterE>(delim, std::forward<TIterB>(b), std::forward<TIterE>(e));
}
template<class TContainer> constexpr auto MakeRangeJoiner(TStringBuf delim, const TContainer& data) {
return MakeRangeJoiner(delim, std::cbegin(data), std::cend(data));
}
template<class TVal> constexpr auto MakeRangeJoiner(TStringBuf delim, const std::initializer_list<TVal>& data) {
return MakeRangeJoiner(delim, std::cbegin(data), std::cend(data));
}
/* We force (std::initializer_list<TStringBuf>) input type for (TString) and (const char*) types because:
* # When (std::initializer_list<TString>) is used, TString objects are copied into the initializer_list object.
* Storing TStringBufs instead is faster, even with COW-enabled strings.
* # For (const char*) we calculate length only once and store it in TStringBuf. Otherwise strlen scan would be executed
* in both GetAppendLength and AppendToString. For string literals constant lengths get propagated in compile-time.
*
* This way JoinSeq(",", { s1, s2 }) always does the right thing whatever types s1 and s2 have.
*
* If someone needs to join std::initializer_list<TString> -- it still works because of the TContainer template above.
*/
template <typename T>
inline std::enable_if_t<
!std::is_same<std::decay_t<T>, TString>::value && !std::is_same<std::decay_t<T>, const char*>::value,
TString>
JoinSeq(const TStringBuf delim, const std::initializer_list<T>& data) {
return JoinRange(delim, data.begin(), data.end());
}
inline TString JoinSeq(const TStringBuf delim, const std::initializer_list<TStringBuf>& data) {
return JoinRange(delim, data.begin(), data.end());
}