create
This commit is contained in:
Yao
317
Pods/abseil/absl/strings/internal/str_join_internal.h
generated
Normal file
317
Pods/abseil/absl/strings/internal/str_join_internal.h
generated
Normal file
@@ -0,0 +1,317 @@
|
||||
//
|
||||
// Copyright 2017 The Abseil Authors.
|
||||
//
|
||||
// Licensed under the Apache License, Version 2.0 (the "License");
|
||||
// you may not use this file except in compliance with the License.
|
||||
// You may obtain a copy of the License at
|
||||
//
|
||||
// https://www.apache.org/licenses/LICENSE-2.0
|
||||
//
|
||||
// Unless required by applicable law or agreed to in writing, software
|
||||
// distributed under the License is distributed on an "AS IS" BASIS,
|
||||
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||||
// See the License for the specific language governing permissions and
|
||||
// limitations under the License.
|
||||
//
|
||||
|
||||
// This file declares INTERNAL parts of the Join API that are inlined/templated
|
||||
// or otherwise need to be available at compile time. The main abstractions
|
||||
// defined in this file are:
|
||||
//
|
||||
// - A handful of default Formatters
|
||||
// - JoinAlgorithm() overloads
|
||||
// - JoinRange() overloads
|
||||
// - JoinTuple()
|
||||
//
|
||||
// DO NOT INCLUDE THIS FILE DIRECTLY. Use this file by including
|
||||
// absl/strings/str_join.h
|
||||
//
|
||||
// IWYU pragma: private, include "absl/strings/str_join.h"
|
||||
|
||||
#ifndef ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
|
||||
#define ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
|
||||
|
||||
#include <cstring>
|
||||
#include <iterator>
|
||||
#include <memory>
|
||||
#include <string>
|
||||
#include <type_traits>
|
||||
#include <utility>
|
||||
|
||||
#include "absl/strings/internal/ostringstream.h"
|
||||
#include "absl/strings/internal/resize_uninitialized.h"
|
||||
#include "absl/strings/str_cat.h"
|
||||
|
||||
namespace absl {
|
||||
ABSL_NAMESPACE_BEGIN
|
||||
namespace strings_internal {
|
||||
|
||||
//
|
||||
// Formatter objects
|
||||
//
|
||||
// The following are implementation classes for standard Formatter objects. The
|
||||
// factory functions that users will call to create and use these formatters are
|
||||
// defined and documented in strings/join.h.
|
||||
//
|
||||
|
||||
// The default formatter. Converts alpha-numeric types to strings.
|
||||
struct AlphaNumFormatterImpl {
|
||||
// This template is needed in order to support passing in a dereferenced
|
||||
// vector<bool>::iterator
|
||||
template <typename T>
|
||||
void operator()(std::string* out, const T& t) const {
|
||||
StrAppend(out, AlphaNum(t));
|
||||
}
|
||||
|
||||
void operator()(std::string* out, const AlphaNum& t) const {
|
||||
StrAppend(out, t);
|
||||
}
|
||||
};
|
||||
|
||||
// A type that's used to overload the JoinAlgorithm() function (defined below)
|
||||
// for ranges that do not require additional formatting (e.g., a range of
|
||||
// strings).
|
||||
|
||||
struct NoFormatter : public AlphaNumFormatterImpl {};
|
||||
|
||||
// Formats types to strings using the << operator.
|
||||
class StreamFormatterImpl {
|
||||
public:
|
||||
// The method isn't const because it mutates state. Making it const will
|
||||
// render StreamFormatterImpl thread-hostile.
|
||||
template <typename T>
|
||||
void operator()(std::string* out, const T& t) {
|
||||
// The stream is created lazily to avoid paying the relatively high cost
|
||||
// of its construction when joining an empty range.
|
||||
if (strm_) {
|
||||
strm_->clear(); // clear the bad, fail and eof bits in case they were set
|
||||
strm_->str(out);
|
||||
} else {
|
||||
strm_.reset(new strings_internal::OStringStream(out));
|
||||
}
|
||||
*strm_ << t;
|
||||
}
|
||||
|
||||
private:
|
||||
std::unique_ptr<strings_internal::OStringStream> strm_;
|
||||
};
|
||||
|
||||
// Formats a std::pair<>. The 'first' member is formatted using f1_ and the
|
||||
// 'second' member is formatted using f2_. sep_ is the separator.
|
||||
template <typename F1, typename F2>
|
||||
class PairFormatterImpl {
|
||||
public:
|
||||
PairFormatterImpl(F1 f1, absl::string_view sep, F2 f2)
|
||||
: f1_(std::move(f1)), sep_(sep), f2_(std::move(f2)) {}
|
||||
|
||||
template <typename T>
|
||||
void operator()(std::string* out, const T& p) {
|
||||
f1_(out, p.first);
|
||||
out->append(sep_);
|
||||
f2_(out, p.second);
|
||||
}
|
||||
|
||||
template <typename T>
|
||||
void operator()(std::string* out, const T& p) const {
|
||||
f1_(out, p.first);
|
||||
out->append(sep_);
|
||||
f2_(out, p.second);
|
||||
}
|
||||
|
||||
private:
|
||||
F1 f1_;
|
||||
std::string sep_;
|
||||
F2 f2_;
|
||||
};
|
||||
|
||||
// Wraps another formatter and dereferences the argument to operator() then
|
||||
// passes the dereferenced argument to the wrapped formatter. This can be
|
||||
// useful, for example, to join a std::vector<int*>.
|
||||
template <typename Formatter>
|
||||
class DereferenceFormatterImpl {
|
||||
public:
|
||||
DereferenceFormatterImpl() : f_() {}
|
||||
explicit DereferenceFormatterImpl(Formatter&& f)
|
||||
: f_(std::forward<Formatter>(f)) {}
|
||||
|
||||
template <typename T>
|
||||
void operator()(std::string* out, const T& t) {
|
||||
f_(out, *t);
|
||||
}
|
||||
|
||||
template <typename T>
|
||||
void operator()(std::string* out, const T& t) const {
|
||||
f_(out, *t);
|
||||
}
|
||||
|
||||
private:
|
||||
Formatter f_;
|
||||
};
|
||||
|
||||
// DefaultFormatter<T> is a traits class that selects a default Formatter to use
|
||||
// for the given type T. The ::Type member names the Formatter to use. This is
|
||||
// used by the strings::Join() functions that do NOT take a Formatter argument,
|
||||
// in which case a default Formatter must be chosen.
|
||||
//
|
||||
// AlphaNumFormatterImpl is the default in the base template, followed by
|
||||
// specializations for other types.
|
||||
template <typename ValueType>
|
||||
struct DefaultFormatter {
|
||||
typedef AlphaNumFormatterImpl Type;
|
||||
};
|
||||
template <>
|
||||
struct DefaultFormatter<const char*> {
|
||||
typedef AlphaNumFormatterImpl Type;
|
||||
};
|
||||
template <>
|
||||
struct DefaultFormatter<char*> {
|
||||
typedef AlphaNumFormatterImpl Type;
|
||||
};
|
||||
template <>
|
||||
struct DefaultFormatter<std::string> {
|
||||
typedef NoFormatter Type;
|
||||
};
|
||||
template <>
|
||||
struct DefaultFormatter<absl::string_view> {
|
||||
typedef NoFormatter Type;
|
||||
};
|
||||
template <typename ValueType>
|
||||
struct DefaultFormatter<ValueType*> {
|
||||
typedef DereferenceFormatterImpl<typename DefaultFormatter<ValueType>::Type>
|
||||
Type;
|
||||
};
|
||||
|
||||
template <typename ValueType>
|
||||
struct DefaultFormatter<std::unique_ptr<ValueType>>
|
||||
: public DefaultFormatter<ValueType*> {};
|
||||
|
||||
//
|
||||
// JoinAlgorithm() functions
|
||||
//
|
||||
|
||||
// The main joining algorithm. This simply joins the elements in the given
|
||||
// iterator range, each separated by the given separator, into an output string,
|
||||
// and formats each element using the provided Formatter object.
|
||||
template <typename Iterator, typename Formatter>
|
||||
std::string JoinAlgorithm(Iterator start, Iterator end, absl::string_view s,
|
||||
Formatter&& f) {
|
||||
std::string result;
|
||||
absl::string_view sep("");
|
||||
for (Iterator it = start; it != end; ++it) {
|
||||
result.append(sep.data(), sep.size());
|
||||
f(&result, *it);
|
||||
sep = s;
|
||||
}
|
||||
return result;
|
||||
}
|
||||
|
||||
// A joining algorithm that's optimized for a forward iterator range of
|
||||
// string-like objects that do not need any additional formatting. This is to
|
||||
// optimize the common case of joining, say, a std::vector<string> or a
|
||||
// std::vector<absl::string_view>.
|
||||
//
|
||||
// This is an overload of the previous JoinAlgorithm() function. Here the
|
||||
// Formatter argument is of type NoFormatter. Since NoFormatter is an internal
|
||||
// type, this overload is only invoked when strings::Join() is called with a
|
||||
// range of string-like objects (e.g., std::string, absl::string_view), and an
|
||||
// explicit Formatter argument was NOT specified.
|
||||
//
|
||||
// The optimization is that the needed space will be reserved in the output
|
||||
// string to avoid the need to resize while appending. To do this, the iterator
|
||||
// range will be traversed twice: once to calculate the total needed size, and
|
||||
// then again to copy the elements and delimiters to the output string.
|
||||
template <typename Iterator,
|
||||
typename = typename std::enable_if<std::is_convertible<
|
||||
typename std::iterator_traits<Iterator>::iterator_category,
|
||||
std::forward_iterator_tag>::value>::type>
|
||||
std::string JoinAlgorithm(Iterator start, Iterator end, absl::string_view s,
|
||||
NoFormatter) {
|
||||
std::string result;
|
||||
if (start != end) {
|
||||
// Sums size
|
||||
auto&& start_value = *start;
|
||||
size_t result_size = start_value.size();
|
||||
for (Iterator it = start; ++it != end;) {
|
||||
result_size += s.size();
|
||||
result_size += (*it).size();
|
||||
}
|
||||
|
||||
if (result_size > 0) {
|
||||
STLStringResizeUninitialized(&result, result_size);
|
||||
|
||||
// Joins strings
|
||||
char* result_buf = &*result.begin();
|
||||
|
||||
memcpy(result_buf, start_value.data(), start_value.size());
|
||||
result_buf += start_value.size();
|
||||
for (Iterator it = start; ++it != end;) {
|
||||
memcpy(result_buf, s.data(), s.size());
|
||||
result_buf += s.size();
|
||||
auto&& value = *it;
|
||||
memcpy(result_buf, value.data(), value.size());
|
||||
result_buf += value.size();
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
return result;
|
||||
}
|
||||
|
||||
// JoinTupleLoop implements a loop over the elements of a std::tuple, which
|
||||
// are heterogeneous. The primary template matches the tuple interior case. It
|
||||
// continues the iteration after appending a separator (for nonzero indices)
|
||||
// and formatting an element of the tuple. The specialization for the I=N case
|
||||
// matches the end-of-tuple, and terminates the iteration.
|
||||
template <size_t I, size_t N>
|
||||
struct JoinTupleLoop {
|
||||
template <typename Tup, typename Formatter>
|
||||
void operator()(std::string* out, const Tup& tup, absl::string_view sep,
|
||||
Formatter&& fmt) {
|
||||
if (I > 0) out->append(sep.data(), sep.size());
|
||||
fmt(out, std::get<I>(tup));
|
||||
JoinTupleLoop<I + 1, N>()(out, tup, sep, fmt);
|
||||
}
|
||||
};
|
||||
template <size_t N>
|
||||
struct JoinTupleLoop<N, N> {
|
||||
template <typename Tup, typename Formatter>
|
||||
void operator()(std::string*, const Tup&, absl::string_view, Formatter&&) {}
|
||||
};
|
||||
|
||||
template <typename... T, typename Formatter>
|
||||
std::string JoinAlgorithm(const std::tuple<T...>& tup, absl::string_view sep,
|
||||
Formatter&& fmt) {
|
||||
std::string result;
|
||||
JoinTupleLoop<0, sizeof...(T)>()(&result, tup, sep, fmt);
|
||||
return result;
|
||||
}
|
||||
|
||||
template <typename Iterator>
|
||||
std::string JoinRange(Iterator first, Iterator last,
|
||||
absl::string_view separator) {
|
||||
// No formatter was explicitly given, so a default must be chosen.
|
||||
typedef typename std::iterator_traits<Iterator>::value_type ValueType;
|
||||
typedef typename DefaultFormatter<ValueType>::Type Formatter;
|
||||
return JoinAlgorithm(first, last, separator, Formatter());
|
||||
}
|
||||
|
||||
template <typename Range, typename Formatter>
|
||||
std::string JoinRange(const Range& range, absl::string_view separator,
|
||||
Formatter&& fmt) {
|
||||
using std::begin;
|
||||
using std::end;
|
||||
return JoinAlgorithm(begin(range), end(range), separator, fmt);
|
||||
}
|
||||
|
||||
template <typename Range>
|
||||
std::string JoinRange(const Range& range, absl::string_view separator) {
|
||||
using std::begin;
|
||||
using std::end;
|
||||
return JoinRange(begin(range), end(range), separator);
|
||||
}
|
||||
|
||||
} // namespace strings_internal
|
||||
ABSL_NAMESPACE_END
|
||||
} // namespace absl
|
||||
|
||||
#endif // ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
|
||||
Reference in New Issue
Block a user