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authorGravatar Abseil Team <absl-team@google.com>2020-11-09 04:09:55 -0800
committerGravatar Mark Barolak <mbar@google.com>2020-11-09 14:47:43 -0500
commita4798817e824a5c45689933bc62338f3c7d6961b (patch)
tree8fc15ab0a4c9aedf3c367aa068fa29143399f8e2 /absl/strings
parente96d49687d9c078f2d47356b6723c3b5715493f7 (diff)
Export of internal Abseil changes
-- 197bd3e5e315f408bdc2f7111a0652be7f47609f by Jorg Brown <jorg@google.com>: ConvertibleToStringView wastes a lot of cycles initializing a std::string member that it never uses. This CL restricts ConvertibleToStringView to just the cases that don't nned a std::string member, and uses an additional StrSplit overload to catch when users pass a temporary string. This makes StrSplit() 0-30% faster depending on the use case. PiperOrigin-RevId: 341378221 GitOrigin-RevId: 197bd3e5e315f408bdc2f7111a0652be7f47609f Change-Id: Id863f2a3d298ed5a086ac912afab42dc30601be5
Diffstat (limited to 'absl/strings')
-rw-r--r--absl/strings/internal/str_split_internal.h51
-rw-r--r--absl/strings/str_split.h42
2 files changed, 51 insertions, 42 deletions
diff --git a/absl/strings/internal/str_split_internal.h b/absl/strings/internal/str_split_internal.h
index 49ec5392..a2f41c15 100644
--- a/absl/strings/internal/str_split_internal.h
+++ b/absl/strings/internal/str_split_internal.h
@@ -51,9 +51,9 @@ ABSL_NAMESPACE_BEGIN
namespace strings_internal {
// This class is implicitly constructible from everything that absl::string_view
-// is implicitly constructible from. If it's constructed from a temporary
-// string, the data is moved into a data member so its lifetime matches that of
-// the ConvertibleToStringView instance.
+// is implicitly constructible from, except for rvalue strings. This means it
+// can be used as a function parameter in places where passing a temporary
+// string might cause memory lifetime issues.
class ConvertibleToStringView {
public:
ConvertibleToStringView(const char* s) // NOLINT(runtime/explicit)
@@ -65,41 +65,12 @@ class ConvertibleToStringView {
: value_(s) {}
// Matches rvalue strings and moves their data to a member.
- ConvertibleToStringView(std::string&& s) // NOLINT(runtime/explicit)
- : copy_(std::move(s)), value_(copy_) {}
-
- ConvertibleToStringView(const ConvertibleToStringView& other)
- : copy_(other.copy_),
- value_(other.IsSelfReferential() ? copy_ : other.value_) {}
-
- ConvertibleToStringView(ConvertibleToStringView&& other) {
- StealMembers(std::move(other));
- }
-
- ConvertibleToStringView& operator=(ConvertibleToStringView other) {
- StealMembers(std::move(other));
- return *this;
- }
+ ConvertibleToStringView(std::string&& s) = delete;
+ ConvertibleToStringView(const std::string&& s) = delete;
absl::string_view value() const { return value_; }
private:
- // Returns true if ctsp's value refers to its internal copy_ member.
- bool IsSelfReferential() const { return value_.data() == copy_.data(); }
-
- void StealMembers(ConvertibleToStringView&& other) {
- if (other.IsSelfReferential()) {
- copy_ = std::move(other.copy_);
- value_ = copy_;
- other.value_ = other.copy_;
- } else {
- value_ = other.value_;
- }
- }
-
- // Holds the data moved from temporary std::string arguments. Declared first
- // so that 'value' can refer to 'copy_'.
- std::string copy_;
absl::string_view value_;
};
@@ -273,7 +244,11 @@ struct SplitterIsConvertibleTo
// the split strings: only strings for which the predicate returns true will be
// kept. A Predicate object is any unary functor that takes an absl::string_view
// and returns bool.
-template <typename Delimiter, typename Predicate>
+//
+// The StringType parameter can be either string_view or string, depending on
+// whether the Splitter refers to a string stored elsewhere, or if the string
+// resides inside the Splitter itself.
+template <typename Delimiter, typename Predicate, typename StringType>
class Splitter {
public:
using DelimiterType = Delimiter;
@@ -281,12 +256,12 @@ class Splitter {
using const_iterator = strings_internal::SplitIterator<Splitter>;
using value_type = typename std::iterator_traits<const_iterator>::value_type;
- Splitter(ConvertibleToStringView input_text, Delimiter d, Predicate p)
+ Splitter(StringType input_text, Delimiter d, Predicate p)
: text_(std::move(input_text)),
delimiter_(std::move(d)),
predicate_(std::move(p)) {}
- absl::string_view text() const { return text_.value(); }
+ absl::string_view text() const { return text_; }
const Delimiter& delimiter() const { return delimiter_; }
const Predicate& predicate() const { return predicate_; }
@@ -443,7 +418,7 @@ class Splitter {
};
};
- ConvertibleToStringView text_;
+ StringType text_;
Delimiter delimiter_;
Predicate predicate_;
};
diff --git a/absl/strings/str_split.h b/absl/strings/str_split.h
index 1ce17f38..bfbca422 100644
--- a/absl/strings/str_split.h
+++ b/absl/strings/str_split.h
@@ -369,6 +369,12 @@ struct SkipWhitespace {
}
};
+template <typename T>
+using EnableSplitIfString =
+ typename std::enable_if<std::is_same<T, std::string>::value ||
+ std::is_same<T, const std::string>::value,
+ int>::type;
+
//------------------------------------------------------------------------------
// StrSplit()
//------------------------------------------------------------------------------
@@ -489,22 +495,50 @@ struct SkipWhitespace {
// Try not to depend on this distinction because the bug may one day be fixed.
template <typename Delimiter>
strings_internal::Splitter<
- typename strings_internal::SelectDelimiter<Delimiter>::type, AllowEmpty>
+ typename strings_internal::SelectDelimiter<Delimiter>::type, AllowEmpty,
+ absl::string_view>
StrSplit(strings_internal::ConvertibleToStringView text, Delimiter d) {
using DelimiterType =
typename strings_internal::SelectDelimiter<Delimiter>::type;
- return strings_internal::Splitter<DelimiterType, AllowEmpty>(
+ return strings_internal::Splitter<DelimiterType, AllowEmpty,
+ absl::string_view>(
+ text.value(), DelimiterType(d), AllowEmpty());
+}
+
+template <typename Delimiter, typename StringType,
+ EnableSplitIfString<StringType> = 0>
+strings_internal::Splitter<
+ typename strings_internal::SelectDelimiter<Delimiter>::type, AllowEmpty,
+ std::string>
+StrSplit(StringType&& text, Delimiter d) {
+ using DelimiterType =
+ typename strings_internal::SelectDelimiter<Delimiter>::type;
+ return strings_internal::Splitter<DelimiterType, AllowEmpty, std::string>(
std::move(text), DelimiterType(d), AllowEmpty());
}
template <typename Delimiter, typename Predicate>
strings_internal::Splitter<
- typename strings_internal::SelectDelimiter<Delimiter>::type, Predicate>
+ typename strings_internal::SelectDelimiter<Delimiter>::type, Predicate,
+ absl::string_view>
StrSplit(strings_internal::ConvertibleToStringView text, Delimiter d,
Predicate p) {
using DelimiterType =
typename strings_internal::SelectDelimiter<Delimiter>::type;
- return strings_internal::Splitter<DelimiterType, Predicate>(
+ return strings_internal::Splitter<DelimiterType, Predicate,
+ absl::string_view>(
+ text.value(), DelimiterType(d), std::move(p));
+}
+
+template <typename Delimiter, typename Predicate, typename StringType,
+ EnableSplitIfString<StringType> = 0>
+strings_internal::Splitter<
+ typename strings_internal::SelectDelimiter<Delimiter>::type, Predicate,
+ std::string>
+StrSplit(StringType&& text, Delimiter d, Predicate p) {
+ using DelimiterType =
+ typename strings_internal::SelectDelimiter<Delimiter>::type;
+ return strings_internal::Splitter<DelimiterType, Predicate, std::string>(
std::move(text), DelimiterType(d), std::move(p));
}