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authorGravatar Abseil Team <absl-team@google.com>2017-12-20 12:34:46 -0800
committerGravatar Xiaoyi Zhang <zhangxy988@gmail.com>2017-12-20 17:03:18 -0500
commitff7045647330f5dc21725a42456091207f3eecd5 (patch)
treecae476d37e272b1a1d48172f07c4a7229a027fea /absl/strings/internal
parent4972c72c5cf2f27e2a0846ce9ff5d377d3f2b7af (diff)
Changes imported from Abseil "staging" branch:
- 20f4e7133d695e9a05e13ebdfd4d78da310b42b5 Remove the warning supressions -Wno-documentation and by Derek Mauro <dmauro@google.com> - e1bde85c0571673b1e7a88b9d45a393606ba7e6c Changed the optimized version of strings_internal::JoinAl... by Abseil Team <absl-team@google.com> - 746e6716b4c15be61547670d68d25a1c850d3954 Add missing absl:: qualification. by Alex Strelnikov <strel@google.com> - 4e5c18c488cbd49ca72b02911cf22d830d5a7f16 Internals change: Remove the ability to pass a custom met... by Greg Falcon <gfalcon@google.com> - 65d58107a5730d4b6468bbffc72bea2f980af826 Moved most common character case (ascii printable) out of... by Abseil Team <absl-team@google.com> - f031331cc55a3d57b9110e12c7cbe50ac3e2a04f Add missing copyright headers to a few source files. by Greg Falcon <gfalcon@google.com> - 6035a77af6fa951c536b42df4c710d16d1817aec Enable libstdc++'s memcmp optimization in absl::equal for... by Abseil Team <absl-team@google.com> - 73a665a4a10781e5d89f75a876ece7ad859f4116 Fix minor spelling error "hexidecimal". by Abseil Team <absl-team@google.com> GitOrigin-RevId: 20f4e7133d695e9a05e13ebdfd4d78da310b42b5 Change-Id: Id8c18ebd331d096935052a6ab259ebe0e2ef13ae
Diffstat (limited to 'absl/strings/internal')
-rw-r--r--absl/strings/internal/str_join_internal.h57
1 files changed, 26 insertions, 31 deletions
diff --git a/absl/strings/internal/str_join_internal.h b/absl/strings/internal/str_join_internal.h
index e73f1dde..c5fdc287 100644
--- a/absl/strings/internal/str_join_internal.h
+++ b/absl/strings/internal/str_join_internal.h
@@ -31,13 +31,15 @@
#ifndef ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
#define ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
-#include <cassert>
+#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 {
@@ -202,28 +204,9 @@ std::string JoinAlgorithm(Iterator start, Iterator end, absl::string_view s,
return result;
}
-// No-op placeholder for input iterators which can not be iterated over.
-template <typename Iterator>
-size_t GetResultSize(Iterator, Iterator, size_t, std::input_iterator_tag) {
- return 0;
-}
-
-// Calculates space to reserve, if the iterator supports multiple passes.
-template <typename Iterator>
-size_t GetResultSize(Iterator it, Iterator end, size_t separator_size,
- std::forward_iterator_tag) {
- assert(it != end);
- size_t length = it->size();
- while (++it != end) {
- length += separator_size;
- length += it->size();
- }
- return length;
-}
-
-// A joining algorithm that's optimized for an iterator range of std::string-like
-// objects that do not need any additional formatting. This is to optimize the
-// common case of joining, say, a std::vector<std::string> or a
+// A joining algorithm that's optimized for a forward iterator range of
+// std::string-like objects that do not need any additional formatting. This is to
+// optimize the common case of joining, say, a std::vector<std::string> or a
// std::vector<absl::string_view>.
//
// This is an overload of the previous JoinAlgorithm() function. Here the
@@ -236,20 +219,32 @@ size_t GetResultSize(Iterator it, Iterator end, size_t separator_size,
// std::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 std::string.
-template <typename Iterator>
+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) {
- typename std::iterator_traits<Iterator>::iterator_category iterator_tag;
- result.reserve(GetResultSize(start, end, s.size(), iterator_tag));
+ // Sums size
+ size_t result_size = start->size();
+ for (Iterator it = start; ++it != end;) {
+ result_size += s.size();
+ result_size += it->size();
+ }
+
+ STLStringResizeUninitialized(&result, result_size);
// Joins strings
- absl::string_view sep("", 0);
- for (Iterator it = start; it != end; ++it) {
- result.append(sep.data(), sep.size());
- result.append(it->data(), it->size());
- sep = s;
+ char* result_buf = &*result.begin();
+ memcpy(result_buf, start->data(), start->size());
+ result_buf += start->size();
+ for (Iterator it = start; ++it != end;) {
+ memcpy(result_buf, s.data(), s.size());
+ result_buf += s.size();
+ memcpy(result_buf, it->data(), it->size());
+ result_buf += it->size();
}
}