Merge "Generalize Join to work for any container/element." (0211d360) · Commits · e / os / android_system_core

base/include/base/strings.h

+19 −3

Original line number	Diff line number	Diff line
		@@ -17,6 +17,7 @@
		#ifndef BASE_STRINGS_H
		#define BASE_STRINGS_H

		#include <sstream>
		#include <string>
		#include <vector>

		@@ -34,9 +35,24 @@ std::vector<std::string> Split(const std::string& s,
		// Trims whitespace off both ends of the given string.
		std::string Trim(const std::string& s);

		// Joins a vector of strings into a single string, using the given separator.
		template <typename StringT>
		std::string Join(const std::vector<StringT>& strings, char separator);
		// Joins a container of things into a single string, using the given separator.
		template <typename ContainerT>
		std::string Join(const ContainerT& things, char separator) {
		if (things.empty()) {
		return "";
		}

		std::ostringstream result;
		result << *things.begin();
		for (auto it = std::next(things.begin()); it != things.end(); ++it) {
		result << separator << *it;
		}
		return result.str();
		}

		// We instantiate the common cases in strings.cpp.
		extern template std::string Join(const std::vector<std::string>&, char);
		extern template std::string Join(const std::vector<const char*>&, char);

		// Tests whether 's' starts with 'prefix'.
		bool StartsWith(const std::string& s, const char* prefix);

+4 −19

Original line number	Diff line number	Diff line
		@@ -79,25 +79,10 @@ std::string Trim(const std::string& s) {
		return s.substr(start_index, end_index - start_index + 1);
		}

		template <typename StringT>
		std::string Join(const std::vector<StringT>& strings, char separator) {
		if (strings.empty()) {
		return "";
		}

		std::string result(strings[0]);
		for (size_t i = 1; i < strings.size(); ++i) {
		result += separator;
		result += strings[i];
		}
		return result;
		}

		// Explicit instantiations.
		template std::string Join<std::string>(const std::vector<std::string>& strings,
		char separator);
		template std::string Join<const char>(const std::vector<const char>& strings,
		char separator);
		// These cases are probably the norm, so we mark them extern in the header to
		// aid compile time and binary size.
		template std::string Join(const std::vector<std::string>&, char);
		template std::string Join(const std::vector<const char*>&, char);

		bool StartsWith(const std::string& s, const char* prefix) {
		return s.compare(0, strlen(prefix), prefix) == 0;

+13 −0

Original line number	Diff line number	Diff line
		@@ -20,6 +20,8 @@

		#include <string>
		#include <vector>
		#include <set>
		#include <unordered_set>

		TEST(strings, split_empty) {
		std::vector<std::string> parts = android::base::Split("", ",");
		@@ -121,6 +123,17 @@ TEST(strings, join_separator_in_vector) {
		ASSERT_EQ(",,,", android::base::Join(list, ','));
		}

		TEST(strings, join_simple_ints) {
		std::set<int> list = {1, 2, 3};
		ASSERT_EQ("1,2,3", android::base::Join(list, ','));
		}

		TEST(strings, join_unordered_set) {
		std::unordered_set<int> list = {1, 2};
		ASSERT_TRUE("1,2" == android::base::Join(list, ',') \|\|
		"2,1" == android::base::Join(list, ','));
		}

		TEST(strings, startswith_empty) {
		ASSERT_FALSE(android::base::StartsWith("", "foo"));
		ASSERT_TRUE(android::base::StartsWith("", ""));