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Siva Chandra Reddy
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[libc] Add a standalone flavor of an equivalent of std::string_view.
This class is to serve as a replacement for llvm::StringRef as part of the plans to limit dependency on other parts of LLVM. One use of llvm::StringRef in MPFRWrapper has been replaced with the new class. Reviewed By: lntue Differential Revision: https://reviews.llvm.org/D97330
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6 files changed

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‎libc/test/utils/CPP/CMakeLists.txt

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@@ -9,3 +9,13 @@ add_libc_unittest(
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DEPENDS
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libc.utils.CPP.standalone_cpp
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)
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add_libc_unittest(
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stringview_test
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SUITE
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libc_cpp_utils_unittests
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SRCS
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stringview_test.cpp
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DEPENDS
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libc.utils.CPP.standalone_cpp
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)

‎libc/test/utils/CPP/stringview_test.cpp

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//===-- Unittests for StringView ------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "utils/CPP/StringView.h"
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#include "utils/UnitTest/Test.h"
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TEST(LlvmLibcStringViewTest, InitializeCheck) {
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__llvm_libc::cpp::StringView v;
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ASSERT_EQ(v.size(), size_t(0));
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ASSERT_TRUE(v.data() == nullptr);
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v = __llvm_libc::cpp::StringView("");
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ASSERT_EQ(v.size(), size_t(0));
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ASSERT_TRUE(v.data() == nullptr);
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v = __llvm_libc::cpp::StringView(nullptr);
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ASSERT_EQ(v.size(), size_t(0));
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ASSERT_TRUE(v.data() == nullptr);
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v = __llvm_libc::cpp::StringView(nullptr, 10);
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ASSERT_EQ(v.size(), size_t(0));
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ASSERT_TRUE(v.data() == nullptr);
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v = __llvm_libc::cpp::StringView("abc", 0);
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ASSERT_EQ(v.size(), size_t(0));
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ASSERT_TRUE(v.data() == nullptr);
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v = __llvm_libc::cpp::StringView("123456789");
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ASSERT_EQ(v.size(), size_t(9));
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}
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TEST(LlvmLibcStringViewTest, Equals) {
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__llvm_libc::cpp::StringView v("abc");
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ASSERT_TRUE(v.equals(__llvm_libc::cpp::StringView("abc")));
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ASSERT_FALSE(v.equals(__llvm_libc::cpp::StringView()));
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ASSERT_FALSE(v.equals(__llvm_libc::cpp::StringView("")));
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ASSERT_FALSE(v.equals(__llvm_libc::cpp::StringView("123")));
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ASSERT_FALSE(v.equals(__llvm_libc::cpp::StringView("abd")));
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ASSERT_FALSE(v.equals(__llvm_libc::cpp::StringView("aaa")));
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ASSERT_FALSE(v.equals(__llvm_libc::cpp::StringView("abcde")));
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}
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TEST(LlvmLibcStringViewTest, RemovePrefix) {
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__llvm_libc::cpp::StringView v("123456789");
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auto p = v.remove_prefix(0);
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ASSERT_EQ(p.size(), size_t(9));
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ASSERT_TRUE(p.equals(__llvm_libc::cpp::StringView("123456789")));
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p = v.remove_prefix(4);
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ASSERT_EQ(p.size(), size_t(5));
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ASSERT_TRUE(p.equals(__llvm_libc::cpp::StringView("56789")));
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p = v.remove_prefix(9);
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ASSERT_EQ(p.size(), size_t(0));
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ASSERT_TRUE(p.data() == nullptr);
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p = v.remove_prefix(10);
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ASSERT_EQ(p.size(), size_t(0));
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ASSERT_TRUE(p.data() == nullptr);
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}
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TEST(LlvmLibcStringViewTest, RemoveSuffix) {
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__llvm_libc::cpp::StringView v("123456789");
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auto p = v.remove_suffix(0);
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ASSERT_EQ(p.size(), size_t(9));
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ASSERT_TRUE(p.equals(__llvm_libc::cpp::StringView("123456789")));
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p = v.remove_suffix(4);
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ASSERT_EQ(p.size(), size_t(5));
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ASSERT_TRUE(p.equals(__llvm_libc::cpp::StringView("12345")));
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p = v.remove_suffix(9);
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ASSERT_EQ(p.size(), size_t(0));
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ASSERT_TRUE(p.data() == nullptr);
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p = v.remove_suffix(10);
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ASSERT_EQ(p.size(), size_t(0));
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ASSERT_TRUE(p.data() == nullptr);
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}
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TEST(LlvmLibcStringViewTest, TrimSingleChar) {
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__llvm_libc::cpp::StringView v(" 123456789 ");
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auto t = v.trim(' ');
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ASSERT_EQ(t.size(), size_t(9));
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ASSERT_TRUE(t.equals(__llvm_libc::cpp::StringView("123456789")));
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v = __llvm_libc::cpp::StringView("====12345==");
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t = v.trim(' ');
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ASSERT_EQ(v.size(), size_t(11));
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ASSERT_TRUE(t.equals(__llvm_libc::cpp::StringView("====12345==")));
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t = v.trim('=');
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ASSERT_EQ(t.size(), size_t(5));
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ASSERT_TRUE(t.equals(__llvm_libc::cpp::StringView("12345")));
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v = __llvm_libc::cpp::StringView("12345===");
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t = v.trim('=');
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ASSERT_EQ(t.size(), size_t(5));
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ASSERT_TRUE(t.equals(__llvm_libc::cpp::StringView("12345")));
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v = __llvm_libc::cpp::StringView("===========12345");
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t = v.trim('=');
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ASSERT_EQ(t.size(), size_t(5));
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ASSERT_TRUE(t.equals(__llvm_libc::cpp::StringView("12345")));
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v = __llvm_libc::cpp::StringView("============");
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t = v.trim('=');
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ASSERT_EQ(t.size(), size_t(0));
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ASSERT_TRUE(t.data() == nullptr);
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v = __llvm_libc::cpp::StringView();
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t = v.trim(' ');
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ASSERT_EQ(t.size(), size_t(0));
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ASSERT_TRUE(t.data() == nullptr);
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v = __llvm_libc::cpp::StringView("");
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t = v.trim(' ');
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ASSERT_EQ(t.size(), size_t(0));
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ASSERT_TRUE(t.data() == nullptr);
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}

‎libc/utils/CPP/CMakeLists.txt

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@@ -5,5 +5,6 @@ add_header_library(
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ArrayRef.h
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Bitset.h
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Functional.h
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StringView.h
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TypeTraits.h
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)

‎libc/utils/CPP/StringView.h

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//===-- Standalone implementation std::string_view --------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_UTILS_CPP_STRINGVIEW_H
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#define LLVM_LIBC_UTILS_CPP_STRINGVIEW_H
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#include <stddef.h>
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namespace __llvm_libc {
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namespace cpp {
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// This is very simple alternate of the std::string_view class. There is no
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// bounds check performed in any of the methods. The callers are expected to
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// do the checks before invoking the methods.
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//
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// This class will be extended as needed in future.
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class StringView {
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private:
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const char *Data;
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size_t Len;
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public:
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StringView() : Data(nullptr), Len(0) {}
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// Assumes Str is a null-terminated string. The length of the string does
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// not include the terminating null character.
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explicit StringView(const char *Str) : Data(Str), Len(0) {
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if (Str == nullptr)
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return;
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for (const char *D = Data; *D != '\0'; ++D, ++Len)
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;
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if (Len == 0)
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Data = nullptr;
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}
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explicit StringView(const char *Str, size_t N)
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: Data(N ? Str : nullptr), Len(Str == nullptr ? 0 : N) {}
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const char *data() const { return Data; }
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size_t size() { return Len; }
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StringView remove_prefix(size_t N) const {
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if (N >= Len)
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return StringView();
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return StringView(Data + N, Len - N);
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}
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StringView remove_suffix(size_t N) const {
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if (N >= Len)
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return StringView();
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return StringView(Data, Len - N);
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}
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// An equivalent method is not available in std::string_view.
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StringView trim(char C) const {
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if (Len == 0)
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return StringView();
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const char *NewStart = Data;
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size_t PrefixLen = 0;
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for (; PrefixLen < Len; ++NewStart, ++PrefixLen) {
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if (*NewStart != C)
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break;
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}
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size_t SuffixLen = 0;
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const char *NewEnd = Data + Len - 1;
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for (; SuffixLen < Len; --NewEnd, ++SuffixLen) {
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if (*NewEnd != C)
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break;
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}
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return remove_prefix(PrefixLen).remove_suffix(SuffixLen);
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}
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// An equivalent method is not available in std::string_view.
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bool equals(StringView Other) const {
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if (Len != Other.Len)
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return false;
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for (size_t I = 0; I < Len; ++I) {
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if (Data[I] != Other.Data[I])
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return false;
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}
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return true;
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}
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};
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} // namespace cpp
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} // namespace __llvm_libc
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#endif // LLVM_LIBC_UTILS_CPP_STRINGVIEW_H

‎libc/utils/MPFRWrapper/CMakeLists.txt

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@@ -12,8 +12,8 @@ if(LIBC_TESTS_CAN_USE_MPFR)
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MPFRUtils.cpp
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MPFRUtils.h
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)
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add_dependencies(libcMPFRWrapper libc.utils.CPP.standalone_cpp libc.utils.FPUtil.fputil LibcUnitTest LLVMSupport)
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target_link_libraries(libcMPFRWrapper -lmpfr -lgmp LibcFPTestHelpers LibcUnitTest LLVMSupport)
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add_dependencies(libcMPFRWrapper libc.utils.CPP.standalone_cpp libc.utils.FPUtil.fputil LibcUnitTest)
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target_link_libraries(libcMPFRWrapper -lmpfr -lgmp LibcFPTestHelpers LibcUnitTest)
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else()
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message(WARNING "Math tests using MPFR will be skipped.")
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endif()

‎libc/utils/MPFRWrapper/MPFRUtils.cpp

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@@ -8,11 +8,10 @@
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#include "MPFRUtils.h"
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#include "utils/CPP/StringView.h"
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#include "utils/FPUtil/FPBits.h"
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#include "utils/FPUtil/TestHelpers.h"
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#include "llvm/ADT/StringRef.h"
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#include <memory>
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#include <stdint.h>
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#include <string>
@@ -226,9 +225,9 @@ class MPFRNumber {
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constexpr size_t printBufSize = 200;
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char buffer[printBufSize];
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mpfr_snprintf(buffer, printBufSize, "%100.50Rf", value);
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llvm::StringRef ref(buffer);
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ref = ref.trim();
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return ref.str();
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cpp::StringView view(buffer);
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view = view.trim(' ');
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return std::string(view.data());
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}
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// These functions are useful for debugging.

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