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[libc] Fix API for remove_{prefix, suffix} 

The API in StringView.h for remove_prefix was incorrect and was returning a
new StringView rather than just altering the view.

As part of this, also removed some of the safety features.  The comment
correctly noted that the behaviour is undefined in some cases,
but the code and test cases checked for that.

One caller was relying on the old behaviour, so fixed it and added some
comments.

Tested:
check-libc
llvmlibc
libc-loader-tests

Reviewed By: gchatelet

Differential Revision: https://reviews.llvm.org/D129950
This commit is contained in:
Jeff Bailey 2022-07-17 02:41:55 +00:00
parent 313f8a20fd
commit 8aad330eeb
3 changed files with 30 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
libc/src/__support/CPP/StringView.h
View File

@ -107,19 +107,14 @@ public:
// Moves the start of the view forward by n characters.
// The behavior is undefined if n > size().
StringView remove_prefix(size_t N) const {
if (N >= Len)
return StringView();
return StringView(Data + N, Len - N);
void remove_prefix(size_t N) {
Len -= N;
Data += N;
}
// Moves the end of the view back by n characters.
// The behavior is undefined if n > size().
StringView remove_suffix(size_t N) const {
if (N >= Len)
return StringView();
return StringView(Data, Len - N);
}
void remove_suffix(size_t N) { Len -= N; }
// An equivalent method is not available in std::string_view.
StringView trim(const char C) const {

6
libc/src/stdlib/getenv.cpp
View File

@ -32,8 +32,10 @@ LLVM_LIBC_FUNCTION(char *, getenv, (const char *name)) {
if (cur[env_var_name.size()] != '=')
continue;
return const_cast<char *>(
cur.remove_prefix(env_var_name.size() + 1).data());
// Remove the name and the equals sign.
cur.remove_prefix(env_var_name.size() + 1);
// We know that data is null terminated, so this is safe.
return const_cast<char *>(cur.data());
}
return nullptr;

52
libc/test/src/__support/CPP/stringview_test.cpp
View File

@ -78,43 +78,35 @@ TEST(LlvmLibcStringViewTest, endsWith) {
}
TEST(LlvmLibcStringViewTest, RemovePrefix) {
StringView v("123456789");
StringView a("123456789");
a.remove_prefix(0);
ASSERT_EQ(a.size(), size_t(9));
ASSERT_TRUE(a.equals(StringView("123456789")));
auto p = v.remove_prefix(0);
ASSERT_EQ(p.size(), size_t(9));
ASSERT_TRUE(p.equals(StringView("123456789")));
StringView b("123456789");
b.remove_prefix(4);
ASSERT_EQ(b.size(), size_t(5));
ASSERT_TRUE(b.equals(StringView("56789")));
p = v.remove_prefix(4);
ASSERT_EQ(p.size(), size_t(5));
ASSERT_TRUE(p.equals(StringView("56789")));
p = v.remove_prefix(9);
ASSERT_EQ(p.size(), size_t(0));
ASSERT_TRUE(p.data() == nullptr);
p = v.remove_prefix(10);
ASSERT_EQ(p.size(), size_t(0));
ASSERT_TRUE(p.data() == nullptr);
StringView c("123456789");
c.remove_prefix(9);
ASSERT_EQ(c.size(), size_t(0));
}
TEST(LlvmLibcStringViewTest, RemoveSuffix) {
StringView v("123456789");
StringView a("123456789");
a.remove_suffix(0);
ASSERT_EQ(a.size(), size_t(9));
ASSERT_TRUE(a.equals(StringView("123456789")));
auto p = v.remove_suffix(0);
ASSERT_EQ(p.size(), size_t(9));
ASSERT_TRUE(p.equals(StringView("123456789")));
StringView b("123456789");
b.remove_suffix(4);
ASSERT_EQ(b.size(), size_t(5));
ASSERT_TRUE(b.equals(StringView("12345")));
p = v.remove_suffix(4);
ASSERT_EQ(p.size(), size_t(5));
ASSERT_TRUE(p.equals(StringView("12345")));
p = v.remove_suffix(9);
ASSERT_EQ(p.size(), size_t(0));
ASSERT_TRUE(p.data() == nullptr);
p = v.remove_suffix(10);
ASSERT_EQ(p.size(), size_t(0));
ASSERT_TRUE(p.data() == nullptr);
StringView c("123456789");
c.remove_suffix(9);
ASSERT_EQ(c.size(), size_t(0));
}
TEST(LlvmLibcStringViewTest, TrimSingleChar) {