[libc] [llvm] [libc] Change ctype to be encoding independent (PR #110574)

[Nick Desaulniers via llvm-commits]

================
@@ -6,18 +6,46 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "src/__support/CPP/span.h"
 #include "src/ctype/isalnum.h"
 
 #include "test/UnitTest/Test.h"
 
+TEST(LlvmLibcIsAlNum, SimpleTest) {
+  EXPECT_NE(LIBC_NAMESPACE::isalnum('a'), 0);
+  EXPECT_NE(LIBC_NAMESPACE::isalnum('B'), 0);
+  EXPECT_NE(LIBC_NAMESPACE::isalnum('3'), 0);
+
+  EXPECT_EQ(LIBC_NAMESPACE::isalnum(' '), 0);
+  EXPECT_EQ(LIBC_NAMESPACE::isalnum('?'), 0);
+  EXPECT_EQ(LIBC_NAMESPACE::isalnum('\0'), 0);
+  EXPECT_EQ(LIBC_NAMESPACE::isalnum(-1), 0);
+}
+
+// TODO: Merge the ctype tests using this framework.
+constexpr char ALNUM_ARRAY[] = {
+    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
+    'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
+    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
+    'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+};
+
+bool in_span(int ch, LIBC_NAMESPACE::cpp::span<const char> arr) {
+  for (size_t i = 0; i < arr.size(); ++i) {
+    if (static_cast<int>(arr[i]) == ch)
+      return true;
+  }
----------------
nickdesaulniers wrote:

```suggestion
  for (size_t i = 0; i < arr.size(); ++i)
    if (static_cast<int>(arr[i]) == ch)
      return true;
```

Here and the 7 other `is*_test.cpp` files below.

https://github.com/llvm/llvm-project/pull/110574