Revert "[libc] utf8 to 32 CharacterConverter" (#144446)

Reverts llvm/llvm-project#143973
This merge broke the build and I'm currently looking into the issue to
fix it.

Author: sribee8

libc/src/__support/wchar/character_converter.cpp

@@ -8,7 +8,6 @@
 
 #include "hdr/types/char32_t.h"
 #include "hdr/types/char8_t.h"
-#include "src/__support/CPP/bit.h"
 #include "src/__support/common.h"
 #include "src/__support/error_or.h"
 #include "src/__support/math_extras.h"
@@ -31,49 +30,6 @@ bool CharacterConverter::isComplete() {
   return state->bytes_processed == state->total_bytes;
 }
 
-int CharacterConverter::push(char8_t utf8_byte) {
-  uint8_t num_ones = static_cast<uint8_t>(cpp::countl_one(utf8_byte));
-  // Checking the first byte if first push
-  if (state->bytes_processed == 0) {
-    // UTF-8 char has 1 byte total
-    if (num_ones == 0) {
-      state->total_bytes = 1;
-    }
-    // UTF-8 char has 2 through 4 bytes total
-    else if (num_ones >= 2 && num_ones <= 4) {
-      /* Since the format is 110xxxxx, 1110xxxx, and 11110xxx for 2, 3, and 4,
-      we will make the base mask with 7 ones and right shift it as necessary. */
-      constexpr size_t SIGNIFICANT_BITS = 7;
-      uint32_t base_mask = mask_trailing_ones<uint32_t, SIGNIFICANT_BITS>();
-      state->total_bytes = num_ones;
-      utf8_byte &= (base_mask >> num_ones);
-    }
-    // Invalid first byte
-    else {
-      // bytes_processed and total_bytes will always be 0 here
-      state->partial = static_cast<char32_t>(0);
-      return -1;
-    }
-    state->partial = static_cast<char32_t>(utf8_byte);
-    state->bytes_processed++;
-    return 0;
-  }
-  // Any subsequent push
-  // Adding 6 more bits so need to left shift
-  constexpr size_t ENCODED_BITS_PER_UTF8 = 6;
-  if (num_ones == 1 && !isComplete()) {
-    char32_t byte =
-        utf8_byte & mask_trailing_ones<uint32_t, ENCODED_BITS_PER_UTF8>();
-    state->partial = state->partial << ENCODED_BITS_PER_UTF8;
-    state->partial |= byte;
-    state->bytes_processed++;
-    return 0;
-  }
-  // Invalid byte -> reset the state
-  clear();
-  return -1;
-}
-
 int CharacterConverter::push(char32_t utf32) {
   // we can't be partially through a conversion when pushing a utf32 value
   if (!isComplete())
@@ -98,17 +54,6 @@ int CharacterConverter::push(char32_t utf32) {
   return -1;
 }
 
-ErrorOr<char32_t> CharacterConverter::pop_utf32() {
-  // If pop is called too early, do not reset the state, use error to determine
-  // whether enough bytes have been pushed
-  if (!isComplete() || state->bytes_processed == 0)
-    return Error(-1);
-  char32_t utf32 = state->partial;
-  // reset if successful pop
-  clear();
-  return utf32;
-}
-
 ErrorOr<char8_t> CharacterConverter::pop_utf8() {
   if (isComplete())
     return Error(-1);

libc/test/src/__support/CMakeLists.txt

@@ -275,8 +275,9 @@ add_subdirectory(fixed_point)
 add_subdirectory(HashTable)
 add_subdirectory(time)
 add_subdirectory(threads)
-# Requires access to uchar header which is not on MacOS
-# Cannot currently build this on MacOS in overlay mode
+
+# Requires access to uchar header which is not on macos
+# Therefore, cannot currently build this on macos in overlay mode
 if(NOT(LIBC_TARGET_OS_IS_DARWIN))
   add_subdirectory(wchar)
 endif()

libc/test/src/__support/wchar/CMakeLists.txt

@@ -1,15 +1,5 @@
 add_custom_target(libc-support-wchar-tests)
 
-add_libc_test(
-  utf8_to_32_test 
-  SUITE
-    libc-support-tests
-  SRCS
-    utf8_to_32_test.cpp 
-  DEPENDS
-    libc.src.__support.wchar.character_converter
-)
-
 add_libc_test(
   utf32_to_8_test
   SUITE