[libc][wchar] implement wcslen

Add internal helper, which may be reusable when implementing wmemchr, wcspbrk,
wcsrchr, wcsstr.

Link: #121183
Link: #124027

Co-authored-by: Nick Desaulniers <[email protected]>

Author: RossComputerGuy

libc/config/gpu/amdgpu/entrypoints.txt

@@ -261,6 +261,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.time.nanosleep
 
     # wchar.h entrypoints
+    libc.src.wchar.wcslen
     libc.src.wchar.wctob
 
     # locale.h entrypoints

libc/config/gpu/nvptx/entrypoints.txt

@@ -261,6 +261,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.time.nanosleep
 
     # wchar.h entrypoints
+    libc.src.wchar.wcslen
     libc.src.wchar.wctob
 
     # locale.h entrypoints

libc/config/linux/aarch64/entrypoints.txt

@@ -350,6 +350,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.write
 
     # wchar.h entrypoints
+    libc.src.wchar.wcslen
     libc.src.wchar.wctob
 
     # sys/uio.h entrypoints

libc/config/linux/riscv/entrypoints.txt

@@ -346,6 +346,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.write
 
     # wchar.h entrypoints
+    libc.src.wchar.wcslen
     libc.src.wchar.wctob
 )
 

libc/config/linux/x86_64/entrypoints.txt

@@ -349,8 +349,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.write
 
     # wchar.h entrypoints
-    libc.src.wchar.wctob
     libc.src.wchar.btowc
+    libc.src.wchar.wcslen
+    libc.src.wchar.wctob
 
     # sys/uio.h entrypoints
     libc.src.sys.uio.writev

libc/include/wchar.yaml

@@ -9,6 +9,12 @@ types:
 enums: []
 objects: []
 functions:
+  - name: wcslen
+    standards:
+      - stdc
+    return_type: size_t
+    arguments:
+      - type: const wchar_t *
   - name: wctob
     standards:
       - stdc

libc/src/wchar/CMakeLists.txt

@@ -1,3 +1,20 @@
+add_header_library(
+  wide_string_utils
+  HDRS
+    wide_string_utils.h
+)
+
+add_entrypoint_object(
+  wcslen
+  SRCS
+    wcslen.cpp
+  HDRS
+    wcslen.h
+  DEPENDS
+    .wide_string_utils
+    libc.hdr.types.size_t
+    libc.hdr.types.wchar_t
+)
 
 add_entrypoint_object(
   wctob

libc/src/wchar/wcslen.cpp

@@ -0,0 +1,23 @@
+//===-- Implementation of wcslen ------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/wchar/wcslen.h"
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/wchar/wide_string_utils.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(size_t, wcslen, (const wchar_t *src)) {
+  return internal::wide_string_length(src);
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wcslen.h

@@ -0,0 +1,22 @@
+//===-- Implementation header for wcslen ----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_WCHAR_WCSLEN_H
+#define LLVM_LIBC_SRC_WCHAR_WCSLEN_H
+
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+size_t wcslen (const wchar_t *src);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSLEN_H

libc/src/wchar/wide_string_utils.h

@@ -0,0 +1,29 @@
+//===-- Wide String utils -------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_WCHAR_WIDE_STRING_UTILS_H
+#define LLVM_LIBC_SRC_WCHAR_WIDE_STRING_UTILS_H
+
+#include "src/__support/macros/config.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/wchar_t.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+LIBC_INLINE size_t wide_string_length(const wchar_t *src) {
+  const wchar_t *cpy = src;
+  while (*cpy)
+    ++cpy;
+  return cpy - src;
+}
+
+} // namespace internal
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif //  LLVM_LIBC_SRC_WCHAR_WIDE_STRING_UTILS_H