[libc] add wcsrchr

Author: RossComputerGuy

libc/config/gpu/entrypoints.txt

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

libc/config/linux/aarch64/entrypoints.txt

@@ -349,6 +349,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.write
 
     # wchar.h entrypoints
+    libc.src.wchar.wcsrchr
     libc.src.wchar.wcschr
     libc.src.wchar.wcslen
     libc.src.wchar.wmemchr

libc/config/linux/riscv/entrypoints.txt

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

libc/config/linux/x86_64/entrypoints.txt

@@ -348,6 +348,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.write
 
     # wchar.h entrypoints
+    libc.src.wchar.wcsrchr
     libc.src.wchar.wcschr
     libc.src.wchar.wcslen
     libc.src.wchar.wmemchr

libc/hdrgen/yaml/wchar.yaml

@@ -35,3 +35,10 @@ functions:
     arguments:
       - type: const wchar_t *
       - type: wchar_t
+  - name: wcsrchr
+    standards:
+      - stdc
+    return_type: const wchar_t *
+    arguments:
+      - type: const wchar_t *
+      - type: wchar_t

libc/src/wchar/CMakeLists.txt

@@ -58,3 +58,14 @@ add_entrypoint_object(
     .wmemchr
     libc.hdr.types.wchar_t
 )
+
+add_entrypoint_object(
+  wcsrchr
+  SRCS
+    wcsrchr.cpp
+  HDRS
+    wcsrchr.h
+  DEPENDS
+    .wcslen
+    libc.hdr.types.wchar_t
+)

libc/src/wchar/wcsrchr.cpp

@@ -0,0 +1,26 @@
+//===-- Implementation of wcsrchr
+//------------------------------------------===//
+//
+// 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/wcsrchr.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "wcslen.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(const wchar_t *, wcsrchr, (const wchar_t *s, wchar_t c)) {
+  size_t length = wcslen(s);
+  for (size_t i = 0; i < length; i++) {
+    if (s[length - i] == c)
+      return &s[length - i];
+  }
+  return nullptr;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wcsrchr.h

@@ -0,0 +1,21 @@
+//===-- Implementation header for wcsrchr -----------------------*- C++ -*-===//
+//
+// 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_WCSRCHR_H
+#define LLVM_LIBC_SRC_WCHAR_WCSRCHR_H
+
+#include "hdr/types/wchar_t.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+const wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_WCHAR_WCSRCHR_H