[libc] add wcsstr

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.wcsstr
     libc.src.wchar.wcspbrk
     libc.src.wchar.wcsrchr
     libc.src.wchar.wcschr

libc/config/linux/aarch64/entrypoints.txt

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

libc/config/linux/riscv/entrypoints.txt

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

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.wcsstr
     libc.src.wchar.wcspbrk
     libc.src.wchar.wcsrchr
     libc.src.wchar.wcschr

libc/hdrgen/yaml/wchar.yaml

@@ -49,3 +49,10 @@ functions:
     arguments:
       - type: const wchar_t *
       - type: const wchar_t *
+  - name: wcsstr
+    standards:
+      - stdc
+    return_type: const wchar_t *
+    arguments:
+      - type: const wchar_t *
+      - type: const wchar_t *

libc/src/wchar/CMakeLists.txt

@@ -80,3 +80,14 @@ add_entrypoint_object(
     .wcslen
     libc.hdr.types.wchar_t
 )
+
+add_entrypoint_object(
+  wcsstr
+  SRCS
+    wcsstr.cpp
+  HDRS
+    wcsstr.h
+  DEPENDS
+    .wcslen
+    libc.hdr.types.wchar_t
+)

libc/src/wchar/wcsstr.cpp

@@ -0,0 +1,44 @@
+//===-- Implementation of wcsstr ------------------------------------------===//
+//
+// 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/wcsstr.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 *, wcsstr,
+                   (const wchar_t *s, const wchar_t *needle)) {
+  size_t s_len = wcslen(s);
+  size_t needle_len = wcslen(needle);
+
+  if (needle_len > s_len)
+    return nullptr;
+
+  for (size_t i = 0; i < s_len; i++) {
+    size_t end = needle_len + i;
+    if (end > s_len)
+      break;
+
+    bool found = true;
+    for (size_t x = 0; x < needle_len; x++) {
+      if (s[i + x] != needle[x]) {
+        found = false;
+        break;
+      }
+    }
+
+    if (!found)
+      continue;
+    return &s[i];
+  }
+  return nullptr;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/wchar/wcsstr.h

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