[libc][search] implement posix lfind function

libc/config/baremetal/arm/entrypoints.txt

@@ -26,6 +26,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # errno.h entrypoints
     libc.src.errno.errno
 
+	# search.h entrypoints
+	libc.src.search.lfind
+
     # setjmp.h entrypoints
     libc.src.setjmp.longjmp
     libc.src.setjmp.setjmp

libc/config/baremetal/riscv/entrypoints.txt

@@ -26,6 +26,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # errno.h entrypoints
     libc.src.errno.errno
 
+	# search.h entrypoints
+	libc.src.search.lfind
+
     # string.h entrypoints
     libc.src.string.bcmp
     libc.src.string.bcopy

libc/config/darwin/arm/entrypoints.txt

@@ -20,6 +20,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # errno.h entrypoints
     libc.src.errno.errno
 
+	# search.h entrypoints
+	libc.src.search.lfind    
+
     # string.h entrypoints
     libc.src.string.bcmp
     libc.src.string.bcopy

libc/config/darwin/x86_64/entrypoints.txt

@@ -17,6 +17,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.tolower
     libc.src.ctype.toupper
 
+	# search.h entrypoints
+	libc.src.search.lfind    
+
     # string.h entrypoints
     libc.src.string.bcmp
     libc.src.string.bzero

libc/config/linux/aarch64/entrypoints.txt

@@ -942,6 +942,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.search.hsearch
     libc.src.search.hsearch_r
     libc.src.search.insque
+    libc.src.search.lfind
     libc.src.search.remque
 
     # threads.h entrypoints

libc/config/linux/arm/entrypoints.txt

@@ -20,6 +20,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # errno.h entrypoints
     libc.src.errno.errno
 
+	# search.h entrypoints
+	libc.src.search.lfind    
+
     # string.h entrypoints
     libc.src.string.bcmp
     libc.src.string.bcopy

libc/config/linux/riscv/entrypoints.txt

@@ -872,6 +872,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.search.hsearch
     libc.src.search.hsearch_r
     libc.src.search.insque
+    libc.src.search.lfind
     libc.src.search.remque
 
     # threads.h entrypoints

libc/config/linux/x86_64/entrypoints.txt

@@ -1005,6 +1005,7 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.search.hsearch
     libc.src.search.hsearch_r
     libc.src.search.insque
+    libc.src.search.lfind
     libc.src.search.remque
 
     # threads.h entrypoints

libc/config/windows/entrypoints.txt

@@ -17,6 +17,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.ctype.tolower
     libc.src.ctype.toupper
 
+	# search.h entrypoints
+	libc.src.search.lfind
+
     # string.h entrypoints
     libc.src.string.bcmp
     libc.src.string.bcopy

libc/docs/libc_search.rst

@@ -42,7 +42,7 @@ hcreate                      |check|
 hdestroy                     |check|
 hsearch                      |check|
 insque                       |check|
-lfind
+lfind                        |check|
 lsearch
 remque                       |check|
 tdelete

libc/newhdrgen/yaml/search.yaml

@@ -57,3 +57,13 @@ functions:
     return_type: void
     arguments:
       - type: void *
+  - name: lfind
+    standards:
+      - POSIX
+    return_type: void *
+    arguments:
+      - type: void *
+      - type: void *
+      - type: size_t *
+      - type: size_t
+      - type: int(*compar)(const void *, const void *)

libc/spec/posix.td

@@ -1618,6 +1618,17 @@ def POSIX : StandardSpec<"POSIX"> {
                 ArgSpec<VoidPtr>
             ]
         >,
+        FunctionSpec<
+            "lfind",
+            RetValSpec<VoidPtr>,
+            [
+                ArgSpec<VoidPtr>,
+                ArgSpec<VoidPtr>,
+                ArgSpec<SizeTPtr>,
+                ArgSpec<SizeTType>,
+                // TODO: Unsure how to specify int(*compar)(void *, void *)
+            ]
+        >
     ]
   >;
 

libc/src/search/CMakeLists.txt

@@ -98,3 +98,14 @@ add_entrypoint_object(
     libc.include.search
     libc.src.__support.intrusive_list
 )
+
+add_entrypoint_object(
+  lfind
+  SRCS
+    lfind.cpp
+  HDRS
+    lfind.h
+  DEPENDS
+    libc.include.search
+    libc.src.__support.CPP.cstddef
+)

libc/src/search/lfind.cpp

@@ -0,0 +1,29 @@
+//===-- Implementation of lfind   -------------------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/search/lfind.h"
+#include "src/__support/CPP/cstddef.h" // cpp::byte
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+LLVM_LIBC_FUNCTION(void *, lfind,
+                   (void *key, void *base, size_t *nmemb, size_t size,
+                    int (*compar)(void *, void *))) {
+  cpp::byte *next = reinterpret_cast<cpp::byte *>(base);
+  cpp::byte *end = next + (*nmemb * size);
+  while (next < end) {
+    if (compar(key, next) == 0) {
+      return next;
+    }
+    next += size;
+  }
+  return nullptr;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/search/lfind.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for lfind -------------------------*- 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_SEARCH_LFIND_H
+#define LLVM_LIBC_SRC_SEARCH_LFIND_H
+
+#include "src/__support/macros/config.h"
+#include <search.h> // size_t
+
+namespace LIBC_NAMESPACE_DECL {
+void *lfind(void *key, void *base, size_t *nmemb, size_t size,
+            int (*compar)(void *, void *));
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SEARCH_LFIND_H

libc/test/src/search/CMakeLists.txt

@@ -25,3 +25,13 @@ add_libc_unittest(
     libc.src.search.insque
     libc.src.search.remque
 )
+
+add_libc_unittest(
+  lfind_test
+  SUITE
+    libc_search_unittests
+  SRCS
+    lfind_test.cpp
+  DEPENDS
+    libc.src.search.lfind
+)

libc/test/src/search/lfind_test.cpp

@@ -0,0 +1,46 @@
+//===-- Unittests for lfind -----------------------------------------------===//
+//
+// 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/search/lfind.h"
+#include "test/UnitTest/Test.h"
+
+int compar(void *a, void *b) {
+  return *reinterpret_cast<int *>(a) - *reinterpret_cast<int *>(b);
+}
+
+TEST(LlvmLibcLfindTest, SearchHead) {
+  int list[3] = {1, 2, 3};
+  size_t len = 3;
+  int key = 1;
+  void *ret = LIBC_NAMESPACE::lfind(&key, list, &len, sizeof(int), compar);
+  ASSERT_TRUE(ret == &list[0]);
+}
+
+TEST(LlvmLibcLfindTest, SearchMiddle) {
+  int list[3] = {1, 2, 3};
+  size_t len = 3;
+  int key = 2;
+  void *ret = LIBC_NAMESPACE::lfind(&key, list, &len, sizeof(int), compar);
+  ASSERT_TRUE(ret == &list[1]);
+}
+
+TEST(LlvmLibcLfindTest, SearchTail) {
+  int list[3] = {1, 2, 3};
+  size_t len = 3;
+  int key = 3;
+  void *ret = LIBC_NAMESPACE::lfind(&key, list, &len, sizeof(int), compar);
+  ASSERT_TRUE(ret == &list[2]);
+}
+
+TEST(LlvmLibcLfindTest, SearchNonExistent) {
+  int list[3] = {1, 2, 3};
+  size_t len = 3;
+  int key = 5;
+  void *ret = LIBC_NAMESPACE::lfind(&key, list, &len, sizeof(int), compar);
+  ASSERT_TRUE(ret == nullptr);
+}