libc: Add bsearch (with a test!!)

libs/libc/include/stdlib.h

@@ -116,7 +116,10 @@ extern "C"
     /* Sorts the array pointed to by base of nmemb items of the specified size using the comparison function compar. */
     void qsort(void* base, size_t nmemb, size_t size, int (*compar)(const void*, const void*));
 
-    void* bsearch(const void*, const void*, size_t, size_t, int (*)(const void*, const void*)); // Not implemented.
+    /* Searches the sorted array base of nmemb items of the specified size for the given key using the comparison
+     * function compar. */
+    void* bsearch(const void* key, const void* base, size_t nmemb, size_t size,
+                  int (*compar)(const void*, const void*));
 
     size_t mbstowcs(wchar_t* dest, const char* src,
                     size_t n); // Not implemented.

libs/libc/src/stdlib.cpp

@@ -122,6 +122,26 @@ static void quicksort(void* base, size_t start, size_t end, size_t size, int (*c
     }
 }
 
+void* binary_search(const void* key, const void* base, size_t start, size_t end, size_t size,
+                    int (*compar)(const void*, const void*))
+{
+    auto atindex = [&base, &size](size_t index) { return (const void*)((const char*)base + (index * size)); };
+
+    if (end >= start)
+    {
+        size_t middle = start + (end - start) / 2;
+        int rc = compar(atindex(middle), key);
+
+        if (rc == 0) return const_cast<void*>(atindex(middle)); // we found it!!
+
+        if (rc < 0) return binary_search(key, base, middle + 1, end, size, compar);
+
+        return binary_search(key, base, start, middle - 1, size, compar);
+    }
+
+    return NULL;
+}
+
 extern "C"
 {
     __lc_noreturn void abort()
@@ -225,9 +245,9 @@ extern "C"
         quicksort(base, 0, nmemb - 1, size, compar);
     }
 
-    void* bsearch(const void*, const void*, size_t, size_t, int (*)(const void*, const void*))
+    void* bsearch(const void* key, const void* base, size_t nmemb, size_t size, int (*compar)(const void*, const void*))
     {
-        NOT_IMPLEMENTED("bsearch");
+        return binary_search(key, base, 0, nmemb - 1, size, compar);
     }
 
     size_t mbstowcs(wchar_t*, const char*, size_t)

tests/libc/Test.c

@@ -26,6 +26,7 @@ DEFINE_TEST(malloc);
 DEFINE_TEST(calloc);
 DEFINE_TEST(mktemp);
 DEFINE_TEST(qsort);
+DEFINE_TEST(bsearch);
 
 int main()
 {
@@ -55,4 +56,5 @@ int main()
     RUN_TEST(calloc);
     RUN_TEST(mktemp);
     RUN_TEST(qsort);
+    RUN_TEST(bsearch);
 }

tests/libc/stdlib.c

@@ -207,3 +207,28 @@ DEFINE_TEST(qsort)
 
     TEST_SUCCESS();
 }
+
+DEFINE_TEST(bsearch)
+{
+    START_TEST(bsearch);
+
+    const char sorted[] = "abcdefjkl";
+    char key = 'j';
+
+    char* ptr = bsearch(&key, sorted, 9, sizeof(char), compare_char); // try with sorted array first
+
+    EXPECT_EQ(*ptr, 'j');
+    EXPECT_EQ(ptr, &sorted[6]);
+
+    int unsorted[] = {1500, 45, 3, 11, 41, 90, 6, 32, 5, 76};
+    qsort(unsorted, 10, sizeof(int), compare_int);
+
+    int key2 = 90;
+
+    int* ptr2 = bsearch(&key2, unsorted, 10, sizeof(int), compare_int);
+
+    EXPECT_EQ(*ptr2, 90);
+    EXPECT_EQ(ptr2, &unsorted[8]);
+
+    TEST_SUCCESS();
+}