libc: Add qsort (with a test!!)

libs/libc/include/stdlib.h

@@ -113,7 +113,8 @@ extern "C"
     /* Runs a shell command. */
     int system(const char* command);
 
-    void qsort(void*, size_t, size_t, int (*)(const void*, const void*)); // Not implemented.
+    /* 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.
 

libs/libc/src/stdlib.cpp

@@ -77,6 +77,51 @@ template <typename Arg, typename Struct> static inline Struct common_div(Arg a,
     return result;
 }
 
+static void qswap(void* ptr1, void* ptr2, size_t size)
+{
+    char* x = (char*)ptr1;
+    char* y = (char*)ptr2;
+
+    while (size--)
+    {
+        char t = *x;
+        *x = *y;
+        *y = t;
+        x += 1;
+        y += 1;
+    }
+}
+
+static size_t partition(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 (void*)((char*)base + (index * size)); };
+
+    void* pivot = atindex(end);
+    size_t i = (start - 1);
+
+    for (size_t j = start; j <= end - 1; j++)
+    {
+        if (compar(atindex(j), pivot) < 0)
+        {
+            i++;
+            qswap(atindex(i), atindex(j), size);
+        }
+    }
+
+    qswap(atindex(i + 1), pivot, size);
+    return i + 1;
+}
+
+static void quicksort(void* base, size_t start, size_t end, size_t size, int (*compar)(const void*, const void*))
+{
+    if (start < end)
+    {
+        size_t pivot = partition(base, start, end, size, compar);
+        quicksort(base, start, pivot - 1, size, compar);
+        quicksort(base, pivot + 1, end, size, compar);
+    }
+}
+
 extern "C"
 {
     __lc_noreturn void abort()
@@ -175,9 +220,9 @@ extern "C"
         return status;
     }
 
-    void qsort(void*, size_t, size_t, int (*)(const void*, const void*))
+    void qsort(void* base, size_t nmemb, size_t size, int (*compar)(const void*, const void*))
     {
-        NOT_IMPLEMENTED("qsort");
+        quicksort(base, 0, nmemb - 1, size, compar);
     }
 
     void* bsearch(const void*, const void*, size_t, size_t, int (*)(const void*, const void*))

tests/libc/Test.c

@@ -25,6 +25,7 @@ DEFINE_TEST(srand);
 DEFINE_TEST(malloc);
 DEFINE_TEST(calloc);
 DEFINE_TEST(mktemp);
+DEFINE_TEST(qsort);
 
 int main()
 {
@@ -53,4 +54,5 @@ int main()
     RUN_TEST(malloc);
     RUN_TEST(calloc);
     RUN_TEST(mktemp);
+    RUN_TEST(qsort);
 }

tests/libc/stdlib.c

@@ -155,12 +155,55 @@ DEFINE_TEST(mktemp)
 
     int rc = access(ptr, F_OK);
 
-    EXPECT_NOT_EQ(rc, 0); // FIXME: This could actually happen, since that's why mktemp is deprecated. 
+    EXPECT_NOT_EQ(rc, 0); // FIXME: This could actually happen, since that's why mktemp is deprecated.
                           // Another process could create the file between generating the name and actually using it.
 
     rc = strcmp(ptr, template2);
 
     EXPECT_NOT_EQ(rc, 0);
 
+    TEST_SUCCESS();
+}
+
+static int compare_char(const void* p1, const void* p2)
+{
+    const char* c1 = (const char*)p1;
+    const char* c2 = (const char*)p2;
+    if (*c1 < *c2) return -1;
+    if (*c1 > *c2) return 1;
+    return 0;
+}
+
+static int compare_int(const void* p1, const void* p2)
+{
+    const int* c1 = (const int*)p1;
+    const int* c2 = (const int*)p2;
+    if (*c1 < *c2) return -1;
+    if (*c1 > *c2) return 1;
+    return 0;
+}
+
+DEFINE_TEST(qsort)
+{
+    START_TEST(qsort);
+
+    char unsorted[] = "elacbkdjf";
+    const char sorted[] = "abcdefjkl";
+
+    qsort(unsorted, 9, sizeof(char), compare_char);
+
+    int rc = memcmp(sorted, unsorted, 9);
+
+    EXPECT_EQ(rc, 0);
+
+    int unsorted2[] = {1500, 45, 3, 11, 41, 90, 6, 32, 5, 76};
+    const int sorted2[] = {3, 5, 6, 11, 32, 41, 45, 76, 90, 1500};
+
+    qsort(unsorted2, 10, sizeof(int), compare_int);
+
+    rc = memcmp(unsorted2, sorted2, 10);
+
+    EXPECT_EQ(rc, 0);
+
     TEST_SUCCESS();
 }