Move everything into a new repo.

1 files changed, 29 insertions, 0 deletions

diff --git a/userland/libc/stdlib/qsort.c b/userland/libc/stdlib/qsort.c
new file mode 100644
index 0000000..3f87db5
--- /dev/null
+++ b/userland/libc/stdlib/qsort.c
@@ -0,0 +1,29 @@
+#include <stdlib.h>
+#include <string.h>
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/functions/qsort.html
+void qsort(void *base, size_t nel, size_t width,
+           int (*compar)(const void *, const void *)) {
+  // If the nel argument has the value zero, the comparison function pointed to
+  // by compar shall not be called and no rearrangement shall take place.
+  if (0 == nel)
+    return;
+  
+  // AB
+  // Results in negative
+  // BA
+  // Results in positive
+
+  // Using bubblesort
+  unsigned char *p = base;
+  for (size_t i = 1; i < nel; i++) {
+    for (size_t j = 0; j < nel; j++) {
+      if (compar((p + i * width), (p + j * width)) < 0) {
+        unsigned char tmp[width];
+        memcpy(tmp, (p + i * width), width);
+        memcpy((p + i * width), (p + j * width), width);
+        memcpy((p + j * width), tmp, width);
+      }
+    }
+  }
+}