stdlib.h: qsort (slow)

inc/stdlib.h

@@ -85,8 +85,20 @@ int             at_quick_exit(void (*func)(void));
 char           *getenv       (const char *name);
 int             system       (const char *string);
 
-const void *bsearch(const void *key, const void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *));
-// void qsort(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *));
+const void *bsearch(
+    const void *key,
+    const void *base,
+    size_t nmemb,
+    size_t size,
+    int (*compar)(const void *, const void *)
+);
+
+void qsort(
+    void *base,
+    size_t nmemb,
+    size_t size,
+    int (*compar)(const void *, const void *)
+);
 
 // Multibyte strings
 // int mblen(const char *s, size_t n);

src/code/stdlib/algorithm.c

@@ -36,7 +36,13 @@ lldiv_t lldiv(long long x, long long y) {
     return res;
 }
 
-const void *bsearch(const void *key, const void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *)) {
+const void *bsearch(
+    const void *key,
+    const void *base,
+    size_t nmemb,
+    size_t size,
+    int (*compar)(const void *, const void *)
+) {
     size_t left = 0;
     size_t right = nmemb;
 
@@ -52,3 +58,26 @@ const void *bsearch(const void *key, const void *base, size_t nmemb, size_t size
 
     return NULL;
 }
+
+void qsort(
+    void *base,
+    size_t nmemb,
+    size_t size,
+    int (*diff)(const void *, const void *)
+) {
+    // Ima be doing bublbe sort for now
+    char *bytes = base;
+    for(size_t i = 0; i != nmemb-1; ++i) {
+        for(size_t j = 0; j < nmemb-i-1; ++j) {
+            char *this = bytes+j*size;
+            char *that = this+size;
+            if(diff(this, that) > 0) {
+                for(size_t b=0;b!=size;++b) {
+                    char temp = this[b];
+                    this[b] = that[b];
+                    that[b] = temp;
+                }
+            }
+        }
+    }
+}

test/test_qsort.c

@@ -0,0 +1,34 @@
+
+#include <stdlib.h>
+#include <stdio.h>
+
+int compare_ints(const void *p, const void *q) {
+    int x = *(const int *)p;
+    int y = *(const int *)q;
+
+    /* Avoid return x - y, which can cause undefined behaviour
+       because of signed integer overflow. */
+    if (x < y)
+        return -1;  // Return -1 if you want ascending, 1 if you want descending order. 
+    else if (x > y)
+        return 1;   // Return 1 if you want ascending, -1 if you want descending order.
+
+    return 0;
+    // All the logic is often alternatively written:
+    return (x > y) - (x < y);
+}
+
+/* Sort an array of n integers, pointed to by a. */
+void sort_ints(int *a, size_t n) {
+    qsort(a, n, sizeof(*a), compare_ints);
+}
+
+int main() {
+    int arr[] = {-1,10,155, 256-10,0,0,0};
+    int count = sizeof arr / sizeof *arr;
+    sort_ints(arr, count);
+    for(int i = 0; i != count; ++i) {
+        printf("%d\t", arr[i]);
+    }
+}
+