Add list slice

src/list/copy.c

@@ -107,3 +107,80 @@ void list_extend(list_t* x, const list_t* s) {
         push_next(x, vnode_duplicate(&c->node, c->type), c->type);
     } while (!is_null(c = c->next));
 }
+
+
+
+size_t list_slice(list_t* x, list_t* s, ssize_t i, size_t n, _Bool cut) {
+
+    ldir_t dir;
+    lnode_t* c;
+    lnode_t* e;
+    size_t   r;
+
+    r = n;
+
+    if (!n || is_null(s->first)) {
+        memset(x, 0, sizeof(*x));
+        return 0;
+    }
+
+    if (i < 0) {
+        c = s->last;
+        e = s->last;
+        i = ~i;
+
+        while (i && !is_null(c)) {
+            c = c->prev;
+            --i;
+            if (!n) { e = e->prev; }
+            else --n;
+        }
+
+        if (is_null(c)) c = x->first;
+    } else {
+        c = s->first;
+
+        while (i && !is_null(c)) {
+            c = c->next;
+            --i;
+        }
+
+        e = c;
+
+        while (n && !is_null(e)) {
+            e = e->next;
+            --n;
+        }
+
+        if (is_null(e)) e = x->last;
+    }
+
+    if (is_null(c)) return 0;
+    else r -= n;
+
+    if (!cut) {
+        init_first(x, vnode_duplicate(&c->node, c->type), c->type);
+
+        while ((c = c->next) != e) {
+            push_next(x, vnode_duplicate(&c->node, c->type), c->type);
+        }
+
+        push_next(x, vnode_duplicate(&e->node, e->type), e->type);
+    } else {
+        if (c->prev) {
+            c->prev->next = e->next;
+        } else x->first = e->next;
+
+        if (e->next) {
+            e->next->prev = c->prev;
+        } else s->last = c->prev;
+
+        e->next = nullptr;
+        c->prev = nullptr;
+
+        x->first = c;
+        x->last  = e;
+    }
+
+    return r;
+}

src/list/extra.c

@@ -59,14 +59,15 @@ ssize_t libcdsb_list_get(val_t* x, list_t* s, ssize_t i, _Bool cut) {
 /*#####################################################################################################################*/
 
 ssize_t libcdsb_list_find(val_t* x, list_t* s, const void* v, vtype t, _Bool r, _Bool cut) {
-    ldir_t dir = r ? LD_PREV : LD_NEXT;
 
+    ldir_t dir;
     lnode_t* c;
     ssize_t  i;
     int    cmp;
 
-    c = ldir_dir((lnode_t*)s, dir);
-    i = 0;
+    dir = r ? LD_PREV : LD_NEXT;
+    c   = ldir_dir((lnode_t*)s, dir);
+    i   = 0;
 
     if (!is_null(x)) memset(x, 0, sizeof(*x));
 
@@ -178,7 +179,7 @@ int libcdsb_list_foreach(vtype_list* x, void* data, list_foreach_callback callba
             break;
 
         n = c->next;
-        
+
         if (flush) {
             vnode_free(&c->node, c->type);
             free(c);