util: add range remap util

This util allows a range of values to be remapped to a single
pointer.

Acked-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36997>

src/util/meson.build

@@ -142,6 +142,8 @@ files_mesa_util = files(
   'u_pointer.h',
   'u_queue.c',
   'u_queue.h',
+  'u_range_remap.c',
+  'u_range_remap.h',
   'u_string.c',
   'u_string.h',
   'u_thread.c',

src/util/u_range_remap.c

@@ -0,0 +1,155 @@
+/*
+ * Copyright © 2025 Valve Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "ralloc.h"
+#include "u_range_remap.h"
+
+/* Loop over the list and get the list entry after i interations*/
+static struct range_entry *
+get_list_entry(unsigned n, const struct list_head *r_list)
+{
+   unsigned i = 0;
+   list_for_each_entry_safe(struct range_entry, entry, r_list, node) {
+      if (i == n)
+         return entry;
+
+      i++;
+   }
+
+   return NULL;
+}
+
+/* Binary search for the range that contains n */
+static struct range_entry *
+get_range_entry(unsigned n, const struct list_head *r_list)
+{
+   if (list_is_empty(r_list))
+      return NULL;
+
+   unsigned low = 0;
+   unsigned high = list_length(r_list) - 1;
+
+   while (low <= high) {
+      int mid = (low + high) / 2;
+      struct range_entry *mid_entry = get_list_entry(mid, r_list);
+      if (n < mid_entry->start) {
+         if (low == high || low == mid) {
+            /* No entry found for n */
+            return NULL;
+         }
+
+         high = mid - 1;
+      } else if (n > mid_entry->end) {
+         if (low == high) {
+            /* No entry found for n */
+            return NULL;
+         }
+
+         low = mid + 1;
+      } else {
+         return mid_entry;
+      }
+   }
+
+   return NULL;
+}
+
+/* Insert a new range entry or update an existing entries pointer value if
+ * start and end match exactly. If the range overlaps an existing entry we
+ * return NULL.
+ */
+struct range_entry *
+util_range_insert_remap(unsigned start, unsigned end,
+                        struct list_head *r_list, void *ptr)
+{
+   struct range_entry *entry = NULL;
+   if (list_is_empty(r_list)) {
+      entry = rzalloc(r_list, struct range_entry);
+      list_addtail(&entry->node, r_list);
+      goto insert_end;
+   }
+
+   unsigned low = 0;
+   unsigned high = list_length(r_list) - 1;
+
+   while (low <= high) {
+      int mid = (low + high) / 2;
+
+      struct range_entry *mid_entry = get_list_entry(mid, r_list);
+      if (end < mid_entry->start) {
+         if (low == high || low == mid) {
+            entry = rzalloc(r_list, struct range_entry);
+            list_addtail(&entry->node, &mid_entry->node);
+            break;
+         }
+
+         high = mid - 1;
+      } else if (start > mid_entry->end) {
+         if (low == high) {
+            entry = rzalloc(r_list, struct range_entry);
+            list_add(&entry->node, &mid_entry->node);
+            break;
+         }
+
+         low = mid + 1;
+      } else if (mid_entry->start == start && mid_entry->end == end) {
+         entry = mid_entry;
+         break;
+      } else {
+         /* Attempting to insert an entry that overlaps an existing range */
+         return NULL;
+      }
+   }
+
+insert_end:
+   entry->start = start;
+   entry->end = end;
+   entry->ptr = ptr;
+
+   return entry;
+}
+
+/* Return the range entry that maps to n or NULL if no match found. */
+struct range_entry *
+util_range_remap(unsigned n, const struct list_head *r_list)
+{
+   return get_range_entry(n, r_list);
+}
+
+struct list_head *
+util_create_range_remap()
+{
+   struct range_entry *r = rzalloc(NULL, struct range_entry);
+   list_inithead(&r->node);
+   return &r->node;
+}
+
+/* Free previous list and create a new empty list */
+struct list_head *
+util_reset_range_remap(struct list_head *r_list)
+{
+   if (r_list)
+      ralloc_free(r_list);
+
+   return util_create_range_remap();
+}

src/util/u_range_remap.h

@@ -0,0 +1,52 @@
+/*
+ * Copyright © 2025 Valve Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "list.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct range_entry {
+    struct list_head node;
+
+    unsigned start, end;
+    void *ptr;
+};
+
+struct range_entry *
+util_range_insert_remap(unsigned start, unsigned end,
+                        struct list_head *r_list, void *ptr);
+
+struct range_entry *
+util_range_remap(unsigned n, const struct list_head *r_list);
+
+struct list_head *
+util_create_range_remap(void);
+
+struct list_head *
+util_reset_range_remap(struct list_head *r_list);
+
+#ifdef __cplusplus
+}
+#endif