Mesa (main): util: add ptralloc

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Module: Mesa
Branch: main
Commit: 171ccdbf1c40068fcea2cc36ff7eef1a49155928
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=171ccdbf1c40068fcea2cc36ff7eef1a49155928

Author: Mike Blumenkrantz <michael.blumenkrantz at gmail.com>
Date:   Thu Nov  4 12:23:05 2021 -0400

util: add ptralloc

many times it will be the case that an allocation for a block of data
needs to be done in one alloc() call such that the members of a struct as well
as some extra trailing data are all in the same allocation like

```
struct Test {
  unsigned a[4];
  unsigned c;
};
unsigned *b; //ptr to uint[8]
```

should be allocated as a single block of (13 * sizeof(unsigned)) memory using
C pointer offsets to allocate the memory as

```
| Test | b |
```

with something like

```
struct Test *t = malloc(sizeof(struct Test) + (8 * sizeof(unsigned)));
```

and then set `b` with

```
t->b = ((uint8_t*)t) + sizeof(struct Test);
```

this is annoying, awful to read, and (at least for dum-dums like me) prone to errors,
however, so having some utility functions which can deliver the same
functionality with better readability helps out this case by transforming it to

```
unsigned *b;
void **ptrs[] = {(void*)&b};
size_t sizes[] = {8 * sizeof(unsigned));
struct Test *t = ptralloc(sizeof(struct Test), 1, sizes, ptrs);
```

where `b` is now set to the appropriate offset in memory

Acked-by: Dave Airlie <airlied at redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13678>

---

 src/util/meson.build |  1 +
 src/util/ptralloc.h  | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/src/util/meson.build b/src/util/meson.build
index fe46352ce16..6e77a2f0364 100644
--- a/src/util/meson.build
+++ b/src/util/meson.build
@@ -78,6 +78,7 @@ files_mesa_util = files(
   'os_misc.h',
   'os_socket.c',
   'os_socket.h',
+  'ptralloc.h',
   'perf/u_trace.h',
   'perf/u_trace.c',
   'perf/u_trace_priv.h',
diff --git a/src/util/ptralloc.h b/src/util/ptralloc.h
new file mode 100644
index 00000000000..019bc7b8e12
--- /dev/null
+++ b/src/util/ptralloc.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright © 2021 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.
+ * 
+ * Authors:
+ *    Mike Blumenkrantz <michael.blumenkrantz at gmail.com>
+ */
+
+#pragma once
+
+#include <stdlib.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include "c99_compat.h"
+#include "macros.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static inline void *
+ptralloc(size_t base_size, unsigned member_count, size_t *member_sizes, void ***members)
+{
+   size_t size = base_size;
+   for (unsigned i = 0; i < member_count; i++)
+      size += member_sizes[i];
+
+   uint8_t *ptr = (uint8_t*)malloc(size);
+   if (!ptr)
+      return NULL;
+
+   size_t accum = base_size;
+   for (unsigned i = 0; i < member_count; i++) {
+      *members[i] = (void*)(ptr + accum);
+      accum += member_sizes[i];
+   }
+   return (void*)ptr;
+}
+
+static inline void *
+ptrzalloc(size_t base_size, unsigned member_count, size_t *member_sizes, void ***members)
+{
+   size_t size = base_size;
+   for (unsigned i = 0; i < member_count; i++)
+      size += member_sizes[i];
+
+   uint8_t *ptr = (uint8_t*)calloc(1, size);
+   if (!ptr)
+      return NULL;
+
+   size_t accum = base_size;
+   for (unsigned i = 0; i < member_count; i++) {
+      *members[i] = (void*)(ptr + accum);
+      accum += member_sizes[i];
+   }
+   return (void*)ptr;
+}
+
+#ifdef __cplusplus
+}
+#endif