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171ccdbf1c
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@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13678>
79 lines
2.3 KiB
C
79 lines
2.3 KiB
C
/*
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* Copyright © 2021 Valve Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*
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* Authors:
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* Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
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*/
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#pragma once
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#include <stdlib.h>
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#include <inttypes.h>
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#include <stdbool.h>
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#include "c99_compat.h"
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#include "macros.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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static inline void *
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ptralloc(size_t base_size, unsigned member_count, size_t *member_sizes, void ***members)
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{
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size_t size = base_size;
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for (unsigned i = 0; i < member_count; i++)
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size += member_sizes[i];
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uint8_t *ptr = (uint8_t*)malloc(size);
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if (!ptr)
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return NULL;
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size_t accum = base_size;
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for (unsigned i = 0; i < member_count; i++) {
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*members[i] = (void*)(ptr + accum);
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accum += member_sizes[i];
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}
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return (void*)ptr;
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}
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static inline void *
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ptrzalloc(size_t base_size, unsigned member_count, size_t *member_sizes, void ***members)
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{
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size_t size = base_size;
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for (unsigned i = 0; i < member_count; i++)
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size += member_sizes[i];
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uint8_t *ptr = (uint8_t*)calloc(1, size);
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if (!ptr)
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return NULL;
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size_t accum = base_size;
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for (unsigned i = 0; i < member_count; i++) {
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*members[i] = (void*)(ptr + accum);
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accum += member_sizes[i];
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}
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return (void*)ptr;
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}
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#ifdef __cplusplus
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}
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#endif
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