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/*
* Copyright (C) the libgit2 contributors. All rights reserved.
*
* This file is part of libgit2, distributed under the GNU GPL v2 with
* a Linking Exception. For full terms see the included COPYING file.
*/
#include "clar_libgit2_alloc.h"
static size_t bytes_available;
/*
* The clar allocator uses a tagging mechanism for pointers that
* prepends the actual pointer's number bytes as `size_t`.
*
* First, this is required in order to be able to implement
* proper bookkeeping of allocated bytes in both `free` and
* `realloc`.
*
* Second, it may also be able to spot bugs that are
* otherwise hard to grasp, as the returned pointer cannot be
* free'd directly via free(3P). Instead, one is forced to use
* the tandem of `cl__malloc` and `cl__free`, as otherwise the
* code is going to crash hard. This is considered to be a
* feature, as it helps e.g. in finding cases where by accident
* malloc(3P) and free(3P) were used instead of git__malloc and
* git__free, respectively.
*
* The downside is obviously that each allocation grows by
* sizeof(size_t) bytes. As the allocator is for testing purposes
* only, this tradeoff is considered to be perfectly fine,
* though.
*/
static void *cl__malloc(size_t len, const char *file, int line)
{
char *ptr = NULL;
size_t alloclen;
GIT_UNUSED(file);
GIT_UNUSED(line);
if (len > bytes_available)
goto out;
if (GIT_ADD_SIZET_OVERFLOW(&alloclen, len, sizeof(size_t)) ||
(ptr = malloc(alloclen)) == NULL)
goto out;
memcpy(ptr, &len, sizeof(size_t));
bytes_available -= len;
out:
return ptr ? ptr + sizeof(size_t) : NULL;
}
static void cl__free(void *ptr)
{
if (ptr) {
char *p = ptr;
size_t len;
memcpy(&len, p - sizeof(size_t), sizeof(size_t));
free(p - sizeof(size_t));
bytes_available += len;
}
}
static void *cl__realloc(void *ptr, size_t size, const char *file, int line)
{
size_t copybytes = 0;
char *p = ptr;
void *new;
if (p)
memcpy(©bytes, p - sizeof(size_t), sizeof(size_t));
if (copybytes > size)
copybytes = size;
if ((new = cl__malloc(size, file, line)) == NULL)
goto out;
if (p) {
memcpy(new, p, copybytes);
cl__free(p);
}
out:
return new;
}
void cl_alloc_limit(size_t bytes)
{
git_allocator alloc;
alloc.gmalloc = cl__malloc;
alloc.grealloc = cl__realloc;
alloc.gfree = cl__free;
git_allocator_setup(&alloc);
bytes_available = bytes;
}
void cl_alloc_reset(void)
{
git_allocator stdalloc;
git_stdalloc_init_allocator(&stdalloc);
git_allocator_setup(&stdalloc);
}
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