janwas
5738bd4820
* replace all "return ERR_*" with WARN_RETURN(ERR_*) - makes sure function failures are noticed *at the cause*, not later * LibError_from_* now take bool warn_if_failed param * replace more debug_warns with dedicated error codes (allows localized error reports and doesn't spam the EXE with strings) This was SVN commit r3722.
386 lines
12 KiB
C++
386 lines
12 KiB
C++
// suballocators
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// Copyright (c) 2005 Jan Wassenberg
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// Contact info:
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// Jan.Wassenberg@stud.uni-karlsruhe.de
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// http://www.stud.uni-karlsruhe.de/~urkt/
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#ifndef ALLOCATORS_H__
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#define ALLOCATORS_H__
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#include "lib/types.h"
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#include "lib/posix.h" // PROT_* constants for da_set_prot
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//
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// allocator optimized for single instances
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//
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// intended for applications that frequently alloc/free a single
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// fixed-size object. caller provides static storage and an in-use flag;
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// we use that memory if available and otherwise fall back to the heap.
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// if the application only has one object in use at a time, malloc is
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// avoided; this is faster and avoids heap fragmentation.
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//
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// thread-safe.
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extern void* single_calloc(void* storage, volatile uintptr_t* in_use_flag, size_t size);
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extern void single_free(void* storage, volatile uintptr_t* in_use_flag, void* p);
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// C++ wrapper
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#ifdef __cplusplus
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// T must be POD (Plain Old Data) because it is memset to 0!
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template<class T> class SingleAllocator
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{
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T storage;
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volatile uintptr_t is_in_use;
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public:
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SingleAllocator()
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{
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is_in_use = 0;
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}
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void* alloc()
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{
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return single_calloc(&storage, &is_in_use, sizeof(storage));
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}
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void release(void* p)
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{
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single_free(&storage, &is_in_use, p);
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}
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};
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#endif // #ifdef __cplusplus
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//
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// dynamic (expandable) array
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//
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// provides a memory range that can be expanded but doesn't waste
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// physical memory or relocate itself. building block for other allocators.
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struct DynArray
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{
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u8* base;
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size_t max_size_pa; // reserved
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size_t cur_size; // committed
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int prot; // applied to newly committed pages
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size_t pos;
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};
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// ready the DynArray object for use. preallocates max_size bytes
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// (rounded up to the next page size multiple) of address space for the
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// array; it can never grow beyond this.
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// no virtual memory is actually committed until calls to da_set_size.
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extern LibError da_alloc(DynArray* da, size_t max_size);
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// free all memory (address space + physical) that constitutes the
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// given array. use-after-free is impossible because the memory is
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// marked not-present via MMU. also zeroes the contents of <da>.
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extern LibError da_free(DynArray* da);
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// expand or shrink the array: changes the amount of currently committed
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// (i.e. usable) memory pages. pages are added/removed until
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// new_size (rounded up to the next page size multiple) is met.
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extern LibError da_set_size(DynArray* da, size_t new_size);
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// make sure at least <size> bytes starting at <pos> are committed and
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// ready for use.
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extern LibError da_reserve(DynArray* da, size_t size);
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// change access rights of the array memory; used to implement
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// write-protection. affects the currently committed pages as well as
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// all subsequently added pages.
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// prot can be a combination of the PROT_* values used with mprotect.
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extern LibError da_set_prot(DynArray* da, int prot);
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// "wrap" (i.e. store information about) the given buffer in a
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// DynArray object, preparing it for use with da_read or da_append.
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// da_free should be called when the DynArray is no longer needed,
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// even though it doesn't free this memory (but does zero the DynArray).
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extern LibError da_wrap_fixed(DynArray* da, u8* p, size_t size);
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// "read" from array, i.e. copy into the given buffer.
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// starts at offset DynArray.pos and advances this.
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extern LibError da_read(DynArray* da, void* data_dst, size_t size);
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// "write" to array, i.e. copy from the given buffer.
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// starts at offset DynArray.pos and advances this.
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extern LibError da_append(DynArray* da, const void* data_src, size_t size);
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//
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// pool allocator
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//
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// design parameters:
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// - O(1) alloc and free;
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// - fixed- XOR variable-sized blocks;
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// - doesn't preallocate the entire pool;
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// - returns sequential addresses.
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// opaque! do not read/write any fields!
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struct Pool
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{
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DynArray da;
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// size of elements. = 0 if pool set up for variable-sized
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// elements, otherwise rounded up to pool alignment.
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size_t el_size;
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// pointer to freelist (opaque); see freelist_*.
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// never used (remains 0) if elements are of variable size.
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void* freelist;
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};
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// pass as pool_create's <el_size> param to indicate variable-sized allocs
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// are required (see below).
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const size_t POOL_VARIABLE_ALLOCS = ~0u;
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// ready <p> for use. <max_size> is the upper limit [bytes] on
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// pool size (this is how much address space is reserved).
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//
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// <el_size> can be 0 to allow variable-sized allocations
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// (which cannot be freed individually);
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// otherwise, it specifies the number of bytes that will be
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// returned by pool_alloc (whose size parameter is then ignored).
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extern LibError pool_create(Pool* p, size_t max_size, size_t el_size);
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// free all memory that ensued from <p>. all elements are made unusable
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// (it doesn't matter if they were "allocated" or in freelist or unused);
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// future alloc and free calls on this pool will fail.
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extern LibError pool_destroy(Pool* p);
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// indicate whether <el> was allocated from the given pool.
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// this is useful for callers that use several types of allocators.
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extern bool pool_contains(Pool* p, void* el);
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// return an entry from the pool, or 0 if it would have to be expanded and
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// there isn't enough memory to do so.
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// exhausts the freelist before returning new entries to improve locality.
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//
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// if the pool was set up with fixed-size elements, <size> is ignored;
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// otherwise, <size> bytes are allocated.
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extern void* pool_alloc(Pool* p, size_t size);
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// make <el> available for reuse in the given Pool.
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//
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// this is not allowed if created for variable-size elements.
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// rationale: avoids having to pass el_size here and compare with size when
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// allocating; also prevents fragmentation and leaking memory.
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extern void pool_free(Pool* p, void* el);
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// "free" all allocations that ensued from the given Pool.
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// this resets it as if freshly pool_create-d, but doesn't release the
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// underlying memory.
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extern void pool_free_all(Pool* p);
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//
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// bucket allocator
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//
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// design goals:
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// - fixed- XOR variable-sized blocks;
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// - allow freeing individual blocks if they are all fixed-size;
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// - never relocates;
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// - no fixed limit.
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// note: this type of allocator is called "region-based" in the literature.
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// see "Reconsidering Custom Memory Allocation" (Berger, Zorn, McKinley).
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// if individual variable-size elements must be freeable, consider "reaps":
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// basically a combination of region and heap, where frees go to the heap and
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// allocs exhaust that memory first and otherwise use the region.
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// opaque! do not read/write any fields!
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struct Bucket
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{
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// currently open bucket.
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u8* bucket;
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// offset of free space at end of current bucket (i.e. # bytes in use).
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size_t pos;
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void* freelist;
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size_t el_size : 16;
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// records # buckets allocated; verifies the list of buckets is correct.
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uint num_buckets : 16;
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};
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// ready <b> for use.
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//
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// <el_size> can be 0 to allow variable-sized allocations
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// (which cannot be freed individually);
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// otherwise, it specifies the number of bytes that will be
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// returned by bucket_alloc (whose size parameter is then ignored).
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extern LibError bucket_create(Bucket* b, size_t el_size);
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// free all memory that ensued from <b>.
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// future alloc and free calls on this Bucket will fail.
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extern void bucket_destroy(Bucket* b);
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// return an entry from the bucket, or 0 if another would have to be
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// allocated and there isn't enough memory to do so.
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// exhausts the freelist before returning new entries to improve locality.
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//
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// if the bucket was set up with fixed-size elements, <size> is ignored;
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// otherwise, <size> bytes are allocated.
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extern void* bucket_alloc(Bucket* b, size_t size);
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// make <el> available for reuse in <b>.
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//
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// this is not allowed if created for variable-size elements.
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// rationale: avoids having to pass el_size here and compare with size when
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// allocating; also prevents fragmentation and leaking memory.
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extern void bucket_free(Bucket* b, void* el);
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//
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// matrix allocator
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//
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// takes care of the dirty work of allocating 2D matrices:
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// - aligns data
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// - only allocates one memory block, which is more efficient than
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// malloc/new for each row.
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// allocate a 2D cols x rows matrix of <el_size> byte cells.
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// this must be freed via matrix_free. returns 0 if out of memory.
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//
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// the returned pointer should be cast to the target type (e.g. int**) and
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// can then be accessed by matrix[col][row].
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//
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extern void** matrix_alloc(uint cols, uint rows, size_t el_size);
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// free the given matrix (allocated by matrix_alloc). no-op if matrix == 0.
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// callers will likely want to pass variables of a different type
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// (e.g. int**); they must be cast to void**.
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extern void matrix_free(void** matrix);
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//
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// overrun protection
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//
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/*
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OverrunProtector wraps an arbitrary object in DynArray memory and can detect
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inadvertent writes to it. this is useful for tracking down memory overruns.
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the basic idea is to require users to request access to the object and
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notify us when done; memory access permission is temporarily granted.
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(similar in principle to Software Transaction Memory).
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since this is quite slow, the protection is disabled unless
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CONFIG_OVERRUN_PROTECTION == 1; this avoids having to remove the
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wrapper code in release builds and re-write when looking for overruns.
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example usage:
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OverrunProtector<your_class> your_class_wrapper;
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..
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your_class* yc = your_class_wrapper.get(); // unlock, make ready for use
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if(!yc) // your_class_wrapper's one-time alloc of a your_class-
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abort(); // instance had failed - can't continue.
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doSomethingWith(yc); // read/write access
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your_class_wrapper.lock(); // disallow further access until next .get()
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..
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*/
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template<class T> class OverrunProtector
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{
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DynArray da;
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T* cached_ptr;
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uintptr_t initialized;
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public:
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OverrunProtector()
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{
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memset(&da, 0, sizeof(da));
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cached_ptr = 0;
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initialized = 0;
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}
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~OverrunProtector()
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{
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shutdown();
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}
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void lock()
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{
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#if CONFIG_OVERRUN_PROTECTION
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da_set_prot(&da, PROT_NONE);
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#endif
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}
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private:
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void unlock()
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{
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#if CONFIG_OVERRUN_PROTECTION
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da_set_prot(&da, PROT_READ|PROT_WRITE);
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#endif
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}
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void init()
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{
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if(da_alloc(&da, sizeof(T)) < 0)
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{
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fail:
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WARN_ERR(ERR_NO_MEM);
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return;
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}
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if(da_set_size(&da, sizeof(T)) < 0)
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goto fail;
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#include "nommgr.h"
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cached_ptr = new(da.base) T();
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#include "mmgr.h"
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lock();
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}
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void shutdown()
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{
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if(!CAS(&initialized, 1, 2))
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return; // never initialized or already shut down - abort
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unlock();
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cached_ptr->~T(); // call dtor (since we used placement new)
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cached_ptr = 0;
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(void)da_free(&da);
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}
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public:
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T* get()
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{
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// this could theoretically be done in the ctor, but we try to
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// minimize non-trivial code at NLSO ctor time
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// (avoids init order problems).
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if(CAS(&initialized, 0, 1))
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init();
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debug_assert(initialized != 2 && "OverrunProtector: used after dtor called:");
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unlock();
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return cached_ptr;
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}
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};
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#endif // #ifndef ALLOCATORS_H__
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