383 lines
14 KiB
C
383 lines
14 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* This is a memory allocator designed to provide reasonable management of free
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* space and fast access to allocated data. More than one allocator can be used
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* at a time by initializing multiple contexts.
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*
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* Copyright (C) 2009 Andrew Mahone
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* Copyright (C) 2011 Thomas Martitz
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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
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#ifndef _BUFLIB_H_
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#define _BUFLIB_H_
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#include <stdint.h>
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#include <stdbool.h>
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#include <string.h>
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/* enable single block debugging */
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#define BUFLIB_DEBUG_BLOCK_SINGLE
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union buflib_data
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{
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intptr_t val; /* length of the block in n*sizeof(union buflib_data).
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Includes buflib metadata overhead. A negative value
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indicates block is unallocated */
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char name[1]; /* name, actually a variable sized string */
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struct buflib_callbacks* ops; /* callback functions for move and shrink. Can be NULL */
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char* alloc; /* start of allocated memory area */
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union buflib_data *handle; /* pointer to entry in the handle table.
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Used during compaction for fast lookup */
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uint32_t crc; /* checksum of this data to detect corruption */
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};
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struct buflib_context
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{
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union buflib_data *handle_table;
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union buflib_data *first_free_handle;
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union buflib_data *last_handle;
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union buflib_data *buf_start;
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union buflib_data *alloc_end;
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bool compact;
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};
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/**
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* This declares the minimal overhead that is required per alloc. These
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* are bytes that are allocated from the context's pool in addition
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* to the actually requested number of bytes.
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*
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* The total number of bytes consumed by an allocation is
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* BUFLIB_ALLOC_OVERHEAD + requested bytes + strlen(<name passed to
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* buflib_alloc_ex()) + pad to pointer size
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*/
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#define BUFLIB_ALLOC_OVERHEAD (6*sizeof(union buflib_data))
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/**
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* Callbacks used by the buflib to inform allocation that compaction
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* is happening (before data is moved)
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*
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* Note that buflib tries to move to satisfy new allocations before shrinking.
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* So if you have something to resize try to do it outside of the callback.
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*
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* Regardless of the above, if the allocation is SHRINKABLE, but not
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* MUST_NOT_MOVE buflib will move the allocation before even attempting to
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* shrink.
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*/
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struct buflib_callbacks {
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/**
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* This is called before data is moved. Use this to fix up any cached
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* pointers pointing to inside the allocation. The size is unchanged.
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*
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* This is not needed if you don't cache the data pointer (but always
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* call buflib_get_data()) and don't pass pointer to the data to yielding
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* functions.
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*
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* handle: The corresponding handle
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* current: The current start of the allocation
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* new: The new start of the allocation, after data movement
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*
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* Return: Return BUFLIB_CB_OK, or BUFLIB_CB_CANNOT_MOVE if movement
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* is impossible at this moment.
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*
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* If NULL: this allocation must not be moved around
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* by the buflib when compaction occurs. Attention: Don't confuse
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* that with passing NULL for the whole callback structure
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* to buflib_alloc_ex(). This would enable moving buffers by default.
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* You have to pass NULL inside the "struct buflib_callbacks" structure.
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*/
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int (*move_callback)(int handle, void* current, void* new);
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/**
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* This is called when the buflib desires to shrink a buffer
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* in order to satisfy new allocation. This happens when buflib runs
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* out of memory, e.g. because buflib_alloc_maximum() was called.
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* Move data around as you need to make space and call core_shrink() as
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* appropriate from within the callback to complete the shrink operation.
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* buflib will not move data as part of shrinking.
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*
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* hint: bit mask containing hints on how shrinking is desired (see below)
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* handle: The corresponding handle
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* start: The old start of the allocation
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*
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* Return: Return BUFLIB_CB_OK, or BUFLIB_CB_CANNOT_SHRINK if shirinking
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* is impossible at this moment.
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*
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* if NULL: this allocation cannot be resized.
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* It is recommended that allocation that must not move are
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* at least shrinkable
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*/
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int (*shrink_callback)(int handle, unsigned hints, void* start, size_t old_size);
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/**
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* This is called when special steps must be taken for synchronization
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* both before the move_callback is called and after the data has been
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* moved.
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*/
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void (*sync_callback)(int handle, bool sync_on);
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};
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#define BUFLIB_SHRINK_SIZE_MASK (~BUFLIB_SHRINK_POS_MASK)
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#define BUFLIB_SHRINK_POS_FRONT (1u<<31)
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#define BUFLIB_SHRINK_POS_BACK (1u<<30)
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#define BUFLIB_SHRINK_POS_MASK (BUFLIB_SHRINK_POS_FRONT|BUFLIB_SHRINK_POS_BACK)
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/**
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* Possible return values for the callbacks, some of them can cause
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* compaction to fail and therefore new allocations to fail
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*/
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/* Everything alright */
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#define BUFLIB_CB_OK 0
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/* Tell buflib that moving failed. Buflib may retry to move at any point */
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#define BUFLIB_CB_CANNOT_MOVE 1
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/* Tell buflib that resizing failed, possibly future making allocations fail */
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#define BUFLIB_CB_CANNOT_SHRINK 1
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/**
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* Initializes buflib with a caller allocated context instance and memory pool.
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*
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* The buflib_context instance needs to be passed to every other buflib
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* function. It's should be considered opaque, even though it is not yet
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* (that's to make inlining core_get_data() possible). The documentation
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* of the other functions will not describe the context
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* instance parameter further as it's obligatory.
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*
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* context: The new buflib instance to be initialized, allocated by the caller
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* size: The size of the memory pool
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*/
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void buflib_init(struct buflib_context *context, void *buf, size_t size);
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/**
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* Returns the amount of unallocated bytes. It does not mean this amount
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* can be actually allocated because they might not be contiguous.
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*
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* Returns: The number of unallocated bytes in the memory pool.
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*/
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size_t buflib_available(struct buflib_context *ctx);
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/**
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* Returns the biggest possible allocation that can be determined to succeed.
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*
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* Returns: The amount of bytes of the biggest unallocated, contiguous region.
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*/
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size_t buflib_allocatable(struct buflib_context *ctx);
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/**
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* Relocates the fields in *ctx to the new buffer position pointed to by buf.
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* This does _not_ move any data but updates the pointers. The data has
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* to be moved afterwards manually and only if this function returned true.
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*
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* This is intended to be called from within a move_callback(), for
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* buflib-on-buflib scenarios (i.e. a new buflib instance backed by a buffer
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* that was allocated by another buflib instance). Be aware that if the parent
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* move_callback() moves the underlying buffer _no_ move_callback() of the
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* underlying buffer are called.
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*
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* Returns true of the relocation was successful. If it returns false no
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* change to *ctx was made.
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*/
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bool buflib_context_relocate(struct buflib_context *ctx, void *buf);
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/**
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* Allocates memory from buflib's memory pool
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*
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* size: How many bytes to allocate
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*
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* This function passes NULL for the callback structure "ops", so buffers
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* are movable. Don't pass them to functions that yield().
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*
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* Returns: A positive integer handle identifying this allocation, or
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* a negative value on error (0 is also not a valid handle)
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*/
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int buflib_alloc(struct buflib_context *context, size_t size);
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/**
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* Allocates memory from the buflib's memory pool with additional callbacks
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* and flags
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*
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* name: A string identifier giving this allocation a name
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* size: How many bytes to allocate
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* ops: a struct with pointers to callback functions (see above).
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* if "ops" is NULL: Buffer is movable.
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*
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* Returns: A positive integer handle identifying this allocation, or
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* a negative value on error (0 is also not a valid handle)
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*/
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int buflib_alloc_ex(struct buflib_context *ctx, size_t size, const char *name,
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struct buflib_callbacks *ops);
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/**
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* Gets all available memory from buflib, for temporary use.
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*
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* Since this effectively makes all future allocations fail (unless
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* another allocation is freed in the meantime), you should definitely provide
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* a shrink callback if you plan to hold the buffer for a longer period. This
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* will allow buflib to permit allocations by shrinking the buffer returned by
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* this function.
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*
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* Note that this might return many more bytes than buflib_available() or
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* buflib_allocatable() return, because it aggressively compacts the pool
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* and even shrinks other allocations. However, do not depend on this behavior,
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* it may change.
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*
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* name: A string identifier giving this allocation a name
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* size: The actual size will be returned into size
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* ops: a struct with pointers to callback functions
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*
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* Returns: A positive integer handle identifying this allocation, or
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* a negative value on error (0 is also not a valid handle)
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*/
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int buflib_alloc_maximum(struct buflib_context* ctx, const char* name,
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size_t *size, struct buflib_callbacks *ops);
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/**
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* Queries the data pointer for the given handle. It's actually a cheap
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* operation, don't hesitate using it extensively.
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*
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* Notice that you need to re-query after every direct or indirect yield(),
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* because compaction can happen by other threads which may get your data
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* moved around (or you can get notified about changes by callbacks,
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* see further above).
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*
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* handle: The handle corresponding to the allocation
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*
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* Returns: The start pointer of the allocation
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*/
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#ifdef DEBUG
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void* buflib_get_data(struct buflib_context *ctx, int handle);
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#else
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static inline void* buflib_get_data(struct buflib_context *ctx, int handle)
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{
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return (void*)(ctx->handle_table[-handle].alloc);
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}
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#endif
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/**
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* Shrink the memory allocation associated with the given handle
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* Mainly intended to be used with the shrink callback, but it can also
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* be called outside as well, e.g. to give back buffer space allocated
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* with buflib_alloc_maximum().
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*
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* Note that you must move/copy data around yourself before calling this,
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* buflib will not do this as part of shrinking.
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*
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* handle: The handle identifying this allocation
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* new_start: the new start of the allocation
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* new_size: the new size of the allocation
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*
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* Returns: true if shrinking was successful. Otherwise it returns false,
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* without having modified memory.
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*
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*/
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bool buflib_shrink(struct buflib_context *ctx, int handle, void* newstart, size_t new_size);
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/**
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* Frees memory associated with the given handle
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*
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* Returns: 0 (to invalidate handles in one line, 0 is not a valid handle)
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*/
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int buflib_free(struct buflib_context *context, int handle);
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/**
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* Moves the underlying buflib buffer up by size bytes (as much as
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* possible for size == 0) without moving the end. This effectively
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* reduces the available space by taking away manageable space from the
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* front. This space is not available for new allocations anymore.
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*
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* To make space available in the front, everything is moved up.
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* It does _NOT_ call the move callbacks
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*
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*
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* size: size in bytes to move the buffer up (take away). The actual
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* bytes moved is returned in this
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* Returns: The new start of the underlying buflib buffer
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*/
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void* buflib_buffer_out(struct buflib_context *ctx, size_t *size);
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/**
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* Moves the underlying buflib buffer down by size bytes without
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* moving the end. This grows the buflib buffer by adding space to the front.
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* The new bytes are available for new allocations.
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*
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* Everything is moved down, and the new free space will be in the middle.
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* It does _NOT_ call the move callbacks.
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*
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* size: size in bytes to move the buffer down (new free space)
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*/
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void buflib_buffer_in(struct buflib_context *ctx, int size);
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/* debugging */
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/**
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* Returns the name, as given to buflib_alloc() and buflib_allloc_ex(), of the
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* allocation associated with the given handle. As naming allocations
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* is optional, there might be no name associated.
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*
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* handle: The handle indicating the allocation
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*
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* Returns: A pointer to the string identifier of the allocation, or NULL
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* if none was specified with buflib_alloc_ex().
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*/
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const char* buflib_get_name(struct buflib_context *ctx, int handle);
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/**
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* Prints an overview of all current allocations with the help
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* of the passed printer helper
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*
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* This walks only the handle table and prints only valid allocations
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*
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* Only available if BUFLIB_DEBUG_BLOCKS is defined
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*/
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void buflib_print_allocs(struct buflib_context *ctx, void (*print)(int, const char*));
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/**
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* Prints an overview of all blocks in the buflib buffer, allocated
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* or unallocated, with the help of the passed printer helper
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*
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* This walks the entire buffer and prints unallocated space also.
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* The output is also different from buflib_print_allocs().
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*
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* Only available if BUFLIB_DEBUG_BLOCKS is defined
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*/
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void buflib_print_blocks(struct buflib_context *ctx, void (*print)(int, const char*));
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/**
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* Gets the number of blocks in the entire buffer, allocated or unallocated
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*
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* Only available if BUFLIB_DEBUG_BLOCK_SIGNLE is defined
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*/
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int buflib_get_num_blocks(struct buflib_context *ctx);
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/**
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* Print information about a single block as indicated by block_num
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* into buf
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*
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* buflib_get_num_blocks() beforehand to get the total number of blocks,
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* as passing an block_num higher than that is undefined
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*
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* Only available if BUFLIB_DEBUG_BLOCK_SIGNLE is defined
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*/
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void buflib_print_block_at(struct buflib_context *ctx, int block_num,
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char* buf, size_t bufsize);
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/**
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* Check integrity of given buflib context
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*/
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void buflib_check_valid(struct buflib_context *ctx);
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#endif
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