800bc000a0
These are more efficient than separate pin/unpin calls because pin count increment and decrement can be done cheaply when the data pointer is known. Secondly, pinned access can be made safe against preemption by hardware interrupts or other CPU cores; buflib_get_data() can't. This makes it more useful under different threading models and for SMP targets; both of which are not particularly relevant to Rockbox now, but might be in the future. Change-Id: I09284251b83bbbc59ef88a494c8fda26a7f7ef26
97 lines
3.3 KiB
C
97 lines
3.3 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_MEMPOOL_H_
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#define _BUFLIB_MEMPOOL_H_
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#ifndef _BUFLIB_H_
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# error "include buflib.h instead"
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#endif
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#include "system.h"
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/* Indices used to access block fields as block[BUFLIB_IDX_XXX] */
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enum {
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BUFLIB_IDX_LEN, /* length of the block, must come first */
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BUFLIB_IDX_HANDLE, /* pointer to entry in the handle table */
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BUFLIB_IDX_OPS, /* pointer to an ops struct */
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BUFLIB_IDX_PIN, /* pin count */
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BUFLIB_NUM_FIELDS,
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};
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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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volatile unsigned pincount; /* number of pins */
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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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};
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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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#define BUFLIB_ALLOC_OVERHEAD (BUFLIB_NUM_FIELDS * sizeof(union buflib_data))
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#ifndef BUFLIB_DEBUG_GET_DATA
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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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static inline union buflib_data *_buflib_get_block_header(void *data)
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{
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union buflib_data *bd = ALIGN_DOWN(data, sizeof(*bd));
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return bd - BUFLIB_NUM_FIELDS;
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}
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static inline void *buflib_get_data_pinned(struct buflib_context *ctx, int handle)
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{
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void *data = buflib_get_data(ctx, handle);
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union buflib_data *bd = _buflib_get_block_header(data);
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bd[BUFLIB_IDX_PIN].pincount++;
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return data;
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}
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static inline void buflib_put_data_pinned(struct buflib_context *ctx, void *data)
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{
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(void)ctx;
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union buflib_data *bd = _buflib_get_block_header(data);
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bd[BUFLIB_IDX_PIN].pincount--;
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}
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#endif /* _BUFLIB_MEMPOOL_H_ */
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