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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** ThreadX Component */
/** */
/** Byte Pool */
/** */
/**************************************************************************/
/**************************************************************************/
#define TX_SOURCE_CODE
/* Include necessary system files. */
#include "tx_api.h"
#include "tx_thread.h"
#include "tx_byte_pool.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _tx_byte_pool_search PORTABLE C */
/* 6.1.7 */
/* AUTHOR */
/* */
/* William E. Lamie, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function searches a byte pool for a memory block to satisfy */
/* the requested number of bytes. Merging of adjacent free blocks */
/* takes place during the search and a split of the block that */
/* satisfies the request may occur before this function returns. */
/* */
/* It is assumed that this function is called with interrupts enabled */
/* and with the tx_pool_owner field set to the thread performing the */
/* search. Also note that the search can occur during allocation and */
/* release of a memory block. */
/* */
/* INPUT */
/* */
/* pool_ptr Pointer to pool control block */
/* memory_size Number of bytes required */
/* */
/* OUTPUT */
/* */
/* UCHAR * Pointer to the allocated memory, */
/* if successful. Otherwise, a */
/* NULL is returned */
/* */
/* CALLS */
/* */
/* None */
/* */
/* CALLED BY */
/* */
/* _tx_byte_allocate Allocate bytes of memory */
/* _tx_byte_release Release bytes of memory */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 William E. Lamie Initial Version 6.0 */
/* 09-30-2020 Yuxin Zhou Modified comment(s), */
/* resulting in version 6.1 */
/* 06-02-2021 Scott Larson Improve possible free bytes */
/* calculation, */
/* resulting in version 6.1.7 */
/* */
/**************************************************************************/
UCHAR *_tx_byte_pool_search(TX_BYTE_POOL *pool_ptr, ULONG memory_size)
{
TX_INTERRUPT_SAVE_AREA
UCHAR *current_ptr;
UCHAR *next_ptr;
UCHAR **this_block_link_ptr;
UCHAR **next_block_link_ptr;
ULONG available_bytes;
UINT examine_blocks;
UINT first_free_block_found = TX_FALSE;
TX_THREAD *thread_ptr;
ALIGN_TYPE *free_ptr;
UCHAR *work_ptr;
ULONG total_theoretical_available;
/* Disable interrupts. */
TX_DISABLE
/* First, determine if there are enough bytes in the pool. */
/* Theoretical bytes available = free bytes + ((fragments-2) * overhead of each block) */
total_theoretical_available = pool_ptr -> tx_byte_pool_available + ((pool_ptr -> tx_byte_pool_fragments - 2) * ((sizeof(UCHAR *)) + (sizeof(ALIGN_TYPE))));
if (memory_size >= total_theoretical_available)
{
/* Restore interrupts. */
TX_RESTORE
/* Not enough memory, return a NULL pointer. */
current_ptr = TX_NULL;
}
else
{
/* Pickup thread pointer. */
TX_THREAD_GET_CURRENT(thread_ptr)
/* Setup ownership of the byte pool. */
pool_ptr -> tx_byte_pool_owner = thread_ptr;
/* Walk through the memory pool in search for a large enough block. */
current_ptr = pool_ptr -> tx_byte_pool_search;
examine_blocks = pool_ptr -> tx_byte_pool_fragments + ((UINT) 1);
available_bytes = ((ULONG) 0);
do
{
#ifdef TX_BYTE_POOL_ENABLE_PERFORMANCE_INFO
/* Increment the total fragment search counter. */
_tx_byte_pool_performance_search_count++;
/* Increment the number of fragments searched on this pool. */
pool_ptr -> tx_byte_pool_performance_search_count++;
#endif
/* Check to see if this block is free. */
work_ptr = TX_UCHAR_POINTER_ADD(current_ptr, (sizeof(UCHAR *)));
free_ptr = TX_UCHAR_TO_ALIGN_TYPE_POINTER_CONVERT(work_ptr);
if ((*free_ptr) == TX_BYTE_BLOCK_FREE)
{
/* Determine if this is the first free block. */
if (first_free_block_found == TX_FALSE)
{
/* This is the first free block. */
pool_ptr->tx_byte_pool_search = current_ptr;
/* Set the flag to indicate we have found the first free
block. */
first_free_block_found = TX_TRUE;
}
/* Block is free, see if it is large enough. */
/* Pickup the next block's pointer. */
this_block_link_ptr = TX_UCHAR_TO_INDIRECT_UCHAR_POINTER_CONVERT(current_ptr);
next_ptr = *this_block_link_ptr;
/* Calculate the number of bytes available in this block. */
available_bytes = TX_UCHAR_POINTER_DIF(next_ptr, current_ptr);
available_bytes = available_bytes - ((sizeof(UCHAR *)) + (sizeof(ALIGN_TYPE)));
/* If this is large enough, we are done because our first-fit algorithm
has been satisfied! */
if (available_bytes >= memory_size)
{
/* Get out of the search loop! */
break;
}
else
{
/* Clear the available bytes variable. */
available_bytes = ((ULONG) 0);
/* Not enough memory, check to see if the neighbor is
free and can be merged. */
work_ptr = TX_UCHAR_POINTER_ADD(next_ptr, (sizeof(UCHAR *)));
free_ptr = TX_UCHAR_TO_ALIGN_TYPE_POINTER_CONVERT(work_ptr);
if ((*free_ptr) == TX_BYTE_BLOCK_FREE)
{
/* Yes, neighbor block can be merged! This is quickly accomplished
by updating the current block with the next blocks pointer. */
next_block_link_ptr = TX_UCHAR_TO_INDIRECT_UCHAR_POINTER_CONVERT(next_ptr);
*this_block_link_ptr = *next_block_link_ptr;
/* Reduce the fragment total. We don't need to increase the bytes
available because all free headers are also included in the available
count. */
pool_ptr -> tx_byte_pool_fragments--;
#ifdef TX_BYTE_POOL_ENABLE_PERFORMANCE_INFO
/* Increment the total merge counter. */
_tx_byte_pool_performance_merge_count++;
/* Increment the number of blocks merged on this pool. */
pool_ptr -> tx_byte_pool_performance_merge_count++;
#endif
/* See if the search pointer is affected. */
if (pool_ptr -> tx_byte_pool_search == next_ptr)
{
/* Yes, update the search pointer. */
pool_ptr -> tx_byte_pool_search = current_ptr;
}
}
else
{
/* Neighbor is not free so we can skip over it! */
next_block_link_ptr = TX_UCHAR_TO_INDIRECT_UCHAR_POINTER_CONVERT(next_ptr);
current_ptr = *next_block_link_ptr;
/* Decrement the examined block count to account for this one. */
if (examine_blocks != ((UINT) 0))
{
examine_blocks--;
#ifdef TX_BYTE_POOL_ENABLE_PERFORMANCE_INFO
/* Increment the total fragment search counter. */
_tx_byte_pool_performance_search_count++;
/* Increment the number of fragments searched on this pool. */
pool_ptr -> tx_byte_pool_performance_search_count++;
#endif
}
}
}
}
else
{
/* Block is not free, move to next block. */
this_block_link_ptr = TX_UCHAR_TO_INDIRECT_UCHAR_POINTER_CONVERT(current_ptr);
current_ptr = *this_block_link_ptr;
}
/* Another block has been searched... decrement counter. */
if (examine_blocks != ((UINT) 0))
{
examine_blocks--;
}
/* Restore interrupts temporarily. */
TX_RESTORE
/* Disable interrupts. */
TX_DISABLE
/* Determine if anything has changed in terms of pool ownership. */
if (pool_ptr -> tx_byte_pool_owner != thread_ptr)
{
/* Pool changed ownership in the brief period interrupts were
enabled. Reset the search. */
current_ptr = pool_ptr -> tx_byte_pool_search;
examine_blocks = pool_ptr -> tx_byte_pool_fragments + ((UINT) 1);
/* Setup our ownership again. */
pool_ptr -> tx_byte_pool_owner = thread_ptr;
}
} while(examine_blocks != ((UINT) 0));
/* Determine if a block was found. If so, determine if it needs to be
split. */
if (available_bytes != ((ULONG) 0))
{
/* Determine if we need to split this block. */
if ((available_bytes - memory_size) >= ((ULONG) TX_BYTE_BLOCK_MIN))
{
/* Split the block. */
next_ptr = TX_UCHAR_POINTER_ADD(current_ptr, (memory_size + ((sizeof(UCHAR *)) + (sizeof(ALIGN_TYPE)))));
/* Setup the new free block. */
next_block_link_ptr = TX_UCHAR_TO_INDIRECT_UCHAR_POINTER_CONVERT(next_ptr);
this_block_link_ptr = TX_UCHAR_TO_INDIRECT_UCHAR_POINTER_CONVERT(current_ptr);
*next_block_link_ptr = *this_block_link_ptr;
work_ptr = TX_UCHAR_POINTER_ADD(next_ptr, (sizeof(UCHAR *)));
free_ptr = TX_UCHAR_TO_ALIGN_TYPE_POINTER_CONVERT(work_ptr);
*free_ptr = TX_BYTE_BLOCK_FREE;
/* Increase the total fragment counter. */
pool_ptr -> tx_byte_pool_fragments++;
/* Update the current pointer to point at the newly created block. */
*this_block_link_ptr = next_ptr;
/* Set available equal to memory size for subsequent calculation. */
available_bytes = memory_size;
#ifdef TX_BYTE_POOL_ENABLE_PERFORMANCE_INFO
/* Increment the total split counter. */
_tx_byte_pool_performance_split_count++;
/* Increment the number of blocks split on this pool. */
pool_ptr -> tx_byte_pool_performance_split_count++;
#endif
}
/* In any case, mark the current block as allocated. */
work_ptr = TX_UCHAR_POINTER_ADD(current_ptr, (sizeof(UCHAR *)));
this_block_link_ptr = TX_UCHAR_TO_INDIRECT_UCHAR_POINTER_CONVERT(work_ptr);
*this_block_link_ptr = TX_BYTE_POOL_TO_UCHAR_POINTER_CONVERT(pool_ptr);
/* Reduce the number of available bytes in the pool. */
pool_ptr -> tx_byte_pool_available = (pool_ptr -> tx_byte_pool_available - available_bytes) - ((sizeof(UCHAR *)) + (sizeof(ALIGN_TYPE)));
/* Determine if the search pointer needs to be updated. This is only done
if the search pointer matches the block to be returned. */
if (current_ptr == pool_ptr -> tx_byte_pool_search)
{
/* Yes, update the search pointer to the next block. */
this_block_link_ptr = TX_UCHAR_TO_INDIRECT_UCHAR_POINTER_CONVERT(current_ptr);
pool_ptr -> tx_byte_pool_search = *this_block_link_ptr;
}
/* Restore interrupts. */
TX_RESTORE
/* Adjust the pointer for the application. */
current_ptr = TX_UCHAR_POINTER_ADD(current_ptr, (((sizeof(UCHAR *)) + (sizeof(ALIGN_TYPE)))));
}
else
{
/* Restore interrupts. */
TX_RESTORE
/* Set current pointer to NULL to indicate nothing was found. */
current_ptr = TX_NULL;
}
}
/* Return the search pointer. */
return(current_ptr);
}
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