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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. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** USBX Component */
/** */
/** USBX main stack */
/** */
/**************************************************************************/
/**************************************************************************/
/* Include necessary system files. */
#define UX_SOURCE_CODE
#include "ux_api.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _ux_utility_memory_free_block_best_get PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* Chaoqiong Xiao, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function returns the best free memory block. */
/* */
/* INPUT */
/* */
/* memory_cache_flag Memory pool source */
/* memory_size_requested Size of memory requested */
/* */
/* OUTPUT */
/* */
/* Pointer to best free block */
/* */
/* CALLS */
/* */
/* None */
/* */
/* CALLED BY */
/* */
/* USBX Components */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Chaoqiong Xiao Initial Version 6.0 */
/* 09-30-2020 Chaoqiong Xiao Modified comment(s), */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
UX_MEMORY_BLOCK *_ux_utility_memory_free_block_best_get(ULONG memory_cache_flag,
ULONG memory_size_requested)
{
UX_MEMORY_BLOCK *memory_block;
UX_MEMORY_BLOCK *best_memory_block;
/* Reset the free memory block. */
best_memory_block = UX_NULL;
/* Check the type of memory we need. */
switch (memory_cache_flag)
{
case UX_REGULAR_MEMORY :
/* Start at the beginning of the regular memory pool. */
memory_block = _ux_system -> ux_system_regular_memory_pool_start;
break;
case UX_CACHE_SAFE_MEMORY :
/* Start at the beginning of the cache safe memory pool. */
memory_block = _ux_system -> ux_system_cache_safe_memory_pool_start;
break;
default :
/* Wrong memory type. */
return(UX_NULL);
}
/* Loop on all memory blocks from the beginning. */
while (memory_block != UX_NULL)
{
/* Check the memory block status. */
if (memory_block -> ux_memory_block_status == UX_MEMORY_UNUSED)
{
/* Check the size of this free block and see if it will
fit the memory requirement. */
if (memory_block -> ux_memory_block_size > memory_size_requested)
{
/* This memory block will do. Now see if it is the best.
The best memory block is the one whose memory is closest
to the memory requested. */
if (best_memory_block == UX_NULL)
/* Initialize the best block with the first free one. */
best_memory_block = memory_block;
else
{
if (memory_block -> ux_memory_block_size < best_memory_block -> ux_memory_block_size)
/* We have discovered a better fit block. */
best_memory_block = memory_block;
}
}
}
/* Search the next free block until the end. */
memory_block = memory_block -> ux_memory_block_next;
}
/* If no free memory block was found, the return value will be NULL. */
return(best_memory_block);
}