1 /**************************************************************************/
2 /*                                                                        */
3 /*       Copyright (c) Microsoft Corporation. All rights reserved.        */
4 /*                                                                        */
5 /*       This software is licensed under the Microsoft Software License   */
6 /*       Terms for Microsoft Azure RTOS. Full text of the license can be  */
7 /*       found in the LICENSE file at https://aka.ms/AzureRTOS_EULA       */
8 /*       and in the root directory of this software.                      */
9 /*                                                                        */
10 /**************************************************************************/
11 
12 
13 /**************************************************************************/
14 /**************************************************************************/
15 /**                                                                       */
16 /** USBX Component                                                        */
17 /**                                                                       */
18 /**   USBX main stack                                                     */
19 /**                                                                       */
20 /**************************************************************************/
21 /**************************************************************************/
22 
23 
24 /* Include necessary system files.  */
25 
26 #define UX_SOURCE_CODE
27 
28 #include "ux_api.h"
29 
30 
31 /**************************************************************************/
32 /*                                                                        */
33 /*  FUNCTION                                               RELEASE        */
34 /*                                                                        */
35 /*    _ux_utility_memory_free_block_best_get              PORTABLE C      */
36 /*                                                           6.1          */
37 /*  AUTHOR                                                                */
38 /*                                                                        */
39 /*    Chaoqiong Xiao, Microsoft Corporation                               */
40 /*                                                                        */
41 /*  DESCRIPTION                                                           */
42 /*                                                                        */
43 /*    This function returns the best free memory block.                   */
44 /*                                                                        */
45 /*  INPUT                                                                 */
46 /*                                                                        */
47 /*    memory_cache_flag                     Memory pool source            */
48 /*    memory_size_requested                 Size of memory requested      */
49 /*                                                                        */
50 /*  OUTPUT                                                                */
51 /*                                                                        */
52 /*    Pointer to best free block                                          */
53 /*                                                                        */
54 /*  CALLS                                                                 */
55 /*                                                                        */
56 /*    None                                                                */
57 /*                                                                        */
58 /*  CALLED BY                                                             */
59 /*                                                                        */
60 /*    USBX Components                                                     */
61 /*                                                                        */
62 /*  RELEASE HISTORY                                                       */
63 /*                                                                        */
64 /*    DATE              NAME                      DESCRIPTION             */
65 /*                                                                        */
66 /*  05-19-2020     Chaoqiong Xiao           Initial Version 6.0           */
67 /*  09-30-2020     Chaoqiong Xiao           Modified comment(s),          */
68 /*                                            resulting in version 6.1    */
69 /*                                                                        */
70 /**************************************************************************/
_ux_utility_memory_free_block_best_get(ULONG memory_cache_flag,ULONG memory_size_requested)71 UX_MEMORY_BLOCK  *_ux_utility_memory_free_block_best_get(ULONG memory_cache_flag,
72                                                         ULONG memory_size_requested)
73 {
74 
75 UX_MEMORY_BLOCK     *memory_block;
76 UX_MEMORY_BLOCK     *best_memory_block;
77 
78 
79     /* Reset the free memory block.  */
80     best_memory_block =  UX_NULL;
81 
82     /* Check the type of memory we need.  */
83     switch (memory_cache_flag)
84     {
85 
86         case UX_REGULAR_MEMORY            :
87 
88             /* Start at the beginning of the regular memory pool.  */
89             memory_block =  _ux_system -> ux_system_regular_memory_pool_start;
90             break;
91 
92         case UX_CACHE_SAFE_MEMORY       :
93 
94             /* Start at the beginning of the cache safe memory pool.  */
95             memory_block =  _ux_system -> ux_system_cache_safe_memory_pool_start;
96             break;
97 
98         default                            :
99 
100             /* Wrong memory type.  */
101             return(UX_NULL);
102 
103     }
104 
105     /* Loop on all memory blocks from the beginning.  */
106     while (memory_block != UX_NULL)
107     {
108 
109         /* Check the memory block status.  */
110         if (memory_block -> ux_memory_block_status == UX_MEMORY_UNUSED)
111         {
112 
113             /* Check the size of this free block and see if it will
114                fit the memory requirement.  */
115             if (memory_block -> ux_memory_block_size > memory_size_requested)
116             {
117 
118                 /* This memory block will do. Now see if it is the best.
119                    The best memory block is the one whose memory is closest
120                    to the memory requested.  */
121                 if (best_memory_block == UX_NULL)
122 
123                     /* Initialize the best block with the first free one.  */
124                     best_memory_block =  memory_block;
125                 else
126                 {
127 
128                     if (memory_block -> ux_memory_block_size < best_memory_block -> ux_memory_block_size)
129 
130                         /* We have discovered a better fit block.  */
131                         best_memory_block =  memory_block;
132                 }
133             }
134         }
135 
136         /* Search the next free block until the end.  */
137         memory_block =  memory_block -> ux_memory_block_next;
138     }
139 
140     /* If no free memory block was found, the return value will be NULL.  */
141     return(best_memory_block);
142 }
143 
144