1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
|
/* SPDX-License-Identifier: BSD-2-Clause */
/*
* COPYRIGHT (c) 2012, 2018 Chris Johns <chrisj@rtems.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/**
* @file
*
* @ingroup rtems_rtl
*
* @brief RTEMS Run-Time Linker Object File cache buffers a section of the
* object file in a buffer to localise read performance.
*
* This is a simple object file cache that holds a buffer of data from the
* offset in the file the read is requested from. Writes are not supported.
*
* The cache holds the file descriptor, the offset into the file and the amount
* of valid data in the cache. If the file is ever modified the user of the
* cache to responsible for flushing the cache. For example the cache should be
* flused if the file is closed.
*
* The cache can return by reference or by value. By reference allow access to
* the cache buffer. Do not modify the cache's data. By value will copy the
* requested data into the user supplied buffer.
*
* The read by reference call allows you to probe the file's data. For example
* a string in an object file can be an unknown length. You can request a read
* up to the cache's size by reference. The code will attempt to have this data
* in the buffer. If there is not enough data in the file the length will be
* modifed to reflect this.
*
* You can have more than one cache for a single file all looking at different
* parts of the file.
*/
#if !defined (_RTEMS_RTL_OBJ_CACHE_H_)
#define _RTEMS_RTL_OBJ_CACHE_H_
#include <fcntl.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
/**
* The buffer cache.
*/
typedef struct rtems_rtl_obj_cache
{
int fd; /**< The file descriptor of the data in the cache. */
size_t file_size; /**< The size of the file. */
off_t offset; /**< The base offset of the buffer. */
size_t size; /**< The size of the cache. */
size_t level; /**< The amount of data in the cache. A file can be
* smaller than the cache file. */
uint8_t* buffer; /**< The buffer */
} rtems_rtl_obj_cache;
/**
* Open a cache allocating a single buffer of the size passed. The default
* state of the cache is flushed. No already open checks are made.
*
* @param cache The cache to initialise.
* @param size The size of the cache.
* @retval true The cache is open.
* @retval false The cache is not open. The RTL error is set.
*/
bool rtems_rtl_obj_cache_open (rtems_rtl_obj_cache* cache, size_t size);
/**
* Close a cache.
*
* @param cache The cache to close.
*/
void rtems_rtl_obj_cache_close (rtems_rtl_obj_cache* cache);
/**
* Flush the cache. Any further read will read the data from the file.
*
* @param cache The cache to flush.
*/
void rtems_rtl_obj_cache_flush (rtems_rtl_obj_cache* cache);
/**
* Read data by reference. The length contains the amount of data that should
* be available in the cache and referenced by the buffer handle. It must be
* less than or equal to the size of the cache. This call will return the
* amount of data that is available. It can be less than you ask if the offset
* and size is past the end of the file.
*
* @param cache The cache to reference data from.
* @param fd The file descriptor. Must be an open file.
* @param offset The offset in the file to reference the data to.
* @param buffer The location to reference the data from.
* @param length The length of data to reference. Can be modified to a
* lesser value and true is still returned so check it.
* @retval true The data referenced is in the cache.
* @retval false The read failed and the RTL error has been set.
*/
bool rtems_rtl_obj_cache_read (rtems_rtl_obj_cache* cache,
int fd,
off_t offset,
void** buffer,
size_t* length);
/**
* Read data by value. The data is copied to the user supplied buffer.
*
* @param cache The cache to read the data from.
* @param fd The file descriptor. Must be an open file.
* @param offset The offset in the file to read the data from.
* @param buffer The location the data is written into.
* @param length The length of data to read.
* @retval true The data has been read from the cache.
* @retval false The read failed and the RTL error has been set.
*/
bool rtems_rtl_obj_cache_read_byval (rtems_rtl_obj_cache* cache,
int fd,
off_t offset,
void* buffer,
size_t length);
#ifdef __cplusplus
}
#endif /* __cplusplus */
#endif
|
