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
152
153
154
155
156
157
158
159
160
161
|
/* Copyright 2024 Ján Sučan <jan@jansucan.com>
*
* 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
* HOLDER 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.
*/
#include "buffered_file.h"
#include "exception.h"
#include <cstring>
#include <filesystem>
#include <fstream>
BufferedFileReader::BufferedFileReader(std::filesystem::path path,
size_t buffer_capacity)
: m_buffer_offset(0), m_buffer_capacity(buffer_capacity)
{
m_file.open(path, std::ifstream::in | std::ifstream::binary);
if (!m_file) {
throw BufferedFileError("cannot open input file");
}
try {
m_buffer = std::make_unique<char[]>(m_buffer_capacity);
} catch (const std::bad_alloc &e) {
throw BufferedFileError("cannot allocate buffer for input file data");
}
refill_buffer();
};
size_t
BufferedFileReader::read(char *data, size_t data_size)
{
const size_t size_left = m_buffer_size - m_buffer_offset;
if (data_size <= size_left) {
return read_buffer(data, data_size);
} else {
const size_t size_outside_buffer = data_size - size_left;
read_buffer(data, size_left);
const size_t read_outside =
read_file(data + size_left, size_outside_buffer);
refill_buffer();
return size_left + read_outside;
}
};
size_t
BufferedFileReader::read_buffer(char *data, size_t data_size)
{
// Assumes that the caller makes sure there is enough data in the buffer
// to read
memcpy(data, reinterpret_cast<char *>(m_buffer.get()) + m_buffer_offset,
data_size);
m_buffer_offset += data_size;
return data_size;
};
void
BufferedFileReader::refill_buffer()
{
m_buffer_size = read_file(m_buffer.get(), m_buffer_capacity);
m_buffer_offset = 0;
};
size_t
BufferedFileReader::read_file(char *data, size_t data_size)
{
m_file.read(data, data_size);
if (!m_file.good() && !m_file.eof()) {
throw BufferedFileError("cannot read from file");
}
return m_file.gcount();
};
BufferedFileWriter::BufferedFileWriter(std::filesystem::path path,
size_t buffer_capacity)
: m_buffer_size(0), m_buffer_capacity(buffer_capacity)
{
/* When backing up, the output file is truncated to hold the
* new data
*/
m_file.open(path, std::ifstream::out | std::ifstream::trunc |
std::ifstream::binary);
if (!m_file) {
throw BufferedFileError("cannot open output file");
}
try {
m_buffer = std::make_unique<char[]>(m_buffer_capacity);
} catch (const std::bad_alloc &e) {
throw BufferedFileError("cannot allocate buffer for output file data");
}
};
BufferedFileWriter::~BufferedFileWriter() { flush_buffer(); };
void
BufferedFileWriter::write(const char *data, size_t data_size)
{
size_t free{m_buffer_capacity - m_buffer_size};
if (data_size <= free) {
// There is free space in the buffer
write_buffer(data, data_size);
} else {
// No free space
flush_buffer();
if (data_size <= m_buffer_capacity) {
// Data fits into the buffer
write_buffer(data, data_size);
} else {
// Doesn't fit
write_file(data, data_size);
}
}
};
void
BufferedFileWriter::write_buffer(const char *data, size_t data_size)
{
memcpy(reinterpret_cast<char *>(m_buffer.get()) + m_buffer_size, data,
data_size);
m_buffer_size += data_size;
};
void
BufferedFileWriter::flush_buffer()
{
write_file(m_buffer.get(), m_buffer_size);
m_buffer_size = 0;
};
void
BufferedFileWriter::write_file(const char *data, size_t data_size)
{
m_file.write(data, data_size);
if (!m_file) {
throw BufferedFileError("cannot write to output file");
}
};
|
