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
|
/*
* This source code is released into the public domain.
*/
#ifndef LFJAIL_READ_FILE_HH
#define LFJAIL_READ_FILE_HH
#include <array>
#include <iterator>
#include <ranges>
#include <span>
#include <string>
#include <vector>
#include <fcntl.h>
#include <unistd.h>
#include "context.hh"
#include "io_error.hh"
#include "guard.hh"
namespace lfjail {
void ensure_dir(context const &ctx, std::string_view dir);
/*
* Load the contents of a file into an output iterator. Throws io_error
* on failure.
*/
void read_file(std::string filename,
std::output_iterator<char> auto &&iter)
{
constexpr std::size_t bufsize = 1024;
std::array<char, bufsize> buffer;
int fd, err;
if ((fd = ::open(filename.c_str(), O_RDONLY)) == -1)
throw io_error(filename, errno);
auto fd_guard = guard([fd] { ::close(fd); });
while ((err = ::read(fd, &buffer[0], buffer.size())) > 0) {
auto data = std::span(buffer).subspan(0, err);
std::ranges::copy(data, iter);
}
if (err == -1)
throw io_error(filename, errno);
}
/*
* Write the contents of a range to a file. Throws io_error on error.
*/
void write_file(std::string filename, std::ranges::range auto &&range) {
// Convert the range into an array.
std::vector<char> chars;
std::ranges::copy(range, std::back_inserter(chars));
// Open the output file.
int fd;
if ((fd = ::open(filename.c_str(), O_CREAT|O_WRONLY, 0777)) == -1)
throw io_error(filename, errno);
auto fd_guard = guard([fd] { ::close(fd); });
// Write the data.
if (int err = ::write(fd, chars.data(), chars.size()); err < 0)
throw io_error(filename, errno);
}
/*
* Write the contents of a range to a file safely. The data will be written
* to "<filename>.tmp", and if the write succeeds, the temporary file will be
* renamed to the target filename. If an error occurs, the target file will
* not be modified.
*/
void safe_write_file(std::string filename, std::ranges::range auto &&range) {
auto tmpfile = filename + ".tmp";
auto tmpfile_guard = guard([tmpfile] { ::unlink(tmpfile.c_str()); });
write_file(tmpfile, range);
int err = ::rename(tmpfile.c_str(), filename.c_str());
if (err != 0)
throw io_error(filename, errno);
}
} // namespace lfjail
#endif // !LFJAIL_FILEUTILS_HH
|
