blob: 1373a8ab8f7ec7a929fe5d5586f3d63d9cb20837 (
plain)
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
|
#include "change_tracker.h"
#include <sstream>
#include <boost/optional.hpp>
#include <boost/filesystem/fstream.hpp>
namespace {
// constants for increasing pair access readability
constexpr unsigned int EMPLACE_SUCCESS = 1;
constexpr unsigned int FILE_NAME = 0;
constexpr unsigned int DIFF_PROCESS = 1;
boost::process::context createContext() {
boost::process::context context;
context.environment = boost::process::self::get_environment();
context.stdout_behavior = boost::process::capture_stream();
context.stdin_behavior = boost::process::capture_stream();
return context;
}
}
namespace utility {
ChangeTracker::ChangeTracker(utility::Logger* logger):
logger_(logger),
children_() { }
ChangeTracker::~ChangeTracker() {
for ( auto&& tracked : this->children_ ) {
std::get<DIFF_PROCESS>(tracked)->get_stdin().close();
this->logger_->forward(std::get<DIFF_PROCESS>(tracked)->get_stdout());
tracked.second->wait();
}
}
bool ChangeTracker::is_tracked(const std::string& file_path) const {
return this->children_.find(file_path) != this->children_.end();
}
// Begins tracking changes to a file reachable by a given path
//
// The actual tracking is performed by a `diff` instance that is
// spawned by this method and managed by this class.
// As `diff` is called as a new subprocess and because there is no
// straight forward way for checking / enforcing if it has already
// completed reading the initial contents of the file the command
// is structured in the following sequence:
//
// diff -p - $file_path
//
// This means that reading the final file contents is delegated to
// `diff` while the initial file contents are read by this method
// and written to `diff`'s standard input.
//
// If the `-` and `$file_path` arguments were exchanged there would
// be no way to:
// - be sure the initial contents are read before the changing
// syscall that triggered this tracking in the first place is
// performed
// - be sure that the initial file contents are read completly
// as `diff` seemingly only reads the first block of the first
// file provided if the second file argument is standard input
//
bool ChangeTracker::track(const std::string& file_path) {
auto result = this->children_.emplace(
file_path,
std::make_unique<boost::process::child>(
boost::process::launch_shell("diff -p - " + file_name, createContext())
)
);
if ( std::get<EMPLACE_SUCCESS>(result) ) {
boost::filesystem::ifstream file(
std::get<FILE_NAME>(*result.first)
);
if ( file.is_open() ) {
std::get<DIFF_PROCESS>(*result.first)->get_stdin() << file.rdbuf();
}
return true;
} else {
return false;
}
}
}
|
