about summary refs log tree commit diff
path: root/src/libstore/references.cc
blob: bfb4f8d0a3aff7d36753fecaf1fa5443979c7efa (plain) (blame)
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
#include "references.hh"
#include "hash.hh"
#include "util.hh"

#include <cerrno>
#include <cstring>
#include <cstdlib>
#include <map>

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <dirent.h>
#include <fcntl.h>


namespace nix {


static unsigned int refLength = 32; /* characters */


static void search(size_t len, const unsigned char * s,
    StringSet & ids, StringSet & seen)
{
    static bool initialised = false;
    static bool isBase32[256];
    if (!initialised) {
        for (unsigned int i = 0; i < 256; ++i) isBase32[i] = false;
        for (unsigned int i = 0; i < base32Chars.size(); ++i)
            isBase32[(unsigned char) base32Chars[i]] = true;
        initialised = true;
    }
    
    for (unsigned int i = 0; i + refLength <= len; ) {
        int j;
        bool match = true;
        for (j = refLength - 1; j >= 0; --j)
            if (!isBase32[(unsigned char) s[i + j]]) {
                i += j + 1;
                match = false;
                break;
            }
        if (!match) continue;
        string ref((const char *) s + i, refLength);
        if (ids.find(ref) != ids.end()) {
            debug(format("found reference to `%1%' at offset `%2%'")
                  % ref % i);
            seen.insert(ref);
            ids.erase(ref);
        }
        ++i;
    }
}


void checkPath(const string & path,
    StringSet & ids, StringSet & seen)
{
    checkInterrupt();
    
    debug(format("checking `%1%'") % path);

    struct stat st;
    if (lstat(path.c_str(), &st))
        throw SysError(format("getting attributes of path `%1%'") % path);

    if (S_ISDIR(st.st_mode)) {
        Strings names = readDirectory(path);
	for (Strings::iterator i = names.begin(); i != names.end(); i++) {
            search(i->size(), (const unsigned char *) i->c_str(), ids, seen);
            checkPath(path + "/" + *i, ids, seen);
        }
    }

    else if (S_ISREG(st.st_mode)) {
        
        AutoCloseFD fd = open(path.c_str(), O_RDONLY);
        if (fd == -1) throw SysError(format("opening file `%1%'") % path);

        size_t bufSize = 1024 * 1024;
        assert(refLength <= bufSize);
        unsigned char * buf = new unsigned char[bufSize];

        size_t left = st.st_size;
        bool firstBlock = true;
        
        while (left > 0) {
            checkInterrupt();
            
            size_t read = left > bufSize ? bufSize : left;
            size_t copiedBytes = 0;

            if (!firstBlock) {
                /* Move the last (refLength - 1) bytes from the last
                   block to the start of the buffer to deal with
                   references that cross block boundaries. */
                copiedBytes = refLength - 1;
                if (read + copiedBytes > bufSize)
                    read -= copiedBytes;
                memcpy(buf, buf + (bufSize - copiedBytes), copiedBytes);
            }
            firstBlock = false;

            readFull(fd, buf + copiedBytes, read);
            left -= read;

            search(copiedBytes + read, buf, ids, seen);
        }
        
        delete[] buf; /* !!! autodelete */
    }
    
    else if (S_ISLNK(st.st_mode)) {
        string target = readLink(path);
        search(target.size(), (const unsigned char *) target.c_str(), ids, seen);
    }
    
    else throw Error(format("unknown file type: %1%") % path);
}


PathSet scanForReferences(const string & path, const PathSet & paths)
{
    std::map<string, Path> backMap;
    StringSet ids;
    StringSet seen;

    /* For efficiency (and a higher hit rate), just search for the
       hash part of the file name.  (This assumes that all references
       have the form `HASH-bla'). */
    for (PathSet::const_iterator i = paths.begin(); i != paths.end(); i++) {
        string baseName = baseNameOf(*i);
        string::size_type pos = baseName.find('-');
        if (pos == string::npos)
            throw Error(format("bad reference `%1%'") % *i);
        string s = string(baseName, 0, pos);
        assert(s.size() == refLength);
        assert(backMap.find(s) == backMap.end());
        // parseHash(htSHA256, s);
        ids.insert(s);
        backMap[s] = *i;
    }

    checkPath(path, ids, seen);

    PathSet found;
    for (StringSet::iterator i = seen.begin(); i != seen.end(); i++) {
        std::map<string, Path>::iterator j;
        if ((j = backMap.find(*i)) == backMap.end()) abort();
        found.insert(j->second);
    }

    return found;
}

 
}