summaryrefslogtreecommitdiffstats
path: root/path.c
blob: ef3f277f17ac436cbb2b37856b52ae50ae2fa2ed (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
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
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
/* Code to mangle pathnames into those matching a given prefix.
   eg. open("/lib/foo.so") => open("/usr/gnemul/i386-linux/lib/foo.so");

   The assumption is that this area does not change.
*/
#include <sys/types.h>
#include <sys/param.h>
#include <dirent.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>
#include "qemu-common.h"

struct pathelem
{
    /* Name of this, eg. lib */
    char *name;
    /* Full path name, eg. /usr/gnemul/x86-linux/lib. */
    char *pathname;
    struct pathelem *parent;
    /* Children */
    unsigned int num_entries;
    struct pathelem *entries[0];
};

static struct pathelem *base;

/* First N chars of S1 match S2, and S2 is N chars long. */
static int strneq(const char *s1, unsigned int n, const char *s2)
{
    unsigned int i;

    for (i = 0; i < n; i++)
        if (s1[i] != s2[i])
            return 0;
    return s2[i] == 0;
}

static struct pathelem *add_entry(struct pathelem *root, const char *name,
                                  unsigned char type);

static struct pathelem *new_entry(const char *root,
                                  struct pathelem *parent,
                                  const char *name)
{
    struct pathelem *new = malloc(sizeof(*new));
    new->name = strdup(name);
    if (asprintf(&new->pathname, "%s/%s", root, name) == -1) {
        printf("Cannot allocate memory\n");
        exit(1);
    }
    new->num_entries = 0;
    return new;
}

#define streq(a,b) (strcmp((a), (b)) == 0)

/* Not all systems provide this feature */
#if defined(DT_DIR) && defined(DT_UNKNOWN)
# define dirent_type(dirent) ((dirent)->d_type)
# define is_dir_maybe(type)  ((type) == DT_DIR || (type) == DT_UNKNOWN)
#else
# define dirent_type(dirent) (1)
# define is_dir_maybe(type)  (type)
#endif

static struct pathelem *add_dir_maybe(struct pathelem *path)
{
    DIR *dir;

    if ((dir = opendir(path->pathname)) != NULL) {
        struct dirent *dirent;

        while ((dirent = readdir(dir)) != NULL) {
            if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
                path = add_entry(path, dirent->d_name, dirent_type(dirent));
            }
        }
        closedir(dir);
    }
    return path;
}

static struct pathelem *add_entry(struct pathelem *root, const char *name,
                                  unsigned char type)
{
    struct pathelem **e;

    root->num_entries++;

    root = realloc(root, sizeof(*root)
                   + sizeof(root->entries[0])*root->num_entries);
    e = &root->entries[root->num_entries-1];

    *e = new_entry(root->pathname, root, name);
    if (is_dir_maybe(type)) {
        *e = add_dir_maybe(*e);
    }

    return root;
}

/* This needs to be done after tree is stabilized (ie. no more reallocs!). */
static void set_parents(struct pathelem *child, struct pathelem *parent)
{
    unsigned int i;

    child->parent = parent;
    for (i = 0; i < child->num_entries; i++)
        set_parents(child->entries[i], child);
}

/* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
static const char *
follow_path(const struct pathelem *cursor, const char *name)
{
    unsigned int i, namelen;

    name += strspn(name, "/");
    namelen = strcspn(name, "/");

    if (namelen == 0)
        return cursor->pathname;

    if (strneq(name, namelen, ".."))
        return follow_path(cursor->parent, name + namelen);

    if (strneq(name, namelen, "."))
        return follow_path(cursor, name + namelen);

    for (i = 0; i < cursor->num_entries; i++)
        if (strneq(name, namelen, cursor->entries[i]->name))
            return follow_path(cursor->entries[i], name + namelen);

    /* Not found */
    return NULL;
}

void init_paths(const char *prefix)
{
    char pref_buf[PATH_MAX];

    if (prefix[0] == '\0' ||
        !strcmp(prefix, "/"))
        return;

    if (prefix[0] != '/') {
        char *cwd = getcwd(NULL, 0);
        size_t pref_buf_len = sizeof(pref_buf);

        if (!cwd)
            abort();
        pstrcpy(pref_buf, sizeof(pref_buf), cwd);
        pstrcat(pref_buf, pref_buf_len, "/");
        pstrcat(pref_buf, pref_buf_len, prefix);
        free(cwd);
    } else
        pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);

    base = new_entry("", NULL, pref_buf);
    base = add_dir_maybe(base);
    if (base->num_entries == 0) {
        free (base);
        base = NULL;
    } else {
        set_parents(base, base);
    }
}

/* Look for path in emulation dir, otherwise return name. */
const char *path(const char *name)
{
    /* Only do absolute paths: quick and dirty, but should mostly be OK.
       Could do relative by tracking cwd. */
    if (!base || !name || name[0] != '/')
        return name;

    return follow_path(base, name) ?: name;
}