xref: /illumos-kvm-cmd/path.c (revision 68396ea9)
1 /* Code to mangle pathnames into those matching a given prefix.
2    eg. open("/lib/foo.so") => open("/usr/gnemul/i386-linux/lib/foo.so");
3 
4    The assumption is that this area does not change.
5 */
6 #include <sys/types.h>
7 #include <sys/param.h>
8 #include <dirent.h>
9 #include <unistd.h>
10 #include <stdlib.h>
11 #include <string.h>
12 #include <errno.h>
13 #include <stdio.h>
14 #include "qemu-common.h"
15 
16 struct pathelem
17 {
18     /* Name of this, eg. lib */
19     char *name;
20     /* Full path name, eg. /usr/gnemul/x86-linux/lib. */
21     char *pathname;
22     struct pathelem *parent;
23     /* Children */
24     unsigned int num_entries;
25     struct pathelem *entries[0];
26 };
27 
28 static struct pathelem *base;
29 
30 /* First N chars of S1 match S2, and S2 is N chars long. */
strneq(const char * s1,unsigned int n,const char * s2)31 static int strneq(const char *s1, unsigned int n, const char *s2)
32 {
33     unsigned int i;
34 
35     for (i = 0; i < n; i++)
36         if (s1[i] != s2[i])
37             return 0;
38     return s2[i] == 0;
39 }
40 
41 static struct pathelem *add_entry(struct pathelem *root, const char *name);
42 
new_entry(const char * root,struct pathelem * parent,const char * name)43 static struct pathelem *new_entry(const char *root,
44                                   struct pathelem *parent,
45                                   const char *name)
46 {
47     struct pathelem *new = malloc(sizeof(*new));
48     new->name = strdup(name);
49     if (asprintf(&new->pathname, "%s/%s", root, name) == -1) {
50         printf("Cannot allocate memory\n");
51         exit(1);
52     }
53     new->num_entries = 0;
54     return new;
55 }
56 
57 #define streq(a,b) (strcmp((a), (b)) == 0)
58 
add_dir_maybe(struct pathelem * path)59 static struct pathelem *add_dir_maybe(struct pathelem *path)
60 {
61     DIR *dir;
62 
63     if ((dir = opendir(path->pathname)) != NULL) {
64         struct dirent *dirent;
65 
66         while ((dirent = readdir(dir)) != NULL) {
67             if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
68                 path = add_entry(path, dirent->d_name);
69             }
70         }
71         closedir(dir);
72     }
73     return path;
74 }
75 
add_entry(struct pathelem * root,const char * name)76 static struct pathelem *add_entry(struct pathelem *root, const char *name)
77 {
78     root->num_entries++;
79 
80     root = realloc(root, sizeof(*root)
81                    + sizeof(root->entries[0])*root->num_entries);
82 
83     root->entries[root->num_entries-1] = new_entry(root->pathname, root, name);
84     root->entries[root->num_entries-1]
85         = add_dir_maybe(root->entries[root->num_entries-1]);
86     return root;
87 }
88 
89 /* This needs to be done after tree is stabilized (ie. no more reallocs!). */
set_parents(struct pathelem * child,struct pathelem * parent)90 static void set_parents(struct pathelem *child, struct pathelem *parent)
91 {
92     unsigned int i;
93 
94     child->parent = parent;
95     for (i = 0; i < child->num_entries; i++)
96         set_parents(child->entries[i], child);
97 }
98 
99 /* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
100 static const char *
follow_path(const struct pathelem * cursor,const char * name)101 follow_path(const struct pathelem *cursor, const char *name)
102 {
103     unsigned int i, namelen;
104 
105     name += strspn(name, "/");
106     namelen = strcspn(name, "/");
107 
108     if (namelen == 0)
109         return cursor->pathname;
110 
111     if (strneq(name, namelen, ".."))
112         return follow_path(cursor->parent, name + namelen);
113 
114     if (strneq(name, namelen, "."))
115         return follow_path(cursor, name + namelen);
116 
117     for (i = 0; i < cursor->num_entries; i++)
118         if (strneq(name, namelen, cursor->entries[i]->name))
119             return follow_path(cursor->entries[i], name + namelen);
120 
121     /* Not found */
122     return NULL;
123 }
124 
init_paths(const char * prefix)125 void init_paths(const char *prefix)
126 {
127     char pref_buf[PATH_MAX];
128 
129     if (prefix[0] == '\0' ||
130         !strcmp(prefix, "/"))
131         return;
132 
133     if (prefix[0] != '/') {
134         char *cwd = getcwd(NULL, 0);
135         size_t pref_buf_len = sizeof(pref_buf);
136 
137         if (!cwd)
138             abort();
139         pstrcpy(pref_buf, sizeof(pref_buf), cwd);
140         pstrcat(pref_buf, pref_buf_len, "/");
141         pstrcat(pref_buf, pref_buf_len, prefix);
142         free(cwd);
143     } else
144         pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
145 
146     base = new_entry("", NULL, pref_buf);
147     base = add_dir_maybe(base);
148     if (base->num_entries == 0) {
149         free (base);
150         base = NULL;
151     } else {
152         set_parents(base, base);
153     }
154 }
155 
156 /* Look for path in emulation dir, otherwise return name. */
path(const char * name)157 const char *path(const char *name)
158 {
159     /* Only do absolute paths: quick and dirty, but should mostly be OK.
160        Could do relative by tracking cwd. */
161     if (!base || !name || name[0] != '/')
162         return name;
163 
164     return follow_path(base, name) ?: name;
165 }
166