bsd-user/path.c

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