LXR qemu/util/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 "qemu/osdep.h"
   7#include <sys/param.h>
   8#include <dirent.h>
   9#include "qemu-common.h"
  10#include "qemu/cutils.h"
  11#include "qemu/path.h"
  12
  13struct pathelem
  14{
  15    /* Name of this, eg. lib */
  16    char *name;
  17    /* Full path name, eg. /usr/gnemul/x86-linux/lib. */
  18    char *pathname;
  19    struct pathelem *parent;
  20    /* Children */
  21    unsigned int num_entries;
  22    struct pathelem *entries[0];
  23};
  24
  25static struct pathelem *base;
  26
  27/* First N chars of S1 match S2, and S2 is N chars long. */
  28static int strneq(const char *s1, unsigned int n, const char *s2)
  29{
  30    unsigned int i;
  31
  32    for (i = 0; i < n; i++)
  33        if (s1[i] != s2[i])
  34            return 0;
  35    return s2[i] == 0;
  36}
  37
  38static struct pathelem *add_entry(struct pathelem *root, const char *name,
  39                                  unsigned type);
  40
  41static struct pathelem *new_entry(const char *root,
  42                                  struct pathelem *parent,
  43                                  const char *name)
  44{
  45    struct pathelem *new = g_malloc(sizeof(*new));
  46    new->name = g_strdup(name);
  47    new->pathname = g_strdup_printf("%s/%s", root, name);
  48    new->num_entries = 0;
  49    return new;
  50}
  51
  52#define streq(a,b) (strcmp((a), (b)) == 0)
  53
  54/* Not all systems provide this feature */
  55#if defined(DT_DIR) && defined(DT_UNKNOWN) && defined(DT_LNK)
  56# define dirent_type(dirent) ((dirent)->d_type)
  57# define is_dir_maybe(type) \
  58    ((type) == DT_DIR || (type) == DT_UNKNOWN || (type) == DT_LNK)
  59#else
  60# define dirent_type(dirent) (1)
  61# define is_dir_maybe(type)  (type)
  62#endif
  63
  64static struct pathelem *add_dir_maybe(struct pathelem *path)
  65{
  66    DIR *dir;
  67
  68    if ((dir = opendir(path->pathname)) != NULL) {
  69        struct dirent *dirent;
  70
  71        while ((dirent = readdir(dir)) != NULL) {
  72            if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
  73                path = add_entry(path, dirent->d_name, dirent_type(dirent));
  74            }
  75        }
  76        closedir(dir);
  77    }
  78    return path;
  79}
  80
  81static struct pathelem *add_entry(struct pathelem *root, const char *name,
  82                                  unsigned type)
  83{
  84    struct pathelem **e;
  85
  86    root->num_entries++;
  87
  88    root = g_realloc(root, sizeof(*root)
  89                   + sizeof(root->entries[0])*root->num_entries);
  90    e = &root->entries[root->num_entries-1];
  91
  92    *e = new_entry(root->pathname, root, name);
  93    if (is_dir_maybe(type)) {
  94        *e = add_dir_maybe(*e);
  95    }
  96
  97    return root;
  98}
  99
 100/* This needs to be done after tree is stabilized (ie. no more reallocs!). */
 101static void set_parents(struct pathelem *child, struct pathelem *parent)
 102{
 103    unsigned int i;
 104
 105    child->parent = parent;
 106    for (i = 0; i < child->num_entries; i++)
 107        set_parents(child->entries[i], child);
 108}
 109
 110/* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
 111static const char *
 112follow_path(const struct pathelem *cursor, const char *name)
 113{
 114    unsigned int i, namelen;
 115
 116    name += strspn(name, "/");
 117    namelen = strcspn(name, "/");
 118
 119    if (namelen == 0)
 120        return cursor->pathname;
 121
 122    if (strneq(name, namelen, ".."))
 123        return follow_path(cursor->parent, name + namelen);
 124
 125    if (strneq(name, namelen, "."))
 126        return follow_path(cursor, name + namelen);
 127
 128    for (i = 0; i < cursor->num_entries; i++)
 129        if (strneq(name, namelen, cursor->entries[i]->name))
 130            return follow_path(cursor->entries[i], name + namelen);
 131
 132    /* Not found */
 133    return NULL;
 134}
 135
 136void init_paths(const char *prefix)
 137{
 138    char pref_buf[PATH_MAX];
 139
 140    if (prefix[0] == '\0' ||
 141        !strcmp(prefix, "/"))
 142        return;
 143
 144    if (prefix[0] != '/') {
 145        char *cwd = getcwd(NULL, 0);
 146        size_t pref_buf_len = sizeof(pref_buf);
 147
 148        if (!cwd)
 149            abort();
 150        pstrcpy(pref_buf, sizeof(pref_buf), cwd);
 151        pstrcat(pref_buf, pref_buf_len, "/");
 152        pstrcat(pref_buf, pref_buf_len, prefix);
 153        free(cwd);
 154    } else
 155        pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
 156
 157    base = new_entry("", NULL, pref_buf);
 158    base = add_dir_maybe(base);
 159    if (base->num_entries == 0) {
 160        g_free(base->pathname);
 161        g_free(base->name);
 162        g_free(base);
 163        base = NULL;
 164    } else {
 165        set_parents(base, base);
 166    }
 167}
 168
 169/* Look for path in emulation dir, otherwise return name. */
 170const char *path(const char *name)
 171{
 172    /* Only do absolute paths: quick and dirty, but should mostly be OK.
 173       Could do relative by tracking cwd. */
 174    if (!base || !name || name[0] != '/')
 175        return name;
 176
 177    return follow_path(base, name) ?: name;
 178}
 179