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