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 #include "qemu/thread.h"
  12
  13 static const char *base;
  14 static GHashTable *hash;
  15 static QemuMutex lock;
  16
  17 void init_paths(const char *prefix)
  18 {
  19     if (prefix[0] == '\0' || !strcmp(prefix, "/")) {
  20         return;
  21     }
  22
  23     if (prefix[0] == '/') {
  24         base = g_strdup(prefix);
  25     } else {
  26         char *cwd = g_get_current_dir();
  27         base = g_build_filename(cwd, prefix, NULL);
  28         g_free(cwd);
  29     }
  30
  31     hash = g_hash_table_new(g_str_hash, g_str_equal);
  32     qemu_mutex_init(&lock);
  33 }
  34
  35 /* Look for path in emulation dir, otherwise return name. */
  36 const char *path(const char *name)
  37 {
  38     gpointer key, value;
  39     const char *ret;
  40
  41     /* Only do absolute paths: quick and dirty, but should mostly be OK.  */
  42     if (!base || !name || name[0] != '/') {
  43         return name;
  44     }
  45
  46     qemu_mutex_lock(&lock);
  47
  48     /* Have we looked up this file before?  */
  49     if (g_hash_table_lookup_extended(hash, name, &key, &value)) {
  50         ret = value ? value : name;
  51     } else {
  52         char *save = g_strdup(name);
  53         char *full = g_build_filename(base, name, NULL);
  54
  55         /* Look for the path; record the result, pass or fail.  */
  56         if (access(full, F_OK) == 0) {
  57             /* Exists.  */
  58             g_hash_table_insert(hash, save, full);
  59             ret = full;
  60         } else {
  61             /* Does not exist.  */
  62             g_free(full);
  63             g_hash_table_insert(hash, save, NULL);
  64             ret = name;
  65         }
  66     }
  67
  68     qemu_mutex_unlock(&lock);
  69     return ret;
  70 }