LXR qemu/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-common.h"
  15
  16struct 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
  28static struct pathelem *base;
  29
  30/* First N chars of S1 match S2, and S2 is N chars long. */
  31static 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
  41static struct pathelem *add_entry(struct pathelem *root, const char *name,
  42                                  unsigned char type);
  43
  44static 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    if (asprintf(&new->pathname, "%s/%s", root, name) == -1) {
  51        printf("Cannot allocate memory\n");
  52        exit(1);
  53    }
  54    new->num_entries = 0;
  55    return new;
  56}
  57
  58#define streq(a,b) (strcmp((a), (b)) == 0)
  59
  60/* Not all systems provide this feature */
  61#if defined(DT_DIR) && defined(DT_UNKNOWN)
  62# define dirent_type(dirent) ((dirent)->d_type)
  63# define is_dir_maybe(type)  ((type) == DT_DIR || (type) == DT_UNKNOWN)
  64#else
  65# define dirent_type(dirent) (1)
  66# define is_dir_maybe(type)  (type)
  67#endif
  68
  69static struct pathelem *add_dir_maybe(struct pathelem *path)
  70{
  71    DIR *dir;
  72
  73    if ((dir = opendir(path->pathname)) != NULL) {
  74        struct dirent *dirent;
  75
  76        while ((dirent = readdir(dir)) != NULL) {
  77            if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
  78                path = add_entry(path, dirent->d_name, dirent_type(dirent));
  79            }
  80        }
  81        closedir(dir);
  82    }
  83    return path;
  84}
  85
  86static struct pathelem *add_entry(struct pathelem *root, const char *name,
  87                                  unsigned char type)
  88{
  89    struct pathelem **e;
  90
  91    root->num_entries++;
  92
  93    root = realloc(root, sizeof(*root)
  94                   + sizeof(root->entries[0])*root->num_entries);
  95    e = &root->entries[root->num_entries-1];
  96
  97    *e = new_entry(root->pathname, root, name);
  98    if (is_dir_maybe(type)) {
  99        *e = add_dir_maybe(*e);
 100    }
 101
 102    return root;
 103}
 104
 105/* This needs to be done after tree is stabilized (ie. no more reallocs!). */
 106static void set_parents(struct pathelem *child, struct pathelem *parent)
 107{
 108    unsigned int i;
 109
 110    child->parent = parent;
 111    for (i = 0; i < child->num_entries; i++)
 112        set_parents(child->entries[i], child);
 113}
 114
 115/* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
 116static const char *
 117follow_path(const struct pathelem *cursor, const char *name)
 118{
 119    unsigned int i, namelen;
 120
 121    name += strspn(name, "/");
 122    namelen = strcspn(name, "/");
 123
 124    if (namelen == 0)
 125        return cursor->pathname;
 126
 127    if (strneq(name, namelen, ".."))
 128        return follow_path(cursor->parent, name + namelen);
 129
 130    if (strneq(name, namelen, "."))
 131        return follow_path(cursor, name + namelen);
 132
 133    for (i = 0; i < cursor->num_entries; i++)
 134        if (strneq(name, namelen, cursor->entries[i]->name))
 135            return follow_path(cursor->entries[i], name + namelen);
 136
 137    /* Not found */
 138    return NULL;
 139}
 140
 141void init_paths(const char *prefix)
 142{
 143    char pref_buf[PATH_MAX];
 144
 145    if (prefix[0] == '\0' ||
 146        !strcmp(prefix, "/"))
 147        return;
 148
 149    if (prefix[0] != '/') {
 150        char *cwd = getcwd(NULL, 0);
 151        size_t pref_buf_len = sizeof(pref_buf);
 152
 153        if (!cwd)
 154            abort();
 155        pstrcpy(pref_buf, sizeof(pref_buf), cwd);
 156        pstrcat(pref_buf, pref_buf_len, "/");
 157        pstrcat(pref_buf, pref_buf_len, prefix);
 158        free(cwd);
 159    } else
 160        pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
 161
 162    base = new_entry("", NULL, pref_buf);
 163    base = add_dir_maybe(base);
 164    if (base->num_entries == 0) {
 165        free (base);
 166        base = NULL;
 167    } else {
 168        set_parents(base, base);
 169    }
 170}
 171
 172/* Look for path in emulation dir, otherwise return name. */
 173const char *path(const char *name)
 174{
 175    /* Only do absolute paths: quick and dirty, but should mostly be OK.
 176       Could do relative by tracking cwd. */
 177    if (!base || !name || name[0] != '/')
 178        return name;
 179
 180    return follow_path(base, name) ?: name;
 181}
 182