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
  43static struct pathelem *new_entry(const char *root,
  44                                  struct pathelem *parent,
  45                                  const char *name)
  46{
  47    struct pathelem *new = malloc(sizeof(*new));
  48    new->name = strdup(name);
  49    if (asprintf(&new->pathname, "%s/%s", root, name) == -1) {
  50        printf("Cannot allocate memory\n");
  51        exit(1);
  52    }
  53    new->num_entries = 0;
  54    return new;
  55}
  56
  57#define streq(a,b) (strcmp((a), (b)) == 0)
  58
  59static struct pathelem *add_dir_maybe(struct pathelem *path)
  60{
  61    DIR *dir;
  62
  63    if ((dir = opendir(path->pathname)) != NULL) {
  64        struct dirent *dirent;
  65
  66        while ((dirent = readdir(dir)) != NULL) {
  67            if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
  68                path = add_entry(path, dirent->d_name);
  69            }
  70        }
  71        closedir(dir);
  72    }
  73    return path;
  74}
  75
  76static struct pathelem *add_entry(struct pathelem *root, const char *name)
  77{
  78    root->num_entries++;
  79
  80    root = realloc(root, sizeof(*root)
  81                   + sizeof(root->entries[0])*root->num_entries);
  82
  83    root->entries[root->num_entries-1] = new_entry(root->pathname, root, name);
  84    root->entries[root->num_entries-1]
  85        = add_dir_maybe(root->entries[root->num_entries-1]);
  86    return root;
  87}
  88
  89/* This needs to be done after tree is stabilized (ie. no more reallocs!). */
  90static void set_parents(struct pathelem *child, struct pathelem *parent)
  91{
  92    unsigned int i;
  93
  94    child->parent = parent;
  95    for (i = 0; i < child->num_entries; i++)
  96        set_parents(child->entries[i], child);
  97}
  98
  99/* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
 100static const char *
 101follow_path(const struct pathelem *cursor, const char *name)
 102{
 103    unsigned int i, namelen;
 104
 105    name += strspn(name, "/");
 106    namelen = strcspn(name, "/");
 107
 108    if (namelen == 0)
 109        return cursor->pathname;
 110
 111    if (strneq(name, namelen, ".."))
 112        return follow_path(cursor->parent, name + namelen);
 113
 114    if (strneq(name, namelen, "."))
 115        return follow_path(cursor, name + namelen);
 116
 117    for (i = 0; i < cursor->num_entries; i++)
 118        if (strneq(name, namelen, cursor->entries[i]->name))
 119            return follow_path(cursor->entries[i], name + namelen);
 120
 121    /* Not found */
 122    return NULL;
 123}
 124
 125void init_paths(const char *prefix)
 126{
 127    char pref_buf[PATH_MAX];
 128
 129    if (prefix[0] == '\0' ||
 130        !strcmp(prefix, "/"))
 131        return;
 132
 133    if (prefix[0] != '/') {
 134        char *cwd = getcwd(NULL, 0);
 135        size_t pref_buf_len = sizeof(pref_buf);
 136
 137        if (!cwd)
 138            abort();
 139        pstrcpy(pref_buf, sizeof(pref_buf), cwd);
 140        pstrcat(pref_buf, pref_buf_len, "/");
 141        pstrcat(pref_buf, pref_buf_len, prefix);
 142        free(cwd);
 143    } else
 144        pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
 145
 146    base = new_entry("", NULL, pref_buf);
 147    base = add_dir_maybe(base);
 148    if (base->num_entries == 0) {
 149        free (base);
 150        base = NULL;
 151    } else {
 152        set_parents(base, base);
 153    }
 154}
 155
 156/* Look for path in emulation dir, otherwise return name. */
 157const char *path(const char *name)
 158{
 159    /* Only do absolute paths: quick and dirty, but should mostly be OK.
 160       Could do relative by tracking cwd. */
 161    if (!base || !name || name[0] != '/')
 162        return name;
 163
 164    return follow_path(base, name) ?: name;
 165}
 166