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      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 #ifdef __linux__
      7 #define _GNU_SOURCE 1
      8 #endif
      9 #include <sys/types.h>
     10 #include <sys/param.h>
     11 #include <dirent.h>
     12 #include <unistd.h>
     13 #include <stdlib.h>
     14 #include <string.h>
     15 #include <errno.h>
     16 #include <stdio.h>
     17 #include "qemu-common.h"
     18 
     19 struct pathelem
     20 {
     21     /* Name of this, eg. lib */
     22     char *name;
     23     /* Full path name, eg. /usr/gnemul/x86-linux/lib. */
     24     char *pathname;
     25     struct pathelem *parent;
     26     /* Children */
     27     unsigned int num_entries;
     28     struct pathelem *entries[0];
     29 };
     30 
     31 static struct pathelem *base;
     32 
     33 /* First N chars of S1 match S2, and S2 is N chars long. */
     34 static int strneq(const char *s1, unsigned int n, const char *s2)
     35 {
     36     unsigned int i;
     37 
     38     for (i = 0; i < n; i++)
     39         if (s1[i] != s2[i])
     40             return 0;
     41     return s2[i] == 0;
     42 }
     43 
     44 static struct pathelem *add_entry(struct pathelem *root, const char *name,
     45                                   unsigned char type);
     46 
     47 static struct pathelem *new_entry(const char *root,
     48                                   struct pathelem *parent,
     49                                   const char *name)
     50 {
     51     struct pathelem *new = malloc(sizeof(*new));
     52     new->name = strdup(name);
     53     if (asprintf(&new->pathname, "%s/%s", root, name) == -1) {
     54         printf("Cannot allocate memory\n");
     55         exit(1);
     56     }
     57     new->num_entries = 0;
     58     return new;
     59 }
     60 
     61 #define streq(a,b) (strcmp((a), (b)) == 0)
     62 
     63 /* Not all systems provide this feature */
     64 #if defined(DT_DIR) && defined(DT_UNKNOWN)
     65 # define dirent_type(dirent) ((dirent)->d_type)
     66 # define is_dir_maybe(type)  ((type) == DT_DIR || (type) == DT_UNKNOWN)
     67 #else
     68 # define dirent_type(dirent) (1)
     69 # define is_dir_maybe(type)  (type)
     70 #endif
     71 
     72 static struct pathelem *add_dir_maybe(struct pathelem *path)
     73 {
     74     DIR *dir;
     75 
     76     if ((dir = opendir(path->pathname)) != NULL) {
     77         struct dirent *dirent;
     78 
     79         while ((dirent = readdir(dir)) != NULL) {
     80             if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
     81                 path = add_entry(path, dirent->d_name, dirent_type(dirent));
     82             }
     83         }
     84         closedir(dir);
     85     }
     86     return path;
     87 }
     88 
     89 static struct pathelem *add_entry(struct pathelem *root, const char *name,
     90                                   unsigned char type)
     91 {
     92     struct pathelem **e;
     93 
     94     root->num_entries++;
     95 
     96     root = realloc(root, sizeof(*root)
     97                    + sizeof(root->entries[0])*root->num_entries);
     98     e = &root->entries[root->num_entries-1];
     99 
    100     *e = new_entry(root->pathname, root, name);
    101     if (is_dir_maybe(type)) {
    102         *e = add_dir_maybe(*e);
    103     }
    104 
    105     return root;
    106 }
    107 
    108 /* This needs to be done after tree is stabilized (ie. no more reallocs!). */
    109 static void set_parents(struct pathelem *child, struct pathelem *parent)
    110 {
    111     unsigned int i;
    112 
    113     child->parent = parent;
    114     for (i = 0; i < child->num_entries; i++)
    115         set_parents(child->entries[i], child);
    116 }
    117 
    118 /* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
    119 static const char *
    120 follow_path(const struct pathelem *cursor, const char *name)
    121 {
    122     unsigned int i, namelen;
    123 
    124     name += strspn(name, "/");
    125     namelen = strcspn(name, "/");
    126 
    127     if (namelen == 0)
    128         return cursor->pathname;
    129 
    130     if (strneq(name, namelen, ".."))
    131         return follow_path(cursor->parent, name + namelen);
    132 
    133     if (strneq(name, namelen, "."))
    134         return follow_path(cursor, name + namelen);
    135 
    136     for (i = 0; i < cursor->num_entries; i++)
    137         if (strneq(name, namelen, cursor->entries[i]->name))
    138             return follow_path(cursor->entries[i], name + namelen);
    139 
    140     /* Not found */
    141     return NULL;
    142 }
    143 
    144 void init_paths(const char *prefix)
    145 {
    146     char pref_buf[PATH_MAX];
    147 
    148     if (prefix[0] == '\0' ||
    149         !strcmp(prefix, "/"))
    150         return;
    151 
    152     if (prefix[0] != '/') {
    153         char *cwd = getcwd(NULL, 0);
    154         size_t pref_buf_len = sizeof(pref_buf);
    155 
    156         if (!cwd)
    157             abort();
    158         pstrcpy(pref_buf, sizeof(pref_buf), cwd);
    159         pstrcat(pref_buf, pref_buf_len, "/");
    160         pstrcat(pref_buf, pref_buf_len, prefix);
    161         free(cwd);
    162     } else
    163         pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
    164 
    165     base = new_entry("", NULL, pref_buf);
    166     base = add_dir_maybe(base);
    167     if (base->num_entries == 0) {
    168         free (base);
    169         base = NULL;
    170     } else {
    171         set_parents(base, base);
    172     }
    173 }
    174 
    175 /* Look for path in emulation dir, otherwise return name. */
    176 const char *path(const char *name)
    177 {
    178     /* Only do absolute paths: quick and dirty, but should mostly be OK.
    179        Could do relative by tracking cwd. */
    180     if (!base || !name || name[0] != '/')
    181         return name;
    182 
    183     return follow_path(base, name) ?: name;
    184 }
    185