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Annotation of qemu/linux-user/path.c, revision 1.1.1.1

1.1       root        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 <dirent.h>
                      8: #include <unistd.h>
                      9: #include <stdlib.h>
                     10: #include <string.h>
                     11: #include <errno.h>
                     12: #include <stdio.h>
                     13: #include "qemu.h"
                     14: 
                     15: struct pathelem
                     16: {
                     17:     /* Name of this, eg. lib */
                     18:     char *name;
                     19:     /* Full path name, eg. /usr/gnemul/x86-linux/lib. */
                     20:     char *pathname;
                     21:     struct pathelem *parent;
                     22:     /* Children */
                     23:     unsigned int num_entries;
                     24:     struct pathelem *entries[0];
                     25: };
                     26: 
                     27: static struct pathelem *base;
                     28: 
                     29: /* First N chars of S1 match S2, and S2 is N chars long. */
                     30: static int strneq(const char *s1, unsigned int n, const char *s2)
                     31: {
                     32:     unsigned int i;
                     33: 
                     34:     for (i = 0; i < n; i++)
                     35:        if (s1[i] != s2[i])
                     36:            return 0;
                     37:     return s2[i] == 0;
                     38: }
                     39: 
                     40: static struct pathelem *add_entry(struct pathelem *root, const char *name);
                     41: 
                     42: static struct pathelem *new_entry(const char *root,
                     43:                                  struct pathelem *parent,
                     44:                                  const char *name)
                     45: {
                     46:     struct pathelem *new = malloc(sizeof(*new));
                     47:     new->name = strdup(name);
                     48:     asprintf(&new->pathname, "%s/%s", root, name);
                     49:     new->num_entries = 0;
                     50:     return new;
                     51: }
                     52: 
                     53: #define streq(a,b) (strcmp((a), (b)) == 0)
                     54: 
                     55: static struct pathelem *add_dir_maybe(struct pathelem *path)
                     56: {
                     57:     DIR *dir;
                     58: 
                     59:     if ((dir = opendir(path->pathname)) != NULL) {
                     60:        struct dirent *dirent;
                     61: 
                     62:        while ((dirent = readdir(dir)) != NULL) {
                     63:            if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
                     64:                path = add_entry(path, dirent->d_name);
                     65:            }
                     66:        }
                     67:         closedir(dir);
                     68:     }
                     69:     return path;
                     70: }
                     71: 
                     72: static struct pathelem *add_entry(struct pathelem *root, const char *name)
                     73: {
                     74:     root->num_entries++;
                     75: 
                     76:     root = realloc(root, sizeof(*root)
                     77:                   + sizeof(root->entries[0])*root->num_entries);
                     78: 
                     79:     root->entries[root->num_entries-1] = new_entry(root->pathname, root, name);
                     80:     root->entries[root->num_entries-1]
                     81:        = add_dir_maybe(root->entries[root->num_entries-1]);
                     82:     return root;
                     83: }
                     84: 
                     85: /* This needs to be done after tree is stabalized (ie. no more reallocs!). */
                     86: static void set_parents(struct pathelem *child, struct pathelem *parent)
                     87: {
                     88:     unsigned int i;
                     89: 
                     90:     child->parent = parent;
                     91:     for (i = 0; i < child->num_entries; i++)
                     92:        set_parents(child->entries[i], child);
                     93: }
                     94: 
                     95: void init_paths(const char *prefix)
                     96: {
                     97:     if (prefix[0] != '/' ||
                     98:         prefix[0] == '\0' ||
                     99:         !strcmp(prefix, "/"))
                    100:         return;
                    101: 
                    102:     base = new_entry("", NULL, prefix+1);
                    103:     base = add_dir_maybe(base);
                    104:     if (base->num_entries == 0) {
                    105:         free (base);
                    106:         base = NULL;
                    107:     } else {
                    108:         set_parents(base, base);
                    109:     }
                    110: }
                    111: 
                    112: /* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
                    113: static const char *
                    114: follow_path(const struct pathelem *cursor, const char *name)
                    115: {
                    116:     unsigned int i, namelen;
                    117: 
                    118:     name += strspn(name, "/");
                    119:     namelen = strcspn(name, "/");
                    120: 
                    121:     if (namelen == 0)
                    122:        return cursor->pathname;
                    123: 
                    124:     if (strneq(name, namelen, ".."))
                    125:        return follow_path(cursor->parent, name + namelen);
                    126: 
                    127:     if (strneq(name, namelen, "."))
                    128:        return follow_path(cursor, name + namelen);
                    129: 
                    130:     for (i = 0; i < cursor->num_entries; i++)
                    131:        if (strneq(name, namelen, cursor->entries[i]->name))
                    132:            return follow_path(cursor->entries[i], name + namelen);
                    133: 
                    134:     /* Not found */
                    135:     return NULL;
                    136: }
                    137: 
                    138: /* Look for path in emulation dir, otherwise return name. */
                    139: const char *path(const char *name)
                    140: {
                    141:     /* Only do absolute paths: quick and dirty, but should mostly be OK.
                    142:        Could do relative by tracking cwd. */
                    143:     if (!base || name[0] != '/')
                    144:        return name;
                    145: 
                    146:     return follow_path(base, name) ?: name;
                    147: }

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