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

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