Annotation of qemu/path.c, revision 1.1.1.2

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);
1.1.1.2 ! root       49:     if (asprintf(&new->pathname, "%s/%s", root, name) == -1) {
        !            50:         printf("Cannot allocate memory\n");
        !            51:         exit(1);
        !            52:     }
1.1       root       53:     new->num_entries = 0;
                     54:     return new;
                     55: }
                     56: 
                     57: #define streq(a,b) (strcmp((a), (b)) == 0)
                     58: 
                     59: static 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: 
                     76: static 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!). */
                     90: static 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. */
                    100: static const char *
                    101: follow_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: 
                    125: void 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. */
                    157: const 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: }

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