Annotation of qemu/path.c, revision 1.1.1.3

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: 
1.1.1.3 ! root       41: static struct pathelem *add_entry(struct pathelem *root, const char *name,
        !            42:                                   unsigned char type);
1.1       root       43: 
                     44: static struct pathelem *new_entry(const char *root,
                     45:                                   struct pathelem *parent,
                     46:                                   const char *name)
                     47: {
                     48:     struct pathelem *new = malloc(sizeof(*new));
                     49:     new->name = strdup(name);
1.1.1.2   root       50:     if (asprintf(&new->pathname, "%s/%s", root, name) == -1) {
                     51:         printf("Cannot allocate memory\n");
                     52:         exit(1);
                     53:     }
1.1       root       54:     new->num_entries = 0;
                     55:     return new;
                     56: }
                     57: 
                     58: #define streq(a,b) (strcmp((a), (b)) == 0)
                     59: 
1.1.1.3 ! root       60: /* Not all systems provide this feature */
        !            61: #if defined(DT_DIR) && defined(DT_UNKNOWN)
        !            62: # define dirent_type(dirent) ((dirent)->d_type)
        !            63: # define is_dir_maybe(type)  ((type) == DT_DIR || (type) == DT_UNKNOWN)
        !            64: #else
        !            65: # define dirent_type(dirent) (1)
        !            66: # define is_dir_maybe(type)  (type)
        !            67: #endif
        !            68: 
1.1       root       69: static struct pathelem *add_dir_maybe(struct pathelem *path)
                     70: {
                     71:     DIR *dir;
                     72: 
                     73:     if ((dir = opendir(path->pathname)) != NULL) {
                     74:         struct dirent *dirent;
                     75: 
                     76:         while ((dirent = readdir(dir)) != NULL) {
                     77:             if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
1.1.1.3 ! root       78:                 path = add_entry(path, dirent->d_name, dirent_type(dirent));
1.1       root       79:             }
                     80:         }
                     81:         closedir(dir);
                     82:     }
                     83:     return path;
                     84: }
                     85: 
1.1.1.3 ! root       86: static struct pathelem *add_entry(struct pathelem *root, const char *name,
        !            87:                                   unsigned char type)
1.1       root       88: {
1.1.1.3 ! root       89:     struct pathelem **e;
        !            90: 
1.1       root       91:     root->num_entries++;
                     92: 
                     93:     root = realloc(root, sizeof(*root)
                     94:                    + sizeof(root->entries[0])*root->num_entries);
1.1.1.3 ! root       95:     e = &root->entries[root->num_entries-1];
        !            96: 
        !            97:     *e = new_entry(root->pathname, root, name);
        !            98:     if (is_dir_maybe(type)) {
        !            99:         *e = add_dir_maybe(*e);
        !           100:     }
1.1       root      101: 
                    102:     return root;
                    103: }
                    104: 
                    105: /* This needs to be done after tree is stabilized (ie. no more reallocs!). */
                    106: static void set_parents(struct pathelem *child, struct pathelem *parent)
                    107: {
                    108:     unsigned int i;
                    109: 
                    110:     child->parent = parent;
                    111:     for (i = 0; i < child->num_entries; i++)
                    112:         set_parents(child->entries[i], child);
                    113: }
                    114: 
                    115: /* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
                    116: static const char *
                    117: follow_path(const struct pathelem *cursor, const char *name)
                    118: {
                    119:     unsigned int i, namelen;
                    120: 
                    121:     name += strspn(name, "/");
                    122:     namelen = strcspn(name, "/");
                    123: 
                    124:     if (namelen == 0)
                    125:         return cursor->pathname;
                    126: 
                    127:     if (strneq(name, namelen, ".."))
                    128:         return follow_path(cursor->parent, name + namelen);
                    129: 
                    130:     if (strneq(name, namelen, "."))
                    131:         return follow_path(cursor, name + namelen);
                    132: 
                    133:     for (i = 0; i < cursor->num_entries; i++)
                    134:         if (strneq(name, namelen, cursor->entries[i]->name))
                    135:             return follow_path(cursor->entries[i], name + namelen);
                    136: 
                    137:     /* Not found */
                    138:     return NULL;
                    139: }
                    140: 
                    141: void init_paths(const char *prefix)
                    142: {
                    143:     char pref_buf[PATH_MAX];
                    144: 
                    145:     if (prefix[0] == '\0' ||
                    146:         !strcmp(prefix, "/"))
                    147:         return;
                    148: 
                    149:     if (prefix[0] != '/') {
                    150:         char *cwd = getcwd(NULL, 0);
                    151:         size_t pref_buf_len = sizeof(pref_buf);
                    152: 
                    153:         if (!cwd)
                    154:             abort();
                    155:         pstrcpy(pref_buf, sizeof(pref_buf), cwd);
                    156:         pstrcat(pref_buf, pref_buf_len, "/");
                    157:         pstrcat(pref_buf, pref_buf_len, prefix);
                    158:         free(cwd);
                    159:     } else
                    160:         pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
                    161: 
                    162:     base = new_entry("", NULL, pref_buf);
                    163:     base = add_dir_maybe(base);
                    164:     if (base->num_entries == 0) {
                    165:         free (base);
                    166:         base = NULL;
                    167:     } else {
                    168:         set_parents(base, base);
                    169:     }
                    170: }
                    171: 
                    172: /* Look for path in emulation dir, otherwise return name. */
                    173: const char *path(const char *name)
                    174: {
                    175:     /* Only do absolute paths: quick and dirty, but should mostly be OK.
                    176:        Could do relative by tracking cwd. */
                    177:     if (!base || !name || name[0] != '/')
                    178:         return name;
                    179: 
                    180:     return follow_path(base, name) ?: name;
                    181: }

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