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tag: 20130418
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/* Code to mangle pathnames into those matching a given prefix.
eg. open("/lib/foo.so") => open("/usr/gnemul/i386-linux/lib/foo.so");
The assumption is that this area does not change.
*/
#include <sys/types.h>
#include <sys/param.h>
#include <dirent.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>
#include "qemu-common.h"
struct pathelem
{
/* Name of this, eg. lib */
char *name;
/* Full path name, eg. /usr/gnemul/x86-linux/lib. */
char *pathname;
struct pathelem *parent;
/* Children */
unsigned int num_entries;
struct pathelem *entries[0];
};
static struct pathelem *base;
/* First N chars of S1 match S2, and S2 is N chars long. */
static int strneq(const char *s1, unsigned int n, const char *s2)
{
unsigned int i;
for (i = 0; i < n; i++)
if (s1[i] != s2[i])
return 0;
return s2[i] == 0;
}
static struct pathelem *add_entry(struct pathelem *root, const char *name);
static struct pathelem *new_entry(const char *root,
struct pathelem *parent,
const char *name)
{
struct pathelem *new = malloc(sizeof(*new));
new->name = strdup(name);
if (asprintf(&new->pathname, "%s/%s", root, name) == -1) {
printf("Cannot allocate memory\n");
exit(1);
}
new->num_entries = 0;
return new;
}
#define streq(a,b) (strcmp((a), (b)) == 0)
static struct pathelem *add_dir_maybe(struct pathelem *path)
{
DIR *dir;
if ((dir = opendir(path->pathname)) != NULL) {
struct dirent *dirent;
while ((dirent = readdir(dir)) != NULL) {
if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
path = add_entry(path, dirent->d_name);
}
}
closedir(dir);
}
return path;
}
static struct pathelem *add_entry(struct pathelem *root, const char *name)
{
root->num_entries++;
root = realloc(root, sizeof(*root)
+ sizeof(root->entries[0])*root->num_entries);
root->entries[root->num_entries-1] = new_entry(root->pathname, root, name);
root->entries[root->num_entries-1]
= add_dir_maybe(root->entries[root->num_entries-1]);
return root;
}
/* This needs to be done after tree is stabilized (ie. no more reallocs!). */
static void set_parents(struct pathelem *child, struct pathelem *parent)
{
unsigned int i;
child->parent = parent;
for (i = 0; i < child->num_entries; i++)
set_parents(child->entries[i], child);
}
/* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
static const char *
follow_path(const struct pathelem *cursor, const char *name)
{
unsigned int i, namelen;
name += strspn(name, "/");
namelen = strcspn(name, "/");
if (namelen == 0)
return cursor->pathname;
if (strneq(name, namelen, ".."))
return follow_path(cursor->parent, name + namelen);
if (strneq(name, namelen, "."))
return follow_path(cursor, name + namelen);
for (i = 0; i < cursor->num_entries; i++)
if (strneq(name, namelen, cursor->entries[i]->name))
return follow_path(cursor->entries[i], name + namelen);
/* Not found */
return NULL;
}
void init_paths(const char *prefix)
{
char pref_buf[PATH_MAX];
if (prefix[0] == '\0' ||
!strcmp(prefix, "/"))
return;
if (prefix[0] != '/') {
char *cwd = getcwd(NULL, 0);
size_t pref_buf_len = sizeof(pref_buf);
if (!cwd)
abort();
pstrcpy(pref_buf, sizeof(pref_buf), cwd);
pstrcat(pref_buf, pref_buf_len, "/");
pstrcat(pref_buf, pref_buf_len, prefix);
free(cwd);
} else
pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
base = new_entry("", NULL, pref_buf);
base = add_dir_maybe(base);
if (base->num_entries == 0) {
free (base);
base = NULL;
} else {
set_parents(base, base);
}
}
/* Look for path in emulation dir, otherwise return name. */
const char *path(const char *name)
{
/* Only do absolute paths: quick and dirty, but should mostly be OK.
Could do relative by tracking cwd. */
if (!base || !name || name[0] != '/')
return name;
return follow_path(base, name) ?: name;
}
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