path patch

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@96 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 142 insertions, 0 deletions

diff --git a/linux-user/path.c b/linux-user/path.c
new file mode 100644
index 0000000..9e49076
--- /dev/null
+++ b/linux-user/path.c
@@ -0,0 +1,142 @@
+/* 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 <dirent.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <stdio.h>
+#include "qemu.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);
+    asprintf(&new->pathname, "%s/%s", root, name);
+    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 stabalized (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);
+}
+
+void init_paths(const char *prefix)
+{
+    if (prefix[0] != '/' ||
+        prefix[0] == '\0' ||
+        !strcmp(prefix, "/"))
+        return;
+
+    base = new_entry("", NULL, prefix+1);
+    base = add_dir_maybe(base);
+    set_parents(base, base);
+}
+
+/* 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;
+}
+
+/* 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[0] != '/')
+	return name;
+
+    return follow_path(base, name) ?: name;
+}