1 files changed, 120 insertions, 0 deletions
diff --git a/libc/unistd/getcwd.c b/libc/unistd/getcwd.c
new file mode 100644
index 000000000..12eda45ca
--- /dev/null
+++ b/libc/unistd/getcwd.c
@@ -0,0 +1,120 @@
+
+#include <errno.h>
+#include <sys/stat.h>
+#include <dirent.h>
+#include <string.h>
+/*
+ * These functions find the absolute path to the current working directory.
+ *
+ * They don't use malloc or large amounts of stack space.
+ */
+
+static char *recurser();		/* Routine to go up tree */
+static char *search_dir();		/* Routine to find the step back down */
+static char *path_buf;
+static int path_size;
+
+static dev_t root_dev;
+static ino_t root_ino;
+
+static struct stat st;
+
+char *getcwd(buf, size)
+char *buf;
+int size;
+{
+	path_buf = buf;
+	path_size = size;
+
+	if (size < 3) {
+		errno = ERANGE;
+		return 0;
+	}
+	strcpy(path_buf, ".");
+
+	if (stat("/", &st) < 0)
+		return 0;
+
+	root_dev = st.st_dev;
+	root_ino = st.st_ino;
+
+	return recurser();
+}
+
+static char *recurser()
+{
+	dev_t this_dev;
+	ino_t this_ino;
+
+	if (stat(path_buf, &st) < 0)
+		return 0;
+	this_dev = st.st_dev;
+	this_ino = st.st_ino;
+	if (this_dev == root_dev && this_ino == root_ino) {
+		strcpy(path_buf, "/");
+		return path_buf;
+	}
+	if (strlen(path_buf) + 4 > path_size) {
+		errno = ERANGE;
+		return 0;
+	}
+	strcat(path_buf, "/..");
+	if (recurser() == 0)
+		return 0;
+
+	return search_dir(this_dev, this_ino);
+}
+
+static char *search_dir(this_dev, this_ino)
+dev_t this_dev;
+ino_t this_ino;
+{
+	DIR *dp;
+	struct dirent *d;
+	char *ptr;
+	int slen;
+
+	/* The test is for ELKS lib 0.0.9, this should be fixed in the real kernel */
+	int slow_search = (sizeof(ino_t) != sizeof(d->d_ino));
+
+	if (stat(path_buf, &st) < 0)
+		return 0;
+	if (this_dev != st.st_dev)
+		slow_search = 1;
+
+	slen = strlen(path_buf);
+	ptr = path_buf + slen - 1;
+	if (*ptr != '/') {
+		if (slen + 2 > path_size) {
+			errno = ERANGE;
+			return 0;
+		}
+		strcpy(++ptr, "/");
+		slen++;
+	}
+	slen++;
+
+	dp = opendir(path_buf);
+	if (dp == 0)
+		return 0;
+
+	while ((d = readdir(dp)) != 0) {
+		if (slow_search || this_ino == d->d_ino) {
+			if (slen + strlen(d->d_name) > path_size) {
+				errno = ERANGE;
+				return 0;
+			}
+			strcpy(ptr + 1, d->d_name);
+			if (stat(path_buf, &st) < 0)
+				continue;
+			if (st.st_ino == this_ino && st.st_dev == this_dev) {
+				closedir(dp);
+				return path_buf;
+			}
+		}
+	}
+
+	closedir(dp);
+	errno = ENOENT;
+	return 0;
+}