Andy ROSS: functions to check for stat()[2] flags, such as isdir()

mf: fixpath(): function to normalize file paths (doesn't handle escaped
    characters yet)

Nasal/io.nas

@@ -6,3 +6,40 @@ var readfile = func(file) {
     read(open(file), buf, sz);
     return buf;
 }
+
+# Generates a stat() test routine that is passed the "mode" field
+# (stat(...)[2]) from a stat() call (index 2), extracts the IFMT
+# subfield and compares it with the given type, assumes S_IFMT ==
+# 0xf000.
+var _gen_ifmt_test = func(ifmt) {
+    func(stat_mode) {
+        var buf = bits.buf(2);
+        bits.setfld(buf, 0, 16, stat_mode);
+        return ifmt == bits.fld(buf, 12, 4);
+    }
+}
+
+# Generate file type test predicates for the following types:
+# Usage: io.isdir(io.stat(filename)[2]);
+var ifmts = {dir:4, reg:8, lnk:10, sock:12, fifo:1, blk:6, chr:2};
+foreach(fmt; keys(ifmts))
+    caller(0)[0]["is" ~ fmt] = _gen_ifmt_test(ifmts[fmt]);
+
+# Removes trailing slashes, emtpy and "." elements, and expands
+# all ".." elements.
+var fixpath = func(d) {
+    while(size(d) and d[0] == `/`) d = substr(d, 1);
+    while(size(d) and d[size(d) - 1] == `/`) d = substr(d, 0, size(d) - 1);
+
+    var stack = [];
+    foreach(var e; split("/", d)) {
+        if(e == "." or e == "") continue;
+        elsif(e == "..") pop(stack);
+        else append(stack, e);
+    }
+    if(!size(stack)) return "/";
+    var path = "";
+    foreach(var s; stack) path ~= "/" ~ s;
+    return path;
+}
+