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fgdata/Nasal/io.nas
2008-06-13 12:09:45 +00:00

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# Reads and returns a complete file as a string
var readfile = func(file) {
if((var st = stat(file)) == nil) die("Cannot stat file: " ~ file);
var sz = st[7];
var buf = bits.buf(sz);
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 isdir(), isreg(), islnk(), etc.
# Usage: var s = io.stat(filename); # nil -> doesn't exist, broken link
# if (s != nil and io.isdir(s[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]);
# The following two functions are for reading generic XML files into
# the property tree and for writing them from there to the disk. The
# built-in fgcommands (load, save, loadxml, savexml) are for FlightGear's
# own <PropertyList> XML files only, as they only handle a limited
# number of very specific attributes. The io.readxml() loader turns
# attributes into regular children with a configurable prefix prepended
# to their name, while io.writexml() turns such nodes back into
# attributes. The two functions have their own limitations, but can
# easily get extended to whichever needs. The underlying parsexml()
# command will handle any XML file.
# Reads an XML file from an absolute path and returns it as property
# tree. All nodes will be of type STRING. Data are only written to
# leafs. Attributes are written as regular nodes with the optional
# prefix prepended to the name. If the prefix is nil, then attributes
# are ignored. Returns nil on error.
#
var readxml = func(path, prefix = "___") {
var stack = [[{}, ""]];
var node = props.Node.new();
var tree = node; # prevent GC
var start = func(name, attr) {
var index = stack[-1][0];
if(!contains(index, name))
index[name] = 0;
node = node.getChild(name, index[name], 1);
if(prefix != nil)
foreach(var n; keys(attr))
node.getNode(prefix ~ n, 1).setValue(attr[n]);
index[name] += 1;
append(stack, [{}, ""]);
}
var end = func(name) {
var buf = pop(stack);
if(!size(buf[0]) and size(buf[1]))
node.setValue(buf[1]);
node = node.getParent();
}
var data = func(d) {
stack[-1][1] ~= d;
}
return parsexml(path, start, end, data) == nil ? nil : tree;
}
# Writes a property tree as returned by readxml() to a file. Children
# with name starting with <prefix> are again turned into attributes of
# their parent. <node> must contain exactly one child, which will
# become the XML file's outermost element.
#
var writexml = func(path, node, indent = "\t", prefix = "___") {
var root = node.getChildren();
if(!size(root))
die("writexml(): tree doesn't have a root node");
if(substr(path, -4) != ".xml")
path ~= ".xml";
var file = open(path, "w");
write(file, "<?xml version=\"1.0\"?>\n\n");
var writenode = func(n, ind = "") {
var name = n.getName();
var name_attr = name;
var children = [];
foreach(var c; n.getChildren()) {
var a = c.getName();
if(substr(a, 0, size(prefix)) == prefix)
name_attr ~= " " ~ substr(a, size(prefix)) ~ '="' ~ c.getValue() ~ '"';
else
append(children, c);
}
if(size(children)) {
write(file, ind ~ "<" ~ name_attr ~ ">\n");
foreach(var c; children)
writenode(c, ind ~ indent);
write(file, ind ~ "</" ~ name ~ ">\n");
} elsif((var value = n.getValue()) != nil) {
write(file, ind ~ "<" ~ name_attr ~ ">" ~ value ~ "</" ~ name ~ ">\n");
} else {
write(file, ind ~ "<" ~ name_attr ~ "/>\n");
}
}
writenode(root[0]);
close(file);
if(size(root) != 1)
die("writexml(): tree has more than one root node");
}
# Removes superfluous slashes, empty and "." elements, expands
# all ".." elements, and turns all backslashes into slashes.
# The result will start with a slash if it started with a slash
# or backslash, it will end without slash. Should be applied on
# absolute property or file paths, otherwise ".." elements might
# be resolved wrongly.
#
var fixpath = func(path) {
var d = "";
for(var i = 0; i < size(path); i += 1)
d ~= path[i] == `\\` ? "/" : chr(path[i]);
var prefix = d[0] == `/` ? "/" : "";
var stack = [];
foreach(var e; split("/", d)) {
if(e == "." or e == "")
continue;
elsif(e == "..")
pop(stack);
else
append(stack, e);
}
if(!size(stack))
return "/";
path = stack[0];
foreach(var s; subvec(stack, 1))
path ~= "/" ~ s;
return prefix ~ path;
}
# Redefine io.open() such that files can only be written under authorized directories.
#
setlistener("/sim/signals/nasal-dir-initialized", func {
var _open = open;
var writable_dirs = [
# "*", # any
# fixpath(getprop("/sim/fg-root")) ~ "/Scenery/",
fixpath(getprop("/sim/fg-home")) ~ "/",
"/tmp/", "/var/tmp/",
"[A-Za-z]:TMP/", "[A-Za-z]:TEMP/",
"[A-Za-z]:/TMP/", "[A-Za-z]:/TEMP/",
];
open = func(path, mode = "rb") {
var c = caller(1);
print(debug._path("SECURITY: io.open(\"" ~ path ~ "\", \"" ~ mode ~ "\")\n in file "
~ c[2] ~ ", line " ~ c[3]));
if(mode == "r" or mode == "rb") {
print(debug._nil("SECURITY: allow reading of file '" ~ path ~ "'"));
return _open(path, mode);
}
var fpath = fixpath(path);
if(fpath != path) print(debug._error("SECURITY: fix path '" ~ path ~ "' -> '" ~ fpath ~ "'"));
foreach(var p; writable_dirs) {
print("SECURITY: check for path '" ~ p ~ "'");
if(string.match(fpath, p ~ '*')) {
print(debug._nil("SECURITY: allow path '" ~ p ~ "'"));
return _open(fpath, mode);
}
}
die("io.open(): security: writing to file '" ~ path ~ "' denied\n ");
}
});