Start on Unicode property data reader

Makefile

@@ -8,7 +8,7 @@ CP=cp
 
 cskernel=Kernel.cs Builtins.cs Cursor.cs JSYNC.cs NieczaCLR.cs Utils.cs \
 	 ObjModel.cs BigInteger.cs Printf.cs CodeGen.cs \
-	 GeneratedTrigFunctions.cs Serialize.cs
+	 GeneratedTrigFunctions.cs Serialize.cs UCD.cs
 
 # Tell make to regard the following targets as not being filenames
 .PHONY: all aot test spectest clean realclean

lib/UCD.cs

@@ -0,0 +1,102 @@
+using System;
+using System.Runtime.CompilerServices;
+using System.Collections.Generic;
+using System.IO;
+using Niecza;
+using Niecza.UCD;
+
+// Subsystem of Niecza that access the Unicode Character Database
+//
+// UCD data within Niecza is represented as a collection of named
+// tables.  Most of these are property tables, which associate a
+// character to one or two strings.
+//
+// Tables are identified by names.  Non-property tables never have
+// names not starting with !.
+namespace Niecza.UCD {
+    static class DataSet {
+        static Dictionary<string,object> cache;
+        static byte[] bits;
+        static Dictionary<string,int[]> directory;
+        static bool Trace;
+
+        const int FILES = 4;
+        static int Int(ref int from) {
+            from += 4;
+            return (bits[from-4] << 24) | (bits[from-3] << 16) |
+                (bits[from-2] << 8) | (bits[from-1]);
+        }
+
+        static string AsciiZ(ref int from) {
+            int to = from;
+            while (bits[to] != 0) to++;
+            char[] buf = new char[to - from];
+            for (int i = from; i < to; i++)
+                buf[i - from] = (char)bits[i];
+            from = to+1;
+            return new string(buf);
+        }
+
+        static void InflateDirectory() {
+            directory = new Dictionary<string,int[]>();
+            Trace = Environment.GetEnvironmentVariable("NIECZA_UCD_TRACE") != null;
+            if (Trace) Console.WriteLine("Unpacking directory ...");
+
+            int rpos = 0;
+
+            int[] fstart = new int[FILES];
+            for (int i = 0; i < FILES; i++)
+                fstart[i] = (i == 0 ? 20 : fstart[i-1]) + Int(ref rpos);
+            rpos += 4; // skip the extra length
+
+            int dend = fstart[0];
+
+            while (rpos < dend) {
+                int rpos0 = rpos;
+                int[] loc = new int[FILES * 2];
+                string name = AsciiZ(ref rpos);
+                int nfiles = bits[rpos++];
+                for (int i = 0; i < nfiles; i++) {
+                    loc[2*i] = fstart[i];
+                    fstart[i] += Int(ref rpos);
+                    loc[2*i+1] = fstart[i];
+                }
+                if (Trace)
+                    Console.WriteLine("Entry {0} (d.e. {1}): {2}",
+                            name, rpos0, Kernel.JoinS(", ", loc));
+                directory[name] = loc;
+            }
+            if (Trace) Console.WriteLine("done.");
+        }
+
+        [MethodImpl(MethodImplOptions.Synchronized)]
+        public static object GetTable(string name) {
+            if (cache == null)
+                cache = new Dictionary<string,object>();
+            object r;
+            if (cache.TryGetValue(name, out r))
+                return r;
+
+            if (bits == null) {
+                bits = File.ReadAllBytes("unidata");
+                InflateDirectory();
+            }
+
+            int[] loc;
+            if (!directory.TryGetValue(name, out loc))
+                throw new NieczaException(name + " does not exist as a UCD table");
+
+            switch (bits[loc[0]]) {
+                default:
+                    throw new NieczaException("Unhandled type code " + bits[loc[0]]);
+            }
+        }
+    }
+}
+
+public partial class Builtins {
+    public static Variable ucd_test() {
+        DataSet.GetTable("gc");
+        return null;
+    }
+}