Changeset 862 for cs420

Timestamp:

09/27/07 12:58:18 (2 years ago)

Author:

vasi

Message:

Merging should work

Files:

• cs420/asst3/asst3420.java (modified) (2 diffs)

cs420/asst3/asst3420.java

@@ -14 +14 @@
         private static final int compareBlocks(byte[] a, byte[] b) {
                 // We'll just assume a lexical comparison
-                return a.compareTo(b);
+                for (int i = 0; i < BLOCKSIZE; ++i) {
+                        int d = a[i] - b[i];
+                        if (d != 0)
+                                return d;
+                }
+                return 0;
         }
         
@@ -32 +37 @@
         }
         
+        private static void copy(DataInputStream in, DataOutputStream out,
+                        byte[] buf) throws IOException {
+                try {
+                        while (true) {
+                                in.readFully(buf);
+                                out.write(buf);
+                        }
+                } catch (EOFException e) {
+                        // done!
+                } finally {
+                        in.close();
+                }
+        }
+        
         private static class Statistics {
                 public int onlyFirst = 0, onlySecond = 0, both = 0;
         }
         
-        private static String readBlock(DataInput in, byte[] buf) {
-                return 
-        }
-        
         // Do a two way merge
         private static Statistics merge2(InputStream is1, InputStream is2,
-                        OutputStream os) {
+                        OutputStream os) throws IOException {
                 Statistics stats = new Statistics();
-                DataInput in1 = new DataInputStream(is1),
+                DataInputStream in1 = new DataInputStream(is1),
                         in2 = new DataInputStream(is2);
-                DataOutput out = new DataOutputStream(os);
+                DataOutputStream out = new DataOutputStream(os);
                 
+                byte[] b1 = new byte[BLOCKSIZE], b2 = new byte[BLOCKSIZE];
+                boolean v1 = false, v2 = false; // Do b1 and b2 have valid, cur data?
                 
-                String d1 = null, d2 = null;
-                
+                try {
+                        while (true) {
+                                // Do any reading necessary
+                                if (!v1) {
+                                        in1.readFully(b1);
+                                        v1 = true;
+                                }
+                                if (!v2) {
+                                        in1.readFully(b2);
+                                        v2 = true;
+                                }
+                                
+                                int c = compareBlocks(b1, b2);
+                                if (c == 0) {
+                                        out.write(b1);
+                                        // Assume streams are already filtered for dupes!
+                                        v1 = v2 = false;
+                                        ++stats.both;
+                                } else if (c < 0) {
+                                        out.write(b1);
+                                        v1 = false;
+                                        ++stats.onlyFirst;
+                                } else {
+                                        out.write(b2);
+                                        v2 = false;
+                                        ++stats.onlySecond;
+                                }
+                        }
+                } catch (EOFException e) {
+                        // Just output whatever's left
+                        if (v1)
+                                out.write(b1);
+                        if (v2)
+                                out.write(b2);                  
+                        copy(in1, out, b1);
+                        copy(in2, out, b2);
+                } finally {
+                        out.close();
+                }
                 
                 return stats;