/*
 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

/**
 * HexDumpReader provides utility methods to read a hex dump text file
 * and convert to an InputStream.  The format supported by the methods
 * can be generated by the following command.
 *
 * $ od -vw -t x1 foo | sed -r -e 's/^[0-9]+ ?//' -e 's/ //g' -e '/^$/d'
 */
public class HexDumpReader {
    public static InputStream getStreamFromHexDump(String fileName) {
        return getStreamFromHexDump(new File(System.getProperty("test.src", "."),
                                             fileName));
    }

    public static InputStream getStreamFromHexDump(File hexFile) {
        ByteArrayBuilder bab = new ByteArrayBuilder();
        int lineNo = 0;
        try (BufferedReader reader
                 = new BufferedReader(new InputStreamReader(new FileInputStream(hexFile),
                                                            "us-ascii"))) {
            String line;
            while ((line = reader.readLine()) != null) {
                lineNo++;
                line = line.trim();
                // Skip blank and comment lines.
                if (line.length() == 0) {
                    continue;
                }
                int x = line.indexOf('#');
                if (x == 0) {
                    continue;
                }
                if (x > 0) {
                    line = line.substring(0, x).trim();
                }
                int len = line.length();
                for (int i = 0; i < len; i += 2) {
                    bab.put((byte)Integer.parseInt(line, i, i + 2, 16));
                }
            }
        } catch (Exception e) {
            throw new RuntimeException(hexFile.getName() + ":error:" + lineNo + ": " + e, e);
        }
        return new ByteArrayInputStream(bab.toArray());
    }


    private static class ByteArrayBuilder {
        private static final int BUFFER_SIZE = 4096;

        private int size;
        private List<byte[]> bytes;
        private byte[] current;
        private int offset;

        ByteArrayBuilder() {
            bytes = new ArrayList<>();
            current = new byte[BUFFER_SIZE];
        }

        void put(byte b) {
            if (offset == BUFFER_SIZE) {
                bytes.add(current);
                current = new byte[BUFFER_SIZE];
                offset = 0;
            }
            current[offset++] = b;
            size++;
        }

        byte[] toArray() {
            byte[] buf = new byte[size];
            int ptr = 0;
            for (byte[] ba : bytes) {
                System.arraycopy(ba, 0, buf, ptr, ba.length);
                ptr += ba.length;
            }
            System.arraycopy(current, 0, buf, ptr, offset);
            assert ptr + offset == size;
            return buf;
        }
    }

}