decompress XML String - Java XML

Description

decompress XML String

Demo Code

//package com.java2s;

public class Main {
    public static void main(String[] argv) throws Exception {
        byte[] xml = new byte[] { 34, 35, 36, 37, 37, 37, 67, 68, 69 };
        System.out.println(decompressXML(xml));
    }/*  w w w.ja  va2s.  c  o  m*/

    private static int endDocTag = 0x00100101;
    private static int startTag = 0x00100102;
    private static int endTag = 0x00100103;
    private static String spaces = "                                             ";

    public static String decompressXML(final byte[] xml) {

        StringBuilder finalXML = new StringBuilder();

        // Compressed XML file/bytes starts with 24x bytes of data,
        // 9 32 bit words in little endian order (LSB first):
        // 0th word is 03 00 08 00
        // 3rd word SEEMS TO BE: Offset at then of StringTable
        // 4th word is: Number of strings in string table
        // WARNING: Sometime I indiscriminently display or refer to word in
        // little endian storage format, or in integer format (ie MSB first).
        int numbStrings = LEW(xml, 4 * 4);

        // StringIndexTable starts at offset 24x, an array of 32 bit LE offsets
        // of the length/string data in the StringTable.
        int sitOff = 0x24; // Offset of start of StringIndexTable

        // StringTable, each string is represented with a 16 bit little endian
        // character count, followed by that number of 16 bit (LE) (Unicode)
        // chars.
        int stOff = sitOff + numbStrings * 4; // StringTable follows
                                              // StrIndexTable

        // XMLTags, The XML tag tree starts after some unknown content after the
        // StringTable. There is some unknown data after the StringTable, scan
        // forward from this point to the flag for the start of an XML start
        // tag.
        int xmlTagOff = LEW(xml, 3 * 4); // Start from the offset in the 3rd
                                         // word.
        // Scan forward until we find the bytes: 0x02011000(x00100102 in normal
        // int)
        for (int ii = xmlTagOff; ii < xml.length - 4; ii += 4) {
            if (LEW(xml, ii) == startTag) {
                xmlTagOff = ii;
                break;
            }
        } // end of hack, scanning for start of first start tag

        // XML tags and attributes:
        // Every XML start and end tag consists of 6 32 bit words:
        // 0th word: 02011000 for startTag and 03011000 for endTag
        // 1st word: a flag?, like 38000000
        // 2nd word: Line of where this tag appeared in the original source file
        // 3rd word: FFFFFFFF ??
        // 4th word: StringIndex of NameSpace name, or FFFFFFFF for default NS
        // 5th word: StringIndex of Element Name
        // (Note: 01011000 in 0th word means end of XML document, endDocTag)

        // Start tags (not end tags) contain 3 more words:
        // 6th word: 14001400 meaning??
        // 7th word: Number of Attributes that follow this tag(follow word 8th)
        // 8th word: 00000000 meaning??

        // Attributes consist of 5 words:
        // 0th word: StringIndex of Attribute Name's Namespace, or FFFFFFFF
        // 1st word: StringIndex of Attribute Name
        // 2nd word: StringIndex of Attribute Value, or FFFFFFF if ResourceId
        // used
        // 3rd word: Flags?
        // 4th word: str ind of attr value again, or ResourceId of value

        // TMP, dump string table to tr for debugging
        // tr.addSelect("strings", null);
        // for (int ii=0; ii<numbStrings; ii++) {
        // // Length of string starts at StringTable plus offset in StrIndTable
        // String str = compXmlString(xml, sitOff, stOff, ii);
        // tr.add(String.valueOf(ii), str);
        // }
        // tr.parent();

        // Step through the XML tree element tags and attributes
        int off = xmlTagOff;
        int indent = 0;
        int startTagLineNo = -2;
        while (off < xml.length) {
            int tag0 = LEW(xml, off);
            // int tag1 = LEW(xml, off+1*4);
            int lineNo = LEW(xml, off + 2 * 4);
            // int tag3 = LEW(xml, off+3*4);
            int nameNsSi = LEW(xml, off + 4 * 4);
            int nameSi = LEW(xml, off + 5 * 4);

            if (tag0 == startTag) { // XML START TAG
                int tag6 = LEW(xml, off + 6 * 4); // Expected to be 14001400
                int numbAttrs = LEW(xml, off + 7 * 4); // Number of Attributes
                                                       // to follow
                // int tag8 = LEW(xml, off+8*4); // Expected to be 00000000
                off += 9 * 4; // Skip over 6+3 words of startTag data
                String name = compXmlString(xml, sitOff, stOff, nameSi);
                // tr.addSelect(name, null);
                startTagLineNo = lineNo;

                // Look for the Attributes
                StringBuffer sb = new StringBuffer();
                for (int ii = 0; ii < numbAttrs; ii++) {
                    int attrNameNsSi = LEW(xml, off); // AttrName Namespace Str
                                                      // Ind, or FFFFFFFF
                    int attrNameSi = LEW(xml, off + 1 * 4); // AttrName String
                                                            // Index
                    int attrValueSi = LEW(xml, off + 2 * 4); // AttrValue Str
                                                             // Ind, or
                                                             // FFFFFFFF
                    int attrFlags = LEW(xml, off + 3 * 4);
                    int attrResId = LEW(xml, off + 4 * 4); // AttrValue
                                                           // ResourceId or dup
                                                           // AttrValue StrInd
                    off += 5 * 4; // Skip over the 5 words of an attribute

                    String attrName = compXmlString(xml, sitOff, stOff,
                            attrNameSi);
                    String attrValue = attrValueSi != -1 ? compXmlString(
                            xml, sitOff, stOff, attrValueSi)
                            : "resourceID 0x"
                                    + Integer.toHexString(attrResId);
                    sb.append(" " + attrName + "=\"" + attrValue + "\"");
                    // tr.add(attrName, attrValue);
                }
                finalXML.append("<" + name + sb + ">");
                prtIndent(indent, "<" + name + sb + ">");
                indent++;

            } else if (tag0 == endTag) { // XML END TAG
                indent--;
                off += 6 * 4; // Skip over 6 words of endTag data
                String name = compXmlString(xml, sitOff, stOff, nameSi);
                finalXML.append("</" + name + ">");
                prtIndent(indent, "</" + name + "> (line " + startTagLineNo
                        + "-" + lineNo + ")");
                // tr.parent(); // Step back up the NobTree

            } else if (tag0 == endDocTag) { // END OF XML DOC TAG
                break;

            } else {
                prt("  Unrecognized tag code '" + Integer.toHexString(tag0)
                        + "' at offset " + off);
                break;
            }
        } // end of while loop scanning tags and attributes of XML tree
          // prt("    end at offset " + off);
        return finalXML.toString();
    }

    private static int LEW(final byte[] arr, final int off) {
        return arr[off + 3] << 24 & 0xff000000 | arr[off + 2] << 16
                & 0xff0000 | arr[off + 1] << 8 & 0xff00 | arr[off] & 0xFF;
    }

    private static String compXmlString(final byte[] xml, final int sitOff,
            final int stOff, final int strInd) {
        if (strInd < 0) {
            return null;
        }
        int strOff = stOff + LEW(xml, sitOff + strInd * 4);
        return compXmlStringAt(xml, strOff);
    }

    private static void prtIndent(final int indent, final String str) {
        prt(spaces.substring(0, Math.min(indent * 2, spaces.length()))
                + str);
    }

    private static void prt(final String str) {
        // System.err.print(str);
    }

    private static String compXmlStringAt(final byte[] arr, final int strOff) {
        int strLen = arr[strOff + 1] << 8 & 0xff00 | arr[strOff] & 0xff;
        byte[] chars = new byte[strLen];
        for (int ii = 0; ii < strLen; ii++) {
            chars[ii] = arr[strOff + 2 + ii * 2];
        }
        return new String(chars); // Hack, just use 8 byte chars
    }
}

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