gdal/frmts/msg/xritheaderparser.cpp

/******************************************************************************
 *
 * Purpose:  Implementation of XRITHeaderParser class. Parse the header
 *           of the combined XRIT header/data files.
 * Author:   Bas Retsios, retsios@itc.nl
 *
 ******************************************************************************
 * Copyright (c) 2007, ITC
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 ******************************************************************************/

#include "cpl_port.h"  // Must be first.

#include "xritheaderparser.h"
#include <cstdlib>  // malloc, free
#include <cstring>  // memcpy

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//
// Upon successful parsing of a header in ifile, isValid() returns true
// and ifile is sought to the beginning of the image data
//////////////////////////////////////////////////////////////////////

XRITHeaderParser::XRITHeaderParser(std::ifstream &ifile)
    : m_isValid(false), m_isPrologue(false), m_dataSize(0), m_nrBitsPerPixel(0),
      m_nrColumns(0), m_nrRows(0), m_scanNorth(false)
{
    const unsigned int probeSize = 8;

    unsigned char probeBuf[probeSize];
    ifile.read((char *)probeBuf,
               probeSize);  // Probe file by reading first 8 bytes

    if (probeBuf[0] == 0 && probeBuf[1] == 0 &&
        probeBuf[2] == 16)  // Check for primary header record
    {
        long totalHeaderLength = parseInt32(&probeBuf[4]);
        if ((totalHeaderLength >= 10) &&
            (totalHeaderLength <= 10000))  // Check for valid header length
        {
            unsigned char *buf =
                (unsigned char *)std::malloc(totalHeaderLength);
            std::memcpy(
                buf, probeBuf,
                probeSize);  // save what we have already read when probing
            ifile.read((char *)buf + probeSize,
                       totalHeaderLength -
                           probeSize);  // read the rest of the header section
            parseHeader(buf, totalHeaderLength);
            std::free(buf);

            m_isValid = true;
        }
    }

    if (!m_isValid)  // seek back to original position
    {
        ifile.seekg(-static_cast<int>(probeSize), std::ios_base::cur);
    }
}

XRITHeaderParser::~XRITHeaderParser()
{
}

int XRITHeaderParser::parseInt16(unsigned char *num)
{
    return (num[0] << 8) | num[1];
}

long XRITHeaderParser::parseInt32(unsigned char *num)
{
    int i;
    memcpy(&i, num, 4);
    CPL_MSBPTR32(&i);
    return i;
}

void XRITHeaderParser::parseHeader(unsigned char *buf, long totalHeaderLength)
{
    int remainingHeaderLength = static_cast<int>(totalHeaderLength);

    while (remainingHeaderLength > 0)
    {
        int headerType = buf[0];
        int headerRecordLength = parseInt16(&buf[1]);
        if (headerRecordLength > remainingHeaderLength)
            break;

        switch (headerType)
        {
            case 0:  // primary header
            {
                int fileTypeCode =
                    buf[3];  // 0 = image data file, 128 = prologue
                if (fileTypeCode == 128)
                    m_isPrologue = true;

                long dataFieldLengthH = parseInt32(
                    &buf[8]);  // length of data field in bits (High DWORD)
                long dataFieldLengthL = parseInt32(
                    &buf[12]);  // length of data field in bits (Low DWORD)
                m_dataSize = (dataFieldLengthH << 5) +
                             (dataFieldLengthL >>
                              3);  // combine and convert bits to bytes
            }
            break;
            case 1:                         // image structure
                m_nrBitsPerPixel = buf[3];  // NB, number of bits per pixel
                m_nrColumns = parseInt16(&buf[4]);  // NC, number of columns
                m_nrRows = parseInt16(&buf[6]);     // NL, number of lines
                break;
            case 2:  // image navigation
            {
#if 0
          /*long cfac =*/ parseInt32(&buf[35]); // column scaling factor
#endif
                long lfac = parseInt32(&buf[39]);  // line scaling factor
#if 0
          /*long coff =*/ parseInt32(&buf[43]); // column offset
          /*long loff =*/ parseInt32(&buf[47]); // line offset
#endif
                if (lfac >= 0)
                    m_scanNorth = true;
                else
                    m_scanNorth = false;
            }
            break;
            case 3:    // image data function
            case 4:    // annotation
            case 5:    // time stamp
            case 6:    // ancillary text
            case 7:    // key header
            case 128:  // image segment identification
            case 129:  // encryption key message header
            case 130:  // image compensation information header
            case 131:  // image observation time header
            case 132:  // image quality information header
                break;
            default:  // ignore unknown header type
                break;
        }

        buf += headerRecordLength;
        remainingHeaderLength -= headerRecordLength;
    }
}