e00read.c

这是一个GPS相关的程序

/**********************************************************************
 * $Id: e00read.c,v 1.1.1.1 2006/06/26 15:38:27 oconrad Exp $
 *
 * Name:     e00read.c
 * Project:  Compressed E00 Read/Write library
 * Language: ANSI C
 * Purpose:  Functions to read Compressed E00 files and return a stream 
 *           of uncompressed lines.
 * Author:   Daniel Morissette, [e-mail]
 *
 * $Log: e00read.c,v $
 * Revision 1.1.1.1  2006/06/26 15:38:27  oconrad
 * no message
 *
 * Revision 1.1.1.1  2005/08/31 14:01:00  oconrad
 * no message
 *
 * Revision 1.1.1.1  2005/08/17 08:25:16  oconrad
 * no message
 *
 * Revision 1.1.1.1  2005/08/15 13:35:12  oconrad
 * no message
 *
 * Revision 1.1  2004/04/16 13:36:45  oconrad
 * no message
 *
 * Revision 1.8  1999/02/25 18:45:56  daniel
 * Now use CPL for Error handling, Memory allocation, and File access
 *
 * Revision 1.7  1999/01/08 17:39:08  daniel
 * Added E00ReadCallbackOpen()
 *
 * Revision 1.6  1998/11/13 16:34:08  daniel
 * Fixed '\r' problem when reading E00 files from a PC under Unix
 *
 * Revision 1.5  1998/11/13 15:48:08  daniel
 * Simplified the decoding of the compression codes for numbers
 * (use a logical rule instead of going case by case)
 *
 * Revision 1.4  1998/11/02 18:34:29  daniel
 * Added E00ErrorReset() calls.  Replace "EXP  1" by "EXP  0" on read.
 *
 * Revision 1.1  1998/10/29 13:26:00  daniel
 * Initial revision
 *
 **********************************************************************
 * Copyright (c) 1998, 1999, Daniel Morissette
 *
 * All rights reserved.  This software may be copied or reproduced, in
 * all or in part, without the prior written consent of its author,
 * Daniel Morissette ([e-mail]).  However, any material copied
 * or reproduced must bear the original copyright notice (above), this 
 * original paragraph, and the original disclaimer (below).
 * 
 * The entire risk as to the results and performance of the software,
 * supporting text and other information contained in this file
 * (collectively called the "Software") is with the user.  Although 
 * considerable efforts have been used in preparing the Software, the 
 * author does not warrant the accuracy or completeness of the Software.
 * In no event will the author be liable for damages, including loss of
 * profits or consequential damages, arising out of the use of the 
 * Software.
 * 
 **********************************************************************/

#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>

#include "e00compr.h"

static void _ReadNextSourceLine(E00ReadPtr psInfo);
static const char *_UncompressNextLine(E00ReadPtr psInfo);

/**********************************************************************
 *                          _E00ReadTestOpen()
 *
 * Given a pre-initialized E00ReadPtr, this function will make sure
 * that the file is really a E00 file, and also establish if it is
 * compressed or not... setting the structure members by the same way.
 *
 * Returns NULL (and destroys the E00ReadPtr) if the file does not
 * appear to be a valid E00 file.
 **********************************************************************/
static E00ReadPtr  _E00ReadTestOpen(E00ReadPtr psInfo)
{

    /* Check that the file is in E00 format.
     */
    _ReadNextSourceLine(psInfo);
    if (!psInfo->bEOF && strncmp(psInfo->szInBuf, "EXP ", 4) == 0)
    {
        /* We should be in presence of a valid E00 file... 
         * Is the file compressed or not?
         *
         * Note: we cannot really rely on the number that follows the EXP to
         * establish if the file is compressed since we sometimes encounter
         * uncompressed files that start with a "EXP 1" line!!!
         *
         * The best test is to read the first non-empty line: if the file is
         * compressed, the first line of data should be 79 or 80 characters 
         * long and contain several '~' characters.
         */
        do
        {
            _ReadNextSourceLine(psInfo);
        }while(!psInfo->bEOF && 
               (psInfo->szInBuf[0] == '\0' || isspace(psInfo->szInBuf[0])) );

         if (!psInfo->bEOF && 
             (strlen(psInfo->szInBuf)==79 || strlen(psInfo->szInBuf)==80) &&
             strchr(psInfo->szInBuf, '~') != NULL )
             psInfo->bIsCompressed = 1;

         /* Move the Read ptr ready to read at the beginning of the file
          */
         E00ReadRewind(psInfo);
    }
    else
    {
        CPLFree(psInfo);
        psInfo = NULL;
    }

    return psInfo;
}

/**********************************************************************
 *                          E00ReadOpen()
 *
 * Try to open a E00 file given its filename and return a E00ReadPtr handle.
 *
 * Returns NULL if the file could not be opened or if it does not 
 * appear to be a valid E00 file.
 **********************************************************************/
E00ReadPtr  E00ReadOpen(const char *pszFname)
{
    E00ReadPtr  psInfo = NULL;
    FILE        *fp;

    CPLErrorReset();

    /* Open the file 
     */
    fp = VSIFOpen(pszFname, "rt");
    if (fp == NULL)
    {
        CPLError(CE_Failure, CPLE_OpenFailed,
                 "Failed to open %s: %s", pszFname, strerror(errno));
        return NULL;
    }

    /* File was succesfully opened, allocate and initialize a 
     * E00ReadPtr handle and check that the file is valid.
     */
    psInfo = (E00ReadPtr)CPLCalloc(1, sizeof(struct _E00ReadInfo));

    psInfo->fp = fp;

    psInfo = _E00ReadTestOpen(psInfo);

    if (psInfo == NULL)
    {
        CPLError(CE_Failure, CPLE_OpenFailed,
                 "%s is not a valid E00 file.", pszFname);
    }

    return psInfo;
}

/**********************************************************************
 *                          E00ReadCallbackOpen()
 *
 * This is an alternative to E00ReadOpen() for cases where you want to
 * do all the file management yourself.  You open/close the file yourself
 * and provide 2 callback functions: to read from the file and rewind the
 * file pointer.  pRefData is your handle on the physical file and can
 * be whatever you want... it is not used by the library, it will be
 * passed directly to your 2 callback functions when they are called.
 *
 * The callback functions must have the following C prototype:
 *
 *   const char *myReadNextLine(void *pRefData);
 *   void        myReadRewind(void *pRefData);
 *
 *   myReadNextLine() should return a reference to its own internal 
 *   buffer, or NULL if an error happens or EOF is reached.
 *
 * E00ReadCallbackOpen() returns a E00ReadPtr handle or NULL if the file
 * does not appear to be a valid E00 file.
 **********************************************************************/
E00ReadPtr  E00ReadCallbackOpen(void *pRefData,
                                const char * (*pfnReadNextLine)(void *),
                                void (*pfnReadRewind)(void *))
{
    E00ReadPtr  psInfo = NULL;

    CPLErrorReset();

    /* Make sure we received valid function pointers
     */
    if (pfnReadNextLine == NULL || pfnReadRewind == NULL)
    {
        CPLError(CE_Failure, CPLE_IllegalArg,
                 "Invalid function pointers!");
        return NULL;
    }

    /* Allocate and initialize a 
     * E00ReadPtr handle and check that the file is valid.
     */
    psInfo = (E00ReadPtr)CPLCalloc(1, sizeof(struct _E00ReadInfo));

    psInfo->pRefData = pRefData;
    psInfo->pfnReadNextLine = pfnReadNextLine;
    psInfo->pfnReadRewind = pfnReadRewind;

    psInfo = _E00ReadTestOpen(psInfo);

    if (psInfo == NULL)
    {
        CPLError(CE_Failure, CPLE_OpenFailed,
                 "This is not a valid E00 file.");
    }

    return psInfo;
}

/**********************************************************************
 *                          E00ReadClose()
 *
 * Close input file and release any memory used by the E00ReadPtr.
 **********************************************************************/
void    E00ReadClose(E00ReadPtr psInfo)
{
    CPLErrorReset();

    if (psInfo)
    {
        if (psInfo->fp)
            VSIFClose(psInfo->fp);
        CPLFree(psInfo);
    }
}

/**********************************************************************
 *                          E00ReadRewind()
 *
 * Rewind the E00ReadPtr.  Allows to start another read pass on the 
 * input file.
 **********************************************************************/
void    E00ReadRewind(E00ReadPtr psInfo)
{
    CPLErrorReset();

    psInfo->szInBuf[0] = psInfo->szOutBuf[0] = '\0';
    psInfo->iInBufPtr = 0;

    psInfo->nInputLineNo = 0;

    if (psInfo->pfnReadRewind == NULL)
        VSIRewind(psInfo->fp);
    else
        psInfo->pfnReadRewind(psInfo->pRefData);

    psInfo->bEOF = 0;
}

/**********************************************************************
 *                          E00ReadNextLine()
 *
 * Return the next line of input from the E00 file or NULL if we reached EOF.
 *
 * Returns a reference to an internal buffer whose contents will be valid
 * only until the next call to this function.
 **********************************************************************/
const char *E00ReadNextLine(E00ReadPtr psInfo)
{
    const char *pszLine = NULL;
    char *pszPtr;

    CPLErrorReset();

    if (psInfo && !psInfo->bEOF)
    {
        if (!psInfo->bIsCompressed)
        {
            /* Uncompressed file... return line directly. 
             */
            _ReadNextSourceLine(psInfo);
            pszLine = psInfo->szInBuf;
        }
        else if (psInfo->bIsCompressed && psInfo->nInputLineNo == 0)
        {
            /* Header line in a compressed file... return line 
             * after replacing "EXP  1" with "EXP  0".  E00ReadOpen()
             * has already verified that this line starts with "EXP "
             */
            _ReadNextSourceLine(psInfo);
            if ( (pszPtr = strstr(psInfo->szInBuf, " 1")) != NULL)
                pszPtr[1] = '0';
            pszLine = psInfo->szInBuf;
        }
        else
        {
            if (psInfo->nInputLineNo == 1)
            {
                /* We just read the header line... reload the input buffer
                 */
                _ReadNextSourceLine(psInfo);
            }

            /* Uncompress the next line of input and return it 
             */
            pszLine = _UncompressNextLine(psInfo);
        }

        /* If we just reached EOF then make sure we don't add an extra
         * empty line at the end of the uncompressed oputput.
         */
        if (psInfo->bEOF && strlen(pszLine) == 0)
            pszLine = NULL;
    }

    return pszLine;