e00read.c

这是一个GPS相关的程序

}

/**********************************************************************
 *                          _ReadNextSourceLine()
 *
 * Loads the next line from the source file in psInfo.
 *
 * psInfo->bEOF should be checked after this call.
 **********************************************************************/
static void _ReadNextSourceLine(E00ReadPtr psInfo)
{
    if (!psInfo->bEOF)
    {
        psInfo->iInBufPtr = 0;
        psInfo->szInBuf[0] = '\0';

        /* Read either using fgets() or psInfo->pfnReadNextLine() 
         * depending on the way the file was opened...
         */
        if (psInfo->pfnReadNextLine == NULL)
        {
            if (VSIFGets(psInfo->szInBuf,E00_READ_BUF_SIZE,psInfo->fp) == NULL)
            {
                /* We reached EOF
                 */
                psInfo->bEOF = 1;
            }
        }
        else
        {
            const char *pszLine;
            pszLine = psInfo->pfnReadNextLine(psInfo->pRefData);
            if (pszLine)
            {
                strncpy(psInfo->szInBuf, pszLine, E00_READ_BUF_SIZE);
            }
            else
            {
                /* We reached EOF
                 */
                psInfo->bEOF = 1;
            }
        }

        if (!psInfo->bEOF)
        {
            /* A new line was succesfully read.  Remove trailing '\n' if any.
             * (Note: For Unix systems, we also have to check for '\r')
             */
            int nLen;
            nLen = strlen(psInfo->szInBuf);
            while(nLen > 0 && (psInfo->szInBuf[nLen-1] == '\n' ||
                               psInfo->szInBuf[nLen-1] == '\r'   ) )
            {
                nLen--;
                psInfo->szInBuf[nLen] = '\0';
            }

            psInfo->nInputLineNo++;
        }
    }
}


/**********************************************************************
 *                          _GetNextSourceChar()
 *
 * Returns the next char from the source file input buffer... and 
 * reload the input buffer when necessary... this function makes the
 * whole input file appear as one huge null-terminated string with
 * no line delimiters.
 *
 * Will return '\0' when EOF is reached.
 **********************************************************************/
static char _GetNextSourceChar(E00ReadPtr psInfo)
{
    char c = '\0';

    if (!psInfo->bEOF)
    {
        if (psInfo->szInBuf[psInfo->iInBufPtr] == '\0')
        {
            _ReadNextSourceLine(psInfo);
            c = _GetNextSourceChar(psInfo);
        }
        else
        {
            c = psInfo->szInBuf[psInfo->iInBufPtr++];
        }
    }

    return c;
}

/**********************************************************************
 *                          _UngetSourceChar()
 *
 * Reverse the effect of the previous call to _GetNextSourceChar() by
 * moving the input buffer pointer back 1 character.
 *
 * This function can be called only once per call to _GetNextSourceChar()
 * (i.e. you cannot unget more than one character) otherwise the pointer
 * could move before the beginning of the input buffer.
 **********************************************************************/
static void _UngetSourceChar(E00ReadPtr psInfo)
{
    if (psInfo->iInBufPtr > 0)
        psInfo->iInBufPtr--;
    else
    {
        /* This error can happen only if _UngetSourceChar() is called
         * twice in a row (which should never happen!).
         */
        CPLError(CE_Failure, CPLE_AssertionFailed,
                 "UNEXPECTED INTERNAL ERROR: _UngetSourceChar() "
                      "failed while reading line %d.", psInfo->nInputLineNo);
    }
}

/**********************************************************************
 *                          _UncompressNextLine()
 *
 * Uncompress one line of input and return a reference to an internal
 * buffer containing the uncompressed output.
 **********************************************************************/
static const char *_UncompressNextLine(E00ReadPtr psInfo)
{
    char    c;
    int     bEOL = 0;   /* Set to 1 when End of Line reached */
    int     iOutBufPtr = 0, i, n;
    int     iDecimalPoint, bOddNumDigits, iCurDigit;
    char    *pszExp;
    int     bPreviousCodeWasNumeric = 0;

    while(!bEOL && (c=_GetNextSourceChar(psInfo)) != '\0')
    {
        if (c != '~')
        {
            /* Normal character... just copy it 
             */
            psInfo->szOutBuf[iOutBufPtr++] = c;
            bPreviousCodeWasNumeric = 0;
        }
        else /* c == '~' */
        {
            /* ========================================================
             * Found an encoded sequence.
             * =======================================================*/
            c = _GetNextSourceChar(psInfo);

            /* --------------------------------------------------------
             * Compression level 1: only spaces, '~' and '\n' are encoded
             * -------------------------------------------------------*/
            if (c == ' ')
            {
                /* "~ " followed by number of spaces
                 */
                c = _GetNextSourceChar(psInfo);
                n = c - ' ';
                for(i=0; i<n; i++)
                    psInfo->szOutBuf[iOutBufPtr++] = ' ';
                bPreviousCodeWasNumeric = 0;
            }
            else if (c == '}')
            {
                /* "~}" == '\n'
                 */
                bEOL = 1;
                bPreviousCodeWasNumeric = 0;
            }
            else if (bPreviousCodeWasNumeric)
            {
                /* If the previous code was numeric, then the only valid code
                 * sequences are the ones above: "~ " and "~}".  If we end up
                 * here, it is because the number was followed by a '~' but
                 * this '~' was not a code, it only marked the end of a 
                 * number that was not followed by any space.
                 *
                 * We should simply ignore the '~' and return the character
                 * that follows it directly.
                 */
                psInfo->szOutBuf[iOutBufPtr++] = c;
                bPreviousCodeWasNumeric = 0;
            }
            else if (c == '~' || c == '-')
            {
                /* "~~" and "~-" are simple escape sequences for '~' and '-'
                 */
                psInfo->szOutBuf[iOutBufPtr++] = c;
            }
            /* --------------------------------------------------------
             * Compression level 2: numeric values are encoded.
             *
             * All codes for this level are in the form "~ c0 c1 c2 ... cn"
             * where:
             *
             *  ~             marks the beginning of a new code sequence
             *
             *  c0            is a single character code defining the format
             *                of the number (decimal position, exponent, 
             *                and even or odd number of digits)
             *
             *  c1 c2 ... cn  each of these characters represent a pair of 
             *                digits of the encoded value with '!' == 00
             *                values 92..99 are encoded on 2 chars that
             *                must be added to each other 
             *                (i.e. 92 == }!, 93 == }", ...)
             *
             *  The sequence ends with a ' ' or a '~' character
             * -------------------------------------------------------*/
            else if (c >= '!' && c <= 'z')
            {
                /* The format code defines 3 characteristics of the final number:
                 * - Presence of a decimal point and its position
                 * - Presence of an exponent, and its sign
                 * - Odd or even number of digits
                 */
                n = c - '!';
                iDecimalPoint = n % 15; /* 0 = no decimal point         */
                bOddNumDigits = n / 45; /* 0 = even num.digits, 1 = odd */
                n = n / 15;
                if ( n % 3 == 1 )
                    pszExp = "E+";
                else if (n % 3 == 2 )
                    pszExp = "E-";
                else 
                    pszExp = NULL;

                /* Decode the c1 c2 ... cn value and apply the format.
                 * Read characters until we encounter a ' ' or a '~'
                 */
                iCurDigit = 0;
                while((c=_GetNextSourceChar(psInfo)) != '\0' && 
                      c != ' ' && c != '~')
                {
                    n = c - '!';
                    if (n == 92 && (c=_GetNextSourceChar(psInfo)) != '\0')
                        n += c - '!';

                    psInfo->szOutBuf[iOutBufPtr++] = '0' + n/10;

                    if (++iCurDigit == iDecimalPoint)
                        psInfo->szOutBuf[iOutBufPtr++] = '.';

                    psInfo->szOutBuf[iOutBufPtr++] = '0' + n%10;

                    if (++iCurDigit == iDecimalPoint)
                        psInfo->szOutBuf[iOutBufPtr++] = '.';
                }

                if (c == '~' || c == ' ')
                {
                    bPreviousCodeWasNumeric = 1;
                    _UngetSourceChar(psInfo);
                }

                /* If odd number of digits, then flush the last one
                 */
                if (bOddNumDigits)
                    iOutBufPtr--;

                /* Insert the exponent string before the 2 last digits
                 * (we assume the exponent string is 2 chars. long)
                 */
                if (pszExp)
                {
                    for(i=0; i<2;i++)
                    {
                        psInfo->szOutBuf[iOutBufPtr] = 
                                   psInfo->szOutBuf[iOutBufPtr-2];
                        psInfo->szOutBuf[iOutBufPtr-2] = pszExp[i];
                        iOutBufPtr++;
                    }
                }
            }
            else
            {
                /* Unsupported code sequence... this is a possibility
                 * given the fact that this library was written by 
                 * reverse-engineering the format!
                 *
                 * Send an error to the user and abort.
                 *
                 * If this error ever happens, and you are convinced that
                 * the input file is not corrupted, then please report it to
                 * me at [e-mail], quoting the section of the input
                 * file that produced it, and I'll do my best to add support
                 * for this code sequence.
                 */
                CPLError(CE_Failure, CPLE_NotSupported,
                         "Unexpected code \"~%c\" encountered in line %d.",
                          c, psInfo->nInputLineNo);
    
                /* Force the program to abort by simulating a EOF 
                 */
                psInfo->bEOF = 1;
                bEOL = 1;
            }

        }/* if c == '~' */

        /* E00 lines should NEVER be longer than 80 chars.  if we passed
         * that limit, then the input file is likely corrupt.
         */
         if (iOutBufPtr > 80)
         {
            CPLError(CE_Failure, CPLE_FileIO,
                      "Uncompressed line longer than 80 chars. "
                      "Input file possibly corrupt around line %d.",
                      psInfo->nInputLineNo);
            /* Force the program to abort by simulating a EOF 
             */
            psInfo->bEOF = 1;
            bEOL = 1;
         }

    }/* while !EOL */

    psInfo->szOutBuf[iOutBufPtr++] = '\0';

    return psInfo->szOutBuf;
}