segdread.c

su 的源代码库

 *
 * Credits:
 *      EOPG: Marc Schaming, Jean-Daniel Tissot
 *      SEP:  Stew Levin - fixed low-order bit error in conversion
 *            of negative values on 2's complement machines.
 *            Use ldexp() function instead of much slower value*pow(2,expo)
 *      SEP:  Adapted F8015 to F0015 conversion
 *
 *
 * Parameters:
 *    from   - input vector
 *    to     - output vector
 *    len    - number of packets of 4 floats in vectors
 *
 */
/*
 *
 * Format 0015 is a 10 byte per 4 words (2 1/2 bytes per word)
 * representation.  According to the SEG specifications, the
 * bit layout of the 10 bytes is:
 *
 *
 *  Bit       0     1     2     3     4     5     6     7
 *-----------------------------------------------------------
 * Byte 1    C3    C2    C1    C0    C3    C2    C1    C0    Exponents for
 * Byte 2    C3    C2    C1    C0    C3    C2    C1    C0    channels 1 thru 4
 *
 * Byte 3     S    Q-1   Q-2   Q-3   Q-4   Q-5   Q-6   Q-7   Channel 1
 * Byte 4    Q-8   Q-9   Q-10  Q-11  Q-12  Q-13  Q-14   0
 * Byte 5     S    Q-1   Q-2   Q-3   Q-4   Q-5   Q-6   Q-7   Channel 2
 * Byte 6    Q-8   Q-9   Q-10  Q-11  Q-12  Q-13  Q-14   0
 * Byte 7     S    Q-1   Q-2   Q-3   Q-4   Q-5   Q-6   Q-7   Channel 3
 * Byte 8    Q-8   Q-9   Q-10  Q-11  Q-12  Q-13  Q-14   0
 * Byte 9     S    Q-1   Q-2   Q-3   Q-4   Q-5   Q-6   Q-7   Channel 4
 * Byte 10   Q-8   Q-9   Q-10  Q-11  Q-12  Q-13  Q-14   0
 *
 * S=sign bit. - (One = negative number)
 * C=binary exponents. - This is a 4 bit positive binary exponent of 2
 *               CCCC
 *   written as 2     where CCCC can assume values of 0-15.  The four
 *   exponents are in channel number order for the four channels starting
 *   with channel one in bits 0-3 of Byte 1.
 * Q1-14-fraction. - This is a 14 bit one's complement binary fraction.
 *   The radix point is to the left of the most significant bit (Q-1)
 *                                  -1
 *   with the MSB being defined as 2 .  The sign and fraction can assume
 *                  -14       -14
 *   values from 1-2   to -1+2  .  Note that bit 7 of the second byte
 *   of each sample must be zero in order to guarantee the uniqueness of
 *   the start of scan.  Negative zero is invalid and must be converted
 *   to positive zero.
 *                                       CCCC    MP                   MP
 * Input signal = S.QQQQ,QQQQ,QQQQ,QQ x 2    x 2    millivolts where 2
 *   is the value required to descale the data word to the recording
 *   system input level.  MP is defined in Byte 8 of each of the corre-
 *   sponding channel set descriptors in the scan type header.
 * Note that in utilizing this data recording method, the number of data
 *   channels per channel set must be exactly divisible by 4 in order to
 *   preserve the data grouping of this method.
 */
 
static void F0015_to_float (Sfio_t *from, float to[], int len)
{
 register int i;
 register short ex1_4;
 int expo;
 short fraction;

 for (i = 0; i < len; i += 4) {
	ex1_4 = GET_S(from);
 	expo = ((ex1_4 >> 12) & 0x0F) - 15;
	fraction = GET_S(from);
	if (fraction < 0) fraction = -((~fraction)&(~1));
 	*(to++) = ldexp((double) fraction, expo);

 	expo = ((ex1_4 >> 8) & 0x0F) - 15;
	fraction = GET_S(from);
	if (fraction < 0) fraction = -((~fraction)&(~1));
 	*(to++) = ldexp((double) fraction, expo);

 	expo = ((ex1_4 >> 4) & 0x0F) - 15;
	fraction = GET_S(from);
	if (fraction < 0) fraction = -((~fraction)&(~1));
 	*(to++) = ldexp((double) fraction, expo);

 	expo = (ex1_4 & 0x0F) - 15;
	fraction = GET_S(from);
	if (fraction < 0) fraction = -((~fraction)&(~1));
 	*(to++) = ldexp((double) fraction, expo);
 }
} 

/* F8015_to_float - convert 20 bit binary demultiplexed data into floating numbers
 *
 * Credits:
 *      EOPG: Marc Schaming, Jean-Daniel Tissot
 *      SEP:  Stew Levin - fixed low-order bit error in conversion
 *            of negative values on 2's complement machines.
 *            Use ldexp() function instead of much slower value*pow(2,expo)
 *
 * Parameters:
 *    from   - input vector
 *    to     - output vector
 *    len    - number of packets of 4 floats in vectors
 *
 */
/*
 *
 * Format 8015 is a 10 byte per 4 words (2 1/2 bytes per word)
 * representation.  According to the SEG specifications, the
 * bit layout of the 10 bytes is:
 *
 *
 *  Bit       0     1     2     3     4     5     6     7
 *-----------------------------------------------------------
 * Byte 1    C3    C2    C1    C0    C3    C2    C1    C0    Exponents for
 * Byte 2    C3    C2    C1    C0    C3    C2    C1    C0    channels 1 thru 4
 *
 * Byte 3     S    Q-1   Q-2   Q-3   Q-4   Q-5   Q-6   Q-7   Channel 1
 * Byte 4    Q-8   Q-9   Q-10  Q-11  Q-12  Q-13  Q-14  Q-15
 * Byte 5     S    Q-1   Q-2   Q-3   Q-4   Q-5   Q-6   Q-7   Channel 2
 * Byte 6    Q-8   Q-9   Q-10  Q-11  Q-12  Q-13  Q-14  Q-15
 * Byte 7     S    Q-1   Q-2   Q-3   Q-4   Q-5   Q-6   Q-7   Channel 3
 * Byte 8    Q-8   Q-9   Q-10  Q-11  Q-12  Q-13  Q-14  Q-15
 * Byte 9     S    Q-1   Q-2   Q-3   Q-4   Q-5   Q-6   Q-7   Channel 4
 * Byte 10   Q-8   Q-9   Q-10  Q-11  Q-12  Q-13  Q-14  Q-15
 *
 * S=sign bit. - (One = negative number)
 * C=binary exponents. - This is a 4 bit positive binary exponent of 2
 *               CCCC
 *   written as 2     where CCCC can assume values of 0-15.  The four
 *   exponents are in channel number order for the four channels starting
 *   with channel one in bits 0-3 of Byte 1.
 * Q1-15-fraction. - This is a 15 bit one's complement binary fraction.
 *   The radix point is to the left of the most significant bit (Q-1)
 *                                  -1
 *   with the MSB being defined as 2 .  The sign and fraction can assume
 *                  -15       -15
 *   values from 1-2   to -1+2  .  Negative zero is invalid and must be
 *   converted to positive zero.
 *                                        CCCC    MP                   MP
 * Input signal = S.QQQQ,QQQQ,QQQQ,QQQ x 2    x 2    millivolts where 2
 *   is the value required to descale the data word to the recording
 *   system input level.  MP is defined in Byte 8 of each of the corre-
 *   sponding channel set descriptors in the scan type header.
 * Note that in utilizing this data recording method, the number of data
 *   channels per channel set must be exactly divisible by 4 in order to
 *   preserve the data grouping of this method.
 */

static void F8015_to_float (Sfio_t *from, float to[], int len)
{
 register int i;
 register short ex1_4;
 int expo;
 short fraction;

 for (i = 0; i < len; i += 4) {
      ex1_4 = GET_S(from);
 	expo = ((ex1_4 >> 12) & 15) - 15;
      fraction = GET_S(from);
	if (fraction < 0) fraction = -(~fraction);
 	*(to++) = ldexp((double) fraction, expo);

 	expo = ((ex1_4 >> 8) & 15) - 15;
      fraction = GET_S(from);
	if (fraction < 0) fraction = -(~fraction);
 	*(to++) = ldexp((double) fraction, expo);

 	expo = ((ex1_4 >> 4) & 15) - 15;
      fraction = GET_S(from);
	if (fraction < 0) fraction = -(~fraction);
 	*(to++) = ldexp((double) fraction, expo);

 	expo = (ex1_4 & 15) - 15;
      fraction = GET_S(from);
	if (fraction < 0) fraction = -(~fraction);
 	*(to++) = ldexp((double) fraction, expo);
 }
} 

/* F8022_to_float - convert 8 bit quaternary demultiplexed data into floating numbers
 *
 * Credits:
 *      SEP:  Stew Levin
 *
 * Parameters:
 *    from   - input sfio unit
 *    to     - output vector
 *    len    - number of packets of 4 floats in vectors
 *
 */
/*
 *
 * Format 8022 is a 1 byte per word representation.
 * According to the SEG specifications, the bit
 * layout of the byte is:
 *
 *
 *  Bit       0     1     2     3     4     5     6     7
 *-----------------------------------------------------------
 * Byte 1     S    C2    C1    C0    Q-1   Q-2   Q-3   Q-4
 *
 * S=sign bit. - (One = negative number)
 * C=quaternary exponent. - This is a 3 bit positive binary exponent of 4
 *               CCC
 *   written as 4    where CCC can assume values of 0-7.
 * Q1-4-fraction. - This is a 4 bit one's complement binary fraction.
 *   The radix point is to the left of the most significant bit (Q-1)
 *                                  -1
 *   with the MSB being defined as 2 .  The fraction can have values
 *           -4        -4
 *   from 1-2   to -1+2  .  Negative zero is invalid and must be
 *   converted to positive zero.
 *                          CCC   MP                   MP
 * Input signal = S.QQQQ x 4   x 2   millivolts where 2    is the
 *   value required to descale the data word to the recording system
 *   input level.  MP is defined in Byte 8 of each of the corre-
 *   sponding channel set descriptors in the scan type header.
 */

static void F8022_to_float (Sfio_t *from, float to[], int len)
{
 register int i;
 register int ex1_4;
 int expo;
 short fraction;

 for (i = 0; i < len; i ++) {
      ex1_4 = GET_C(from);
      expo = ((ex1_4 >> 3) & 14) - 4;
      fraction = ex1_4 & 15;
	if (ex1_4 & 128) fraction = -(15^fraction);
 	*(to++) = ldexp((double) fraction, expo);
 }
} 

/* F8024_to_float - convert 16 bit quaternary demultiplexed data into floating numbers
 *
 * Credits:
 *      SEP:  Stew Levin
 *
 * Parameters:
 *    from   - input sfio unit
 *    to     - output vector
 *    len    - number of packets of 4 floats in vectors
 *
 */
/*
 *
 * Format 8024 is a 2 byte per word representation.
 * According to the SEG specifications, the bit
 * layout of the bytes is:
 *
 *
 *  Bit       0     1     2     3     4     5     6     7
 *-----------------------------------------------------------
 * Byte 1     S    C2    C1    C0    Q-1   Q-2   Q-3   Q-4
 * Byte 2    Q-5   Q-6   Q-7   Q-8   Q-9   Q-10  Q-11  Q-12
 *
 * S=sign bit. - (One = negative number)
 * C=quaternary exponent. - This is a 3 bit positive binary exponent of 4
 *               CCC
 *   written as 4    where CCC can assume values of 0-7.
 * Q1-12-fraction. - This is a 12 bit one's complement binary fraction.
 *   The radix point is to the left of the most significant bit (Q-1)
 *                                  -1
 *   with the MSB being defined as 2 .  The fraction can have values
 *           -12        -12
 *   from 1-2    to -1+2   .  Negative zero is invalid and must be
 *   converted to positive zero.
 *                                    CCC   MP                   MP
 * Input signal = S.QQQQ,QQQQ,QQQQ x 4   x 2   millivolts where 2  
 *   is the value required to descale the data word to the recording
 *   system input level.  MP is defined in Byte 8 of each of the corre-
 *   sponding channel set descriptors in the scan type header.
 */

static void F8024_to_float (Sfio_t *from, float to[], int len)
{
 register int i;
 register int ex1_4;
 int expo;
 short fraction;

 for (i = 0; i < len; i ++) {
      ex1_4 = GET_S(from);
      expo = ((ex1_4 >> 11) & 14) - 12;
      fraction = ex1_4 & 4095;
      if (ex1_4 & 32768) fraction = -(4095^fraction);
      *(to++) = ldexp((double) fraction, expo);
 }
} 

/* F8036_to_float - convert 24 bit quaternary demultiplexed data into floating numbers
 *
 * Credits:
 *      SEP:  Stew Levin
 *
 * Parameters:
 *    from   - input sfio unit
 *    to     - output vector
 *    len    - number of packets of 4 floats in vectors
 *
 */
/*
 *
 * Format 8036 is a 3 byte per word representation.
 * According to the SEG specifications, the bit
 * layout of the bytes is:
 *
 *
 *  Bit       0     1     2     3     4     5     6     7
 *-----------------------------------------------------------
 * Byte 1    Q-1   Q-2   Q-3   Q-4   Q-5   Q-6   Q-7   Q-8
 * Byte 2    Q-9   Q-10  Q-11  Q-12  Q-13  Q-14  Q-15  Q-16
 * Byte 3    Q-17  Q-18  Q-19  Q-20  Q-21  Q-22  Q-23  Q-24
 *
 * Q1-24-integer. - This is a 24 bit two's complement binary integer.
 *                         MP                   MP
 * Input signal = Q...Q x 2   millivolts where 2  
 *   is the value required to descale the data word to the recording
 *   system input level.  MP is defined in Byte 8 of each of the corre-
 *   sponding channel set descriptors in the scan type header.
 */

static void F8036_to_float (Sfio_t *from, float to[], int len)
{
 register int i;
 register long int ival;

 for (i = 0; i < len; i ++) {
      ival = GET_UC(from);
      ival <<= 8; ival |= GET_UC(from);
      ival <<= 8; ival |= GET_UC(from);
      if(ival > 8388607) ival -= 16777216;
      *(to++) = (float) ival;
 }
} 

/* F8038_to_float - convert 32 bit quaternary demultiplexed data into floating numbers
 *
 * Credits:
 *      SEP:  Stew Levin
 *
 * Parameters:
 *    from   - input sfio unit
 *    to     - output vector
 *    len    - number of packets of 4 floats in vectors
 *
 */
/*
 *
 * Format 8038 is a 4 byte per word representation.
 * According to the SEG specifications, the bit
 * layout of the bytes is:
 *
 *
 *  Bit       0     1     2     3     4     5     6     7
 *-----------------------------------------------------------
 * Byte 1    Q-1   Q-2   Q-3   Q-4   Q-5   Q-6   Q-7   Q-8
 * Byte 2    Q-9   Q-10  Q-11  Q-12  Q-13  Q-14  Q-15  Q-16
 * Byte 3    Q-17  Q-18  Q-19  Q-20  Q-21  Q-22  Q-23  Q-24
 * Byte 4    Q-25  Q-26  Q-27  Q-28  Q-29  Q-30  Q-31  Q-32
 *
 * Q1-32-fraction. - This is a 32 bit two's complement binary integer.
 *                         MP                   MP
 * Input signal = Q...Q x 2   millivolts where 2  
 *   is the value required to descale the data word to the recording
 *   system input level.  MP is defined in Byte 8 of each of the corre-
 */
 /* Note this conversion routine assumes the target architecture is
  * already 2's complement.