fgettr.c

su 的源代码库

   if(fp != lastfp)  searchlist(fp);

   if (infoptr == ((struct insegyinfo *) NULL)) {
      /* initialize new segy input stream */
      unsigned int databytes; /* bytes from nsfirst   */

      /* allocate new segy input information table */
      *oldinfoptr = (struct insegyinfo *)
	 malloc(sizeof(struct insegyinfo));
      infoptr = *oldinfoptr;
      infoptr->nextinfo = (struct insegyinfo *) NULL;
      infoptr->infp = fp;  /* save FILE * ptr */
      infoptr->itr = 0;
      infoptr->ntr = -1;
      
      switch (infoptr->ftype = filestat(fileno(fp))) {
	 case DIRECTORY:
	    err("%s: segy input can't be a directory", __FILE__);

	 case TTY:
	    err("%s: segy input can't be tty", __FILE__);

	 default:
	    /* all others are ok */
	    break;
      }

/*--------------------------------------------------------------------*\
   Check for the presence of a line header and set a flag if one is
   found. The decision of what to do will be delayed until the call
   to fputtr(). This allows us to accept data w/ or w/o a line
   header.

   Reginald H. Beardsley [e-mail]
\*--------------------------------------------------------------------*/

      /* Attempt to get a text header */

      nread=efread(buf ,1 ,HDRBYTES ,infoptr->infp);

      switch( nread ){

	 case 0:   
	    return 0; /* no traces; trap in mains */

	 default:  

	    if (nread < HDRBYTES ){
		return 0; 

	    }else if( isascii_txt( buf ,HDRBYTES  )
		  || isebcdic_txt( buf ,HDRBYTES  ) ){
		in_line_hdr = 1;
		memcpy( su_text_hdr ,buf ,HDRBYTES );
		nread += efread(&(su_text_hdr[HDRBYTES]) ,1 
			,3200-HDRBYTES ,infoptr->infp);

	    }else{
		in_line_hdr=0;
		memcpy( tp ,buf ,HDRBYTES );

	    }
      }		

      
      if( in_line_hdr ){

	 /* Get the binary header */
	 nread = efread(&su_binary_hdr, 1, sizeof(bhed), infoptr->infp);
	 switch( nread ){
	    case 0:   
		return 0; /* no traces; trap in mains */

		default:  
		 if (nread != sizeof(su_binary_hdr)){
		    err("%s:%d bad binary header" , __FILE__ ,__LINE__ );
		 }
	 }	 

	 /* Get the first trace header */
	 nread = efread(tp, 1, HDRBYTES, infoptr->infp);
	 switch( nread ){
	    case 0:   
		return 0; /* no traces; trap in mains */

	    default:  
		if (nread != HDRBYTES){ 
		  err("%s: bad first header", __FILE__);
		}
	 }	 


      }

      /* Have the header, now for the data */
      infoptr->nsfirst = tp->ns;
      if (infoptr->nsfirst > SU_NFLTS){
	 err("%s: unable to handle %d > %d samples per trace",
		__FILE__, infoptr->nsfirst, SU_NFLTS);
      }

      switch (tp->trid) {
	 case CHARPACK:
	    infoptr->bytesper = sizeof(char); break;
	 case SHORTPACK:
	    infoptr->bytesper = 2*sizeof(char); break;
	 default:
	    infoptr->bytesper = sizeof(float); break;
      }

      databytes = infoptr->bytesper * tp->ns;

      infoptr->nsegy = HDRBYTES + databytes;


      /* Inconvenient to bump nread here; do it in the switch */
      nread = dataread(tp, infoptr, fixed_length);
      
      switch (nread) {
	 case 0:   
	    err("%s: no data on first trace", __FILE__);

	 default:  
	    if (nread != databytes){
		err("%s: first trace: " "read only %d bytes of %u",
		  __FILE__, nread, databytes);

	    }else{
		nread += HDRBYTES;
	    }
      }
      
      
      if (infoptr->ftype == DISK) { /* compute ntr */
	 efseeko(fp, (off_t) 0LL,SEEK_END);

	 if( in_line_hdr ){
	    infoptr->ntr = (eftello(fp)-3600)/infoptr->nsegy;
	    efseeko(fp, (off_t) 3600+infoptr->nsegy,SEEK_SET);

	 }else{
	    infoptr->ntr = eftello(fp)/infoptr->nsegy;
	    efseeko(fp, (off_t) infoptr->nsegy ,SEEK_SET);

	 }
	 
      }

   }else{

      /* not first trace */

/*--------------------------------------------------------------------*\
   A number of programs seek on the input file using either fseek(3c)
   or rewind(3c) and then expect to read trace data.  As a consequence
   we need to check and offset the filepointer if needed.
\*--------------------------------------------------------------------*/

      if( in_line_hdr && ftello( infoptr->infp ) == 0 ){

	 fseeko( infoptr->infp ,(off_t)3600L ,SEEK_SET );

      }

      nread = (int) efread(tp, 1, HDRBYTES, infoptr->infp);

      switch( nread ){

	 case 0: 
	    lastfp = infoptr->infp;
	    return 0; /* finished */

	 default:  
	    if (nread != HDRBYTES){
		err("%s: on trace #%ld read %d bytes expected %d bytes",
		  __FILE__,(infoptr->itr)+1,nread,HDRBYTES);
	    }
      }

      nread += dataread(tp, infoptr, fixed_length);

      if (fixed_length && (tp->ns != infoptr->nsfirst)){
	 err("%s: on trace #%ld number of samples in header (%d) differs from number for first trace (%d)"
	      ,__FILE__, (infoptr->itr)+1, tp->ns,

	      infoptr->nsfirst);
      }
   }

   ++(infoptr->itr);
   lastfp = infoptr->infp;
   return (nread);
}


int fgettr(FILE *fp, segy *tp)
{
	return(fgettr_internal(fp,tp,cwp_true));
}

int fvgettr(FILE *fp, segy *tp)
{
	return(fgettr_internal(fp,tp,cwp_false));
}

int fgettra(FILE *fp, segy *tp, int itr)
{
	int nread;
	if(lastfp != fp)  searchlist(fp);  /* search for match */
		
	
	if(infoptr == (struct insegyinfo *) NULL) {
		/* get first trace */
		if(0 >= fgettr(fp, tp)) return(0); /* error return */

		switch(infoptr->ftype) {
		case TTY:
			warn("stdin not redirected");
		break;
		case DISK:	/* correct */
		break;
		default:
			err("%s: input must be disk file",__FILE__);
		}
      


		efseeko(fp,(off_t) 0LL,SEEK_END);
		if( in_line_hdr ){
			infoptr->ntr = (off_t)((eftello(fp)-3600)/infoptr->nsegy);
			efseeko(fp, (off_t) 3600+infoptr->nsegy,SEEK_SET);
		}else{
			infoptr->ntr = (off_t)(eftello(fp)/infoptr->nsegy);
			efseeko(fp, (off_t) infoptr->nsegy,SEEK_SET);
		}
	} /* end first entry initialization */
	
	/* Check on requested trace number */
	if(itr >= infoptr->ntr)
		err("%s: trying to read off end of file",__FILE__);
	
	/* Position file pointer at start of requested trace */
	if( in_line_hdr ){
		efseeko(fp, (off_t) 3600+itr*infoptr->nsegy,SEEK_SET);
	}else{
		efseeko(fp, (off_t) itr*infoptr->nsegy,SEEK_SET);
	}
	
	nread=fgettr(fp, tp); /* let fgettr do the work */
	if(nread != infoptr->nsegy)
		err("%s: read %d bytes in trace of %d bytes",
		    __FILE__,nread,infoptr->nsegy);
	
	if(tp->ns != infoptr->nsfirst)
		warn("%s: header ns field = %d differs from first trace = %d",
		     __FILE__,tp->ns,infoptr->nsfirst);
	
	return(infoptr->ntr);
}

#endif /* end of XDR choice */
 
/*====================================================================*\
   These functions determine the presence of a SEGY text header based
   on the character set statistics of the first 3200 bytes in the
   file.

   Reginald H. Beardsley			    [e-mail]

\*====================================================================*/

static  unsigned char asciitext[256] = {
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
    1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 
};

  
static  unsigned char ebcdictext[256] = {
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
    1,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,
    1,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,
    1,1,0,0,0,0,0,0,0,0,0,1,1,1,1,1,
    0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,
    0,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,
    0,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,
    0,0,1,1,1,1,1,1,1,1,0,0,0,0,0,0,
    0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,
    0,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,
    0,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,
    0,0,1,1,1,1,1,1,1,1,0,0,0,0,0,0,
    1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0 
};

  
int isascii_txt( unsigned char* a ,int n){

  int ascii  = 0;
  int ebcdic = 0;
  int i;

  for (i=0; i<n; i++){

     ascii += asciitext[a[i]];
     ebcdic += ebcdictext[a[i]];
  }

  if( ascii > ebcdic && ascii > (int)(n*0.9) ){
    return(1);
  }else{
    return(0);
  }
}

  
int isebcdic_txt( unsigned char* a ,int n ){

  int ascii  = 0;
  int ebcdic = 0;
  int i;

  for (i=0; i<n; i++){

     ascii += asciitext[a[i]];
     ebcdic += ebcdictext[a[i]];
  }

  if( ascii < ebcdic && ebcdic > (int)(n*0.9) ){
    return(1);
  }else{
    return(0);
  }
}

#else

#include <stdio.h>

#include "su.h"
#include "segy.h"

char *sdoc[] = {
"								",
" tgettr <stdin >stdout						",
"								",
" 	Test harness for gettr.c				",
"	Changes cdp to abs(cdp)					",
"	Contrast the following results:	 			",
"	suplane offset=-100 | sugethw offset 			",
"	suplane offset=-100 | tgettr | sugethw offset		",
"								",
NULL};

segy tr;

main(int argc, char **argv)
{
	initargs(argc, argv);
	requestdoc(1);

 	while (gettr(&tr)) {
 		tr.offset = abs(tr.offset);
 		puttr(&tr);
 	}

	return EXIT_SUCCESS;
}
#endif