source: sans/utils/Teabag/sa_futil.c @ 838

#include <stdio.h>

#define BYTE2(a)  ((a & 0xff00) >> 8) + ((a & 0x00ff) << 8)
#define BYTE4(a)  ((a & 0xff000000)>>24) + ((a & 0x00ff0000)>> 8) \
                 +((a & 0x0000ff00)<< 8) + ((a & 0x000000ff)<<24)

/* 
 * Operate on the premise that: short = 2 bytes
 *                              int   = 4 bytes
 *                              float = 4 bytes
 */
int fgetshort(FILE *fp, short *outval, int byteorder) {
  short val;

  if (feof(fp)) return -1;
  fread(&val,sizeof(short),1,fp);
  if (byteorder) val = BYTE2(val);
  *outval=val;
  return 0;
}

int fputshort(FILE *fp, short *outval, int byteorder) {
  short val;
  val = *outval;
  if (byteorder) val = BYTE2(val);
  fwrite(&val,sizeof(short),1,fp);
  return 0;
}



int fgetint(FILE *fp, int *outval, int byteorder) {
  int val;

  if (feof(fp)) return -1;
  fread(&val,sizeof(int),1,fp);
  if (byteorder) val = BYTE4(val);
  *outval = val;
  return 0;
}

int fputint(FILE *fp, int *outval, int byteorder) {
  int val;
  val = *outval;
  if (byteorder) val = BYTE4(val);
  fwrite(&val,sizeof(int),1,fp);
  return 0;
}

int fgetbool(FILE *fp, int *outval, int byteorder) {
  int val;

  if (feof(fp)) return -1;
  fread(&val,sizeof(int),1,fp);
  if (byteorder) val = BYTE4(val);
  *outval = val;
  return 0;
}

int fputbool(FILE *fp, int *outval, int byteorder) {
  int val;
  val = *outval;
  if (byteorder) val = BYTE4(val);
  fwrite(&val,sizeof(int),1,fp);
  return 0;
}

int fgetstring(FILE *fp, char *string, int stringlen) {
  if (feof(fp)) return -1;
  fread(string,stringlen * sizeof(char),1,fp);
  string[stringlen] = 0;
  return 0;
}

int fputstring(FILE *fp, char *string, int stringlen) {
  int retn;

  retn = fwrite(string,1,stringlen,fp);
  if (retn <= 0) return -1;
  return 0;
}

void
pbin(int val, int len, char * trailer){
    int j,bit;
    printf("-->");
    for(j=len;j>0;j--){
        bit = ((val & (0x00000001 << (j-1))) ? 1 : 0);
        if (!(j%4)) printf(" ");
        printf("%d",bit);
    }
    printf("%s",trailer);
}


/*
 * GetVaxFloat
 *
 * Convert a VMS 4 byte F-float number to a IEEE 754 single precision floating
 * point number. The method is as follows: detect invalid numbers and zero;
 * for all other values subtract 2 from exponent (VAX uses excess-128 and
 * mantissa of the form 0.(1)fffff..., whereas IEEE uses excess-127 and
 * (1).fffffff..., where parentheses mean the implied MSB.
 * The bit layout is:  VMS format                    IEEE format
 *    ffffffffffffffffseeeeeeeefffffff    seeeeeeeefffffffffffffffffffffff
 *
 * Based on the function ftoi() by Przemek Klosowski at NIST
 */

int 
GetVaxFloat(FILE *fp, float *flt, int byteorder) {
  register unsigned int sign, exp;
  union intflo {
    int   intnum;
    float fltnum;
  } val;

  if (feof(fp)) return -1;
  *flt = 0;
  fread(&val.intnum,sizeof(int),1,fp);
  if (byteorder) {
    val.intnum = BYTE4(val.intnum);
  }

  sign = (val.intnum & 0x00008000);
  exp  = (val.intnum & 0x00007f80);

  if ( ! exp ) {/* zero if sign==0 or else VAX Invalid number */        
                /* that is what DEC ftoi() does */
                /* Integer zero is also floating zero, all ones is a NaN */
    val.intnum = sign?  0xffffffff : 0;
    *flt = val.fltnum;
    return 0;
  } else { 
    if (exp <= 0x100) {      /* IEEE exp 0 is underflow; could try but won't */
      //        return -1;
    }
    exp -= 0x100;            /* decrease exponent by 2 */
    exp &= 0x00007f80;       /* kill any borrow beyond exp field */
    /* put back sign, exp and mantissa; swap halves. >> must be logical shift*/
    //printf("float(V): ");    pbin(val.intnum,32,"\n");
    val.intnum = ((exp | sign | (val.intnum & 0x0000007f)) << 16) |
                                ((val.intnum & 0xffff0000) >> 16);
    // printf("float(I): ");pbin(val.intnum,32," ");printf("%f\n",val.fltnum);
    *flt = val.fltnum;
    return 0;
  }
}

int
PutVaxFloat(FILE *fp, float *flt, int byteorder) {
  register unsigned int sign, exp, bits;
  union intflo {
    int intnum;
    float fltnum;
  } val;

  val.fltnum = *flt;
  
  sign = (val.intnum & 0x80000000)>>16;
  exp  = (val.intnum & 0x7f800000)>>16;
  bits = (val.intnum & 0x007fffff);
  //  if (*flt != 0) {
  //    printf("float(I):"); pbin(val.intnum,32," "); printf("%f\n",*flt);
  //  }


  /* Recompose image of floating point number */
  exp += 0x100;
  
  val.intnum = (sign | exp | ((bits & 0x00ff0000) >> 16) |
                ((bits & 0x0000ffff) << 16));

  //  if (*flt != 0) {
  //    printf("float(V):"); pbin(val.intnum,32,"\n");
  //  }
  fwrite(&val.intnum,sizeof(int),1,fp);
  return 0;
}

int fgetfloat(FILE *fp, float * outval, int byteorder) {
  float val;

  if (GetVaxFloat(fp, &val, byteorder)) return -1;
  *outval = val;
  return 0;
}

int fputfloat(FILE *fp, float * outval, int byteorder) {
  return PutVaxFloat(fp, outval, byteorder);
}