Matlab和Fortran之间的数据解释

Question

I have some Fortran code that interprets a binary file. Thanks to another question I asked I understand how the fortran code works but I need help changing it to MATLAB code. Here is the Fortran code:

  IMPLICIT NONE

  DOUBLE PRECISION      SCALE

  CHARACTER*72          BLINE
  CHARACTER*72          DATA_FILE_FULL_NAME
  CHARACTER*6           DATA_FILE_NAME

  CHARACTER*4           CH4, CH4F
  REAL*4                RL4
  EQUIVALENCE          (RL4,CH4)

  CHARACTER*2           C2
  LOGICAL               LFLAG

  INTEGER*2             I2

  if(i2.eq.13881) LFLAG=.FALSE.

  c2='69'
  LFLAG=.TRUE.

  DATA_FILE_FULL_NAME='./'//DATA_FILE_NAME//'.DAT'

  OPEN(UNIT=20, FILE=DATA_FILE_FULL_NAME, ACCESS='DIRECT',
 .     RECL=72, status='OLD')
    READ(20,REC=1) BLINE
    CH4f=BLINE(7:10)
    call flip(4,lflag,ch4f,ch4)
    SCALE=RL4

  RETURN
  END  

c   ..................................................
    subroutine flip(n,lflag,ch1,ch2)
c   ..................................................

  integer*4        n, i
  character*(*)    ch1, ch2
  logical          lflag

  if(lflag) then
    do i=1,n
      ch2(i:i)=ch1(n-i+1:n-i+1)
    enddo
  else
    ch2=ch1
  endif

  return
  end   

So basically (and I believe I understand this correctly) the Fortran code is checking the endianess and flipping it if the machine and the data don't match. Additionally, the data is stored in memory in a place reserved for both CH4 and RL4 so by calling RL4 after defining CH4 the data is simply being cast to the REAL*4 type instead of the CHARACTER*4 type. Now I need to figure out how to port this into Matlab. I already have the capability to read in the raw data, but when I try various forms of interpreting it I always get the wrong answer. So far I have tried:

fid=fopen(LMK_file,'r');
BLINE=fread(fid, 72,'char=>char');
CH4=BLINE(7:10);
SCALE=single(CH4(1)+CH4(2)+CH4(3)+CH4(4));

SCALE=int8(CH4(1)+256*int8(CH4(2))+256^2*int8(CH4(3))+256^3*int8(CH4(4));

in MATLAB but both give me the same wrong answer (which makes sense since its doing pretty much the same thing).

Any suggestions?

Answer 1

For anyone else who is looking for the answer to this question this is what I came up with thanks to the help in the comments.

fid=fopen(LMK_file,'r');  %open the file for reading
IGNORE=fread(fid,6,'*char');  %ignore the first 6 bytes.  This could also be performed using fseek
SCALE=fread(fid,1,'*float32','b');  %reading in the scale value as a floating point 32 bit number. 

where the b indicates the Big endianess of the file. By using the '*float32' option, fread automatically interprets the next 4 characters as a 32 bit floating point number.

This returns the correct value of scale from the given file.