source: trunk/WRF.COMMON/WRFV3/external/io_grib2/g2lib/rdieee.F @ 2759

Last change on this file since 2759 was 2759, checked in by aslmd, 2 years ago

adding unmodified code from WRFV3.0.1.1, expurged from useless data +1M size

File size: 1.8 KB
Line 
1      subroutine rdieee(rieee,a,num)
2!$$$  SUBPROGRAM DOCUMENTATION BLOCK
3!                .      .    .                                       .
4! SUBPROGRAM:    rdieee
5!   PRGMMR: Gilbert         ORG: W/NP11    DATE: 2000-05-09
6!
7! ABSTRACT: This subroutine reads a list of real values in
8!   32-bit IEEE floating point format.
9!
10! PROGRAM HISTORY LOG:
11! 2000-05-09  Gilbert
12!
13! USAGE:    CALL rdieee(rieee,a,num)
14!   INPUT ARGUMENT LIST:
15!     rieee    - Input array of floating point values in 32-bit IEEE format.
16!     num      - Number of floating point values to convert.
17!
18!   OUTPUT ARGUMENT LIST:     
19!     a        - Output array of real values.
20!
21! REMARKS: None
22!
23! ATTRIBUTES:
24!   LANGUAGE: Fortran 90
25!   MACHINE:  IBM SP
26!
27!$$$
28
29      real(4),intent(in) :: rieee(num)
30      real,intent(out) :: a(num)
31      integer,intent(in) :: num
32
33      integer(4) :: ieee
34
35      real,save :: two23
36      real,save :: two126
37      integer,save :: once=0
38
39      if ( once .EQ. 0 ) then
40         once=1
41         two23=scale(1.0,-23)
42         two126=scale(1.0,-126)
43      endif
44
45      do j=1,num
46!
47!  Transfer IEEE bit string to integer variable
48!
49        ieee=transfer(rieee(j),ieee)
50!
51!  Extract sign bit, exponent, and mantissa
52!
53        isign=ibits(ieee,31,1)
54        iexp=ibits(ieee,23,8)
55        imant=ibits(ieee,0,23)
56        sign=1.0
57        if (isign.eq.1) sign=-1.0
58       
59        if ( (iexp.gt.0).and.(iexp.lt.255) ) then
60          temp=2.0**(iexp-127)
61          a(j)=sign*temp*(1.0+(two23*real(imant)))
62
63        elseif ( iexp.eq.0 ) then
64          if ( imant.ne.0 ) then
65            a(j)=sign*two126*two23*real(imant)
66          else
67            a(j)=sign*0.0
68          endif
69
70        elseif ( iexp.eq.255 ) then
71          a(j)=sign*huge(a(j))
72
73        endif
74
75      enddo
76
77      return
78      end
79
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