Translating C Structures to Fortran Equivalents

Question

I'm in the process of translating some C code to Fortran & I have run across some instances which have me scratching my head as to how to properly convert the C to Fortran.

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Example #1-

typedef struct fileheadtype
{
    char    version[128];
    char    notes[256];
} FileHeadType;

typedef struct linetype
{
    LineInfo    info;
    float   latlon[50];
} LineType;

typedef struct vg_dbstruct
{
    VG_HdrStruct hdr;
    union
    {
    FileHeadType    fhed;
    LineType        lin;
    } elem; 
} VG_DBStruct;

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I understand the 'fileheadtype' and 'linetype' structures but I don't understand what the vg_dbstruct is doing, how it relates to the other two structures and how to properly translate to Fortran.

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Example #2-

typedef struct breakpt_t {          /* break point structure */
    float   lat;
    float   lon;
    char    breakPtName[ 100 ];
} Breakpt_T;

enum tca_adv_t {
    WATCH   = 0,
    WARNING = 1
};

typedef struct tcaww_t {        
    enum    tca_adv_t   advisoryType;   
    int numBreakPts;    
    struct  breakpt_t    *breakPnt;     
} TcaWw_T;

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Here, i don't understand what the enumeration operation is doing in the tcaww_t struct nor the "breakpt_t" struct is doing and...how to translate to Fortran.

Any help is greatly appreciated Jeff

Answer 1

Typedef is something Fortran doesn't have. It enables you to call some type or structure by a different name. You can even do

 typedef int myint;

and use myint as name of a type

 myint i;

With the example one you can then use

 FileHeadType fh;

instead of

 struct fileheadtype fh;

which will translate to type(fileheadtype).

In Fortran you always need to use the original type, whether it is integer or type(typename).

The enumerations exist in Fortran for C interoperability, but if you don't want to call C, but you just do a translation in Fortran spirit, you can just use integers:

integer, parameter :: WATCH = 0, WARNING = 1

Unions are not part of Fortran, you must study the intention of the code and either use two separate components, or use transfer() or equivalence.