//genicsbin2gadget_ic.c.cpp: reads in a GENICS created IC bin file (IC_file_ics.bin) and writes binary data to a GADGET-2 
//compatible IC file (IC_file.dat).

#include <stdlib.h>
#include <float.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <wchar.h>

#define NSTARS  50001             // number of particles in simulation: n_stars + 1 (NP - +1 only if adding in the BH or intruder)                                      

/* Gadget-2 data type definitions  */
    struct io_header            
      {
                 int  npart[6];
              double  mass[6];
              double  time;
              double  redshift;
                 int  flag_sfr;
                 int  flag_feedback;
        unsigned int  npartTotal[6];
                 int  flag_cooling;
                 int  num_files;
              double  BoxSize;
              double  Omega0;
              double  OmegaLambda;
              double  HubbleParam;
                 int  flag_stellarage;
                 int  flag_metals;
        unsigned int  npartTotalHighWord[6];
                 int  flag_entropy_instead_u;
                char  fill[256-6*4-6*8-2*8-2*4-6*4-2*4-4*8-2*4-6*4-4]; /* 60 elements */ 
      } header;

int main(int argc, char **argv)
{
    /* initial declarations */
    FILE   *fp_out, *stream;
    float  fp, masses[NSTARS];
    int    i, dummy, id[NSTARS];
    char *buffer;
    unsigned long fileLen;
    
    dummy = 256;
     
    /* Set header values using structure header.names[] */
    header.npart[0] = 0;
    header.npart[1] = 0;
    header.npart[2] = 0;
    header.npart[3] = 0;
    header.npart[4] = NSTARS;
    header.npart[5] = 0;

    header.mass[0] = 0.000000;
    header.mass[1] = 0.000000;     
    header.mass[2] = 0.000000;
    header.mass[3] = 0.000000;
    header.mass[4] = 0.000000;       
    header.mass[5] = 0.000000;
     
    header.time = 0.000000;
    header.redshift = 0.000000;
    header.flag_sfr = 0;
    header.flag_feedback = 0;

    header.npartTotal[0] = 0;
    header.npartTotal[1] = 0;
    header.npartTotal[2] = 0;
    header.npartTotal[3] = 0;
    header.npartTotal[4] = NSTARS;
    header.npartTotal[5] = 0;

    header.flag_cooling = 0;
    header.num_files = 0;
    header.BoxSize = 0.000000;
    header.Omega0 = 0.000000;
    header.OmegaLambda = 0.000000;
    header.HubbleParam = 0.000000;
    header.flag_stellarage = 0;
    header.flag_metals = 0;

    header.npartTotalHighWord[0] = 0;
    header.npartTotalHighWord[1] = 0;
    header.npartTotalHighWord[2] = 0;
    header.npartTotalHighWord[3] = 0;
    header.npartTotalHighWord[4] = 0;
    header.npartTotalHighWord[5] = 0;

    header.flag_entropy_instead_u = 0;

    for (i=0; i < 60; i++)
      header.fill[i] = 0;   

    /* Open binary input file*/
    if((stream = fopen("IC_file50k_ics.bin", "rb")) == NULL)
      {
    printf("Error opening text data file.\n");
    exit(-2);
      }

    /*Get the file length*/
    fseek(stream, 0, SEEK_END);
    fileLen=ftell(stream);
    fseek(stream, 0, SEEK_SET);

    /*Allocate Memory*/
    buffer=(char *)malloc(filLen+1);
    if (!buffer)
      {
    fprintf(stderr, "Memory error!");
    fclose(file);
    return;
      }

    /*Read file contents into the buffer*/
    fread(buffer, fileLen, 1, file);
    fclose(file);

    /* Open binary output file */
    if((fp_out = fopen("IC_file.dat","w")) == NULL)
      {
        printf("Error opening binary data file.\n");
        exit(-2);
      } 
    
    /* errno_t err = fopen_s( &stream, "IC_file.dat", "w+" );
    if( err )
       printf_s( "The file IC_file.dat was not opened.\n" );
    else */

        /* Write header for IC snapshot */
        fwrite(&dummy,sizeof(dummy),1,fp_out);
        fwrite(&header,sizeof(header),1,fp_out);
        fwrite(&dummy,sizeof(dummy),1,fp_out);

        /* Write blocks for IC snapshot */
        dummy = 3*NSTARS*sizeof(float);    /* Set for position and velocity blocks. */

        /* position block */
        fwrite(&dummy,sizeof(dummy),1,fp_out);
        for(i=0; i < 3*NSTARS; i++)
          {
          fscanf(stream,"%f",&fp);
              fwrite(&fp,sizeof(float),1,fp_out);
          }
        fwrite(&dummy,sizeof(dummy),1,fp_out);

        /* velocity block */
        fwrite(&dummy,sizeof(dummy),1,fp_out);
        for(i=0; i < 3*NSTARS; i++)
          {
              fscanf(stream,"%f",&fp);
              fwrite(&fp,sizeof(float),1,fp_out);
          }
        fwrite(&dummy,sizeof(dummy),1,fp_out);
 
        /* id block */
        dummy = sizeof(id);
        fwrite(&dummy,sizeof(dummy),1,fp_out);
        for(i=1; i < NSTARS+1; i++)
          id[i] = i; 
        fwrite(&id[0],sizeof(id),1,fp_out);
        fwrite(&dummy,sizeof(dummy),1,fp_out);
     
        /* mass block must be present but ignored if using equal header masses */         
        dummy = sizeof(masses);
        fwrite(&dummy,sizeof(dummy),1,fp_out);
        for(i=0; i < NSTARS; i++)
          {
              fscanf(stream,"%f",&fp);
              fwrite(&fp,sizeof(float),1,fp_out);
          }
        fwrite(&dummy,sizeof(dummy),1,fp_out);

        /* close files */
        fclose(fp_out);
     fclose(stream);

        printf( "IC_file.dat is ready to load into GADGET-2.\n" );

    return 0;

    free(buffer);
}