/* ------------------------------------------------------------------------ 
**  Use the quicksort algorithm to sort a file of numbers.
**  Figures 21.14:  Calling the quicksort() function. 
**          21.6 :  Setting up the data structures.  (modified).
**          20.15:  Input into an array.
**          20.16:  Output from an array. 
** ------------------------------------------------------------------------ 
*/
#include "tools.h"

typedef struct { float* data; int n; int max; } data_pack; 
#include "f15_quik.c"               /* The quicksort algorithm. */

void setup( data_pack* spec, stream* infile, stream* outfile );
void get_data( data_pack* sortp, stream instream );
void quicksort( data_pack sort );
void print_data( data_pack sort, stream outstream );  
           
/* ------------------------------------------------------------------ */ 
void main( void )
{   
    stream in_str, out_str;          /* Streams for input and output. */       
    data_pack sort;                  /* Specifications for sort. */

    say( "\n Quicksort program." );
    setup ( &sort, &in_str, &out_str );

    get_data( &sort, in_str );
    say( " %i data items read; ready to sort.\n", sort.n );

    quicksort( sort );                                               
    say( " Data sorted; writing to output stream." );

    print_data( sort, out_str );
    bye();                                      
} 

/* ------------------------------------------------------------------------ 
** Read in the names of input and output files; open the files.          
** Allocate memory for data.  Errors are fatal.    
*/
#define MAX  1000
void 
setup( stream* infile, stream* outfile, data_pack* spec )
{  
    char filename[80]; 

    printf( " Enter name of file containing data to sort: " );
    scanf( "%79s", filename );
    *infile = fopen( filename, "r" );    /* open input file in read mode */

    if (*infile == NULL) 
       fatal( " Error: couldn't open input file %s\n", filename ); 

    printf( " Enter name of file for sorted data: " );
    scanf( "%79s", filename );
    *outfile = fopen( filename, "w" ); /* open output file in write mode */

    if (*outfile == NULL) 
       fatal( " Error: couldn't open output file %s\n", filename ); 

    spec->max = MAX;                            /* Read up to MAX items. */
    spec->n = 0;                                /* Currently empty. */
    spec->data = malloc((MAX+1)*sizeof(float)); /* Array holds input + sentinel. */
    if (spec->data == NULL) 
       fatal( " Error: not enough memory for %i floats\n", MAX ); 
}

/* ------------------------------------------------------------------------ 
** Read max data values from instream and store in ary.  
*/ 
void 
get_data( data_pack* sortp, stream instream )
{   
    int stream_status;
    float* cursor = sortp->data; 
    float const* end = cursor + sortp->max;  /* off-board sentinel */
 
    for( ; cursor<end; ++cursor) {
        stream_status = fscanf( instream, "%g", cursor );
        if( stream_status != 1 ) break;
    }
    sortp->n = cursor-sortp->data;  /* Actual # of items read. */
}

/* --------------------------------------------------------------------- 
** Print array values, one per line, to selected stream. 
*/ 
void 
print_data( data_pack sort, stream outstream )
{   
    float* cursor = sort.data; 
    const float* end = cursor + sort.n;    /* an off-board sentinel */

    for( ; cursor < end; ++cursor) {   
        fprintf( outstream, " %.7g\n", *cursor );     
    }
}