The Postman's Sort

Listing 4 (record.h)

/*
Postman's Sort (R) Version 1.0
Copyright (c) Robert Ramey 1991. All Rights Reserved
*/
#include "stack.h"
/*********************************************************************
data structure and data for each data memory held in memory or in
the working file
**********************************************************************/
                                          /* structure for a record */
typedef union {
   size_t field[1];               /* displacement of fields with in record */
   unsigned char data[1];                            /* actual record data */
} RECORD;

/* The usage of a RECORD is as follows:
   field[0]    Total length of record
   field[1]    displacement of first field
   ...
   field[n]    displacement of n th field
   blk num     one character containing block number
   num data    bytes added to permit sorting of numerics
             starts at data_offset
   byte data   data contained-in record
             starts at record_offset
*/
extern size_t record_size;
extern size_t record_offset;
extern STACK *d_stack;

#define blk_offset      (record_offset-1)
/* data[blk_offset] will contain one of three fields
 * depending on what state the record is currently in:
 */
         /* when record is stored in stack memory, it contains the number */
                                              /* of the stack frame */
#define rec_frame(ra)   (ra->data[blk_offset])
       /* when it is stored on disk it contains a flag indicating that is */
       /* is the last record in a chain for the current sublist */
#define rec_eob(ra)     (ra->data[blk_offset])
    /* after the record has been retrieved but before it has been attached */
/* to a new sublist or sent to output this field contains a flag indicating */
                                                /* its provenance. */
#define rec_memflag(ra) (ra->data[blk_offset])
#define rec_size(ra) (ra->field[0])

void
rec_init(int, char **);
RECORD *
rec_variable();
RECORD *
rec_fixed();
void
rec_output(RECORD *);
/* End of File */