C Language Development Kit/Snippets/Database/BinarySearch

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Description Search a record in a sorted database with the binary search method.
Syntax
long BinarySearch( SDBFile *dbFile, char *record, char *searchkey, int checksize, int offset );
Arguments SDBFile *dbFile

dbFile is pointer to a structure that holds information about the database. The SDBFile structure is defined as followed:

typedef struct
{
    short  sRecSz;        // record size of database
    int    fd;            // real handle to the open file
    long   lCurrRecord;   // current record number
    long   lTotalRecords; // total amount of records
    int    bOpen;         // check to see if db is open or closed
}SDBFile;
char *record

Holds the data of the record that is found.

char *searchkey

The string that needs to be found in the database.

int checksize

The length of the searchkey.

int offset

Offset in the record to start the search of the searchkey.

Returns -1L when the record is not found or on an error. The record number is returned when the searchkey has been found in the database.
Remarks The declaration of the SDBFile needs to be static to make sure all items are initialized to 0.

When the BinarySearch() functions returns FALSE the error code can be obtained by making a call to GetDBErrorCode() function.

Example
#include "lib.h"
#include <stdio.h>
#include <stdlib.h>
#include "database.h"  //Holds the database functions
 
void main( void )
{
    static SDBFile dbFile; // static initializes all items to 0
    long recno;
    int i;
    char record[32 + 1];
 
    printf("\fCreate database\n");
    if( !CreateDatabase("file1.txt", 32, &dbFile ))
        printf("Error code = %ld\n", GetDBErrorCode());
 
    memset( record, '\0', sizeof( record ));
    printf("Write 10 records\n");
    for( i = 9; i > -1; i-- )
    {
        sprintf(record, "%01d23456789012345678901234567890\r\n", i);
        if( !WriteRecord( &dbFile, record, WRITE_APPEND ))
        {
            printf("Error code = %ld\n", GetDBErrorCode());
            break;
        }
    }
 
    if( !QuickSort( &dbFile, 0, 2 ))
        printf("Error code = %ld\n", GetDBErrorCode());
 
    if( (recno = BinarySearch( &dbFile, record, (char*) "62", 2, 0 )) == -1L)
        printf("Error code = %ld\n", GetDBErrorCode());
    else
        printf("recnr = %ld, %-30.30s\n", recno, record );
 
    printf("Close database\n");
    CloseDatabase( &dbFile );
 
    while( 1 )
        idle();
}


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