gistfile1.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#define MAX_RECORDS 30
#define MAX_NAME_LEN 20

#define ERR_BAD_PTR -1
#define NOERR       0

/*
    our struct for holding record data
*/
typedef struct
{
    long    m_recordId ;
    char    m_recordName[ MAX_NAME_LEN ] ;
} Record_t ;

//tidiness typedef
typedef Record_t* RecordPtr ;

int
addRecord( RecordPtr record )
{
    //if we're NULL, eject and let the caller know
    if( !record )
        return ERR_BAD_PTR ;

    //Buffer for our input
    char buf [ MAX_NAME_LEN ] ;
    //force initialization to all 0
    memset( &buf[0], 0, MAX_NAME_LEN ) ;

    //if we are of size 0 or just a newline (user just hit enter) keep asking
    while( buf[0] == '\0' || buf[0] == '\n' )
    {
        printf( "\nEnter record name: " ) ;
        //get input from user
        fgets ( &buf[0], MAX_NAME_LEN, stdin ) ;
    }

    //copy our buf into the record
    strncpy( &(record->m_recordName[0]), &buf[0], MAX_NAME_LEN ) ;

    //reset the buf and reuse it
    memset( &buf[0], 0, MAX_NAME_LEN ) ;
    //this pointer will tell us if strtol completely failed
    char*   p = &buf[0] ;

    //loop while strtol is unable to parse any numbers
    while( p == &buf[0] )
    {
        printf( "\nEnter the record number: " ) ;
        fgets ( &buf[0], MAX_NAME_LEN, stdin ) ;

        //strtol will attempt to convert the entered characters in buf to a number.
        //it will stop if a non-numeric character is encountered
        record->m_recordId = strtol( &buf[0], &p, 10 ) ;
    }

    //all is good
    return NOERR ;
}

int
printRecord( RecordPtr record )
{
    if( !record )
        return ERR_BAD_PTR ;

    printf( "\nRecord ID: %ld \nRecord name: %s \n", record->m_recordId, record->m_recordName ) ;

    return NOERR ;
}

int
getRecords( RecordPtr recordList, size_t maxRecords )
{
    if( !recordList )
        return ERR_BAD_PTR ;

    int i = 0 ;
    char add = 'y' ;
    //quit looping if we reach maximum records or user aborts
    for( ; i < maxRecords && (add != 'n' && add != 'N') ; i ++ )
    {
        int ret = addRecord( &recordList[i] ) ;

        //if adding the record went OK, ask for another
        if( ret == NOERR )
        {
            printf( "\nAdd another record (y/n)? " ) ;
            add = getchar() ;   //in truth we actually only care if they enter n/N
            getchar() ; //eat the return, hacky
        }
        //bad pointer, not really possible in this example
        else if( ret == ERR_BAD_PTR )
        {
            printf( "\nNULL pointer at record %d\n", i ) ;
            //return error
            return ret ;
        }
    }

    //we succeeded, return number of valid entries
    return i ;
}

int
main( int argc, char** argv )
{
    //our list of records
    Record_t records[ MAX_RECORDS ] ;

    int r ;
    r = getRecords( &records[0], MAX_RECORDS ) ;

    if( r != ERR_BAD_PTR )
    {
        int i = 0 ;
        //r is the number of records we entered, loop through them
        for( ; i < r ; i ++ )
        {
            printf( "Printing record %d of %d \n", i+1, r ) ;
            printRecord( &records[ i ] ) ;
        }
    }

    return 0 ;
}