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C/C++ Users Group Library 1996 July
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C-C++ Users Group Library July 1996.iso
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v_09_05
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1991-01-15
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/***********************************************
* CreatRec.C
*
* A method of handling the complex memory
* allocation required to create an array of
* character arrays in memory
*
* The function declaration required is:
* char **CreateRecord(int nfields,
* int flen[], int InitString);
* where: nfields is the number of fields or
* strings to be created flen[] is an
* array of nfields-many ints, where each
* array element is the desired length
* of the corresponding field; InitString
* is the value to use when initializing the
* string space allocated by the function.
*
* Returns: (char **).
* The programmer should use this pointer to
* access the strings created, and to free the
* allocated memory when finished.
***********************************************/
#include <stdio.h>
#include <conio.h>
#include <alloc.h>
#include <mem.h>
#include <stdlib.h>
char **CreateRecord(int nfields, int flen[],
int InitString)
{
char **field; /* this value is returned */
char *p;
int i=0, recsize=0, memsize;
while(i<nfields){
recsize += flen[i++]; /* add up field sizes */
}
recsize += nfields; /* add space for a terminator for each field */
/* total to allocate includes space for strings
and pointers to them: */
memsize = nfields*sizeof(char *) +
recsize*sizeof(char);
field = (char **)malloc(memsize);
if(!field){
#ifdef ERR_INTERNAL
puts("Malloc failure in CreateRecord()");
exit(1); /* abort on failure */
#else
return NULL; /* return warning to caller */
#endif
}
/* initialize strings */
memset(field,InitString,memsize);
/* set p to point to the first byte
beyond the last pointer needed: */
p = (char *)&field[nfields];
for(i=0; i<nfields; i++){
field[i] = p; /* initialize the
pointer array */
p = &p[ flen[i] ]; /* get address of
last char of the field */
*p = '\0'; /* terminate the string */
p++; /* next string start address */
}
return field;
} /* CreateRecord() */
/******************************************************
A Example of a Routine that Uses CreateRecord()
******************************************************/
#define ArraySize(x) ( sizeof(x)/sizeof(x[1]) )
/* by ArtS: October, 1990. a general purpose macro to provide
a count of the number of elements in any given array.
NOTE that this works for
char c[] = "Art was here"; ...c is an array
but NOT for
char *c = "Art was here"; ...c is a pointer!
*/
#define SPACE 32
/* This is the declaration you need to use CreateRecord(): */
char **CreateRecord(int nfields, int flen[], int InitString);
/* A sample database fieldset: */
char *label[] = { /* labels for example database record */
" FName",
" LName",
" Address",
" City",
" State",
" Zip",
" Remarks"
};
/* Field lengths for this sample database: */
int array[] = { 20, 20, 30, 25, 2, 10, 50 };
void main(void){
char **set;
int fieldcount;
int i;
puts("\nSample calls to CreateRecord() for allocating string arrays\n");
puts("Initialize a database record to blanks:");
fieldcount = ArraySize(array);
set = CreateRecord(fieldcount, array, SPACE);
if(!set){
printf("Error allocating memory for record\n");
exit(1);
}
for(i=0; i<fieldcount; i++){
printf(" %s: [%s]\n", label[i], set[i] );
}
puts("\nPress Key..."); getch();
puts("Initialize a database record to underline characters:");
fieldcount = ArraySize(array);
set = CreateRecord(fieldcount, array, '_');
if(!set){
printf("Error allocating memory for record\n");
exit(1);
}
for(i=0; i<fieldcount; i++){
printf(" %s: [%s]\n", label[i], set[i] );
}
puts("\nPress Key..."); getch();
free(set);
puts("Initialize a set if five strings of length 12 to 'A':");
for(i=0; i<5; i++){
array[i] = 12; /* set all field lengths to 12 */
}
set = CreateRecord(5, array, 'A' );
if(!set){
printf("Error allocating memory for record\n");
exit(1);
}
for(i=0; i<5; i++){
printf(" item %d: [%s]\n", i, set[i] );
}
}/* main */