C/Structure/Structure Serialization
scan a file and print out a list of words in ASCII order
<source lang="cpp"> /* Practical C Programming, Third Edition By Steve Oualline Third Edition August 1997 ISBN: 1-56592-306-5 Publisher: O"Reilly
- /
- include <stdio.h>
- include <ctype.h>
- include <string.h>
- include <stdlib.h>
struct node {
struct node *left; /* tree to the left */ struct node *right; /* tree to the right */ char *word; /* word for this tree */
}; /* the top of the tree */ static struct node *root = NULL; /*
* memory_error -- write error and die * */
void memory_error(void) {
fprintf(stderr, "Error:Out of memory\n"); exit(8);
} /*
* save_string -- save a string on the heap * * * * Parameters * * string -- string to save * * * * Returns * * pointer to malloc-ed section of memory with * * the string copied into it. * */
char *save_string(char *string) {
char *new_string; /* where we are going to put string */
new_string = malloc((unsigned) (strlen(string) + 1));
if (new_string == NULL)
memory_error();
strcpy(new_string, string);
return (new_string);
} /*
* enter -- enter a word into the tree * * * * Parameters * * node -- current node we are looking at * * word -- word to enter * */
void enter(struct node **node, char *word) {
int result; /* result of strcmp */
char *save_string(char *); /* save a string on the heap */
/*
* If the current node is null, we have reached the bottom
* of the tree and must create a new node.
*/
if ((*node) == NULL) {
/* Allocate memory for a new node */
(*node) = malloc(sizeof(struct node));
if ((*node) == NULL)
memory_error();
/* Initialize the new node */
(*node)->left = NULL;
(*node)->right = NULL;
(*node)->word = save_string(word);
return;
}
/* Check to see where the word goes */
result = strcmp((*node)->word, word);
/* The current node already contains the word, no entry necessary */
if (result == 0)
return;
/* The word must be entered in the left or right sub-tree */
if (result < 0)
enter(&(*node)->right, word);
else
enter(&(*node)->left, word);
} /*
* scan -- scan the file for words * * * * Parameters * * name -- name of the file to scan * */
void scan(char *name) {
char word[100]; /* word we are working on */
int index; /* index into the word */
int ch; /* current character */
FILE *in_file; /* input file */
in_file = fopen(name, "r");
if (in_file == NULL) {
fprintf(stderr, "Error:Unable to open %s\n", name);
exit(8);
}
while (1) {
/* scan past the whitespace */
while (1) {
ch = fgetc(in_file);
if (isalpha(ch) || (ch == EOF))
break;
}
if (ch == EOF)
break;
word[0] = ch;
for (index = 1; index < sizeof(word); ++index) {
ch = fgetc(in_file);
if (!isalpha(ch))
break;
word[index] = ch;
}
/* put a null on the end */
word[index] = "\0";
enter(&root, word);
}
fclose(in_file);
} /*
* print_tree -- print out the words in a tree * * * * Parameters * * top -- the root of the tree to print * */
void print_tree(struct node *top) {
if (top == NULL)
return; /* short tree */
print_tree(top->left);
printf("%s\n", top->word);
print_tree(top->right);
} int main(int argc, char *argv[]) {
if (argc != 2) {
fprintf(stderr, "Error:Wrong number of parameters\n");
fprintf(stderr, " on the command line\n");
fprintf(stderr, "Usage is:\n");
fprintf(stderr, " words "file"\n");
exit(8);
}
scan(argv[1]);
print_tree(root);
return (0);
}
</source>
Write structure into file
<source lang="cpp"> /* C & Data Structures Published in Feb 2004 by CHARLES RIVER MEDIA Author: P. S. Deshpande, O. G. Kakde SKU: 1584503386 ISBN: 1584503386
- /
- include <stdio.h>
- include <string.h>
- include <stdlib.h>
- define MAX 50
typedef struct {
char name[10]; int key;
} file_record; /* this function adds the relatiuve addres to the index for a key */ void create_index(long index[], int key, long rel_add ) {
index[key] = rel_add;
} /* this function writes a record to the file */ void write_rec(FILE *fp, file_record rec) {
fwrite(&rec,sizeof(rec),1,fp);
} void main() {
long rel_add;
int key;
file_record frec;
long index[MAX];/* an index list*/
int n,i;
FILE *recfile=NULL,*ifile=NULL;
/* this initializes the index list to all ? */
for(i=0; i< MAX; i++)
index[i]= (-1);
recfile=fopen("mfile","w");
if(recfile == NULL) {
printf("Error in openeing file mfile\n");
exit(0);
}
rel_add = 0 ;
do {
printf(" Enter the data vlue and the key of the record to be added to file mfile\n");
scanf("%s %d",frec.name,&frec.key);
while(index[frec.key] != (-1)) {
printf(" A record with this key value already exist in a file enter record key value\n");
scanf("%s %d",frec.name,&frec.key);
}
create_index(index,frec.key,rel_add);
write_rec(recfile,frec);
rel_add = ftell(recfile);
/* this sets the relative address for the next record to be
the value of current file position pointer in bytes from
the beginning of the file */
printf("Enter 1 to continue adding records to the file\n");
scanf("%d",&n);
}while(n == 1);
ifile=fopen("index_file","w");
if(ifile == NULL) {
printf("Error in openeing file index_file\n");
exit(0);
}
fwrite(index,sizeof(index),1,ifile);/*writes the complete index into the index_file */
fclose(recfile);
fclose(ifile);
printf("Enter 1 if you want to retrieve a record\n");
scanf("%d",&n);
if( n == 1) {
ifile=fopen("index_file","r");
if(ifile == NULL) {
printf("Error in openeing file index_file\n");
exit(0);
}
fread(index,sizeof(index),1,ifile);
/* reads the complete index into the index list from the index_file*/
fclose(ifile);
recfile=fopen("mfile","r");
if(recfile == NULL) {
printf("Error in openeing file mfile\n");
exit(0);
}
}
printf("THE CONTENTS OF FILE IS \n");
while( (fread(&frec,sizeof(frec),1,recfile)) != 0)
printf("%s %d\n",frec.name,frec.key);
do {
printf("Enter the key of the record to be retrieved\n");
scanf("%d",&key);
rel_add = index[key]; /*gets the relative address of the record from index list */
if( (fseek(recfile,rel_add,SEEK_SET))!= 0) {
printf("Error\n");
exit(0);
}
fread(&frec,sizeof(frec),1,recfile);
printf("The data value of the retrieved record is %s\n",frec.name);
printf("Enter 1 if you want to retrieve a record\n");
scanf("%d",&n);
} while(n == 1);
fclose(recfile);
}
</source>
