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J'ai une affectation pour la classe que je dois écrire un programme pour lire et écrire des paires de valeurs clés sur le disque. J'utilise une liste liée pour stocker les clés, et lire les valeurs chaque fois que je dois partir du disque. Cependant, j'ai de la difficulté à changer et à supprimer des valeurs. J'utilise ceci pour le tester: http://gaming.jhu.edu/~phf/2010/fall/cs120/src/sdbm-examples.tar.gz. Code ci-dessous. Fondamentalement, j'ai besoin d'aide pour trouver des erreurs, parce que c'est la première tâche que nous avons eu à utiliser des pointeurs, et je suis en train de mourir dans toutes les erreurs et tout le reste. Juste quelques conseils seraient grandement appréciés.C Erreurs d'écriture de base de données personnalisées
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include <stdbool.h>
#include "sdbm.h"
FILE *db;
bool opened = false, needNewDB = false;
int err = 0, keyLen = 0;
char *filename;
typedef struct Key_{
char *name;
char *val;
long offset;
struct Key_ *next;
} Key;
Key *head = NULL,*tail = NULL, *lastHas = NULL, *beforeLastHas = NULL;
/**
* Create new database with given name. You still have
* to sdbm_open() the database to access it. Return true
* on success, false on failure.
*/
void listAdd() {
if (tail != NULL) {
tail->next = (Key *) malloc(sizeof(Key));
tail = tail->next;
}
else {
tail = (Key *)malloc(sizeof(Key));
head = tail;
}
tail->next = NULL;
tail->name = NULL;
tail->val = NULL;
}
bool sdbm_create(const char *name) { //Errors: 1) fopen failed 2) fclose failed on new db
filename = malloc(sizeof(*name));
strcpy(filename,name);
FILE *temp = fopen(name, "w");
if (temp == NULL) {
printf("Couldn't create file %s\n",name);
err = 1;
return false;
}
if (fclose(temp) == EOF) {
printf("Couldn't close created file %s\n",name);
err = 2;
return false;
}
return true;
}
/**
* Open existing database with given name. Return true on
* success, false on failure.
*/
bool sdbm_open(const char *name) { //Errors: 3) couldn't open database
db = fopen(name,"r+");
if (db == NULL) {
err = 3;
printf("Couldn't open database file %s\n",name);
return false;
}
opened = true;
int c;
bool inKey = true;
char currKey[MAX_KEY_LENGTH];
while ((c = getc(db)) != EOF) {
if (!inKey && c == '\0') {
inKey = true;
}
else if (inKey && c == '\0') {
currKey[keyLen] = '\0';
listAdd();
tail->offset = ftell(db);
tail->name = malloc(sizeof(*currKey));
strcpy(tail->name,currKey);
keyLen = 0;
inKey = false;
}
else if (inKey) {
currKey[keyLen] = c;
keyLen++;
}
}
Key *curr = head;
while (curr != NULL) {
printf("Key: %s\n",curr->name);
curr = curr->next;
}
return true;
}
void readVal(char *value, long offset) {
fseek(db,offset,SEEK_SET);
int c;
for (int i = 0; (c = getc(db)) != '\0'; i++) {
*(value + i) = c;
}
}
/**
* Synchronize all changes in database (if any) to disk.
* Useful if implementation caches intermediate results
* in memory instead of writing them to disk directly.
* Return true on success, false on failure.
*/
bool sdbm_sync() {
if (!needNewDB) {
Key *curr = head;
fseek(db,0,SEEK_END);
while (curr != NULL) {
if (curr->val != NULL) {
fprintf(db,"%s%c%s%c",curr->name,'\0',curr->val,'\0');
}
curr = curr->next;
}
}
else {
FILE *temp;
sdbm_create("tRpdxD.p4ed");
temp = fopen("tRpdxD.p4ed","w");
Key *curr = head;
while (curr != NULL) {
if (curr->val != NULL) {
fprintf(temp,"%s%c%s%c",curr->name, '\0', curr->val, '\0');
}else {
char *tempS = malloc(MAX_VALUE_LENGTH);
readVal(tempS, curr->offset);
fprintf(temp,"%s%c%s%c",curr->name,'\0',tempS,'\0');
free(tempS);
}
fflush(temp);
fflush(db);
curr = curr->next;
}
fclose(db);
remove(filename);
rename("tRpdxD.p4ed",filename);
db = fopen(filename,"r+");
}
fflush(db);
return true;
}
/**
* Close database, synchronizing changes (if any). Return
* true on success, false on failure.
*/
bool sdbm_close() { // Errors: 5) Couldn't close database
sdbm_sync();
Key *tmp = head;
while (head->next != NULL) {
tmp = head;
head = head->next;
free(tmp->name);
if (tmp->val != NULL) {
free(tmp->val);
}
free(tmp);
}
if (fclose(db) == EOF) {
err = 5;
printf("Couldn't close database.\n");
return false;
}
return true;
}
/**
* Return error code for last failed database operation.
*/
int sdbm_error() {
return err;
}
/**
* Is given key in database?
*/
bool sdbm_has(const char *key) {
if (head == NULL) {
return false;
}
Key *curr = head;
lastHas = NULL;
beforeLastHas = NULL;
while (curr != NULL) {
if (!strcmp(curr->name,key)) {
lastHas = curr;
return true;
}
beforeLastHas = curr;
curr = curr->next;
}
return false;
}
/**
* Get value associated with given key in database.
* Return true on success, false on failure.
*
* Precondition: sdbm_has(key)
*/
bool sdbm_get(const char *key, char *value) { //Errors: 6)Don't have key
if (!sdbm_has(key)) {
printf("Precondition sdbm_has(%s) failed", key);
err = 6;
return false;
}
readVal(value, lastHas->offset);
return true;
}
/**
* Update value associated with given key in database
* to given value. Return true on success, false on
* failure.
*
* Precondition: sdbm_has(key)
*/
bool sdbm_put(const char *key, const char *value) {
if (!sdbm_has(key)) {
printf("Precondition !sdbm_has(%s) failed",key);
err = 7;
return false;
}
sdbm_remove(key);
sdbm_insert(key,value);
return true;
}
/**
* Insert given key and value into database as a new
* association. Return true on success, false on
* failure.
*
* Precondition: !sdbm_has(key)
*/
bool sdbm_insert(const char *key, const char *value) { //Errors: 7)Already have key 8)Invalid key or value length
if (sdbm_has(key)) {
printf("Precondition !sdbm_has(%s) failed",key);
err = 7;
return false;
}
if (strlen(key) < MIN_KEY_LENGTH || strlen(key) > MAX_KEY_LENGTH || strlen(value) < MIN_VALUE_LENGTH || strlen(value) > MAX_VALUE_LENGTH) {
printf("Invalid key or value length");
err = 8;
return false;
}
listAdd();
tail->name = (char *)key;
tail->val = malloc(sizeof(*value));
strcpy(tail->val,value);
return true;
}
/**
* Remove given key and associated value from database.
* Return true on success, false on failure.
*
* Precondition: sdbm_has(key)
*/
bool sdbm_remove(const char *key) {
if (!sdbm_has(key)) {
printf("Precondition !sdbm_has(%s) failed",key);
err = 7;
return false;
}
needNewDB = true;
if (beforeLastHas == NULL) {
head = lastHas->next;
}
else if (lastHas->next == NULL) {
tail = beforeLastHas;
}
else {
beforeLastHas->next = lastHas->next;
}
if (lastHas->val != NULL) {
free(lastHas->val);
}
free(lastHas->name);
free(lastHas);
return true;
}