Adding blank space as padding

temp.c

@@ -20,6 +20,7 @@ sem_t x,y;
 pthread_t tid;
 pthread_t writerthreads[100],readerthreads[100];
 int readercount = 0;
+
 int modulus(char *num, int size, int divisor) {
   int rem = 0;
  
@@ -29,35 +30,18 @@ int modulus(char *num, int size, int divisor) {
   }
   return rem;
 }
-void file_del(char *key)
+void file_del(off_t offset, char *key)
 {   
     int index=modulus(key,256,setSize);
     sem_wait(&mutex[index]);
-    FILE * fp;
-    char * line = malloc(sizeof(char)*514);
-    size_t len = 0;
-    int read;
-
-    fp = fdopen(fds[index], "r+b");
-    if (fp == NULL)
-       printf("\n[Invalid file]\n");
-    int position=ftell(fp);
-    while (fscanf(fp,"%s",line) != EOF )
-    {
-        if(strstr(line,key)!=NULL && strstr(strstr(line,key),":")!=NULL)
-        {
-            //printf("%s\n",line);
-            
-           printf("%d", fseek(fp, position, SEEK_SET));
-            fprintf(fp, "%s", "\0");    
-            break;
-           
-        }
-           position=ftell(fp);
-           printf("\n%d ", position);
+    
+    char blankspace[512];
+    for(int i=0; i<512; i++) {
+        blankspace[i] = 0;
     }
-    if (line)
-        free(line);
+    lseek(fds[index], offset, SEEK_SET);
+    write(fds[index], blankspace, 512);
+
     sem_wait(&readerLocks[index]);
     readercount--;
     if(readercount==0)
@@ -66,34 +50,22 @@ void file_del(char *key)
     }
     sem_post(&readerLocks[index]);
 }
-void file_get(char *key,char *value)
+void file_get(off_t offset, char *key, char *value)
 {   
-    
+    /* Gets the value stored at offset */
+    /* Does not depend on key argument */
+
     int index=modulus(key,256,setSize);
     sem_wait(&readerLocks[index]);
     readCounters[index]++;
     if(readCounters[index]==1)
         sem_wait(&mutex[index]);
     sem_post(&readerLocks[index]);
-    FILE * fp;
-    char * line = NULL;
-    size_t len = 0;
-    int read;
-
-    fp = fdopen(fds[index], "r");
-    if (fp == NULL)
-       printf("\n[Invalid file]\n");
+    
+    lseek(fds[index], offset, SEEK_SET);
+    read(fds[index], key, 256);
+    read(fds[index], value, 256);
 
-    while ((read = getline(&line, &len, fp)) != -1)
-    {
-        if(strstr(line,key)!=NULL && strstr(strstr(line,key),":")!=NULL)
-        {
-            snprintf(value,sizeof((strchr(line,':')+1)),"%s",(strchr(line,':')+1));
-        }   
-    }
-    fclose(fp);
-    if (line)
-        free(line);
     sem_wait(&readerLocks[index]);
     readercount--;
     if(readercount==0)
@@ -102,21 +74,22 @@ void file_get(char *key,char *value)
     }
     sem_post(&readerLocks[index]);
 }
-void file_put(char *key,char *value)
-{
+
+off_t file_put(char *key,char *value) {
+
     int index=modulus(key,256,setSize);
+    int bytes, rembytes, i;
+    off_t position;
+
     sem_wait(&mutex[index]);
-    printf("\n[Write to File: %d]\n",index);
-    char line[514];
-    memcpy(line,key,256);
-    line[strlen(key)]=':';
-    memcpy(line+strlen(line),value,256);
-    line[strlen(line)]='\n';
-    if(write(fds[index],line,strlen(line))<0)
-    {
-        printf("\n[Unable to Write to File]\n");
-    }
+    printf("[Write to File: %d]\n",index);
+    position = lseek(fds[index], 0, SEEK_END);
+    write(fds[index], key, 256);
+    write(fds[index], value, 256);
+    printf("bytes : %d\n",bytes);
     sem_post(&mutex[index]);
+
+    return position;
 }
 int main()
 {
@@ -128,8 +101,10 @@ int main()
         each write should return the line number
     */
     int n2=0;
-    char key[256]="24";
-    char value[256]="value";
+    char prevkey[256]="24";
+    char key[256]="24sadasdasdasdasdsad";
+    char value[256]="valueasdasdad";
+    off_t offset;
     bzero(key+strlen(key),sizeof(key)-strlen(key));
     bzero(value+strlen(value),sizeof(value)-strlen(value));
     fds=(int *)malloc(sizeof(int)*setSize);
@@ -150,33 +125,12 @@ int main()
         sem_init(&mutex[i],0,1);
         readCounters[i]=0;
     }
-    //file_put(key,value);
-    value[0]='\0';
-   // file_get(key,value);
-   /*  for(i=0;i<setSize-1;i++)
-    {
-        close(fds[i]);
-    } */
-   // printf("main vala hai ye!!");
-  //  puts(value);
-   file_del(key);
-    /*
-    printf("%u",modulus(key,256,3));
-    //scanf("%d",&n2);
-    printf("\n");
-    int n1[n2];
-    sem_init(&x,0,1);
-    sem_init(&y,0,1);
-    for(i=0;i<n2;i++)
-    {
-        pthread_create(&writerthreads[i],NULL,reader,NULL);
-        pthread_create(&readerthreads[i],NULL,writer,NULL);
-    }
-    for(i=0;i<n2;i++)
-    {
-        pthread_join(writerthreads[i],NULL);
-        pthread_join(readerthreads[i],NULL);
-    }
-    */
+    
+
+    offset = file_put(prevkey, value);
+    offset = file_put(key, value);
+    file_get(0, prevkey, value);   // Doesnot depend on key arg, returns key and value at offset 0
+    printf("%s\n", value);
+    file_del(0, prevkey);
 
 }