BufferIO.c

/**************************************************************
*  Class::  CSC-415-02 Spring 2024
* Name::Chia-Tung Liu
* Student IDs::923408847
* GitHub-Name::Mob1001
* Group-Name::Alt+F4
* Project:: Basic File System
*
* File:: BufferIO.c
*
* Description:: Basic File System - Functions for bio files
*
**************************************************************/
#include <time.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>

#include "BufferIO.h"
#include "Directory.h"
#include "FreeSpaceManager.h"
#include "stdlib.h"

// Function to get file information given a file name
fileInfo* getFileInfo(char* fileName) {
    // Get the absolute path of the file
    char* concatinate = getAbsolutePath(fileName);
    if (!concatinate) return NULL;  // Return NULL if absolute path cannot be obtained

    // Allocate memory for file information
    fileInfo* theInfo = malloc(sizeof(fileInfo));
    if (!theInfo) {
        free(concatinate);
        concatinate=NULL;
        return NULL;  // Return NULL if memory allocation fails
    }

    // Initialize Parsed Path of Entry (PPOE) structure
    PPOE entryPPOE = {0};

    // Parse the absolute path to obtain directory information
    if (parsePath(concatinate, &entryPPOE) == -1) {
        free(theInfo);
        theInfo=NULL;
        free(concatinate);
        concatinate=NULL;
        return NULL;  // Return NULL if parsing fails
    }

    // Set file information fields
    theInfo->index = entryPPOE.index;
    theInfo->currDIR = entryPPOE.parentDIR;

    // Free memory used for absolute path concatenation
    free(concatinate);
    concatinate=NULL;
    return theInfo;  // Return file information
}

// Function to create file information for a new file
fileInfo* newFileInfo(char* filename) {
    // Attempt to create the file
    if (makeFile(filename) != 0) {
        return NULL;  // Return NULL if file creation fails
    }
    // Return file information for the newly created file
    return getFileInfo(filename);
}

// Function to delete file information and associated memory
int deleteFileInfo(fileInfo* fileinfo) {
    if (!fileinfo) return -1;  // Guard against NULL input

    // Free memory used for directory entries and file information structure
    free(fileinfo->currDIR);
    free(fileinfo);
    

    return 0;  // Return success
}

// Function to truncate a file's content
int bufferTruncate(DIR_Entry* dir, int fileIndex) {
    if (!dir) return -1; // Guard against NULL input

    // Free all associated blocks
    deAllocFAT(dir[fileIndex].location_of_first);

    // Allocate a new block and reset the file size
    dir[fileIndex].location_of_first = allocFAT(1);
    dir[fileIndex].size = 0;

    // Update timestamps
    time_t timestamp;
    time(&timestamp);
    dir[fileIndex].date_modified = timestamp;
    dir[fileIndex].date_accessed = timestamp;

    // Write updates to disk
    writeToLBA(dir, dir->size, &dir->location_of_first);
    return 0;  // Return success
}

// Function to validate file opening flags for conflicts
int validFlags(int flags) {
    // Define conflicting flag combinations
    int conflicts[] = {
        O_CREAT | O_RDONLY,
        O_TRUNC | O_RDONLY,
        O_APPEND | O_RDONLY,
        O_RDWR | O_RDONLY,
        O_RDWR | O_WRONLY,
        O_WRONLY | O_RDONLY
    };

    // Check for conflicting permissions
    for (int i = 0; i < sizeof(conflicts) / sizeof(conflicts[0]); i++) {
        if ((flags & conflicts[i]) == conflicts[i]) {
            printf("ERROR: conflicting permissions\n");
            return -1;  // Return -1 if conflicting permissions are found
        }
    }

    return 0;  // Return success
}