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fat32.c
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fat32.c
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#include "fat32.h"
//Clusters
uint32_t FAT_FREE_CLUSTER = 0x00000000;
uint32_t FAT_EOC = 0x0FFFFFF8;
uint32_t MASK_IGNORE_MSB = 0x0FFFFFFF;
int checkForFileError(int fd)
{
if(fd == -1) {
printf("FATAL ERROR: Problem openning image -- EXITTING!\n");
exit(EXIT_FAILURE);
}
return 1;
}
//-------------END BOOT SECTOR FUNCTIONS -----------------------
/* notes: the alias shown above the functions match up the variables from
* the Microsoft FAT specificatiions
*/
//alias := rootDirSectors
int rootDirSectorCount(fat32BS * bs)
{
return (bs->BPB_RootEntCnt * 32) + (bs->BPB_BytesPerSec - 1) / bs->BPB_BytesPerSec ;
}
//alias := FirstDataSector
int firstDataSector(fat32BS * bs)
{
int FATSz;
if(bs->BPB_FATSz16 != 0)
FATSz = bs->BPB_FATSz16;
else
FATSz = bs->BPB_FATSz32;
return bs->BPB_RsvdSecCnt + (bs->BPB_NumFATs * FATSz) + rootDirSectorCount(bs);
}
//alias := FirstSectorofCluster
uint32_t firstSectorofCluster(fat32BS * bs, uint32_t clusterNum)
{
return (clusterNum - 2) * (bs->BPB_SecPerClus) + firstDataSector(bs);
}
/* decription: feed it a cluster and it returns the byte offset
* of the beginning of that cluster's data
* */
uint32_t byteOffsetOfCluster(fat32BS *bs, uint32_t clusterNum)
{
return firstSectorofCluster(bs, clusterNum) * bs->BPB_BytesPerSec;
}
//alias := DataSec
int sectorsInDataRegion(fat32BS * bs)
{
int FATSz;
int TotSec;
if(bs->BPB_FATSz16 != 0)
FATSz = bs->BPB_FATSz16;
else
FATSz = bs->BPB_FATSz32;
if(bs->BPB_TotSec16 != 0)
TotSec = bs->BPB_TotSec16;
else
TotSec = bs->BPB_TotSec32;
return TotSec - (bs->BPB_RsvdSecCnt + (bs->BPB_NumFATs * FATSz) + rootDirSectorCount(bs));
}
//alias := CountofClusters
int countOfClusters(fat32BS * bs)
{
return sectorsInDataRegion(bs) / bs->BPB_SecPerClus;
}
int getFatType(fat32BS * bs)
{
int clusterCount = countOfClusters(bs);
if(clusterCount < 4085)
return FAT12;
else if(clusterCount < 65525)
return FAT16;
else
return FAT32;
}
int firstFatTableSector(fat32BS *bs)
{
return Partition_LBA_Begin + bs->BPB_RsvdSecCnt;
}
//the sector of the first clustor
//cluster_begin_lba
int firstClusterSector(fat32BS *bs)
{
return Partition_LBA_Begin + bs->BPB_RsvdSecCnt + (bs->BPB_NumFATs * bs->BPB_SecPerClus);
}
//----------------OPEN FILE/DIRECTORY TABLES-----------------
/* create a new file to be put in the file descriptor table
* */
FILEDESCRIPTOR * TBL_createFile(const char * filename, const char * extention, const char * parent,
uint32_t firstCluster, int mode, uint32_t size, int dir,int isOpen)
{
FILEDESCRIPTOR * newFile = (FILEDESCRIPTOR *) malloc(sizeof(FILEDESCRIPTOR));
strcpy(newFile->filename, filename);
strcpy(newFile->extention, extention);
strcpy(newFile->parent, parent);
if(strlen(newFile->extention) > 0) {
strcpy(newFile->fullFilename, newFile->filename);
strcat(newFile->fullFilename, ".");
strcat(newFile->fullFilename, newFile->extention);
}
else
{
strcpy(newFile->fullFilename, newFile->filename);
}
newFile->firstCluster = firstCluster;
newFile->mode = mode;
newFile->size = size;
newFile->dir = dir;
newFile->isOpen = isOpen;
return newFile;
}
/* adds a file object to either the fd table or the dir history table
*/
int TBL_addFileToTbl(FILEDESCRIPTOR * file, int isDir)
{
if(isDir == true) {
if(environment.tbl_dirStatsSize < TBL_DIR_STATS) {
environment.dirStatsTbl[environment.tbl_dirStatsIndex % TBL_DIR_STATS] = *file;
environment.tbl_dirStatsSize++;
environment.tbl_dirStatsIndex = (environment.tbl_dirStatsIndex+1) % TBL_DIR_STATS;
return 0;
}
else {
environment.dirStatsTbl[environment.tbl_dirStatsIndex % TBL_DIR_STATS] = *file;
environment.tbl_dirStatsIndex = (environment.tbl_dirStatsIndex+1) % TBL_DIR_STATS;
return 0;
}
} else {
if(environment.tbl_openFilesSize < TBL_OPEN_FILES) {
environment.openFilesTbl[environment.tbl_openFilesIndex % TBL_OPEN_FILES] = *file;
environment.tbl_openFilesSize++;
environment.tbl_openFilesIndex = (environment.tbl_openFilesIndex+1) % TBL_OPEN_FILES;
return 0;
}
else {
environment.openFilesTbl[environment.tbl_openFilesIndex % TBL_OPEN_FILES] = *file;
environment.tbl_openFilesIndex = (environment.tbl_openFilesIndex+1) % TBL_OPEN_FILES;
return 0;
}
}
}
/* description: if <isDir> is set prints the content of the open files table
* if not prints the open directory table
*/
int TBL_printFileTbl(int isDir)
{
if(isDir == true) {
puts("\nDirectory Table\n");
if(environment.tbl_dirStatsSize > 0) {
int x;
for(x = 0; x < environment.tbl_dirStatsSize; x++) {
printf("[%d] filename: %s, parent: %s, isOpen: %d, Size: %d, mode: %d\n",
x,environment.dirStatsTbl[x % TBL_DIR_STATS].fullFilename,
environment.dirStatsTbl[x % TBL_DIR_STATS].parent,
environment.dirStatsTbl[x % TBL_DIR_STATS].isOpen,
environment.dirStatsTbl[x % TBL_DIR_STATS].size,
environment.dirStatsTbl[x % TBL_DIR_STATS].mode);
}
return 0;
}
else return 1;
}
else {
puts("\nOpen File Table\n");
if(environment.tbl_openFilesSize > 0) {
int x;
for(x = 0; x < environment.tbl_openFilesSize; x++) {
printf("[%d] filename: %s, parent:%s, isOpen: %d, Size: %d, mode: %d\n",
x,environment.openFilesTbl[x % TBL_OPEN_FILES].fullFilename,
environment.openFilesTbl[x % TBL_OPEN_FILES].parent,
environment.openFilesTbl[x % TBL_OPEN_FILES].isOpen,
environment.openFilesTbl[x % TBL_OPEN_FILES].size,
environment.openFilesTbl[x % TBL_OPEN_FILES].mode);
}
return 0;
}
else return 1;
}
}
/* desctipion searches the open directory table for entry if it finds it,
* it returns the name of the parent directory, else it returns an empty string
*/
const char * TBL_getParent(const char * dirName) {
if(environment.tbl_dirStatsSize > 0) {
int x;
for(x = 0; x < environment.tbl_dirStatsSize; x++) {
if(strcmp(environment.dirStatsTbl[x % TBL_DIR_STATS].filename, dirName) == 0) return environment.dirStatsTbl[x % TBL_DIR_STATS].parent;
}
return "";
}
else
{
return "";
}
}
/* description: "index" is set to the index where the found element resides
* returns true if file was found in the file table
*
*/
bool TBL_getFileDescriptor(int * index, const char * filename, bool isDir){
// FILEDESCRIPTOR * b;
if(isDir == true) {
if(environment.tbl_dirStatsSize > 0) {
int x;
for(x = 0; x < environment.tbl_dirStatsSize; x++) {
if(strcmp(environment.dirStatsTbl[x % TBL_DIR_STATS].fullFilename, filename) == 0) {
*index = x;
return true;
}
}
}
else return false;
}
else {
if(environment.tbl_openFilesSize > 0) {
int x;
for(x = 0; x < environment.tbl_openFilesSize; x++) {
if(strcmp(environment.openFilesTbl[x % TBL_OPEN_FILES].fullFilename, filename) == 0) {
*index = x;
return true;
}
}
}
else return false;
}
return false;
}
//-----------------------------------------------------------------------------
/*description: feed this a cluster and it returns an offset, in bytes, where the
* fat entry for this cluster is locted
*
* use: use the result to seek to the place in the image and read
* the FAT entry
* */
uint32_t getFatAddressByCluster(fat32BS * bs, uint32_t clusterNum) {
uint32_t FATOffset = clusterNum * 4;
uint32_t ThisFATSecNum = bs->BPB_RsvdSecCnt + (FATOffset / bs->BPB_BytesPerSec);
uint32_t ThisFATEntOffset = FATOffset % bs->BPB_BytesPerSec;
return (ThisFATSecNum * bs->BPB_BytesPerSec + ThisFATEntOffset);
}
/*description: finds the location of this clusters FAT entry, reads
* and returns the entry value
*
* use: use the result to seek to the place in the image and read
* the FAT entry
* */
uint32_t FAT_getFatEntry(fat32BS * bs, uint32_t clusterNum) {
int fd = open(environment.imageName, O_RDWR);
checkForFileError(fd);
uint8_t aFatEntry[FAT_ENTRY_SIZE];
uint32_t FATOffset = clusterNum * 4;
lseek(fd, getFatAddressByCluster(bs, clusterNum), SEEK_SET);
read(fd,aFatEntry, sizeof(aFatEntry));
close(fd);
uint32_t fatEntry = 0x00000000;
int x;
for(x = 0; x < 4; x++) {
fatEntry |= aFatEntry[(FATOffset % FAT_ENTRY_SIZE ) + x] << 8 * x;
}
return fatEntry;
}
/* description: takes a value, newFatVal, and writes it to the destination
* cluster,
*/
int FAT_writeFatEntry(fat32BS * bs, uint32_t destinationCluster, uint32_t * newFatVal) {
int fd = open(environment.imageName, O_RDWR);
checkForFileError(fd);
lseek(fd, getFatAddressByCluster(bs, destinationCluster), SEEK_SET);
write(fd,newFatVal,4);
close(fd);
return 0;
}
/*description:walks a FAT chain until 0x0fffffff, returns the number of iterations
* which is the size of the cluster chiain
*/
int getFileSizeInClusters(fat32BS * bs, uint32_t firstClusterVal) {
int size = 1;
firstClusterVal = (int) FAT_getFatEntry(bs, firstClusterVal);
while((firstClusterVal = (firstClusterVal & MASK_IGNORE_MSB)) < FAT_EOC) {
size++;
firstClusterVal = FAT_getFatEntry(bs, firstClusterVal);
}
return size;
}
/*description: walks a FAT chain until returns the last cluster, where
* the current EOC is. returns the cluster number passed in if it's empty,
* , you should probly call getFirstFreeCluster if you intend to write to
* the FAT to keep things orderly
*/
uint32_t getLastClusterInChain(fat32BS * bs, uint32_t firstClusterVal) {
uint32_t lastCluster = firstClusterVal;
firstClusterVal = (int) FAT_getFatEntry(bs, firstClusterVal);
//if cluster is empty return cluster number passed in
if((((firstClusterVal & MASK_IGNORE_MSB) | FAT_FREE_CLUSTER) == FAT_FREE_CLUSTER) )
return lastCluster;
//mask the 1st 4 msb, they are special and don't count
while((firstClusterVal = (firstClusterVal & MASK_IGNORE_MSB)) < FAT_EOC) {
lastCluster = firstClusterVal;
firstClusterVal = FAT_getFatEntry(bs, firstClusterVal);
}
return lastCluster;
}
/* description: traverses the FAT sequentially and find the first open cluster
*/
int FAT_findFirstFreeCluster(fat32BS * bs) {
int i = 0;
int totalClusters = countOfClusters(bs);
while(i < totalClusters) {
if(((FAT_getFatEntry(bs, i) & MASK_IGNORE_MSB) | FAT_FREE_CLUSTER) == FAT_FREE_CLUSTER)
break;
i++;
}
return i;
}
/* decription: returns the total number of open clusters
*/
int FAT_findTotalFreeCluster(fat32BS * bs) {
int i = 0;
int fatIndex = 0;
int totalClusters = countOfClusters(bs);
while(fatIndex < totalClusters) {
if((((FAT_getFatEntry(bs, fatIndex) & MASK_IGNORE_MSB) | FAT_FREE_CLUSTER) == FAT_FREE_CLUSTER))
i++;
fatIndex++;
}
return i;
}
/* description: pass in a entry and this properly formats the
* "firstCluster" from the 2 byte segments in the file structure
*/
uint32_t buildClusterAddress(DIR_ENTRY * entry) {
uint32_t firstCluster = 0x00000000;
firstCluster |= entry->DIR_FstClusHI[1] << 24;
firstCluster |= entry->DIR_FstClusHI[0] << 16;
firstCluster |= entry->DIR_FstClusLO[1] << 8;
firstCluster |= entry->DIR_FstClusLO[0];
return firstCluster;
}
/* description: convert uint32_t to DIR_FstClusHI and DIR_FstClusLO byte array
* and stores it into <entry>
*/
int deconstructClusterAddress(DIR_ENTRY * entry, uint32_t cluster) {
entry->DIR_FstClusLO[0] = cluster;
entry->DIR_FstClusLO[1] = cluster >> 8;
entry->DIR_FstClusHI[0] = cluster >> 16;
entry->DIR_FstClusHI[1] = cluster >> 24;
return 0;
}
/* description: takes a directory entry populates a file descriptor
* to be used in the file tables
* */
FILEDESCRIPTOR * makeFileDecriptor(DIR_ENTRY * entry, FILEDESCRIPTOR * fd) {
char newFilename[12];
bzero(fd->filename, 9);
bzero(fd->extention, 4);
memcpy(newFilename, entry->filename, 11);
newFilename[11] = '\0';
int x;
for(x = 0; x < 8; x++) {
if(newFilename[x] == ' ')
break;
fd->filename[x] = newFilename[x];
}
fd->filename[++x] = '\0';
for(x = 8; x < 11; x++) {
if(newFilename[x] == ' ')
break;
fd->extention[x - 8] = newFilename[x];
}
fd->extention[++x - 8] = '\0';
if(strlen(fd->extention) > 0) {
strcpy(fd->fullFilename, fd->filename);
strcat(fd->fullFilename, ".");
strcat(fd->fullFilename, fd->extention);
}
else {
strcpy(fd->fullFilename, fd->filename);
}
fd->firstCluster = buildClusterAddress(entry);
fd->size = entry->DIR_FileSize;
fd->mode = MODE_UNKNOWN;
if((entry->DIR_Attr & ATTR_DIRECTORY) == ATTR_DIRECTORY)
fd->dir = true;
else
fd->dir = false;
return fd;
}
/* description: takes a cluster number where bunch of directories are and
* the offst of the directory you want read and it will store that directory
* info into the variable dir
*/
DIR_ENTRY * readEntry(fat32BS * bs, DIR_ENTRY * entry, uint32_t clusterNum, int offset){
offset *= 32;
uint32_t dataAddress = byteOffsetOfCluster(bs, clusterNum);
int fd = open(environment.imageName, O_RDWR);
checkForFileError(fd);
lseek(fd, dataAddress + offset, SEEK_SET);
read(fd, entry,sizeof(DIR_ENTRY));
close(fd);
return entry;
}
/* description: takes a cluster number and offset where you want an entry written and write to that
* position
*/
DIR_ENTRY * writeEntry(fat32BS * bs, DIR_ENTRY * entry, uint32_t clusterNum, int offset){
offset *= 32;
uint32_t dataAddress = byteOffsetOfCluster(bs, clusterNum);
int fd = open(environment.imageName, O_RDWR);
checkForFileError(fd);
lseek(fd, dataAddress + offset, SEEK_SET);
write(fd,entry,sizeof(DIR_ENTRY));
close(fd);
return entry;
}
/* description: takes a directory cluster and give you the byte address of the entry at
* the offset provided. used to write dot entries. POSSIBLY REDUNDANT
*/
uint32_t byteOffsetofDirectoryEntry(fat32BS * bs, uint32_t clusterNum, int offset) {
offset *= 32;
uint32_t dataAddress = byteOffsetOfCluster(bs, clusterNum);
return (dataAddress + offset);
}
/* This is the workhorse. It is used for ls, cd, filesearching.
* Directory Functionality:
* It is used to perform cd, which you use by setting <cd>. if <goingUp> is set it uses
* the open directory table to find the pwd's parent. if not it searches the pwd for
* <directoryName>. If <cd> is not set this prints the contents of the pwd to the screen
*
* Search Functionality
* if <useAsSearch> is set this short circuits the cd functionality and returns true
* if found
*
* doDir(bs, environment.pwd_cluster, true, fileName, false, searchFile, true, searchForDirectory)
*/
int doDir(fat32BS * bs, uint32_t clusterNum, bool cd, const char * directoryName,
bool goingUp, FILEDESCRIPTOR * searchFile, bool useAsSearch, bool searchForDir)
{
DIR_ENTRY dir;
int dirSizeInCluster = getFileSizeInClusters(bs, clusterNum);
int clusterCount;
int offset;
int increment;
for(clusterCount = 0; clusterCount < dirSizeInCluster; clusterCount++) {
//root doesn't have . and .., so we traverse it differently
// we only increment 1 to get . and .. then we go in 2's to avoid longname entries
if(strcmp(directoryName, ROOT) == 0) {
offset = 1;
increment = 2;
}
else {
offset = 0;
increment = 1;
}
for(; offset < ENTRIES_PER_SECTOR; offset += increment) {
//this is a hack to properly display the dir contents of folders
//with . and .. w/o displaying longname entries
//if not root folder we need to read the 1st 2 entries (. and ..)
//sequential then resume skipping longnames by incrementing by 2
if(strcmp(directoryName, ROOT) != 0 && offset == 2) {
increment = 2;
offset -= 1;
continue;
}
readEntry(bs, &dir, clusterNum, offset+1);
makeFileDecriptor(&dir, searchFile);
if( cd == false ) {
//we don't want to print 0xE5 to the screen
if(searchFile->filename[0] != 0xE5) {
if(searchFile->dir == true)
printf("<%s>\t %d\n", searchFile->fullFilename,searchFile->size);
else
printf("%s\t %d\n", searchFile->fullFilename,searchFile->size);
}
}
else
{
//if there's an extention we expect the user must type it in with the '.' and the extention
//because of this we must compare it to a recontructed filename with the implied '.' put
//back in. also searchForDir tells us whether the file being searched for is a directory or not
if(useAsSearch == true) {
if(strcmp(searchFile->fullFilename, directoryName) == 0 && searchFile->dir == searchForDir )
return true;
}
else {
/* if we're going down we search pwd for directory with the name passed in.
* if we find it we add it to the directory table and return true. else
* we fall out of this loop and return false at the end of the function
*/
if(searchFile->dir == true && strcmp(searchFile->fullFilename, directoryName) == 0 && goingUp == false) {// <--------CHANGED
environment.pwd_cluster = searchFile->firstCluster;
if(strcmp(TBL_getParent(directoryName), "") == 0)//if directory not already in open dir history table
TBL_addFileToTbl(TBL_createFile(searchFile->filename, "", environment.pwd, searchFile->firstCluster, searchFile->mode, searchFile->size, true, false), true);
FAT_setIoWriteCluster(bs, environment.pwd_cluster);
return true;
}
//fetch parent cluster from the directory table
if(searchFile->dir == true && strcmp(directoryName, PARENT) == 0 && goingUp == true) {
const char * parent = TBL_getParent(environment.pwd);
if(strcmp(parent, "") != 0) { //we found parent in the table
if(strcmp(parent, "/") == 0)
environment.pwd_cluster = 2; //sets pwd_cluster to where we're headed
else
environment.pwd_cluster = searchFile->firstCluster;
strcpy(environment.last_pwd, environment.pwd);
strcpy(environment.pwd, TBL_getParent(environment.pwd));
FAT_setIoWriteCluster(bs, environment.pwd_cluster);
return true; //cd to parent was successful
} else
return false; //cd to parent not successful
}
} // end cd block
}
}
clusterNum = FAT_getFatEntry(bs, clusterNum);
}
return false;
}
/* descriptioin: takes a FILEDESCRIPTOR and checks if the entry it was
* created from is empty. Helper function
*/
bool isEntryEmpty(FILEDESCRIPTOR * fd) {
if((fd->filename[0] != 0x00) && (fd->filename[0] != 0xE5) )
return false;
else
return true;
}
/* description: walks a directory cluster chain looking for empty entries, if it finds one
* it returns the byte offset of that entry. If it finds none then it returns -1;
*/
uint32_t FAT_findNextOpenEntry(fat32BS * bs, uint32_t pwdCluster) {
DIR_ENTRY dir;
FILEDESCRIPTOR fd;
int dirSizeInCluster = getFileSizeInClusters(bs, pwdCluster);
int clusterCount;
int offset;
int increment;
for(clusterCount = 0; clusterCount < dirSizeInCluster; clusterCount++) {
if(strcmp(environment.pwd, ROOT) == 0) {
offset = 1;
increment = 2;
} else {
offset = 0;
increment = 1;
}
for(; offset < ENTRIES_PER_SECTOR; offset += increment) {
if(strcmp(environment.pwd, ROOT) != 0 && offset == 2) {
increment = 2;
offset -= 1;
continue;
}
readEntry(bs, &dir, pwdCluster, offset);
makeFileDecriptor(&dir, &fd);
if( isEntryEmpty(&fd) == true ) {
//this should tell me exactly where to write my new entry to
//printf("cluster #%d, byte offset: %d: ", offset, byteOffsetofDirectoryEntry(bs, pwdCluster, offset));
return byteOffsetofDirectoryEntry(bs, pwdCluster, offset);
}
}
//pwdCluster becomes the next cluster in the chain starting at the passed in pwdCluster
pwdCluster = FAT_getFatEntry(bs, pwdCluster);
}
return -1; //cluster chain is full
}
/* description: wrapper for doDir. tries to change the pwd to <directoryName>
* This doesn't use the print to screen functinoality of doDir. if <goingUp>
* is set it uses the open directory table to find the pwd's parent
*/
int doCD(fat32BS * bs, const char * directoryName, int goingUp, FILEDESCRIPTOR * searchFile) {
return doDir(bs, environment.pwd_cluster, true, directoryName, goingUp, searchFile, false, false);
}
/* desctipion: wrapper that uses doDir to search a pwd for a file and puts its info
* into searchFile if found. if <useAsFileSearch> is set it disables the printing enabling
* it to be used as a file search utility. if <searchForDirectory> is set it excludes
* files from the search
*/
bool searchOrPrintFileSize(fat32BS * bs, const char * fileName, bool useAsFileSearch, bool searchForDirectory, FILEDESCRIPTOR * searchFile) {
if(doDir(bs, environment.pwd_cluster, true, fileName, false, searchFile, true, searchForDirectory) == true) {
if(useAsFileSearch == false)
printf("File: %s is %d byte(s) in size", fileName ,searchFile->size);
return true;
} else {
if(useAsFileSearch == false)
printf("ERROR: File: %s was not found", fileName);
return false;
}
}
/* desctipion: wrapper that uses doDir to search a pwd for a file and puts its info
* into searchFile if found. Prints result for both file and directories
*/
bool printFileOrDirectorySize(fat32BS * bs, const char * fileName, FILEDESCRIPTOR * searchFile) {
if(doDir(bs, environment.pwd_cluster, true, fileName, false, searchFile, true, true) == true ||
doDir(bs, environment.pwd_cluster, true, fileName, false, searchFile, true, false) == true) {
printf("File: %s is %d byte(s) in size", fileName ,searchFile->size);
return true;
} else
return false;
}
/* description: wrapper for searchOrPrintFileSize searchs pwd for filename.
* returns true if found, if found the resulting entry is put into searchFile
* for use outside the function. if <searchForDirectory> is set it excludes
* files from the search
*/
bool searchForFile(fat32BS * bs, const char * fileName, bool searchForDirectory, FILEDESCRIPTOR * searchFile) {
return searchOrPrintFileSize(bs, fileName, true, searchForDirectory, searchFile);
}
/* decription: feed this a cluster number that's part of a chain and this
* traverses it to find the last entry as well as finding the first available
* free cluster and adds that free cluster to the chain
*/
uint32_t FAT_extendClusterChain(fat32BS * bs, uint32_t clusterChainMember) {
uint32_t firstFreeCluster = FAT_findFirstFreeCluster(bs);
uint32_t lastClusterinChain = getLastClusterInChain(bs, clusterChainMember);
FAT_writeFatEntry(bs, lastClusterinChain, &firstFreeCluster);
FAT_writeFatEntry(bs, firstFreeCluster, &FAT_EOC);
return firstFreeCluster;
}
/* desctipion: pass in a free cluster and this marks it with EOC and sets
* the environment.io_writeCluster to the end of newly created cluster
* chain
*/
int FAT_allocateClusterChain(fat32BS * bs, uint32_t clusterNum) {
FAT_writeFatEntry(bs, clusterNum, &FAT_EOC);
return 0;
}
/* desctipion: pass in the 1st cluster of a chain and this traverses the
* chain and writes FAT_FREE_CLUSTER to every link, thereby freeing the
* chain for reallocation
*/
int FAT_freeClusterChain(fat32BS * bs, uint32_t firstClusterOfChain){
int dirSizeInCluster = getFileSizeInClusters(bs, firstClusterOfChain);
int currentCluster= firstClusterOfChain;
int nextCluster;
int clusterCount;
for(clusterCount = 0; clusterCount < dirSizeInCluster; clusterCount++) {
nextCluster = FAT_getFatEntry(bs, currentCluster);
FAT_writeFatEntry(bs, currentCluster, &FAT_FREE_CLUSTER);
currentCluster = nextCluster;
}
return 0;
}
/* description: feed this a cluster that's a member of a chain and this
* sets your environment variable "io_writeCluster" to the last in that
* chain. The thinking is this is where you'll write in order to grow
* that file. before writing to cluster check with FAT_findNextOpenEntry()
* to see if there's space or you need to extend the chain using FAT_extendClusterChain()
*/
int FAT_setIoWriteCluster(fat32BS * bs, uint32_t clusterChainMember) {
environment.io_writeCluster = getLastClusterInChain(bs, clusterChainMember);
return 0;
}
/* description: this will write a new entry to <destinationCluster>. if that cluster
* is full it grows the cluster chain and write the entry in the first spot
* of the new cluster. if <isDotEntries> is set this automatically writes both
* '.' and '..' to offsets 0 and 1 of <destinationCluster>
*
*/
int writeFileEntry(fat32BS * bs, DIR_ENTRY * entry, uint32_t destinationCluster, bool isDotEntries) {
int dataAddress;
int freshCluster;
int fd = open(environment.imageName, O_RDWR);
checkForFileError(fd);
if(isDotEntries == false) {
if((dataAddress = FAT_findNextOpenEntry(bs, destinationCluster)) != -1) {//-1 means current cluster is at capacity
lseek(fd, dataAddress, SEEK_SET);
write(fd,entry,sizeof(DIR_ENTRY));
}
else {
freshCluster = FAT_extendClusterChain(bs, destinationCluster);
dataAddress = FAT_findNextOpenEntry(bs, freshCluster);
lseek(fd, dataAddress, SEEK_SET);
write(fd,entry,sizeof(DIR_ENTRY));
}
}
else {
DIR_ENTRY dotEntry;
DIR_ENTRY dotDotEntry;
makeSpecialDirEntries(&dotEntry, &dotDotEntry, destinationCluster, environment.pwd_cluster);
//seek to first spot in new dir cluster chin and write the '.' entry
dataAddress = byteOffsetofDirectoryEntry(bs, destinationCluster, 0);
lseek(fd, dataAddress, SEEK_SET);
write(fd,&dotEntry,sizeof(DIR_ENTRY));
//seek to second spot in new dir cluster chin and write the '..' entry
dataAddress = byteOffsetofDirectoryEntry(bs, destinationCluster, 1);
lseek(fd,dataAddress, SEEK_SET);
write(fd,&dotDotEntry,sizeof(DIR_ENTRY));
}
close(fd);
return 0;
}
/* description: takes a directory entry and all the necesary info
and populates the entry with the info in a correct format for
insertion into a disk.
*/
int createEntry(DIR_ENTRY * entry, const char * filename, const char * ext,
int isDir, uint32_t firstCluster, uint32_t filesize,
bool emptyAfterThis, bool emptyDirectory) {
//set the same no matter the entry
entry->DIR_NTRes = 0;
entry->DIR_CrtTimeTenth = 0;
entry->DIR_CrtTime = 0;
entry->DIR_CrtDate = 0;
entry->DIR_LstAccDate = 0;
entry->DIR_WrtTime = 0;
entry->DIR_WrtDate = 0;
if(emptyAfterThis == false && emptyDirectory == false) { //if both are false
int x;
for(x = 0; x < MAX_FILENAME_SIZE; x++) {
if(x < strlen(filename))
entry->filename[x] = filename[x];
else
entry->filename[x] = ' ';
}
for(x = 0; x < MAX_EXTENTION_SIZE; x++) {
if(x < strlen(ext))
entry->filename[MAX_FILENAME_SIZE + x] = ext[x];
else
entry->filename[MAX_FILENAME_SIZE + x] = ' ';
}
deconstructClusterAddress(entry, firstCluster);
if(isDir == true) {
entry->DIR_FileSize = 0;
entry->DIR_Attr = ATTR_DIRECTORY;
}
else {
entry->DIR_FileSize = filesize;
entry->DIR_Attr = ATTR_ARCHIVE;
}
return 0; //stops execution so we don't flow out into empty entry config code below
}
else if(emptyAfterThis == true) { //if this isn't true, then the other must be
entry->filename[0] = 0xE5;
entry->DIR_Attr = 0x00;
}
else { //hence no condition check here
entry->filename[0] = 0x00;
entry->DIR_Attr = 0x00;
}
//if i made it here we're creating an empty entry and both conditions
//require this setup
int x;
for(x = 1; x < 11; x++) entry->filename[x] = 0x00;
entry->DIR_FstClusLO[0] = 0x00;
entry->DIR_FstClusLO[1] = 0x00;
entry->DIR_FstClusHI[0] = 0x00;
entry->DIR_FstClusHI[1] = 0x00;
entry->DIR_Attr = 0x00;
entry->DIR_FileSize = 0;
return 0;
}
/* description: take two entries and cluster info and populates them with
* '.' and '..' entry information. The entries are ready for writing to
* the disk after this. helper function for mkdir()
*/
int makeSpecialDirEntries(DIR_ENTRY * dot, DIR_ENTRY * dotDot,
uint32_t newlyAllocatedCluster, uint32_t pwdCluster )
{
createEntry(dot, ".", "", true, newlyAllocatedCluster, 0, false, false);
createEntry(dotDot, "..", "", true, pwdCluster, 0, false, false);
return 0;
}
/* returns offset of the entry, <searchName> in the pwd
* if found return the offset, if not return -1
*/
int getEntryOffset(fat32BS * bs, const char * searchName) {
DIR_ENTRY entry;
FILEDESCRIPTOR fd;
uint32_t currentCluster = environment.pwd_cluster;
int dirSizeInCluster = getFileSizeInClusters(bs, currentCluster);
int clusterCount;
int offset;
int increment;
for(clusterCount = 0; clusterCount < dirSizeInCluster; clusterCount++) {
if(strcmp(environment.pwd, ROOT) == 0) {
offset = 1;
increment = 2;
}
else {
offset = 0;
increment = 1;
}
for(; offset < ENTRIES_PER_SECTOR; offset += increment) {
if(strcmp(environment.pwd, ROOT) != 0 && offset == 2) {
increment = 2;
offset -= 1;
continue;
}
readEntry(bs, &entry, currentCluster, offset);
makeFileDecriptor(&entry, &fd);
if(strcmp(searchName, fd.fullFilename) == 0) {
return offset;
}
}
currentCluster = FAT_getFatEntry(bs, currentCluster);
}
return -1;
}
/* description: prints info about the image to the screen
*/
int printInfo(fat32BS * bs) {
printf("---- Device Info ----\n");
printf("OEM Name: %s\n",bs->BS_OEMName);
printf("Label: %.*s\n",BS_VolLab_LENGTH,bs->BS_VolLab);
printf("File System Type: %.*s\n",BS_FilSysType_LENGTH,bs->BS_FilSysType);
if(bs->BPB_Media == 0xf8)printf("Media Type: 0x%X (fixed)\n",bs->BPB_Media);
else if(bs->BPB_Media == 0xf0)printf("Media Type: 0x%X (removable)\n",bs->BPB_Media);
long long int disk_size = bs->BPB_BytesPerSec * bs->BPB_FATSz32/4;
disk_size *= bs->BPB_BytesPerSec * bs->BPB_SecPerClus/1000;
printf("Size: %lld bytes( %lldMB, %.3lfGB)\n",disk_size,disk_size>>10,((double)disk_size)/(1<<20));
if(bs->BS_DrvNum==128)printf("Drive Number: %d (hard disk)\n\n",bs->BS_DrvNum);
else printf("Drive Number: %d (A drive disk)\n\n",bs->BS_DrvNum);
printf("--- Geometry ---\n");
printf("Bytes per Sector: %d\n",bs->BPB_BytesPerSec);
printf("Sectors per Cluster: %d\n",bs->BPB_SecPerClus);
printf("Geom: Sectors per Track: %d\n",bs->BPB_SecPerTrk);
printf("Geom: Heads: %d\n",bs->BPB_NumHeads);
printf("Hidden Sectors: %d\n\n",bs->BPB_HiddSec);
printf("--- FS Info ---\n");
printf("Volume ID: %d\n",bs->BS_VolID);
printf("Version: %d:%d\n",bs->BPB_FSVerHigh,bs->BPB_FSVerLow);
printf("Reserved Sectors: %d\n",bs->BPB_RsvdSecCnt);
printf("Number of FATs: %d\n",bs->BPB_NumFATs);
printf("FAT Size: %d\n",bs->BPB_FATSz32);
if((bs->BPB_ExtFlags&256)!=256)printf("Mirrored FAT: 0 (yes)\n");
else printf("Mirrored FAT: 1 (%d FAT is active)\n",(bs->BPB_ExtFlags&7));
printf("Boot Sector Backup Sector No: %d\n",bs->BPB_BkBootSec);
// puts("\nBoot Sector Info:\n");
// printf("Bytes Per Sector (block size):%d\n", bs->BPB_BytesPerSec);
// printf("Sectors per Cluster: %d\n", bs->BPB_SecPerClus);
// printf("Total clusters: %d\n", countOfClusters(bs));
// printf("Number of FATs: %d\n", bs->BPB_NumFATs);
// printf("Sectors occupied by one FAT: %d\nComputing Free Sectors.......\n", bs->BPB_FATSz32);
// printf("Number of free sectors: %d\n", FAT_findTotalFreeCluster(bs));
return 0;
}
/* description: DOES NOT allocate a cluster chain. Writes a directory
* entry to <targetDirectoryCluster>. Error handling is done in the driver
*/
int touch(fat32BS * bs, const char * filename, const char * extention, uint32_t targetDirectoryCluster) {
DIR_ENTRY newFileEntry;
createEntry(&newFileEntry, filename, extention, false, 0, 0, false, false);
writeFileEntry(bs, &newFileEntry, targetDirectoryCluster, false);
return 0;
}
/* success code: 0 if fclose succeeded
* error code 1: no filename given
* error code 2: filename not found in pwd
* error code 3: filename was never opened
* error code 4: filename is currently closed
*
* description: attempts to change the status of <filename> in the open file table
* from open to closed. see error codes above for assumptions
*
*/
int fClose(fat32BS * bs, int argC, const char * filename) {
int fIndex;
FILEDESCRIPTOR searchFileInflator;
FILEDESCRIPTOR * searchFile = &searchFileInflator;
if(argC != 2) {
return 1;