//------------------------------------------------------------------------------
// free a cluster chain
uint8_t SdVolume::freeChain(uint32_t cluster) {
// clear free cluster location
allocSearchStart_ = 2;
do {
uint32_t next;
if (!fatGet(cluster, &next)) return false;
// free cluster
if (!fatPut(cluster, 0)) return false;
cluster = next;
} while (!isEOC(cluster));
return true;
}
//------------------------------------------------------------------------------
bool FatVolume::allocateCluster(uint32_t current, uint32_t* next) {
uint32_t find = current ? current : m_allocSearchStart;
uint32_t start = find;
while (1) {
find++;
// If at end of FAT go to beginning of FAT.
if (find > m_lastCluster) {
find = 2;
}
uint32_t f;
int8_t fg = fatGet(find, &f);
if (fg < 0) {
DBG_FAIL_MACRO;
goto fail;
}
if (fg && f == 0) {
break;
}
if (find == start) {
// Can't find space checked all clusters.
DBG_FAIL_MACRO;
goto fail;
}
}
// mark end of chain
if (!fatPutEOC(find)) {
DBG_FAIL_MACRO;
goto fail;
}
if (current) {
// link clusters
if (!fatPut(current, find)) {
DBG_FAIL_MACRO;
goto fail;
}
} else {
// Remember place for search start.
m_allocSearchStart = find;
}
updateFreeClusterCount(-1);
*next = find;
return true;
fail:
return false;
}
//------------------------------------------------------------------------------
// find a contiguous group of clusters
uint8_t SdVolume::allocContiguous(uint32_t count, uint32_t* curCluster)
{
// start of group
uint32_t bgnCluster;
// flag to save place to start next search
uint8_t setStart;
// set search start cluster
if (*curCluster)
{
// try to make file contiguous
bgnCluster = *curCluster + 1;
// don't save new start location
setStart = false;
}
else
{
// start at likely place for free cluster
bgnCluster = allocSearchStart_;
// save next search start if one cluster
setStart = 1 == count;
}
// end of group
uint32_t endCluster = bgnCluster;
// last cluster of FAT
uint32_t fatEnd = clusterCount_ + 1;
// search the FAT for free clusters
for (uint32_t n = 0;; n++, endCluster++)
{
// can't find space checked all clusters
if (n >= clusterCount_) return false;
// past end - start from beginning of FAT
if (endCluster > fatEnd)
{
bgnCluster = endCluster = 2;
}
uint32_t f;
if (!fatGet(endCluster, &f)) return false;
if (f != 0)
{
// cluster in use try next cluster as bgnCluster
bgnCluster = endCluster + 1;
}
else if ((endCluster - bgnCluster + 1) == count)
{
// done - found space
break;
}
}
// mark end of chain
if (!fatPutEOC(endCluster))
return false;
// link clusters
while (endCluster > bgnCluster)
{
if (!fatPut(endCluster - 1, endCluster))
return false;
endCluster--;
}
if (*curCluster != 0)
{
// connect chains
if (!fatPut(*curCluster, bgnCluster))
return false;
}
// return first cluster number to caller
*curCluster = bgnCluster;
// remember possible next free cluster
if (setStart)
allocSearchStart_ = bgnCluster + 1;
return true;
}
//------------------------------------------------------------------------------
// find a contiguous group of clusters
bool FatVolume::allocContiguous(uint32_t count, uint32_t* firstCluster) {
// flag to save place to start next search
bool setStart = true;
// start of group
uint32_t bgnCluster;
// end of group
uint32_t endCluster;
// Start at cluster after last allocated cluster.
uint32_t startCluster = m_allocSearchStart;
endCluster = bgnCluster = startCluster + 1;
// search the FAT for free clusters
while (1) {
// If past end - start from beginning of FAT.
if (endCluster > m_lastCluster) {
bgnCluster = endCluster = 2;
}
uint32_t f;
int8_t fg = fatGet(endCluster, &f);
if (fg < 0) {
DBG_FAIL_MACRO;
goto fail;
}
if (f || fg == 0) {
// cluster in use try next cluster as bgnCluster
bgnCluster = endCluster + 1;
// don't update search start if unallocated clusters before endCluster.
if (bgnCluster != endCluster) {
setStart = false;
}
} else if ((endCluster - bgnCluster + 1) == count) {
// done - found space
break;
}
// Can't find space if all clusters checked.
if (startCluster == endCluster) {
DBG_FAIL_MACRO;
goto fail;
}
endCluster++;
}
// remember possible next free cluster
if (setStart) {
m_allocSearchStart = endCluster + 1;
}
// mark end of chain
if (!fatPutEOC(endCluster)) {
DBG_FAIL_MACRO;
goto fail;
}
// link clusters
while (endCluster > bgnCluster) {
if (!fatPut(endCluster - 1, endCluster)) {
DBG_FAIL_MACRO;
goto fail;
}
endCluster--;
}
// Maintain count of free clusters.
updateFreeClusterCount(-count);
// return first cluster number to caller
*firstCluster = bgnCluster;
return true;
fail:
return false;
}
