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Runlist elements are relative to the last runlist, so make that work

This commit is contained in:
Itay Almog 2021-09-29 16:56:42 +03:00
parent 6cd265b497
commit 02ea23abfa
1 changed files with 16 additions and 21 deletions
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37
stage23/fs/ntfs.s2.c
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@ -193,41 +193,36 @@ static bool ntfs_get_next_run_list_element(uint8_t **runlist, uint64_t *out_clus
return false;
}
uint8_t low = runlist_ptr[0] & 0xF;
uint8_t high = (runlist_ptr[0] >> 4) & 0xF;
uint8_t count_size = runlist_ptr[0] & 0xF;
uint8_t cluster_size = (runlist_ptr[0] >> 4) & 0xF;
runlist_ptr++;
// get the run length
uint64_t count = 0;
for (int i = low; i > 0; i--) {
for (int i = count_size; i > 0; i--) {
count <<= 8;
count |= runlist_ptr[i - 1];
}
runlist_ptr += low;
// get the high byte first
int8_t high_byte = (int8_t)runlist_ptr[high - 1];
runlist_ptr += count_size;
// get the run offset
uint64_t cluster = 0;
for (int i = high; i > 0; i--) {
int64_t cluster = 0;
for (int i = cluster_size; i > 0; i--) {
cluster <<= 8;
cluster |= runlist_ptr[i - 1];
}
runlist_ptr += high;
runlist_ptr += cluster_size;
// if the offset is negative, fill the empty bytes with 0xff
if (high_byte < 0 && high < 8) {
uint64_t fill = 0;
for (int i = 8; i > high; i--) {
fill >>= 8;
fill |= 0xFF00000000000000;
// sign exten the run offset
if (cluster >> (cluster_size * 8 - 1)) {
for (int i = 7; i >= cluster_size; i--) {
cluster |= (uint64_t)0xFF << (i * 8);
}
cluster |= fill;
}
// out it
*out_cluster = cluster;
// out it, the cluster is relative to the last cluster
// so add it
*out_cluster += cluster;
*out_cluster_count = count;
// update it
@ -577,8 +572,8 @@ int ntfs_read(struct ntfs_file_handle *file, void *buf, uint64_t loc, uint64_t c
uint64_t bytes_per_cluster = file->bpb.sectors_per_cluster * file->bpb.bytes_per_sector;
do {
// get the next element from the runlist
uint64_t cluster_count;
uint64_t cluster;
uint64_t cluster = 0;
uint64_t cluster_count = 0;
if (!ntfs_get_next_run_list_element(&runlist, &cluster_count, &cluster, true))
break;