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Add fixes for multiple sectors per cluster

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This commit is contained in:
Byron Lathi
2023-12-08 23:11:52 -08:00
parent 5259fa8e65
commit 0aca4af272
5 changed files with 39 additions and 14 deletions
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30
sw/kernel/filesystems/fat32_c.c
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@@ -80,9 +80,12 @@ size_t fat32_file_read(int8_t fd, void* buf, size_t nbytes) {
size_t leftover_length;
size_t bytes_read = 0;
size_t clusters;
uint32_t sector;
struct pcb* pcb = get_pcb_ptr();
struct file_desc* fdesc = &pcb->file_desc_array[fd];
uint32_t cluster_seq = fdesc->file_pos >> 9;
uint32_t cluster_seq = fdesc->file_pos >> (9 + log2_sectors_per_cluster);
uint32_t cluster = ((uint32_t)fdesc->f32_dentry.cluster_high << 16) | fdesc->f32_dentry.cluster_low;
/* validate starting position isn't past end of file */
@@ -95,28 +98,30 @@ size_t fat32_file_read(int8_t fd, void* buf, size_t nbytes) {
}
// This can stay for now, as long as cluster_seq is correct.
for (i = 0; i < cluster_seq; i++) {
cluster = fat32_next_cluster(cluster);
}
// This is an upper bound. It is possible that a 512 chunk can span
// 2 clusters, but the first one will already be handled.
clusters = nbytes >> 9;
clusters = nbytes >> (9 + log2_sectors_per_cluster);
/* Handle first unaligned block */
offset = fdesc->file_pos % 512;
offset = fdesc->file_pos % 512; // This is the offset into the sector, not the cluster
leftover_length = 512 - offset;
sector = (fdesc->file_pos >> 9) & (sectors_per_cluster-1);
if (leftover_length != 0) {
if (nbytes <= leftover_length) {
fat32_read_cluster(cluster, sd_buf);
fat32_read_sector(cluster, sector, sd_buf);
memcpy(buf, sd_buf + offset, nbytes);
bytes_read += nbytes;
fdesc->file_pos += bytes_read;
return bytes_read;
} else {
fat32_read_cluster(cluster, sd_buf);
fat32_read_sector(cluster, sector, sd_buf);
memcpy(buf, sd_buf + offset, leftover_length);
bytes_read += leftover_length;
fdesc->file_pos += bytes_read;
@@ -137,7 +142,7 @@ size_t fat32_file_read(int8_t fd, void* buf, size_t nbytes) {
leftover_length = nbytes - bytes_read;
}
fat32_read_cluster(cluster, sd_buf);
fat32_read_sector(cluster, cluster, sd_buf);
memcpy((uint8_t*)buf+bytes_read, sd_buf, leftover_length);
bytes_read += leftover_length;
fdesc->file_pos += bytes_read;
@@ -149,9 +154,12 @@ size_t fat32_file_read(int8_t fd, void* buf, size_t nbytes) {
return bytes_read;
}
int8_t fat32_read_cluster(uint32_t cluster, void* buf) {
// Read the sector offset from a given cluster into buf
// Why do we need this though, this is just doing a single multiplication?
// No, it is also doing an addition
int8_t fat32_read_sector(uint32_t cluster, uint32_t sector, void* buf) {
uint8_t error;
uint32_t addr = (cluster - 2) + data_start_sector;
uint32_t addr = (cluster - 2) * sectors_per_cluster + sector + data_start_sector;
SD_readSingleBlock(addr, buf, &error);
return error;
}
@@ -176,7 +184,7 @@ int8_t fat32_get_cluster_by_name(const char* name, struct fat32_directory_entry*
cprintf("Sectors per cluster: %hhx\n", sectors_per_cluster);
fat32_read_cluster(root_cluster, sd_buf);
fat32_read_sector(root_cluster, 0, sd_buf);
for (i = 0; i < 16; i++){
local_entry = (struct fat32_directory_entry*)(sd_buf + i*32);
if (local_entry->attr1 == 0xf || local_entry->attr1 & 0x8 || !local_entry->attr1) {