/**
* Performs a single write operation. The data written must be no greater
* than the maximum block data length. If old data gets overwritten, then
* the existing data blocks are superseded as necessary.
*
* @param write_info Describes the write operation being perfomred.
* @param inode_entry The file inode to write to.
* @param data The new data to write.
* @param data_len The number of bytes of new data to write.
*
* @return 0 on success; nonzero on failure.
*/
static int
nffs_write_chunk(struct nffs_inode_entry *inode_entry, uint32_t file_offset,
const void *data, uint16_t data_len)
{
struct nffs_cache_inode *cache_inode;
struct nffs_cache_block *cache_block;
unsigned int gc_count;
uint32_t append_len;
uint32_t data_offset;
uint32_t block_end;
uint32_t dst_off;
uint16_t chunk_off;
uint16_t chunk_sz;
int rc;
assert(data_len <= nffs_block_max_data_sz);
rc = nffs_cache_inode_ensure(&cache_inode, inode_entry);
if (rc != 0) {
return rc;
}
/** Handle the simple append case first. */
if (file_offset == cache_inode->nci_file_size) {
rc = nffs_write_append(cache_inode, data, data_len);
return rc;
}
/** This is not an append; i.e., old data is getting overwritten. */
dst_off = file_offset + data_len;
data_offset = data_len;
cache_block = NULL;
if (dst_off > cache_inode->nci_file_size) {
append_len = dst_off - cache_inode->nci_file_size;
} else {
append_len = 0;
}
do {
if (cache_block == NULL) {
rc = nffs_cache_seek(cache_inode, dst_off - 1, &cache_block);
if (rc != 0) {
return rc;
}
}
if (cache_block->ncb_file_offset < file_offset) {
chunk_off = file_offset - cache_block->ncb_file_offset;
} else {
chunk_off = 0;
}
chunk_sz = cache_block->ncb_block.nb_data_len - chunk_off;
block_end = cache_block->ncb_file_offset +
cache_block->ncb_block.nb_data_len;
if (block_end != dst_off) {
chunk_sz += (int)(dst_off - block_end);
}
/* Remember the current garbage collection count. If the count
* increases during the write, then the block cache has been
* invalidated and we need to reset our pointers.
*/
gc_count = nffs_gc_count;
data_offset = cache_block->ncb_file_offset + chunk_off - file_offset;
rc = nffs_write_over_block(cache_block->ncb_block.nb_hash_entry,
chunk_off, data + data_offset, chunk_sz);
if (rc != 0) {
return rc;
}
dst_off -= chunk_sz;
if (gc_count != nffs_gc_count) {
/* Garbage collection occurred; the current cached block pointer is
* invalid, so reset it. The cached inode is still valid.
*/
cache_block = NULL;
} else {
cache_block = TAILQ_PREV(cache_block, nffs_cache_block_list,
ncb_link);
}
} while (data_offset > 0);
cache_inode->nci_file_size += append_len;
return 0;
}
/**
* Performs a single write operation. The data written must be no greater
* than the maximum block data length. If old data gets overwritten, then
* the existing data blocks are superseded as necessary.
*
* @param write_info Describes the write operation being perfomred.
* @param inode_entry The file inode to write to.
* @param data The new data to write.
* @param data_len The number of bytes of new data to write.
*
* @return 0 on success; nonzero on failure.
*/
static int
nffs_write_chunk(struct nffs_cache_inode *cache_inode, uint32_t file_offset,
const void *data, uint16_t data_len)
{
struct nffs_cache_block *cache_block;
uint32_t append_len;
uint32_t data_offset;
uint32_t block_end;
uint32_t dst_off;
uint16_t chunk_off;
uint16_t chunk_sz;
int rc;
assert(data_len <= nffs_block_max_data_sz);
/** Handle the simple append case first. */
if (file_offset == cache_inode->nci_file_size) {
rc = nffs_write_append(cache_inode, data, data_len);
return rc;
}
/** This is not an append; i.e., old data is getting overwritten. */
dst_off = file_offset + data_len;
data_offset = data_len;
cache_block = NULL;
if (dst_off > cache_inode->nci_file_size) {
append_len = dst_off - cache_inode->nci_file_size;
} else {
append_len = 0;
}
do {
if (cache_block == NULL) {
rc = nffs_cache_seek(cache_inode, dst_off - 1, &cache_block);
if (rc != 0) {
return rc;
}
}
if (cache_block->ncb_file_offset < file_offset) {
chunk_off = file_offset - cache_block->ncb_file_offset;
} else {
chunk_off = 0;
}
chunk_sz = cache_block->ncb_block.nb_data_len - chunk_off;
block_end = cache_block->ncb_file_offset +
cache_block->ncb_block.nb_data_len;
if (block_end != dst_off) {
chunk_sz += (int)(dst_off - block_end);
}
data_offset = cache_block->ncb_file_offset + chunk_off - file_offset;
rc = nffs_write_over_block(cache_block->ncb_block.nb_hash_entry,
chunk_off, data + data_offset, chunk_sz);
if (rc != 0) {
return rc;
}
dst_off -= chunk_sz;
cache_block = TAILQ_PREV(cache_block, nffs_cache_block_list, ncb_link);
} while (data_offset > 0);
cache_inode->nci_file_size += append_len;
return 0;
}
