/* Reads num_sectors from the log (all log sectors are 4096 bytes),
* into buffer 'buffer'. Upon return, *sectors_read will contain
* the number of sectors successfully read.
*
* It is assumed that 'buffer' is already allocated, and of sufficient
* size (i.e. >= 4096*num_sectors).
*
* If 'peek' is true, then the tail (read) pointer for the circular buffer is
* not modified.
*
* 0 is returned on success, -errno otherwise. */
static int vhdx_log_read_sectors(BlockDriverState *bs, VHDXLogEntries *log,
uint32_t *sectors_read, void *buffer,
uint32_t num_sectors, bool peek)
{
int ret = 0;
uint64_t offset;
uint32_t read;
read = log->read;
*sectors_read = 0;
while (num_sectors) {
if (read == log->write) {
/* empty */
break;
}
offset = log->offset + read;
ret = bdrv_pread(bs->file, offset, buffer, VHDX_LOG_SECTOR_SIZE);
if (ret < 0) {
goto exit;
}
read = vhdx_log_inc_idx(read, log->length);
*sectors_read = *sectors_read + 1;
num_sectors--;
}
exit:
if (!peek) {
log->read = read;
}
return ret;
}
/* Writes num_sectors to the log (all log sectors are 4096 bytes),
* from buffer 'buffer'. Upon return, *sectors_written will contain
* the number of sectors successfully written.
*
* It is assumed that 'buffer' is at least 4096*num_sectors large.
*
* 0 is returned on success, -errno otherwise */
static int vhdx_log_write_sectors(BlockDriverState *bs, VHDXLogEntries *log,
uint32_t *sectors_written, void *buffer,
uint32_t num_sectors)
{
int ret = 0;
uint64_t offset;
uint32_t write;
void *buffer_tmp;
BDRVVHDXState *s = bs->opaque;
ret = vhdx_user_visible_write(bs, s);
if (ret < 0) {
goto exit;
}
write = log->write;
buffer_tmp = buffer;
while (num_sectors) {
offset = log->offset + write;
write = vhdx_log_inc_idx(write, log->length);
if (write == log->read) {
/* full */
break;
}
ret = bdrv_pwrite(bs->file->bs, offset, buffer_tmp,
VHDX_LOG_SECTOR_SIZE);
if (ret < 0) {
goto exit;
}
buffer_tmp += VHDX_LOG_SECTOR_SIZE;
log->write = write;
*sectors_written = *sectors_written + 1;
num_sectors--;
}
exit:
return ret;
}
