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SOCKET use readv/writev to write directly into iovectors

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This patch adds support for read/writev to directly read and write
from/to iovectors. Before this patch on read and write from/to socket
the operation was limited by the iovec boundaries. If there is enough
data in the buffer or enough buffer space available its now possible
to transfer the whole data in one atomic operaion.

Signed-off-by: Peter Lieven <pl@kamp.de>
This commit is contained in:
Peter Lieven
2012-12-10 19:24:28 +01:00
parent 752c0ad396
commit 446b1829c8
4 changed files with 124 additions and 85 deletions
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56
lib/scsi-lowlevel.c
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@@ -34,6 +34,7 @@
#include <stddef.h>
#include <string.h>
#include <stdint.h>
#include <errno.h>
#include "slist.h"
#include "scsi-lowlevel.h"
@@ -2593,69 +2594,14 @@ scsi_iovector_add(struct scsi_task *task, struct scsi_iovector *iovector, int le
return 0;
}
unsigned char *
scsi_iovector_get_buffer(struct scsi_iovector *iovector, uint32_t pos, ssize_t *count)
{
if (iovector->iov == NULL) {
return NULL;
}
if (pos == 0 && count == NULL) return iovector->iov[0].iov_base;
if (pos < iovector->offset) {
/* start over in case we are going backwards */
iovector->offset = 0;
iovector->consumed = 0;
}
if (iovector->niov <= iovector->consumed) {
/* someone issued a read but did not provide enough user buffers for all the data.
* maybe someone tried to read just 512 bytes off a MMC device?
*/
return NULL;
}
struct scsi_iovec *iov = &iovector->iov[iovector->consumed];
pos-= iovector->offset;
while (pos >= iov->iov_len) {
iovector->offset += iov->iov_len;
iovector->consumed++;
pos -= iov->iov_len;
if (iovector->niov <= iovector->consumed) {
return NULL;
}
iov = &iovector->iov[iovector->consumed];
}
if (count && *count >= (ssize_t)(iov->iov_len - pos)) {
*count = iov->iov_len - pos;
}
return (unsigned char *) iov->iov_base + pos;
}
int
scsi_task_add_data_in_buffer(struct scsi_task *task, int len, unsigned char *buf)
{
return scsi_iovector_add(task, &task->iovector_in, len, buf);
}
unsigned char *
scsi_task_get_data_in_buffer(struct scsi_task *task, uint32_t pos, ssize_t *count)
{
return scsi_iovector_get_buffer(&task->iovector_in, pos, count);
}
int
scsi_task_add_data_out_buffer(struct scsi_task *task, int len, unsigned char *buf)
{
return scsi_iovector_add(task, &task->iovector_out, len, buf);
}
unsigned char *
scsi_task_get_data_out_buffer(struct scsi_task *task, uint32_t pos, ssize_t *count)
{
return scsi_iovector_get_buffer(&task->iovector_out, pos, count);
}