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authorDavid Gibson <david@gibson.dropbear.id.au>2024-02-28 12:52:01 +1100
committerStefano Brivio <sbrivio@redhat.com>2024-02-29 06:24:07 +0100
commit64b63d9e3e1dc2e4c1f32432cf8954f6cc3f788f (patch)
treebbc7d06c7ccf693f1f563001a779002d4acbabb8 /iov.c
parent2a6f8bcca77ae7391a8943a3791be2fbb98a918b (diff)
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iov: Add helper to find skip over first n bytes of an io vector
Several of the IOV functions in iov.c, and also tap_send_frames_passt() needs to determine which buffer element a byte offset into an IO vector lies in. Split this out into a helper function iov_skip_bytes(). Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Diffstat (limited to 'iov.c')
-rw-r--r--iov.c42
1 files changed, 33 insertions, 9 deletions
diff --git a/iov.c b/iov.c
index 8a48acb..e331262 100644
--- a/iov.c
+++ b/iov.c
@@ -25,6 +25,36 @@
#include "util.h"
#include "iov.h"
+
+/* iov_skip_bytes() - Skip the first n bytes into an IO vector
+ * @iov: IO vector
+ * @n: Number of entries in @iov
+ * @vec_offset: Total byte offset into the IO vector
+ * @buf_offset: Offset into a single buffer of the IO vector
+ *
+ * Return: index I of individual struct iovec which contains the byte at
+ * @vec_offset bytes into the vector (as though all its buffers were
+ * contiguous). If @buf_offset is non-NULL, update it to the offset of
+ * that byte within @iov[I] (guaranteed to be less than @iov[I].iov_len)
+ * If the whole vector has <= @vec_offset bytes, return @n.
+ */
+size_t iov_skip_bytes(const struct iovec *iov, size_t n,
+ size_t vec_offset, size_t *buf_offset)
+{
+ size_t offset = vec_offset, i;
+
+ for (i = 0; i < n; i++) {
+ if (offset < iov[i].iov_len)
+ break;
+ offset -= iov[i].iov_len;
+ }
+
+ if (buf_offset)
+ *buf_offset = offset;
+
+ return i;
+}
+
/**
* iov_from_buf - Copy data from a buffer to an I/O vector (struct iovec)
* efficiently.
@@ -51,9 +81,7 @@ size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt,
return bytes;
}
- /* skipping offset bytes in the iovec */
- for (i = 0; i < iov_cnt && offset >= iov[i].iov_len; i++)
- offset -= iov[i].iov_len;
+ i = iov_skip_bytes(iov, iov_cnt, offset, &offset);
/* copying data */
for (copied = 0; copied < bytes && i < iov_cnt; i++) {
@@ -94,9 +122,7 @@ size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt,
return bytes;
}
- /* skipping offset bytes in the iovec */
- for (i = 0; i < iov_cnt && offset >= iov[i].iov_len; i++)
- offset -= iov[i].iov_len;
+ i = iov_skip_bytes(iov, iov_cnt, offset, &offset);
/* copying data */
for (copied = 0; copied < bytes && i < iov_cnt; i++) {
@@ -155,9 +181,7 @@ unsigned iov_copy(struct iovec *dst_iov, size_t dst_iov_cnt,
{
unsigned int i, j;
- /* skipping offset bytes in the iovec */
- for (i = 0; i < iov_cnt && offset >= iov[i].iov_len; i++)
- offset -= iov[i].iov_len;
+ i = iov_skip_bytes(iov, iov_cnt, offset, &offset);
/* copying data */
for (j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {