git: a1424b75453f - main - uio: provide uioadvance()

The branch main has been updated by glebius:

URL: https://cgit.FreeBSD.org/src/commit/?id=a1424b75453fe0bcf24a9794378287b675ee4517

commit a1424b75453fe0bcf24a9794378287b675ee4517
Author:     Gleb Smirnoff <glebius@FreeBSD.org>
AuthorDate: 2025-04-30 21:23:25 +0000
Commit:     Gleb Smirnoff <glebius@FreeBSD.org>
CommitDate: 2025-04-30 21:23:25 +0000

    uio: provide uioadvance()
    
    The function advances data pointers forward in given uio by offset.  It
    is planned to be used for interaction between aio(4) and unix(4).
    
    Differential Revision:  https://reviews.freebsd.org/D48920
---
 sys/kern/subr_uio.c | 31 +++++++++++++++++++++++++++++++
 sys/sys/uio.h       |  1 +
 2 files changed, 32 insertions(+)

diff --git a/sys/kern/subr_uio.c b/sys/kern/subr_uio.c
index ff63ac3e2dc0..6ac932fb6690 100644
--- a/sys/kern/subr_uio.c
+++ b/sys/kern/subr_uio.c
@@ -287,6 +287,37 @@ out:
 	return (error);
 }
 
+/*
+ * Advance the pointer in the uio by offset.
+ */
+void
+uioadvance(struct uio *uio, size_t offset)
+{
+
+	while (offset > 0) {
+		struct iovec *iov;
+		size_t cnt;
+
+		MPASS(uio->uio_resid >= 0);
+		MPASS((size_t)uio->uio_resid >= offset);
+		MPASS(uio->uio_iovcnt > 0);
+
+		iov = uio->uio_iov;
+		if ((cnt = iov->iov_len) == 0) {
+			uio->uio_iov++;
+			uio->uio_iovcnt--;
+			continue;
+		}
+		if (cnt > offset)
+			cnt = offset;
+		iov->iov_base = (char *)iov->iov_base + cnt;
+		iov->iov_len -= cnt;
+		uio->uio_resid -= cnt;
+		uio->uio_offset += cnt;
+		offset -= cnt;
+	}
+}
+
 /*
  * Wrapper for uiomove() that validates the arguments against a known-good
  * kernel buffer.  Currently, uiomove accepts a signed (n) argument, which
diff --git a/sys/sys/uio.h b/sys/sys/uio.h
index 1c9d2d39cf57..ec4e92d852a6 100644
--- a/sys/sys/uio.h
+++ b/sys/sys/uio.h
@@ -90,6 +90,7 @@ int	physcopyin_vlist(struct bus_dma_segment *src, off_t offset,
 	    vm_paddr_t dst, size_t len);
 int	physcopyout_vlist(vm_paddr_t src, struct bus_dma_segment *dst,
 	    off_t offset, size_t len);
+void	uioadvance(struct uio *, size_t);
 int	uiomove(void *cp, int n, struct uio *uio);
 int	uiomove_frombuf(void *buf, int buflen, struct uio *uio);
 int	uiomove_fromphys(struct vm_page *ma[], vm_offset_t offset, int n,