On Mon, Dec 08, 2025 at 01:18:55AM +0100, Stefano Brivio wrote:

I happened to touch these functions for a change that turned out to be unnecessary, but coding style and documentation could still benefit from some rephrasing and fixes.

Signed-off-by: Stefano Brivio

Reviewed-by: David Gibson

--- v2: Make description of @offset consistent between iov_from_buf() and iov_to_buf()

iov.c | 68 +++++++++++++++++++++++++---------------------------------- 1 file changed, 29 insertions(+), 39 deletions(-)

diff --git a/iov.c b/iov.c index 8c74a59..ad726da 100644 --- a/iov.c +++ b/iov.c @@ -20,24 +20,21 @@ * Contributions after 2012-01-13 are licensed under the terms of the * GNU GPL, version 2 or (at your option) any later version. */ + #include

#include "util.h" #include "iov.h"

- /** - * iov_skip_bytes() - Skip leading bytes of an IO vector - * @iov: IO vector + * iov_skip_bytes() - Find index and offset in iovec array given byte offset + * @iov: iovec array * @n: Number of entries in @iov - * @skip: Number of leading bytes of @iov to skip - * @offset: Offset of first unskipped byte in its @iov entry + * @skip: Byte offset: leading bytes of @iov to skip + * @offset: Offset within matching @iov entry, set on return, can be NULL * - * Return: index I of individual struct iovec which contains the byte at @skip - * bytes into the vector (as though all its buffers were contiguous). - * If @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 <= @skip bytes, return @n. + * Return: index of iovec array containing the @skip byte counted as if buffers + * were contiguous. If iovec has less than @skip bytes, return @n. */ size_t iov_skip_bytes(const struct iovec *iov, size_t n, size_t skip, size_t *offset) @@ -57,17 +54,14 @@ size_t iov_skip_bytes(const struct iovec *iov, size_t n, }

/** - * iov_from_buf() - Copy data from a buffer to an I/O vector (struct iovec) - * efficiently. - * - * @iov: Pointer to the array of struct iovec describing the - * scatter/gather I/O vector. - * @iov_cnt: Number of elements in the iov array. - * @offset: Byte offset in the iov array where copying should start. - * @buf: Pointer to the source buffer containing the data to copy. - * @bytes: Total number of bytes to copy from buf to iov. + * iov_from_buf() - Copy from flat buffer to iovec array + * @iov: Destination iovec array + * @iov_cnt: Number of elements in the iovec array + * @offset: Destination offset in @iov counted as if buffers were contiguous + * @buf: Source buffer + * @bytes: Bytes to copy * - * Return: the number of bytes successfully copied. + * Return: number of bytes copied */ size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt, size_t offset, const void *buf, size_t bytes) @@ -78,12 +72,12 @@ size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt, if (__builtin_constant_p(bytes) && iov_cnt && offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) { memcpy((char *)iov[0].iov_base + offset, buf, bytes); + return bytes; }

i = iov_skip_bytes(iov, iov_cnt, offset, &offset);

- /* copying data */ for (copied = 0; copied < bytes && i < iov_cnt; i++) { size_t len = MIN(iov[i].iov_len - offset, bytes - copied);

@@ -97,17 +91,14 @@ size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt, }

/** - * iov_to_buf() - Copy data from a scatter/gather I/O vector (struct iovec) to - * a buffer efficiently. - * - * @iov: Pointer to the array of struct iovec describing the scatter/gather - * I/O vector. - * @iov_cnt: Number of elements in the iov array. - * @offset: Offset within the first element of iov from where copying should start. - * @buf: Pointer to the destination buffer where data will be copied. - * @bytes: Total number of bytes to copy from iov to buf. + * iov_to_buf() - Copy from iovec to flat buffer + * @iov: Source iovec array + * @iov_cnt: Number of elements in iovec array + * @offset: Source offset in @iov counted as if buffers were contiguous + * @buf: Destination buffer + * @bytes: Bytes to copy * - * Return: the number of bytes successfully copied. + * Return: number of bytes copied */ size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt, size_t offset, void *buf, size_t bytes) @@ -118,15 +109,17 @@ size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt, if (__builtin_constant_p(bytes) && iov_cnt && offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) { memcpy(buf, (char *)iov[0].iov_base + offset, bytes); + return bytes; }

i = iov_skip_bytes(iov, iov_cnt, offset, &offset);

- /* copying data */ for (copied = 0; copied < bytes && i < iov_cnt; i++) { size_t len = MIN(iov[i].iov_len - offset, bytes - copied); + ASSERT(iov[i].iov_base); + memcpy((char *)buf + copied, (char *)iov[i].iov_base + offset, len); copied += len; @@ -137,14 +130,11 @@ size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt, }

/** - * iov_size() - Calculate the total size of a scatter/gather I/O vector - * (struct iovec). + * iov_size() - Calculate total data size of iovec + * @iov: Source iovec array + * @iov_cnt: Number of elements in iovec array * - * @iov: Pointer to the array of struct iovec describing the - * scatter/gather I/O vector. - * @iov_cnt: Number of elements in the iov array. - * - * Return: the total size in bytes. + * Return: total size in bytes */ size_t iov_size(const struct iovec *iov, size_t iov_cnt) { -- 2.43.0

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson