diff options
Diffstat (limited to 'iov.c')
| -rw-r--r-- | iov.c | 42 |
1 files changed, 33 insertions, 9 deletions
@@ -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++) { |