From d336336c8164859e4527cbb9f3df189f8bb406de Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Mon, 24 Sep 2012 13:02:52 +0200 Subject: [PATCH] iov: add iov_cpy Add API to copy part of iovec safely. Signed-off-by: Michael S. Tsirkin --- iov.c | 23 +++++++++++++++++++++++ iov.h | 9 +++++++++ 2 files changed, 32 insertions(+) diff --git a/iov.c b/iov.c index c6a66f0af..b7378bf7c 100644 --- a/iov.c +++ b/iov.c @@ -228,3 +228,26 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt, fprintf(fp, "\n"); } } + +unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt, + const struct iovec *iov, unsigned int iov_cnt, + size_t offset, size_t bytes) +{ + size_t len; + unsigned int i, j; + for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) { + if (offset >= iov[i].iov_len) { + offset -= iov[i].iov_len; + continue; + } + len = MIN(bytes, iov[i].iov_len - offset); + + dst_iov[j].iov_base = iov[i].iov_base + offset; + dst_iov[j].iov_len = len; + j++; + bytes -= len; + offset = 0; + } + assert(offset == 0); + return j; +} diff --git a/iov.h b/iov.h index a73569f94..34c8ec9fa 100644 --- a/iov.h +++ b/iov.h @@ -86,3 +86,12 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, */ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt, FILE *fp, const char *prefix, size_t limit); + +/* + * Partial copy of vector from iov to dst_iov (data is not copied). + * dst_iov overlaps iov at a specified offset. + * size of dst_iov is at most bytes. dst vector count is returned. + */ +unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt, + const struct iovec *iov, unsigned int iov_cnt, + size_t offset, size_t bytes); -- 2.39.2