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iov: add iov_cpy 

Add API to copy part of iovec safely.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2012-09-24 13:02:52 +02:00
parent e35e23f655
commit d336336c81
2 changed files with 32 additions and 0 deletions
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23
iov.c
View File

@ -228,3 +228,26 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
fprintf(fp, "\n"); 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;
}

9
iov.h
View File

@ -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, void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
FILE *fp, const char *prefix, size_t limit); 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);