diff options
Diffstat (limited to 'iov.c')
| -rw-r--r-- | iov.c | 129 |
1 files changed, 91 insertions, 38 deletions
@@ -26,7 +26,8 @@ #include "iov.h" -/* iov_skip_bytes() - Skip leading bytes of an IO vector +/** + * iov_skip_bytes() - Skip leading bytes of an IO vector * @iov: IO vector * @n: Number of entries in @iov * @skip: Number of leading bytes of @iov to skip @@ -56,8 +57,8 @@ 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_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. @@ -68,7 +69,6 @@ size_t iov_skip_bytes(const struct iovec *iov, size_t n, * * Returns: The number of bytes successfully copied. */ -/* cppcheck-suppress unusedFunction */ size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt, size_t offset, const void *buf, size_t bytes) { @@ -97,8 +97,8 @@ 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_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. @@ -137,8 +137,8 @@ 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 the total size of a scatter/gather I/O vector + * (struct iovec). * * @iov: Pointer to the array of struct iovec describing the * scatter/gather I/O vector. @@ -158,40 +158,93 @@ size_t iov_size(const struct iovec *iov, size_t iov_cnt) } /** - * iov_copy - Copy data from one scatter/gather I/O vector (struct iovec) to - * another. - * - * @dst_iov: Pointer to the destination array of struct iovec describing - * the scatter/gather I/O vector to copy to. - * @dst_iov_cnt: Number of elements in the destination iov array. - * @iov: Pointer to the source array of struct iovec describing - * the scatter/gather I/O vector to copy from. - * @iov_cnt: Number of elements in the source iov array. - * @offset: Offset within the source iov from where copying should start. - * @bytes: Total number of bytes to copy from iov to dst_iov. - * - * Returns: The number of elements successfully copied to the destination - * iov array. + * iov_tail_prune() - Remove any unneeded buffers from an IOV tail + * @tail: IO vector tail (modified) + * + * If an IOV tail's offset is large enough, it may not include any bytes from + * the first (or first several) buffers in the underlying IO vector. Modify the + * tail's representation so it contains the same logical bytes, but only + * includes buffers that are actually needed. This will avoid stepping through + * unnecessary elements of the underlying IO vector on future operations. + * + * Return: true if the tail still contains any bytes, otherwise false */ -/* cppcheck-suppress unusedFunction */ -unsigned iov_copy(struct iovec *dst_iov, size_t dst_iov_cnt, - const struct iovec *iov, size_t iov_cnt, - size_t offset, size_t bytes) +bool iov_tail_prune(struct iov_tail *tail) { - unsigned int i, j; + size_t i; - i = iov_skip_bytes(iov, iov_cnt, offset, &offset); + i = iov_skip_bytes(tail->iov, tail->cnt, tail->off, &tail->off); + tail->iov += i; + tail->cnt -= i; - /* copying data */ - for (j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) { - size_t len = MIN(bytes, iov[i].iov_len - offset); + return !!tail->cnt; +} - dst_iov[j].iov_base = (char *)iov[i].iov_base + offset; - dst_iov[j].iov_len = len; - j++; - bytes -= len; - offset = 0; - } +/** + * iov_tail_size - Calculate the total size of an IO vector tail + * @tail: IO vector tail + * + * Returns: The total size in bytes. + */ +size_t iov_tail_size(struct iov_tail *tail) +{ + iov_tail_prune(tail); + return iov_size(tail->iov, tail->cnt) - tail->off; +} + +/** + * iov_peek_header_() - Get pointer to a header from an IOV tail + * @tail: IOV tail to get header from + * @len: Length of header to get, in bytes + * @align: Required alignment of header, in bytes + * + * @tail may be pruned, but will represent the same bytes as before. + * + * Returns: Pointer to the first @len logical bytes of the tail, NULL if that + * overruns the IO vector, is not contiguous or doesn't have the + * requested alignment. + */ +/* cppcheck-suppress [staticFunction,unmatchedSuppression] */ +void *iov_peek_header_(struct iov_tail *tail, size_t len, size_t align) +{ + char *p; + + if (!iov_tail_prune(tail)) + return NULL; /* Nothing left */ + + if (tail->off + len < tail->off) + return NULL; /* Overflow */ + + if (tail->off + len > tail->iov[0].iov_len) + return NULL; /* Not contiguous */ + + p = (char *)tail->iov[0].iov_base + tail->off; + if ((uintptr_t)p % align) + return NULL; /* not aligned */ + + return p; +} + +/** + * iov_remove_header_() - Remove a header from an IOV tail + * @tail: IOV tail to remove header from (modified) + * @len: Length of header to remove, in bytes + * @align: Required alignment of header, in bytes + * + * On success, @tail is updated so that it longer includes the bytes of the + * returned header. + * + * Returns: Pointer to the first @len logical bytes of the tail, NULL if that + * overruns the IO vector, is not contiguous or doesn't have the + * requested alignment. + */ +void *iov_remove_header_(struct iov_tail *tail, size_t len, size_t align) +{ + char *p = iov_peek_header_(tail, len, align); + + if (!p) + return NULL; - return j; + tail->off = tail->off + len; + return p; } |