xref: /openbmc/qemu/include/qemu/iov.h (revision ab938ae4)
1 /*
2  * Helpers for using (partial) iovecs.
3  *
4  * Copyright (C) 2010 Red Hat, Inc.
5  *
6  * Author(s):
7  *  Amit Shah <amit.shah@redhat.com>
8  *  Michael Tokarev <mjt@tls.msk.ru>
9  *
10  * This work is licensed under the terms of the GNU GPL, version 2.  See
11  * the COPYING file in the top-level directory.
12  */
13 
14 #ifndef IOV_H
15 #define IOV_H
16 
17 /**
18  * count and return data size, in bytes, of an iovec
19  * starting at `iov' of `iov_cnt' number of elements.
20  */
21 size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt);
22 
23 /**
24  * Copy from single continuous buffer to scatter-gather vector of buffers
25  * (iovec) and back like memcpy() between two continuous memory regions.
26  * Data in single continuous buffer starting at address `buf' and
27  * `bytes' bytes long will be copied to/from an iovec `iov' with
28  * `iov_cnt' number of elements, starting at byte position `offset'
29  * within the iovec.  If the iovec does not contain enough space,
30  * only part of data will be copied, up to the end of the iovec.
31  * Number of bytes actually copied will be returned, which is
32  *  min(bytes, iov_size(iov)-offset)
33  * `Offset' must point to the inside of iovec.
34  */
35 size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
36                          size_t offset, const void *buf, size_t bytes);
37 size_t iov_to_buf_full(const struct iovec *iov, const unsigned int iov_cnt,
38 		       size_t offset, void *buf, size_t bytes);
39 
40 static inline size_t
41 iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
42              size_t offset, const void *buf, size_t bytes)
43 {
44     if (__builtin_constant_p(bytes) && iov_cnt &&
45         offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
46         memcpy(iov[0].iov_base + offset, buf, bytes);
47         return bytes;
48     } else {
49         return iov_from_buf_full(iov, iov_cnt, offset, buf, bytes);
50     }
51 }
52 
53 static inline size_t
54 iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
55            size_t offset, void *buf, size_t bytes)
56 {
57     if (__builtin_constant_p(bytes) && iov_cnt &&
58         offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
59         memcpy(buf, iov[0].iov_base + offset, bytes);
60         return bytes;
61     } else {
62         return iov_to_buf_full(iov, iov_cnt, offset, buf, bytes);
63     }
64 }
65 
66 /**
67  * Set data bytes pointed out by iovec `iov' of size `iov_cnt' elements,
68  * starting at byte offset `start', to value `fillc', repeating it
69  * `bytes' number of times.  `Offset' must point to the inside of iovec.
70  * If `bytes' is large enough, only last bytes portion of iovec,
71  * up to the end of it, will be filled with the specified value.
72  * Function return actual number of bytes processed, which is
73  * min(size, iov_size(iov) - offset).
74  */
75 size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
76                   size_t offset, int fillc, size_t bytes);
77 
78 /*
79  * Send/recv data from/to iovec buffers directly
80  *
81  * `offset' bytes in the beginning of iovec buffer are skipped and
82  * next `bytes' bytes are used, which must be within data of iovec.
83  *
84  *   r = iov_send_recv(sockfd, iov, iovcnt, offset, bytes, true);
85  *
86  * is logically equivalent to
87  *
88  *   char *buf = malloc(bytes);
89  *   iov_to_buf(iov, iovcnt, offset, buf, bytes);
90  *   r = send(sockfd, buf, bytes, 0);
91  *   free(buf);
92  *
93  * For iov_send_recv() _whole_ area being sent or received
94  * should be within the iovec, not only beginning of it.
95  */
96 ssize_t iov_send_recv(int sockfd, const struct iovec *iov, unsigned iov_cnt,
97                       size_t offset, size_t bytes, bool do_send);
98 #define iov_recv(sockfd, iov, iov_cnt, offset, bytes) \
99   iov_send_recv(sockfd, iov, iov_cnt, offset, bytes, false)
100 #define iov_send(sockfd, iov, iov_cnt, offset, bytes) \
101   iov_send_recv(sockfd, iov, iov_cnt, offset, bytes, true)
102 
103 /**
104  * Produce a text hexdump of iovec `iov' with `iov_cnt' number of elements
105  * in file `fp', prefixing each line with `prefix' and processing not more
106  * than `limit' data bytes.
107  */
108 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
109                  FILE *fp, const char *prefix, size_t limit);
110 
111 /*
112  * Partial copy of vector from iov to dst_iov (data is not copied).
113  * dst_iov overlaps iov at a specified offset.
114  * size of dst_iov is at most bytes. dst vector count is returned.
115  */
116 unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
117                  const struct iovec *iov, unsigned int iov_cnt,
118                  size_t offset, size_t bytes);
119 
120 /*
121  * Remove a given number of bytes from the front or back of a vector.
122  * This may update iov and/or iov_cnt to exclude iovec elements that are
123  * no longer required.
124  *
125  * The number of bytes actually discarded is returned.  This number may be
126  * smaller than requested if the vector is too small.
127  */
128 size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
129                          size_t bytes);
130 size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
131                         size_t bytes);
132 
133 typedef struct QEMUIOVector {
134     struct iovec *iov;
135     int niov;
136     int nalloc;
137     size_t size;
138 } QEMUIOVector;
139 
140 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint);
141 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov);
142 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);
143 void qemu_iovec_concat(QEMUIOVector *dst,
144                        QEMUIOVector *src, size_t soffset, size_t sbytes);
145 size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
146                              struct iovec *src_iov, unsigned int src_cnt,
147                              size_t soffset, size_t sbytes);
148 bool qemu_iovec_is_zero(QEMUIOVector *qiov);
149 void qemu_iovec_destroy(QEMUIOVector *qiov);
150 void qemu_iovec_reset(QEMUIOVector *qiov);
151 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
152                          void *buf, size_t bytes);
153 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
154                            const void *buf, size_t bytes);
155 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
156                          int fillc, size_t bytes);
157 ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b);
158 void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf);
159 void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes);
160 
161 #endif
162