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; 136 137 /* 138 * For external @iov (qemu_iovec_init_external()) or allocated @iov 139 * (qemu_iovec_init()), @size is the cumulative size of iovecs and 140 * @local_iov is invalid and unused. 141 * 142 * For embedded @iov (QEMU_IOVEC_INIT_BUF() or qemu_iovec_init_buf()), 143 * @iov is equal to &@local_iov, and @size is valid, as it has same 144 * offset and type as @local_iov.iov_len, which is guaranteed by 145 * static assertion below. 146 * 147 * @nalloc is always valid and is -1 both for embedded and external 148 * cases. It is included in the union only to ensure the padding prior 149 * to the @size field will not result in a 0-length array. 150 */ 151 union { 152 struct { 153 int nalloc; 154 struct iovec local_iov; 155 }; 156 struct { 157 char __pad[sizeof(int) + offsetof(struct iovec, iov_len)]; 158 size_t size; 159 }; 160 }; 161 } QEMUIOVector; 162 163 QEMU_BUILD_BUG_ON(offsetof(QEMUIOVector, size) != 164 offsetof(QEMUIOVector, local_iov.iov_len)); 165 166 #define QEMU_IOVEC_INIT_BUF(self, buf, len) \ 167 { \ 168 .iov = &(self).local_iov, \ 169 .niov = 1, \ 170 .nalloc = -1, \ 171 .local_iov = { \ 172 .iov_base = (void *)(buf), /* cast away const */ \ 173 .iov_len = (len), \ 174 }, \ 175 } 176 177 /* 178 * qemu_iovec_init_buf 179 * 180 * Initialize embedded QEMUIOVector. 181 * 182 * Note: "const" is used over @buf pointer to make it simple to pass 183 * const pointers, appearing in read functions. Then this "const" is 184 * cast away by QEMU_IOVEC_INIT_BUF(). 185 */ 186 static inline void qemu_iovec_init_buf(QEMUIOVector *qiov, 187 const void *buf, size_t len) 188 { 189 *qiov = (QEMUIOVector) QEMU_IOVEC_INIT_BUF(*qiov, buf, len); 190 } 191 192 static inline void *qemu_iovec_buf(QEMUIOVector *qiov) 193 { 194 /* Only supports embedded iov */ 195 assert(qiov->nalloc == -1 && qiov->iov == &qiov->local_iov); 196 197 return qiov->local_iov.iov_base; 198 } 199 200 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint); 201 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov); 202 void qemu_iovec_init_extended( 203 QEMUIOVector *qiov, 204 void *head_buf, size_t head_len, 205 QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len, 206 void *tail_buf, size_t tail_len); 207 void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source, 208 size_t offset, size_t len); 209 int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len); 210 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len); 211 void qemu_iovec_concat(QEMUIOVector *dst, 212 QEMUIOVector *src, size_t soffset, size_t sbytes); 213 size_t qemu_iovec_concat_iov(QEMUIOVector *dst, 214 struct iovec *src_iov, unsigned int src_cnt, 215 size_t soffset, size_t sbytes); 216 bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t qiov_offeset, size_t bytes); 217 void qemu_iovec_destroy(QEMUIOVector *qiov); 218 void qemu_iovec_reset(QEMUIOVector *qiov); 219 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset, 220 void *buf, size_t bytes); 221 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset, 222 const void *buf, size_t bytes); 223 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset, 224 int fillc, size_t bytes); 225 ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b); 226 void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf); 227 void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes); 228 229 #endif 230