lib/stream.h

   1 /*
   2  * Packet interface
   3  * Copyright (C) 1999 Kunihiro Ishiguro
   4  *
   5  * This file is part of GNU Zebra.
   6  *
   7  * GNU Zebra is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License as published by the
   9  * Free Software Foundation; either version 2, or (at your option) any
  10  * later version.
  11  *
  12  * GNU Zebra is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with GNU Zebra; see the file COPYING.  If not, write to the Free
  19  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  20  * 02111-1307, USA.
  21  */
  22
  23 #ifndef _ZEBRA_STREAM_H
  24 #define _ZEBRA_STREAM_H
  25
  26 #include "prefix.h"
  27
  28 /*
  29  * A stream is an arbitrary buffer, whose contents generally are assumed to
  30  * be in network order.
  31  *
  32  * A stream has the following attributes associated with it:
  33  *
  34  * - size: the allocated, invariant size of the buffer.
  35  *
  36  * - getp: the get position marker, denoting the offset in the stream where
  37  *         the next read (or 'get') will be from. This getp marker is
  38  *         automatically adjusted when data is read from the stream, the
  39  *         user may also manipulate this offset as they wish, within limits
  40  *         (see below)
  41  *
  42  * - endp: the end position marker, denoting the offset in the stream where
  43  *         valid data ends, and if the user attempted to write (or
  44  *         'put') data where that data would be written (or 'put') to.
  45  *
  46  * These attributes are all size_t values.
  47  *
  48  * Constraints:
  49  *
  50  * 1. getp can never exceed endp
  51  *
  52  * - hence if getp is equal to endp, there is no more valid data that can be
  53  *   gotten from the stream (though, the user may reposition getp to earlier in
  54  *   the stream, if they wish).
  55  *
  56  * 2. endp can never exceed size
  57  *
  58  * - hence, if endp is equal to size, then the stream is full, and no more
  59  *   data can be written to the stream.
  60  *
  61  * In other words the following must always be true, and the stream
  62  * abstraction is allowed internally to assert that the following property
  63  * holds true for a stream, as and when it wishes:
  64  *
  65  *        getp <= endp <= size
  66  *
  67  * It is the users responsibility to ensure this property is never violated.
  68  *
  69  * A stream therefore can be thought of like this:
  70  *
  71  *      ---------------------------------------------------
  72  *      |XXXXXXXXXXXXXXXXXXXXXXXX                         |
  73  *      ---------------------------------------------------
  74  *               ^               ^                        ^
  75  *               getp            endp                     size
  76  *
  77  * This shows a stream containing data (shown as 'X') up to the endp offset.
  78  * The stream is empty from endp to size. Without adjusting getp, there are
  79  * still endp-getp bytes of valid data to be read from the stream.
  80  *
  81  * Methods are provided to get and put to/from the stream, as well as
  82  * retrieve the values of the 3 markers and manipulate the getp marker.
  83  *
  84  * Note:
  85  * At the moment, newly allocated streams are zero filled. Hence, one can
  86  * use stream_forward_endp() to effectively create arbitrary zero-fill
  87  * padding. However, note that stream_reset() does *not* zero-out the
  88  * stream. This property should **not** be relied upon.
  89  *
  90  * Best practice is to use stream_put (<stream *>, NULL, <size>) to zero out
  91  * any part of a stream which isn't otherwise written to.
  92  */
  93
  94 /* Stream buffer. */
  95 struct stream
  96 {
  97   struct stream *next;
  98
  99   /* Remainder is ***private*** to stream
 100    * direct access is frowned upon!
 101    * Use the appropriate functions/macros
 102    */
 103   size_t getp;          /* next get position */
 104   size_t endp;          /* last valid data position */
 105   size_t size;          /* size of data segment */
 106   unsigned char *data; /* data pointer */
 107 };
 108
 109 /* First in first out queue structure. */
 110 struct stream_fifo
 111 {
 112   size_t count;
 113
 114   struct stream *head;
 115   struct stream *tail;
 116 };
 117
 118 /* Utility macros. */
 119 #define STREAM_SIZE(S)  ((S)->size)
 120   /* number of bytes which can still be written */
 121 #define STREAM_WRITEABLE(S) ((S)->size - (S)->endp)
 122   /* number of bytes still to be read */
 123 #define STREAM_READABLE(S) ((S)->endp - (S)->getp)
 124
 125 /* deprecated macros - do not use in new code */
 126 #define STREAM_PNT(S)   stream_pnt((S))
 127 #define STREAM_DATA(S)  ((S)->data)
 128 #define STREAM_REMAIN(S) STREAM_WRITEABLE((S))
 129
 130 /* Stream prototypes.
 131  * For stream_{put,get}S, the S suffix mean:
 132  *
 133  * c: character (unsigned byte)
 134  * w: word (two bytes)
 135  * l: long (two words)
 136  * q: quad (four words)
 137  */
 138 extern struct stream *stream_new (size_t);
 139 extern void stream_free (struct stream *);
 140 extern struct stream * stream_copy (struct stream *new, struct stream *src);
 141 extern struct stream *stream_dup (struct stream *);
 142 extern size_t stream_resize (struct stream *, size_t);
 143 extern size_t stream_get_getp (struct stream *);
 144 extern size_t stream_get_endp (struct stream *);
 145 extern size_t stream_get_size (struct stream *);
 146 extern u_char *stream_get_data (struct stream *);
 147
 148 extern void stream_set_getp (struct stream *, size_t);
 149 extern void stream_forward_getp (struct stream *, size_t);
 150 extern void stream_forward_endp (struct stream *, size_t);
 151
 152 /* steam_put: NULL source zeroes out size_t bytes of stream */
 153 extern void stream_put (struct stream *, void *, size_t);
 154 extern int stream_putc (struct stream *, u_char);
 155 extern int stream_putc_at (struct stream *, size_t, u_char);
 156 extern int stream_putw (struct stream *, u_int16_t);
 157 extern int stream_putw_at (struct stream *, size_t, u_int16_t);
 158 extern int stream_putl (struct stream *, u_int32_t);
 159 extern int stream_putl_at (struct stream *, size_t, u_int32_t);
 160 extern int stream_putq (struct stream *, uint64_t);
 161 extern int stream_putq_at (struct stream *, size_t, uint64_t);
 162 extern int stream_put_ipv4 (struct stream *, u_int32_t);
 163 extern int stream_put_in_addr (struct stream *, struct in_addr *);
 164 extern int stream_put_prefix (struct stream *, struct prefix *);
 165
 166 extern void stream_get (void *, struct stream *, size_t);
 167 extern u_char stream_getc (struct stream *);
 168 extern u_char stream_getc_from (struct stream *, size_t);
 169 extern u_int16_t stream_getw (struct stream *);
 170 extern u_int16_t stream_getw_from (struct stream *, size_t);
 171 extern u_int32_t stream_getl (struct stream *);
 172 extern u_int32_t stream_getl_from (struct stream *, size_t);
 173 extern uint64_t stream_getq (struct stream *);
 174 extern uint64_t stream_getq_from (struct stream *, size_t);
 175 extern u_int32_t stream_get_ipv4 (struct stream *);
 176
 177 #undef stream_read
 178 #undef stream_write
 179
 180 /* Deprecated: assumes blocking I/O.  Will be removed.
 181    Use stream_read_try instead.  */
 182 extern int stream_read (struct stream *, int, size_t);
 183
 184 /* Deprecated: all file descriptors should already be non-blocking.
 185    Will be removed.  Use stream_read_try instead. */
 186 extern int stream_read_unblock (struct stream *, int, size_t);
 187
 188 /* Read up to size bytes into the stream.
 189    Return code:
 190      >0: number of bytes read
 191      0: end-of-file
 192      -1: fatal error
 193      -2: transient error, should retry later (i.e. EAGAIN or EINTR)
 194    This is suitable for use with non-blocking file descriptors.
 195  */
 196 extern ssize_t stream_read_try(struct stream *s, int fd, size_t size);
 197
 198 extern ssize_t stream_recvmsg (struct stream *s, int fd, struct msghdr *,
 199                                int flags, size_t size);
 200 extern ssize_t stream_recvfrom (struct stream *s, int fd, size_t len,
 201                                 int flags, struct sockaddr *from,
 202                                 socklen_t *fromlen);
 203 extern size_t stream_write (struct stream *, u_char *, size_t);
 204
 205 /* reset the stream. See Note above */
 206 extern void stream_reset (struct stream *);
 207 extern int stream_flush (struct stream *, int);
 208 extern int stream_empty (struct stream *); /* is the stream empty? */
 209
 210 /* deprecated */
 211 extern u_char *stream_pnt (struct stream *);
 212
 213 /* Stream fifo. */
 214 extern struct stream_fifo *stream_fifo_new (void);
 215 extern void stream_fifo_push (struct stream_fifo *fifo, struct stream *s);
 216 extern struct stream *stream_fifo_pop (struct stream_fifo *fifo);
 217 extern struct stream *stream_fifo_head (struct stream_fifo *fifo);
 218 extern void stream_fifo_clean (struct stream_fifo *fifo);
 219 extern void stream_fifo_free (struct stream_fifo *fifo);
 220
 221 #endif /* _ZEBRA_STREAM_H */