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29 * @(#)mbuf.h 8.3 (Berkeley) 1/21/94
30 * mbuf.h,v 1.9 1994/11/14 13:54:20 bde Exp
36 #define m_freem m_free
39 #define MINCSIZE 4096 /* Amount to increase mbuf if too small */
42 * Macros for type conversion
43 * mtod(m,t) - convert mbuf pointer to data pointer of correct type
45 #define mtod(m,t) ((t)(m)->m_data)
47 /* XXX About mbufs for slirp:
48 * Only one mbuf is ever used in a chain, for each "cell" of data.
49 * m_nextpkt points to the next packet, if fragmented.
50 * If the data is too large, the M_EXT is used, and a larger block
51 * is alloced. Therefore, m_free[m] must check for M_EXT and if set
52 * free the m_ext. This is inefficient memory-wise, but who cares.
55 /* XXX should union some of these! */
56 /* header at beginning of each mbuf: */
58 struct mbuf
*mh_next
; /* Linked list of mbufs */
60 struct mbuf
*mh_nextpkt
; /* Next packet in queue/record */
61 struct mbuf
*mh_prevpkt
; /* Flags aren't used in the output queue */
62 int mh_flags
; /* Misc flags */
64 int mh_size
; /* Size of data */
67 caddr_t mh_data
; /* Location of data */
68 int mh_len
; /* Amount of data in this mbuf */
72 * How much room is in the mbuf, from m_data to the end of the mbuf
74 #define M_ROOM(m) ((m->m_flags & M_EXT)? \
75 (((m)->m_ext + (m)->m_size) - (m)->m_data) \
77 (((m)->m_dat + (m)->m_size) - (m)->m_data))
80 * How much free room there is
82 #define M_FREEROOM(m) (M_ROOM(m) - (m)->m_len)
83 #define M_TRAILINGSPACE M_FREEROOM
88 char m_dat_
[1]; /* ANSI don't like 0 sized arrays */
93 #define m_next m_hdr.mh_next
94 #define m_prev m_hdr.mh_prev
95 #define m_nextpkt m_hdr.mh_nextpkt
96 #define m_prevpkt m_hdr.mh_prevpkt
97 #define m_flags m_hdr.mh_flags
98 #define m_len m_hdr.mh_len
99 #define m_data m_hdr.mh_data
100 #define m_size m_hdr.mh_size
101 #define m_dat M_dat.m_dat_
102 #define m_ext M_dat.m_ext_
103 #define m_so m_hdr.mh_so
105 #define ifq_prev m_prev
106 #define ifq_next m_next
107 #define ifs_prev m_prevpkt
108 #define ifs_next m_nextpkt
111 #define M_EXT 0x01 /* m_ext points to more (malloced) data */
112 #define M_FREELIST 0x02 /* mbuf is on free list */
113 #define M_USEDLIST 0x04 /* XXX mbuf is on used list (for dtom()) */
114 #define M_DOFREE 0x08 /* when m_free is called on the mbuf, free()
115 * it rather than putting it on the free list */
117 extern struct mbuf m_freelist
, m_usedlist
;
119 void m_init
_P((void));
120 struct mbuf
* m_get
_P((void));
121 void m_free
_P((struct mbuf
*));
122 void m_cat
_P((register struct mbuf
*, register struct mbuf
*));
123 void m_inc
_P((struct mbuf
*, int));
124 void m_adj
_P((struct mbuf
*, int));
125 int m_copy
_P((struct mbuf
*, struct mbuf
*, int, int));
126 struct mbuf
* dtom
_P((void *));