1.\" -*- nroff -*- 2.\" 3.\" Copyright (c) 2001 Boris Popov 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. 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25.\" $FreeBSD$ 26.\" 27.Dd February 28, 2001 28.Dt MDCHAIN 9 29.Os 30.Sh NAME 31.Nm mdchain , 32.Nm md_initm , 33.Nm md_done , 34.Nm md_append_record , 35.Nm md_next_record , 36.Nm md_get_uint8 , 37.Nm md_get_uint16 , 38.Nm md_get_uint16be , 39.Nm md_get_uint16le , 40.Nm md_get_uint32 , 41.Nm md_get_uint32be , 42.Nm md_get_uint32le , 43.Nm md_get_int64 , 44.Nm md_get_int64be , 45.Nm md_get_int64le , 46.Nm md_get_mem , 47.Nm md_get_mbuf , 48.Nm md_get_uio 49.Nd "set of functions to dissect an mbuf chain to various data types" 50.Sh SYNOPSIS 51.Cd options LIBMCHAIN 52.Li kldload libmchain 53.Pp 54.In sys/param.h 55.In sys/uio.h 56.In sys/mchain.h 57.Ft void 58.Fn md_initm "struct mdchain *mdp" "struct mbuf *m" 59.Ft void 60.Fn md_done "struct mdchain *mdp" 61.Ft void 62.Fn md_append_record "struct mdchain *mdp" "struct mbuf *top" 63.Ft int 64.Fn md_next_record "struct mdchain *mdp" 65.Ft int 66.Fn md_get_uint8 "struct mdchain *mdp" "uint8_t *x" 67.Ft int 68.Fn md_get_uint16 "struct mdchain *mdp" "uint16_t *x" 69.Ft int 70.Fn md_get_uint16be "struct mdchain *mdp" "uint16_t *x" 71.Ft int 72.Fn md_get_uint16le "struct mdchain *mdp" "uint16_t *x" 73.Ft int 74.Fn md_get_uint32 "struct mdchain *mdp" "uint32_t *x" 75.Ft int 76.Fn md_get_uint32be "struct mdchain *mdp" "uint32_t *x" 77.Ft int 78.Fn md_get_uint32le "struct mdchain *mdp" "uint32_t *x" 79.Ft int 80.Fn md_get_int64 "struct mdchain *mdp" "int64_t *x" 81.Ft int 82.Fn md_get_int64be "struct mdchain *mdp" "int64_t *x" 83.Ft int 84.Fn md_get_int64le "struct mdchain *mdp" "int64_t *x" 85.Ft int 86.Fn md_get_mem "struct mdchain *mdp" "caddr_t target" "int size" "int type" 87.Ft int 88.Fn md_get_mbuf "struct mdchain *mdp" "int size" "struct mbuf **m" 89.Ft int 90.Fn md_get_uio "struct mdchain *mdp" "struct uio *uiop" "int size" 91.Sh DESCRIPTION 92These functions are used to decompose mbuf chains to various data types. 93The 94.Vt mdchain 95structure is used as a working context 96and should be initialized through a call of the 97.Fn mb_initm 98function. 99It has the following fields: 100.Bl -tag -width "md_top" 101.It Va "md_top" 102.Pq Vt "struct mbuf *" 103A pointer to the top of the parsed mbuf chain. 104.It Va md_cur 105.Pq Vt "struct mbuf *" 106A pointer to the currently parsed mbuf. 107.It Va md_pas 108.Pq Vt int 109Offset in the current mbuf. 110.El 111.Pp 112The 113.Fn md_done 114function disposes of an mbuf chain pointed to by the 115.Fa mdp->md_top 116field and sets the field to 117.Dv NULL . 118.Pp 119The 120.Fn md_append_record 121appends a new mbuf chain using 122.Va m_nextpkt 123field to form a single linked list of mbuf chains. 124If the 125.Fa mdp->md_top 126field is 127.Dv NULL , 128then this function behaves exactly as the 129.Fn md_initm 130function. 131.Pp 132The 133.Fn md_next_record 134function extracts the next mbuf chain and disposes the current one, if any. 135For a new mbuf chain it calls the 136.Fn md_initm 137function. 138If there is no data left the function returns 139.Er ENOENT . 140.Pp 141All 142.Fn md_get_* 143functions perform an actual copy of the data from an mbuf chain. 144Functions which have 145.Cm le 146or 147.Cm be 148suffixes will perform conversion to the little\- or big\-endian data formats. 149.Pp 150.Fn md_get_mem 151function copies 152.Fa size 153bytes of data specified by the 154.Fa source 155argument from an mbuf chain. 156The 157.Fa type 158argument specifies the method used to perform a copy, 159and can be one of the following: 160.Bl -tag -width ".Dv MB_MINLINE" 161.It Dv MB_MSYSTEM 162Use the 163.Fn bcopy 164function. 165.It Dv MB_MUSER 166Use the 167.Xr copyin 9 168function. 169.It Dv MB_MINLINE 170Use an 171.Dq inline 172loop which does not call any function. 173.El 174.Pp 175If 176.Fa target 177is 178.Dv NULL , 179an actual copy is not performed 180and the function just skips the given number of bytes. 181.Sh RETURN VALUES 182All 183.Ft int 184functions return zero if successful, 185otherwise an error code is returned. 186.Pp 187.Em Note : 188after failure of any function, 189an mbuf chain is left in the broken state and only the 190.Fn md_done 191function can safely be called to destroy it. 192.Sh EXAMPLES 193.Bd -literal 194struct mdchain *mdp; 195struct mbuf *m; 196uint16_t length; 197uint8_t byte; 198 199receive(so, &m); 200md_initm(mdp, m); 201if (md_get_uint8(mdp, &byte) != 0 || 202 md_get_uint16le(mdp, &length) != 0) 203 error = EBADRPC; 204mb_done(mdp); 205.Ed 206.Sh SEE ALSO 207.Xr mbchain 9 , 208.Xr mbuf 9 209.Sh AUTHORS 210This manual page was written by 211.An Boris Popov Aq Mt bp@FreeBSD.org . 212