.\" $Id: JAM_ReadMsgHeader.3,v 1.1 2002/11/09 00:37:16 raorn Exp $
.\"
.TH JAM_ReadMsgHeader 3 2002-11-07 "" "JAM subroutine library"
.SH NAME
JAM_ReadMsgHeader \- Read a message\'s header and its subfields
.SH SYNOPSIS
.nf
.B #include <jamlib/jam.h>

.BI "int JAM_ReadMsgHeader(s_JamBase*       " Base_PS ","
.BI "                      ulong            " MsgNo_I ","
.BI "                      s_JamMsgHeader*  " Header_PS ","
.BI "                      s_JamSubPacket** " Subfields_PPS ");"
.RE
.fi
.SH DESCRIPTION
Reads a message header and (optionally) the message header
subfields.
.SS Arguments
.TP
.I Base_PS
The message base to use
.TP
.I MsgNo_I
The message number, i.e. the absolute position of the message in the message
base. Message 0 is the first message.
.TP
.I Header_PS
A pointer to a message header structure where the message header will be
stored.
.TP
.I Subfields_PPS
A pointer to a subpacket pointer, where the subfield packet handle will be
stored.  If this parameter is NULL, no subfields are read.
.SH "RETURN VALUE"
.TP
.B 0
if successful
.TP
.B JAM_IO_ERROR
if an I/O error occured. See
.BR JAM_Errno (3)
.TP
.B JAM_NO_MEMORY
if a memory allocation failed
.TP
.B JAM_NO_MESSAGE
if message has been removed
.TP
.B JAM_CORRUPT_MSG
if message subfields are corrupted
.SH EXAMPLES
.nf
s_JamMsgHeader  Header_S;
s_JamSubPacket* SubPack_PS
int             Result_I;

Result_I = JAM_ReadMsgHeader(0, &Header_S, &SubPack_PS);
if (Result_I)
  printf("JAM_ReadMsgHeader returned %d.\\n", Result_I);
.fi
.SH AUTHOR
This manual page was created by Sir Raorn <raorn@altlinux.ru>,
based on original JAMlib documentation by Bjorn Stenberg
<bjorn@haxx.nu> and Johan Billing <billing@df.lth.se>.
.SH SEE ALSO
.BR jamlib (3),
.BR JAM_AddMessage (3),
.BR JAM_AddEmptyMessage (3),
.BR JAM_ChangeMsgHeader (3),
.BR JAM_Errno (3)
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