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magicka/jamlib/jamlib.doc
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JAMLIB
A JAM subroutine library
by Björn Stenberg
modifications by Johan Billing
version 1.3.2
2004-07-10
GENERAL
=======
History
-------
JAMLIB 1.0 was originally released by Björn Stenberg 1996-03-06. Since
the original license did not permit modification of the library,
Johan Billing contacted Björn Stenberg and asked him to change the
license. Björn Stenberg agreed to change the license to the GNU Lesser
General Public License 1999-12-21 (see the accompanying file LICENSE).
After that, some minor additions and bug fixes were made by Johan
Billing and JAMLIB 1.1 was released under the new license.
Changes in 1.3.2:
* Updated the Win32-specific parts of the code to make it compatible with
newer versions of MinGW (tested with 3.1.0-1).
Changes in 1.3.1:
* Backported the following bugfixes and improvements from JAMLIB 1.4.7 while
retaining the platform-independence and high portability of the early
versions of JAMLIB.
- JAMLIB now uses calloc() instead of malloc() followed by memset()
- JAM_OpenMB() and JAM_CreateMB() will set (*NewArea_PPS) to NULL if
calloc() failed
- JAM_CreateMB() no longer attempts indefinitely to lock the newly created
messagebase. If the first attempt fails, it will return an error.
- jam_Lock() now sets Base_PS->Errno under Linux
- JAM_NewSubPacket() and JAM_PutSubField() would give memory leaks under
conditions of low memory conditions. Fixed.
- JAM_ReadMsgHeader() would give memory leaks on failure. Fixed.
- Added JAM_DeleteMessage()
Big thanks to Sir Raorn (and others?) for finding and fixing these bugs!
* JAM_CreateMB() would never unlock or close the newly created messagebase
upon failure. Fixed.
* Improved handling of ActiveMsgs counter. JAM_AddMessage() now only
increases ActiveMsgs if the added message does not have MSG_DELETED set.
JAM_ChangeMsgHeader() decreases ActiveMsgs if MSG_DELETED is set and the
message wasn't already deleted. JAM_DeleteMessage() now only decreases
ActiveMsgs if the message wasn't already deleted.
* Updated the documentation to reflect the need to free() memory after
JAM_CloseMB() and failed calls to JAM_OpenMB() and JAM_CreateMB().
* Eliminated compiler warnings
Changes in 1.3:
* JAM_AddMessage() would fail when trying to add an empty message
to the messagebase under Linux. Fixed.
Changes in 1.2:
* Since JAM_GetSubField() is not reentrant and cannot be used in
multi-threaded applications, JAM_GetSubField_R() was added as a
replacement for cases where a reentrant function is needed.
Changes in 1.1:
* Added support for Win32 and Linux
* Added JAM_AddEmptyMessage()
* Rewrote the Makefiles
* Rewrote the CRC32 routine
* Fixed broken JAM_FindUser()
* Fixed broken JAM_GetSubfield()
* Changed JAM_OpenMB so that files are opened in binary mode. This is
necessary to use JAMLIB under Windows.
* Improved JAM_ReadMsgHeader() to give the error JAM_NO_MESSAGE if
the message no longer exists in the messagebase and JAM_CORRUPT_MSG
if the subfields of the message have been corrupted.
* Improved portability by changing JAMLIB so that it no longer reads
and writes stuctures directly using fread() and fwrite().
* Improved ANSI-C compatibilty by no longer including the non-ANSI
header file memory.h and using feof() to check for EOF instead of
errno == EPASTEOF.
* Added an #ifdef so that ushort and ulong are no longer defined in
jam.h when compiling under Linux. These are normally already defined
in the standard header files.
License
-------
JAMLIB - A JAM subroutine library
Copyright (C) 1999 Björn Stenberg
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Description
-----------
These are a collection of subroutines that encapsulate much of the
format-specific and tedious details of the JAM message base format. The
idea is that application programmers by using these routines can
concentrate on the more high-level issues of their programs instead of
worrying about their JAM routines.
I [Björn Stenberg] wrote these routines primarily because I needed
them myself. I was trying to implement JAM support in my FrexxLink BBS
system and was frustrated by the poor level of documentation supplied in
the JAMAPI archive distributed by the JAM authors. Finally, I dove into
the JAMAPI source code in a desperate attempt at finding out how to use it.
To my despair, I discovered that the JAMAPI is targeted at a very low level.
I would need to implement a lot of JAM-handling code into my own program.
This library is an attempt to do two things:
Firstly, provide an, at least sparingly, _documented_ API, allowing
application programmers to easily implement JAM into their programs.
Secondly, raise the level of functionality above that of the original
JAMAPI package, so that the application programmer does not have to learn
and understand all the internals of the JAM message base format to
implement support for it.
I have not succeded completely on any of the two points, of course.
Documentation can never be too good, and there are still a few things about
JAM you must know in order to use it. But I think I have made it somewhat
easier than perhaps was the case before.
References
----------
If you are extra curious about the JAM message format, I suggest you get
a hold of an archive called JAMAPI.ARJ. That archive contains a file called
JAM.DOC which is the file I have used as reference for the development of
these routines.
Credits
-------
All original code except for the CRC32 routine was written by Björn
Stenberg. The CRC32 code was rewritten by Johan Billing for JAMLIB 1.1
to replace the original CRC32 code whose origin and copyright was unclear.
The jam.h header file is a compilation of the best from the various header
files in the JAMAPI package with some of additions by Björn Stenberg as well.
Additions and modifications by Johan Billing.
The JAM message base proposal is:
JAM(mbp) - Copyright 1993 Joaquim Homrighausen, Andrew Milner,
Mats Birch, Mats Wallin.
ALL RIGHTS RESERVED
Contact Information
-------------------
For questions about JAMLIB, please contact:
Johan Billing
E-mail: billing@df.lth.se
If you wish to contact Björn Stenberg, his current e-mail address (as of
1999-12-21) is bjorn@haxx.nu.
THE LIBRARY
===========
The Source Code
---------------
I made a point of making this library as system independant as I could.
Only one function needs to be altered when porting this to another system:
The file locking. ANSI C does not include file locking so there is not much
I can do about it.
The choice of C over C++ is a part of this philosophy aswell. More
systems have C compilers than C++ compilers, and more people know C than
C++. Also, converting this library to a C++ class should be fairly simple.
If you do, send me a copy.
I use some naming conventions throughout the code and in the examples.
These are invented by myself as a reaction to the stunningly ugly and
hard-to-read Hungarian Notation promoted by some people. The rules of my
notation are simple:
* All library-global identifiers are prefixed with 'JAM_'. All
file-global identifiers are prefixed with 'jam_'. Local identifiers do
not have prefixes.
* All variables have a suffix describing their basic type. Suffixes used
in this library are:
_I - integer (int Example_I)
_C - character (char Example_C)
_S - struct (struct Example_S)
_P - pointer (void* Example_P)
_A - array
Suffixes are then combined, to show the correct type:
_PI - pointer to integer (int* Example_PI)
_PC - pointer to char (char* Example_PC)
_AC - array of char (char Example_AC[x])
_PPS - pointer to pointer to struct (struct** Example_PPS)
* Functions do not have suffixes
The whole idea is that it is quicker to read and comprehend a variable
called 'Text_PC' than one called 'pszText'. We read from left to right, and
thus the most important information - the name - should be the leftmost
data in the word. The variable type is additional information and is
therefore added to the end where it does not disturb the reader.
The Functions
-------------
The library is divided into five groups:
* Message base functions
* Message functions
* Subfield functions
* LastRead functions
* Miscellanous functions
--------------------------------------------------------------------------
Message base functions
----------------------
These functions handle JAM message bases, by opening, locking, scanning
etc the contents of a message base. These are fairly straight-forward and
simple routines that you should have little, if any, trouble with.
A message base is identified by a message base handle, which is obtained
from either JAM_OpenMB() och JAM_CreateMB(). All functions that read or
write from the message base take this handle as parameter, to know which
message base to use.
================================
JAM_OpenMB - Open a message base
================================
Syntax
int JAM_OpenMB( uchar* Basename_PC, t_JamBase** NewBase_PPS );
Description
Opens a message base. Only one message base can be open at a time.
Parameters
Basename_PC The path and base filename of the message base.
"Base filename" means the filename without the
JAM-specific extension.
NewBase_PPS A pointer to a message base handle where the new
message base handle will be written. On error you
must free() this memory if (*NewBase_PPS) not NULL.
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_BAD_PARAM if NewBas_PPS is NULL
Example
{
int Result_I;
Result_I = JAM_OpenMB( "c:\\jam\\mybase", &Base_PS );
if ( Result_I )
printf("JAM_OpenMB returned %d.\n", Result_I );
}
================================
JAM_CloseMB - Close message base
================================
Syntax
int JAM_CloseMB( Base_PS );
Description
Unlocks (if locked) and closes the currently open message base.
Parameters
Base_PS The message base to close. Note, that you must
free() this memory by yourself.
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_LOCK_FAILED if the message base could not be unlocked
Example
{
int Result_I;
Result_I = JAM_CloseMB( Base_PS );
if ( Result_I )
printf("JAM_CloseMB returned %d.\n", Result_I );
}
========================================
JAM_CreateMB - Create a new message base
========================================
Syntax
int JAM_CreateMB( uchar* Basename_PC,
ulong BaseMsg_I,
s_JamBase** NewBase_PPS );
Description
Creates the necessary files for a new message base and writes a
new message base header.
If the message base already exists, its contents are destroyed.
Parameters
Basename_PC The path and base filename of the new message base.
BaseMsg_I The base message number (first message #) for the
new message base. This number is used when
calculating new messages' unique message number. It
should not be set to 0.
NewBase_PPS A pointer to a message base handle where the new
message base handle will be written. On error you
must free() this memory if (*NewBase_PPS) not NULL.
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_BAD_PARAM if BaseMsg_I is 0 or NewBase_PPS is NULL
Example
{
int Result_I;
Result_I = JAM_CreateMB( "c:\\jam\\mybase", 1, &Base_PS );
if ( Result_I )
printf("JAM_CreateMB returned %d.\n", Result_I );
}
====================================
JAM_RemoveMB - Remove a message base
====================================
Syntax
int JAM_RemoveMB( ErrorBase_PS, uchar* Basename_PC );
Description
Deletes all files associated with a message base. No checking is
done as to whether the message base is currently open or not.
Parameters
ErrorBase_PS The message base in which to store the I/O error,
if any. This parameter does *NOT* specify the
message to be removed, it is only used for error
tracking purposes. If an i/o error occurs when
removing the message base files, this message base
handler will simply hold the error code.
Basename_PC The path and base filename of the message base to
remove.
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_BAD_PARAM if ErrorBase_PS is NULL
Example
{
int Result_I;
Result_I = JAM_RemoveMB( Base_PS, "c:\\jam\\mybase" );
if ( Result_I ) {
printf("JAM_RemoveMB returned %d.\n", Result_I );
if ( Result_I == JAM_IO_ERROR )
printf( "i/o error %d\n", JAM_Errno( ErrorBase_PS ) );
}
}
===================================================
JAM_LockMB - Lock message base for exclusive access
===================================================
Syntax
int JAM_LockMB( t_JamBase* Base_PS );
Description
Locks the currently open message base so that no other programs may
modify it. The message base should be locked for only small periods
of time, or the performance of tossers and other software may be
affected.
Parameters
Base_PS The message base to lock
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_LOCK_FAILED if the message base is currently locked by another
process
JAM_BAD_PARAM if Base_PS is NULL
Example
{
int Result_I;
while ( 1 ) {
Result_I = JAM_LockMB( Base_PS );
if ( Result_I ) {
if ( Result_I == JAM_LOCK_FAILED )
/* base locked by someone else, wait for unlock */
sleep( 1 );
else {
/* error */
printf("JAM_LockMB returned %d.\n", Result_I );
return -1;
}
}
}
}
==================================
JAM_UnlockMB - Unlock message base
==================================
Syntax
int JAM_UnlockMB( s_JamBase* Base_PS );
Description
Unlocks message base, allowing other programs to modify it.
Parameters
Base_PS The message base to unlock
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_BAD_PARAM if Base_PS is NULL
Example
{
int Result_I;
Result_I = JAM_UnlockMB( Base_PS );
if ( Result_I )
printf("JAM_UnlockMB returned %d.\n", Result_I );
}
===========================================
JAM_ReadMBHeader - Read message base header
===========================================
Syntax
int JAM_ReadMBHeader( s_JamBase* Base_PS,
s_JamBaseHeader* Header_PS );
Description
Reads the message base header from the start of the JAM header
file.
Parameters
Base_PS The message base to use
Header_PS A pointer to a base header structure where the base
header will be stored.
Returns
0 if successful
JAM_BAD_PARAM if Base_PS or Header_PS is NULL
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
Example
{
s_JamBaseHeader BaseHeader_S;
int Result_I;
Result_I = JAM_ReadMBHeader( Base_PS, &BaseHeader_S );
if ( Result_I )
printf("JAM_ReadMBHeader returned %d.\n", Result_I );
}
=============================================
JAM_WriteMBHeader - Write message base header
=============================================
Syntax
int JAM_WriteMBHeader( s_JamBase* Base_PS,
s_JamBaseHeader* Header_PS );
Description
Increases the ModCounter field by one, resets the header signature
and writes the message base header to the start of the JAM header
file.
Parameters
Base_PS The message base to use
Header_PS A pointer to the base header to be stored
Returns
0 if successful
JAM_BAD_PARAM if Base_PS or Header_PS is NULL
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_NOT_LOCKED if the message base is not locked
Example
{
s_JamBaseHeader BaseHeader_S;
int Result_I;
/* modify header here */
Result_I = JAM_WriteMBHeader( &BaseHeader_S );
if ( Result_I )
printf("JAM_WriteMBHeader returned %d.\n", Result_I );
}
=====================================
JAM_FindUser - Find message to a user
=====================================
Syntax
int JAM_FindUser( s_JamBase* Base_PS,
ulong UserCrc_I,
ulong StartMsg_I,
ulong* MsgNo_PI );
Description
Scans the message base looking for a message written to a specific
user.
Parameters
Base_PS The message base to use
UserCrc_I The CRC32 value for the searched name
StartMsg_I The first message number to look at. This value is
not the message's unique number, but rather the
absolute position of the message in the message
base. Message 0 therefore means the first message.
MsgNo_PI A pointer to a variable where the message number
for the found message will be stored. This number
is the absolute message position in the message
base. Message 0 means the first message.
Returns
0 if a message was found
JAM_NO_USER if no message was found
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
Example
{
uchar Name_AC[32];
int Result_I;
ulong Crc_I;
ulong Msg_I;
strcpy( Name_AC, "Bjorn Stenberg" );
Crc_I = JAM_Crc32( Name_AC, strlen( Name_AC ) );
Result_I = JAM_FindUser( Base_PS, Crc_I, 0, &Msg_I );
switch ( Result_I ) {
case JAM_NO_USER:
printf("No message for me.\n");
break;
case JAM_IO_ERROR:
printf("IO error %d\n", JAM_Errno() );
break;
}
}
==========================================================
JAM_GetMBSize - Get the number of messages in message base
==========================================================
Syntax
int JAM_GetMBSize( s_JamBase* Base_PS,
ulong* Messages_PI );
Description
Finds out the number of messages (deleted and undeleted) in the
message base.
Parameters
Base_PS The message base to use
Messages_PI A pointer to a variable where the number of
messages will be stored.
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
Example
{
int Result_I;
ulong Size_I;
Result_I = JAM_GetMBSize( Base_PS, &Size_I );
if ( Result_I )
printf("JAM_GetMBSize returned %d.\n", Result_I );
}
--------------------------------------------------------------------------
Message functions
-----------------
These functions handle individual JAM messages. A JAM message contains of
three parts:
* Message Header
* Message Header Subfields
* Message Text
The message header is a simple C structure and the message text is a
simple text buffer.
The subfields, however, are a bit more tricky. These contain everything
that is not covered by the header, including the TO, FROM, SUBJECT fields,
origin and destination network adresses etc. There can be an unlimited
number of subfields to a message.
In this routine library the subfields are encapsulated by a 'subfield
packet', which is handled by its own set of routines. See a later section
of this document for an explanation of those.
=============================================================
JAM_ReadMsgHeader - Read a message's header and its subfields
=============================================================
Syntax
int JAM_ReadMsgHeader( s_JamBase* Base_PS,
ulong MsgNo_I,
s_JamMsgHeader* Header_PS,
s_JamSubPacket** Subfields_PPS );
Description
Reads a message header and (optionally) the message header
subfields.
Parameters
Base_PS The message base to use
MsgNo_I The message number, i.e. the absolute position of
the message in the message base. Message 0 is the
first message.
Header_PS A pointer to a message header structure where the
message header will be stored.
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.
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_NO_MEMORY if a memory allocation failed
JAM_NO_MESSAGE if message has been removed
JAM_CORRUPT_MSG if message subfields are corrupted
Example
{
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 );
}
=======================================
JAM_ReadMsgText - Read a message's text
=======================================
Syntax
int JAM_ReadMsgText( s_JamBase* Base_PS,
ulong Offset_I,
ulong Length_I,
uchar* Buffer_PC );
Description
Reads the body text associated with a message.
Parameters
Base_PS The message base to use
Offset_I The text position in the text file. This
information is stored in the message header.
Length_I The text length. This information is stored in the
message header.
Buffer_PC A pointer to where the text should be stored.
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
Example
{
s_JamMsgHeader Header_S;
uchar* Buffer_PC;
int Result_I;
/* read msg header */
Result_I = JAM_ReadMsgHeader( Base_PS, 0, &Header_S, &SubPack_PS );
if ( Result_I ) {
printf("JAM_ReadMsgHeader returned %d.\n", Result_I );
return;
}
/* allocate buffer text */
Buffer_PC = (uchar*) malloc( Header_S.TxtLen );
if ( !Buffer_PC ) {
printf("malloc failed.\n");
return;
}
/* read text */
Result_I = JAM_ReadMsgText( Base_PS,
Header_S.TxtOffset,
Header_S.TxtLen,
Buffer_PC );
if ( Result_I )
printf("JAM_ReadMsgText returned %d.\n", Result_I );
free( Buffer_PC );
}
==============================================
JAM_AddMessage - Add a message to message base
==============================================
Syntax
int JAM_AddMessage( s_JamBase* Base_PS,
s_JamMsgHeader* Header_PS,
s_JamSubPacket* SubPack_PS,
uchar* Text_PC,
ulong TextLen_I );
Description
Adds a message to the message base. Fully automatic.
Parameters
Base_PS The message base to use
Header_PS A pointer to the message header struct. The
function will set the following header fields:
Signature, Revision, TxtOffset, TxtLen, SubfieldLen
and MsgNum. Whatever you set these fields to will
be overwritten.
SubPack_PS A subfield packet handler, containing all subfields
for the message.
Text_PC A pointer to the first byte of the message text.
TextLen_I The length of the message text, excluding any zero
termination characters.
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_NOT_LOCKED if the message base is not locked
Example
{
s_JamSubPacket* SubPacket_PS;
s_JamSubfield Subfield_S;
s_JamMsgHeader Header_S;
uchar Text_AC[64];
uchar Field_AC[64];
/*
** Fix message header
*/
JAM_ClearMsgHeader( &Header_S );
Header_S.DateWritten = time(NULL);
/*
** Create subfield packet
*/
SubPacket_PS = JAM_NewSubPacket();
if ( !SubPacket_PS ) {
printf("JAM_NewSubPacket returned NULL.\n" );
return;
}
/* set up subfield 1 */
strcpy( Field_AC, "This is field #1" );
Subfield_S.LoID = JAMSFLD_SENDERNAME;
Subfield_S.HiID = 0;
Subfield_S.DatLen = strlen( Field_AC );
Subfield_S.Buffer = Field_AC;
JAM_PutSubfield( SubPacket_PS, &Subfield_S );
/* set up subfield 2 */
strcpy( Field_AC, "This is field #2" );
Subfield_S.LoID = JAMSFLD_RECVRNAME;
Subfield_S.HiID = 0;
Subfield_S.DatLen = strlen( Field_AC );
Subfield_S.Buffer = Field_AC;
JAM_PutSubfield( SubPacket_PS, &Subfield_S );
/*
** Add message
*/
strcpy( Text_AC, "Hello world!\nThis is a test.");
/* [lock the message base] */
Result_I = JAM_AddMessage( Base_PS, &Header_S, SubPacket_PS,
Text_AC, strlen( Text_AC ) );
if ( Result_I ) {
printf("JAM_AddMessage returned %d.\n", Result_I );
return;
}
/* [unlock the message base] */
JAM_DelSubPacket( SubPacket_PS );
}
=================================================================
JAM_AddEmptyMessage - Add a empty message entry to a message base
=================================================================
Syntax
int JAM_AddEmptyMessage( s_JamBase* Base_PS);
Description
Adds an empty message header to the message base. Useful
when writing a messagebase maintenance utility.
Parameters
Base_PS The message base to use
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_NOT_LOCKED if the message base is not locked
Example
none
===============================================
JAM_ChangeMsgHeader - Change a message's header
===============================================
Syntax
int JAM_ChangeMsgHeader( s_JamBase* Base_PS,
ulong MsgNo_I,
s_JamMsgHeader* Header_PS );
Description
Writes over an old message header with a new one. Only the header -
not the subfields - can be changed due to the subfields' dynamic
size.
NOTE! Use this function with caution. It is easy to corrupt a
message by giving it an incorrect header.
Parameters
Base_PS The message base to use
MsgNo_I The absolute message number. Message #0 is the
first in the message base.
Header_PS A pointer to the header structure to write.
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_NOT_LOCKED if the message base is not locked
Example
{
s_JamMsgHeader Header_S;
int Result_I;
/* [lock the message base] */
Result_I = JAM_ReadMsgHeader( Base_PS, 0, &Header_S, NULL );
if ( Result_I )
printf("JAM_ReadMsgHeader returned %d.\n", Result_I );
Header_S.TimesRead++;
Result_I = JAM_ChangeMsgHeader( Base_PS, 0, &Header_S );
if ( Result_I )
printf("JAM_ChangeMsgHeader returned %d.\n", Result_I );
/* [unlock the message base] */
}
=====================================================
JAM_ClearMsgHeader - Clear a message header structure
=====================================================
Syntax
int JAM_ClearMsgHeader( s_JamMsgHeader* Header_PS );
Description
Clears a message header structure and prepares it for use. This
includes setting the Signature field and the Revision field to
their correct values, and setting the CRC fields to JAM_NO_CRC.
Parameters
Header_PS A pointer to the structure to prepare.
Returns
0 if successful
JAM_BAD_PARAM if Header_PS is NULL
===================================================
JAM_DeleteMessage - Delete message from messagebase
===================================================
Syntax
int JAM_DeleteMessage( s_JamBase* Base_PS,
ulong MsgNo_I );
Description
Deletes message from messagebase by setting HdrOffset and UserCRC
in index to 0xFFFFFFFF. ActiveMsgs in base header also updated.
Parameters
Base_PS The message base to use
MsgNo_I The absolute message number. Message #0 is the
first in the message base.
Returns
0 if successful
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_NOT_LOCKED if the message base is not locked
Example
none
--------------------------------------------------------------------------
Subfield packet functions
-------------------------
As described earlier, a subfield is a part of the message header. Due to
the complexity of the different network types in use, it is not feasible to
try and cram all data into one header struct. Therefore, JAM uses a fairly
small header struct and instead marks all additional data fields as
'subfields'.
In order to make life a little more easy, I have used the concept of a
container for all subfields. I call it a 'Subfield Packet'. It is
identified by a struct pointer, and should be looked upon as a file or a
list that you manipulate via the following four functions:
===============================================
JAM_NewSubPacket - Create a new subfield packet
===============================================
Syntax
s_JamSubPacket* JAM_NewSubPacket( void );
Description
Creates a new, empty, subfield packet.
Parameters
None
Returns
The subpacket handle, if successful, or NULL if a memory allocation
failed.
Example
{
s_JamSubPacket* SubPacket_PS;
SubPacket_PS = JAM_NewSubPacket();
if ( !SubPacket_PS ) {
printf("JAM_NewSubPacket returned NULL.\n" );
return;
}
}
===========================================
JAM_DelSubPacket - Delete a subfield packet
===========================================
Syntax
int JAM_DelSubPacket( s_JamSubPacket* SubPack_PS );
Description
Frees all memory used by a subfield packet. All subfields in the
packet will be lost and the packet handle will not be valid any
more.
Parameters
SubPack_PS The subfield packet to delete
Returns
0 if successful
JAM_BAD_PARAM if SubPack_PS is NULL.
Example
{
s_JamSubPacket* SubPacket_PS;
SubPacket_PS = JAM_NewSubPacket();
if ( !SubPacket_PS ) {
printf("JAM_NewSubPacket returned NULL.\n" );
return;
}
SubPacket_PS = JAM_DelSubPacket();
if ( !SubPacket_PS ) {
printf("JAM_DelSubPacket returned NULL.\n" );
return;
}
}
=======================================================================
JAM_GetSubfield - Get a subfield from a subfield packet (not reentrant)
=======================================================================
Syntax
s_JamSubfield* JAM_GetSubfield( s_JamSubPacket* SubPack_PS );
Description
Returns a pointer to the first/next subfield struct in the subfield
packet.
WARNING: This function is not reentrant and should not be used in
multi-threaded applications unless you know what you are doing.
Use JAM_GetSubfield_R instead when a reentrant function is needed.
Parameter
SubPack_PS The subfield packet to use. If this parameter is
NULL, the next subfield from the subfield packet
previously scanned will be returned.
Returns
A pointer to a subfield, if successful, or NULL if there are no
more subfields in the packet.
Example
{
s_JamSubPacket* SubPack_PS;
s_JamSubfield* Subfield_PS;
s_JamMsgHeader Header_S;
int Result_I;
Result_I = JAM_ReadMsgHeader( 0, &Header_S, &SubPack_PS );
if ( Result_I )
printf("JAM_ReadMsgHeader returned %d.\n", Result_I );
for ( Subfield_PS = JAM_GetSubfield( SubPack_PS ); Subfield_PS;
Subfield_PS = JAM_GetSubfield( NULL ) )
printf("Subfield id %d\n", Subfield_PS->LoID );
JAM_DelSubPacket( SubPack_PS );
}
=====================================================================
JAM_GetSubfield_R - Get a subfield from a subfield packet (reentrant)
=====================================================================
Syntax
s_JamSubfield* JAM_GetSubfield( s_JamSubPacket* SubPack_PS,
ulong* Count_PI );
Description
Returns a pointer to the first/next subfield struct in the subfield
packet.
This function is a reentrant replacement for JAM_GetSubfield.
Parameter
SubPack_PS The subfield packet to use.
Count_PI Pointer to a variable that contains the number of
the subfield to retrieve. The variable should be
set to zero the first time the function is called
and is then automatically increased by the function
for any subsequent calls.
Returns
A pointer to a subfield, if successful, or NULL if there are no
more subfields in the packet.
Example
{
s_JamSubPacket* SubPack_PS;
s_JamSubfield* Subfield_PS;
s_JamMsgHeader Header_S;
ulong Count_I;
int Result_I;
Result_I = JAM_ReadMsgHeader( 0, &Header_S, &SubPack_PS );
if ( Result_I )
printf("JAM_ReadMsgHeader returned %d.\n", Result_I );
Count_I = 0;
while( ( Subfield_PS = JAM_GetSubfield_R( SubPack_PS , &Count_I ) ) )
printf("Subfield id %d\n", Subfield_PS->LoID );
JAM_DelSubPacket( SubPack_PS );
}
=======================================================
JAM_PutSubfield - Put a subfield into a subfield packet
=======================================================
Syntax
int JAM_PutSubfield( s_JamSubPacket* SubPack_PS,
s_JamSubfield* Subfield_PS );
Description
Puts a subfield into a subfield packet. The subfield is copied
before being put into the subfield packet.
Parameters
SubPack_PS The subfield packet to add to
Subfield_PS The subfield to put in the packet
Returns
0 if successful
JAM_NO_MEMORY if a memory allocation failed
Example
{
s_JamSubPacket* SubPacket_PS;
s_JamSubfield Subfield_S;
uchar Field_AC[64];
SubPacket_PS = JAM_NewSubPacket();
if ( !SubPacket_PS ) {
printf("JAM_NewSubPacket returned NULL.\n" );
return;
}
/* set up subfield 1 */
strcpy( Field_AC, "This is field #1" );
Subfield_S.LoID = JAMSFLD_SENDERNAME;
Subfield_S.HiID = 0;
Subfield_S.DatLen = strlen( Field_AC );
Subfield_S.Buffer = Field_AC;
JAM_PutSubfield( SubPacket_PS, &Subfield_S );
/* set up subfield 2 */
strcpy( Field_AC, "This is field #2" );
Subfield_S.LoID = JAMSFLD_RECVRNAME;
Subfield_S.HiID = 0;
Subfield_S.DatLen = strlen( Field_AC );
Subfield_S.Buffer = Field_AC;
JAM_PutSubfield( SubPacket_PS, &Subfield_S );
JAM_DelSubPacket( SubPacket_PS );
}
--------------------------------------------------------------------------
LastRead functions
------------------
JAM implements the often-used concept of high water marking for
remembering which user read how many messages in each area.
Personally I think this concept stinks, since it does not store *which*
messages a user has read, only the number of the highest message he has
read. But since it's a part of JAM and it's fairly straightforward and
easy, I've implemented two support functions for it.
I would, however, strongly recommend all BBS programmers to use proper
message mapping systems instead, so your users can read their messages in
whatever order they wish.
=========================================
JAM_ReadLastRead - Read a lastread record
=========================================
Syntax
int JAM_ReadLastRead( s_JamBase* Base_PS,
ulong User_I,
s_JamLastRead* Record_PS );
Description
Reads a lastread record from the lastread file.
Parameter
Base_PS The message base to use
User_I A system-unique user number.
Record_PS A pointer to the lastread struct where the record
will be stored.
Returns
0 if successful
JAM_BAD_PARAM if Record_PS is NULL
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
JAM_NO_USER if the user number was not found
Example
{
int Result_I;
s_JamLastRead LastRead_S;
Result_I = JAM_ReadLastRead( Base_PS, 4711, &LastRead_S );
if ( Result_I )
printf("JAM_ReadLastRead returned %d\n", Result_I );
}
===========================================
JAM_WriteLastRead - Write a lastread record
===========================================
Syntax
int JAM_WriteLastRead( s_JamBase* Base_PS,
ulong User_I,
s_JamLastRead* Record_PS );
Description
Writes a lastread record to the lastread file. If the user number
could not be found, the record will be appended to the end of the
file.
Parameter
Base_PS The message base to use
User_I A system-unique user number
Record_PS A pointer to the lastread struct to be written
Returns
0 if successful
JAM_BAD_PARAM if Record_PS is NULL
JAM_IO_ERROR if an I/O error occured. see JAM_Errno()
Example
{
int Result_I;
s_JamLastRead LastRead_S;
Result_I = JAM_WriteLastRead( Base_PS, 4711, &LastRead_S );
if ( Result_I )
printf("JAM_WriteLastRead returned %d\n", Result_I );
}
--------------------------------------------------------------------------
Miscellanous functions
----------------------
==============================================
JAM_Crc32 - Calculate CRC32 on a block of data
==============================================
Syntax
ulong JAM_Crc32( uchar* Buffer_PC,
ulong Length_I );
Description
Calculates the Crc32 value for a block of data. All ASCII
characters are converted to lowercase before calculating
the CRC (the input data is unchanged).
Parameters
Buffer_PC A pointer to the first byte of the data block
Length_I The number of bytes in the data block
Returns
The Crc32 value
Example
{
ulong Crc_I;
uchar Text_AC[32];
strcpy( Text_AC, "Hello world!\n");
Crc_I = JAM_Crc32( Text_AC, strlen( Text_AC ) );
}
=============================
JAM_Errno - Specify I/O error
=============================
Syntax
int JAM_Errno( s_JamBase* Base_PS );
Description
When any of these library routines return JAM_IO_ERROR, you can
call this function to find out exactly what went wrong.
Parameters
Base_PS The message base to use
Returns
Standard 'errno' values, as the C compiler generated them, or if
the I/O error was system specific, the return code is (10000 +
system status code).
Examples
{
int Result_I;
uchar Text_AC[10];
/* generate an I/O error */
Result_I = JAM_ReadMsgText( 0xffffffff, 10, Text_AC );
if ( Result_I ) {
errno = JAM_Errno( Base_PS );
perror("JAM i/o error");
}
}
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