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Annotation of researchv10dc/lbin/kermit/ckuv7.hlp, revision 1.1

1.1     ! root        1: Date:     Fri, 17 May 85 18:53:43 CDT
        !             2: From:     Gregg Wonderly <[email protected]>
        !             3: Subject:  Additional C-Kermit Implementation Notes for Version 7 UNIX
        !             4: 
        !             5:      The Version 7 implementation takes advantage of some information present
        !             6: in the UNIX kernal to obtain the count of characters available for input from
        !             7: a particular file descriptor.  The function initrawq() is used to obtain the
        !             8: kernal address of this value.  It is a structure value that is associated with
        !             9: the clist for the file descriptor passed.  The struture member is the "rawq"
        !            10: count of characters available.  The include file <sys/clist.h> on our system
        !            11: shows this value as the first "int" in the structure.  The operations in
        !            12: initrawq() cause the child process to "block", trying to read from the "tty"
        !            13: file descriptor.  Then, by looking through the "proc" structures, we find the
        !            14: proper process, and get its "wchan" pointer.  This is a pointer to the clist
        !            15: in question, in the kernal memory.
        !            16: 
        !            17:      The "wchan" address can then be used as an offset by lseek to select the
        !            18: proper address in the kernal (/dev/kmem) to read from.  By reading the first
        !            19: "int" at this address, we obtain a count of the characters available on the
        !            20: raw input queue.
        !            21: 
        !            22:      The MAKE variables PROC, NPROCNAME, BOOTNAME, are necessary to get around
        !            23: different naming conventions across systems.  The variable PROC is the name
        !            24: given to the process structure array on your system.  The include file <sys/
        !            25: proc.h> (or some facsimile) should contain a declaration of the form:
        !            26: 
        !            27:      extern struct proc *proc;
        !            28: or
        !            29:      extern struct proc proc[];
        !            30: 
        !            31: The name of the pointer/array, is what you are concerned with.  It may be
        !            32: something like "_proc", "proc", or some deriviation.  You should define
        !            33: the MAKE variable PROC to this string, whatever it may be.  On our system,
        !            34: I use "PROC=proc".  If your definition is for an array, then you should define
        !            35: the MAKE variable DIRECT to be "-DDIRECT", as it is in the MAKEFILE.  If your
        !            36: definition is for a pointer to the array, then you should remove the definition
        !            37: of DIRECT, so the the line reads "DIRECT=" (no value here).  This is necessary
        !            38: for the routine to properly locate the "proc" array.  If you have an array
        !            39: declaration, then the call to nlist() will return the address of the array.
        !            40: However, if you have a pointer, then nlist() returns the address of the
        !            41: pointer.  This requires one extra level of dereference to obtain the address of
        !            42: the array.
        !            43: 
        !            44:      The same thing applies to the variable NPROCNAME.  On our system, this is
        !            45: defined as "NPROCNAME=nproc".  This should also be declared in <sys/proc.h>
        !            46: something like:
        !            47: 
        !            48:      extern int nproc;
        !            49: 
        !            50: This value is the number (Maximum that is) of process entries in the "proc"
        !            51: array.
        !            52: 
        !            53:      BOOTNAME is the name of the kernal image on your system.  On our system,
        !            54: it is "/edition7".  On others, it is probably "/unix", or something close.
        !            55: The nlist() function uses this file to look for the addresses of the kernal
        !            56: variables "proc", and "nproc".

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