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140 lines
4.8 KiB
C
140 lines
4.8 KiB
C
/******************************************************************************
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* *
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* N O T I C E *
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* *
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* Copyright Abandoned, 1987, Fred Fish *
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* *
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* *
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* This previously copyrighted work has been placed into the public *
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* domain by the author and may be freely used for any purpose, *
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* private or commercial. *
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* *
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* Because of the number of inquiries I was receiving about the use *
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* of this product in commercially developed works I have decided to *
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* simply make it public domain to further its unrestricted use. I *
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* specifically would be most happy to see this material become a *
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* part of the standard Unix distributions by AT&T and the Berkeley *
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* Computer Science Research Group, and a standard part of the GNU *
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* system from the Free Software Foundation. *
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* *
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* I would appreciate it, as a courtesy, if this notice is left in *
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* all copies and derivative works. Thank you. *
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* *
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* The author makes no warranty of any kind with respect to this *
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* product and explicitly disclaims any implied warranties of mer- *
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* chantability or fitness for any particular purpose. *
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* *
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******************************************************************************
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*/
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/*
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* FILE
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*
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* vargs.h include file for environments without varargs.h
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*
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* SCCS
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*
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* @(#)vargs.h 1.2 5/8/88
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*
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* SYNOPSIS
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*
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* #include "vargs.h"
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*
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* DESCRIPTION
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*
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* This file implements a varargs macro set for use in those
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* environments where there is no system supplied varargs. This
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* generally works because systems which don't supply a varargs
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* package are precisely those which don't strictly need a varargs
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* package. Using this one then allows us to minimize source
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* code changes. So in some sense, this is a "portable" varargs
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* since it is only used for convenience, when it is not strictly
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* needed.
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*
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*/
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/*
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* These macros allow us to rebuild an argument list on the stack
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* given only a va_list. We can use these to fake a function like
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* vfprintf, which gets a fixed number of arguments, the last of
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* which is a va_list, by rebuilding a stack and calling the variable
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* argument form fprintf. Of course this only works when vfprintf
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* is not available in the host environment, and thus is not available
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* for fprintf to call (which would give us an infinite loop).
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*
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* Note that ARGS_TYPE is a long, which lets us get several bytes
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* at a time while also preventing lots of "possible pointer alignment
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* problem" messages from lint. The messages are valid, because this
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* IS nonportable, but then we should only be using it in very
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* nonrestrictive environments, and using the real varargs where it
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* really counts.
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*
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*/
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#define ARG0 a0
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#define ARG1 a1
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#define ARG2 a2
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#define ARG3 a3
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#define ARG4 a4
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#define ARG5 a5
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#define ARG6 a6
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#define ARG7 a7
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#define ARG8 a8
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#define ARG9 a9
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#define ARGS_TYPE long
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#define ARGS_LIST ARG0,ARG1,ARG2,ARG3,ARG4,ARG5,ARG6,ARG7,ARG8,ARG9
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#define ARGS_DCL auto ARGS_TYPE ARGS_LIST
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/*
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* A pointer of type "va_list" points to a section of memory
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* containing an array of variable sized arguments of unknown
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* number. This pointer is initialized by the va_start
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* macro to point to the first byte of the first argument.
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* We can then use it to walk through the argument list by
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* incrementing it by the size of the argument being referenced.
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*/
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typedef char *va_list;
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/*
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* The first variable argument overlays va_alist, which is
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* nothing more than a "handle" which allows us to get the
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* address of the first argument on the stack. Note that
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* by definition, the va_dcl macro includes the terminating
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* semicolon, which makes use of va_dcl in the source code
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* appear to be missing a semicolon.
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*/
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#define va_dcl ARGS_TYPE va_alist;
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/*
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* The va_start macro takes a variable of type "va_list" and
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* initializes it. In our case, it initializes a local variable
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* of type "pointer to char" to point to the first argument on
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* the stack.
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*/
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#define va_start(list) list = (char *) &va_alist
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/*
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* The va_end macro is a null operation for our use.
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*/
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#define va_end(list)
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/*
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* The va_arg macro is the tricky one. This one takes
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* a va_list as the first argument, and a type as the second
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* argument, and returns a value of the appropriate type
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* while advancing the va_list to the following argument.
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* For our case, we first increment the va_list arg by the
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* size of the type being recovered, cast the result to
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* a pointer of the appropriate type, and then dereference
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* that pointer as an array to get the previous arg (which
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* is the one we wanted.
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*/
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#define va_arg(list,type) ((type *) (list += sizeof (type)))[-1]
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