* This code is Copyright (c) 2002, by the authors of nmh. See the
* COPYRIGHT file in the root directory of the nmh distribution for
* complete copyright information.
+ *
+ * This code compiles the format strings (documented in mh-format(5)) into
+ * an internal form to be later processed by fmt_scan.c.
+ *
+ * What happens here is that the format strings are parsed and an array
+ * of struct format structures are returned. Each format structure is
+ * a single operation interpreted by the the routines in fmt_scan.c.
+ *
+ * There is a NOT a one-to-one correspondence between format strings and
+ * format instructions; some functions have side effects that can result
+ * in multiple instructions being generated. The exact list of instructions
+ * generated by a format string can be seem with the nmh fmtdump utility.
+ *
+ * A list of format instructions can be found in fmt_compile.h.
+ *
+ * If you wish to add a new function, you will need to do the following
+ * things:
+ *
+ * - Add a new instruction to the list of instructions in fmt_compile.h.
+ * Note that test instructions (starting with FT_IF_S_NULL) have special
+ * handling, so if you are NOT writing a test function then you need
+ * to insert it into the list before that _and_ bump all of the
+ * following instruction numbers.
+ *
+ * - Add the function name to the functable[] array below, and write any
+ * special code that your function may require in terms of parsing
+ * (it very well may not need anything).
+ *
+ * - Add the code in fmt_scan.c to handle your new function.
+ *
+ * - Document the new function in the mh-format(5) man page.
+ *
*/
#include <h/mh.h>
#define TFL_PUTS 1 /* implicit putstr if top level */
#define TFL_PUTN 2 /* implicit putnum if top level */
+/*
+ * The functable array maps between the text names of format functions and
+ * the format instructions interpreted by the engine in fmt_scan.c.
+ *
+ * The elements of this structure are as follows:
+ *
+ * name - The name of the function as seen in the format string. This is
+ * what maps a particular function name into a format instruction.
+ * type - The type of argument this function expects. Those types are
+ * listed above (with the TF_ prefix). This affects what gets
+ * placed in the format instruction (the f_un union).
+ * f_type - The instruction corresponding to this function (from the list
+ * in fmt_compile.h).
+ * extra - Used by some functions to provide extra data to the compiler.
+ * Uses include:
+ * - Providing an alternate instruction to combine a load
+ * and test operation (see do_if()).
+ * - Passed in f_value in the format instruction to provide
+ * extra information for the engine (see FT_LV_DAT handling
+ * in fmt_scan.c).
+ * - Provide a hint as to preprocessing that is required for
+ * this instruction (see do_name()).
+ * flags - See the definitions for TFL_PUTS & TFL_PUTN above.
+ */
+
struct ftable {
char *name; /* function name */
char type; /* argument type */
static char *do_if(char *);
+/*
+ * Lookup a function name in the functable
+ */
static struct ftable *
lookup(char *name)
{
}
+/*
+ * Process functions & components (handle field width here as well
+ */
static char *
do_spec(char *sp)
{
return (cp);
}
+/*
+ * Process a component name. Normally this involves generating an FT_COMP
+ * instruction for the specified component. If preprocess is set, then we
+ * do some extra processing.
+ */
static char *
do_name(char *sp, int preprocess)
{
return (cp);
}
+/*
+ * Generate one or more instructions corresponding to the named function.
+ * The different type of function arguments are handled here.
+ */
static char *
do_func(char *sp)
{
return (cp);
}
+/*
+ * Handle an expression as an argument. Basically we call one of do_name(),
+ * do_func(), or do_if()
+ */
static char *
do_expr (char *sp, int preprocess)
{
return (cp);
}
+/*
+ * I am guessing this was for some kind of loop statement, which would have
+ * looked like %[ .... %]. It looks like the way this would have worked
+ * is that the format engine would have seen that FT_DONE had a 1 in the
+ * f_un.f_un_value and then decided whether or not to continue the loop.
+ * There is no support for this in the format engine, so right now if
+ * you try using it you will reach the FT_DONE and simply stop. I'm leaving
+ * this here in case someone wants to continue the work.
+ */
static char *
do_loop(char *sp)
{
return cp;
}
+/*
+ * Handle an if-elsif-endif statement. Note here that the branching
+ * is handled by the f_skip member of the struct format (which is really
+ * just f_width overloaded). This number controls how far to move forward
+ * (or back) in the format instruction array.
+ */
static char *
do_if(char *sp)
{
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