indent: extract reduce_stmt from reduce
This refactoring reduces the indentation of the code, as well as removing any ambiguity as to which 'switch' statement a 'break' belongs, as there are no more nested 'switch' statements. No functional change.
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rillig
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@ -1,4 +1,4 @@
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/* $NetBSD: parse.c,v 1.15 2021/03/09 16:48:28 rillig Exp $ */
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/* $NetBSD: parse.c,v 1.16 2021/03/09 18:21:01 rillig Exp $ */
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/*-
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* SPDX-License-Identifier: BSD-4-Clause
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@ -232,116 +232,78 @@ parse(token_type tk) /* tk: the code for the construct scanned */
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#endif
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}
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/*
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* NAME: reduce
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*
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* FUNCTION: Implements the reduce part of the parsing algorithm
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*
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* ALGORITHM: The following reductions are done. Reductions are repeated
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* until no more are possible.
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*
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* Old TOS New TOS
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* <stmt> <stmt> <stmtl>
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* <stmtl> <stmt> <stmtl>
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* do <stmt> "dostmt"
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* if <stmt> "ifstmt"
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* switch <stmt> <stmt>
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* decl <stmt> <stmt>
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* "ifelse" <stmt> <stmt>
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* for <stmt> <stmt>
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* while <stmt> <stmt>
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* "dostmt" while <stmt>
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*
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* On each reduction, ps.i_l_follow (the indentation for the following line)
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* is set to the indentation level associated with the old TOS.
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*
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* PARAMETERS: None
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*
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* RETURNS: Nothing
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*
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* GLOBALS: ps.cstk ps.i_l_follow = ps.il ps.p_stack = ps.tos =
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*
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* CALLS: None
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*
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* CALLED BY: parse
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*
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* HISTORY: initial coding November 1976 D A Willcox of CAC
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*
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*/
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/*----------------------------------------------*\
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| REDUCTION PHASE |
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\*----------------------------------------------*/
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/*
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* Try to combine the statement on the top of the parse stack with the symbol
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* directly below it, replacing these two symbols with a single symbol.
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*/
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static int
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reduce_stmt(void)
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{
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switch (ps.p_stack[ps.tos - 1]) {
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case stmt: /* stmt stmt */
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case stmtl: /* stmtl stmt */
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ps.p_stack[--ps.tos] = stmtl;
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return true;
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case dolit: /* do <stmt> */
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ps.p_stack[--ps.tos] = dohead;
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ps.i_l_follow = ps.il[ps.tos];
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return true;
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case ifstmt: /* if (<expr>) <stmt> */
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ps.p_stack[--ps.tos] = ifhead;
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int i = ps.tos - 1;
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while (ps.p_stack[i] != stmt &&
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ps.p_stack[i] != stmtl &&
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ps.p_stack[i] != lbrace)
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--i;
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ps.i_l_follow = ps.il[i];
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/*
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* for the time being, we will assume that there is no else on
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* this if, and set the indentation level accordingly. If an
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* else is scanned, it will be fixed up later
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*/
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return true;
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case swstmt: /* switch (<expr>) <stmt> */
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case_ind = ps.cstk[ps.tos - 1];
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/* FALLTHROUGH */
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case decl: /* finish of a declaration */
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case elsehead: /* if (<expr>) <stmt> else <stmt> */
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case forstmt: /* for (<...>) <stmt> */
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case whilestmt: /* while (<expr>) <stmt> */
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ps.p_stack[--ps.tos] = stmt;
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ps.i_l_follow = ps.il[ps.tos];
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return true;
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default: /* <anything else> <stmt> */
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return false;
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}
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}
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/*
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* Repeatedly try to reduce the top two symbols on the parse stack to a
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* single symbol, until no more reductions are possible.
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*
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* On each reduction, ps.i_l_follow (the indentation for the following line)
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* is set to the indentation level associated with the old TOS.
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*/
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static void
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reduce(void)
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{
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int i;
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for (;;) { /* keep looping until there is nothing left to
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* reduce */
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switch (ps.p_stack[ps.tos]) {
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case stmt:
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switch (ps.p_stack[ps.tos - 1]) {
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case stmt: /* stmt stmt */
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case stmtl: /* stmtl stmt */
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ps.p_stack[--ps.tos] = stmtl;
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break;
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case dolit: /* <do> <stmt> */
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ps.p_stack[--ps.tos] = dohead;
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ps.i_l_follow = ps.il[ps.tos];
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break;
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case ifstmt: /* <if> <stmt> */
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ps.p_stack[--ps.tos] = ifhead;
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for (i = ps.tos - 1;
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(
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ps.p_stack[i] != stmt
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&&
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ps.p_stack[i] != stmtl
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&&
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ps.p_stack[i] != lbrace
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);
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--i);
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ps.i_l_follow = ps.il[i];
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/*
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* for the time being, we will assume that there is no else on
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* this if, and set the indentation level accordingly. If an
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* else is scanned, it will be fixed up later
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*/
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break;
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case swstmt: /* <switch> <stmt> */
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case_ind = ps.cstk[ps.tos - 1];
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/* FALLTHROUGH */
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case decl: /* finish of a declaration */
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case elsehead: /* <if> <stmt> else> <stmt> */
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case forstmt: /* <for> <stmt> */
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case whilestmt: /* <while> <stmt> */
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ps.p_stack[--ps.tos] = stmt;
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ps.i_l_follow = ps.il[ps.tos];
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break;
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default: /* <anything else> <stmt> */
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return;
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} /* end of section for <stmt> on top of stack */
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break;
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case whilestmt: /* while (...) on top */
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if (ps.p_stack[ps.tos - 1] == dohead) {
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/* it is termination of a do while */
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ps.tos -= 2;
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break;
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}
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else
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return;
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default: /* anything else on top */
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return;
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again:
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if (ps.p_stack[ps.tos] == stmt) {
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if (reduce_stmt())
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goto again;
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} else if (ps.p_stack[ps.tos] == whilestmt) {
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if (ps.p_stack[ps.tos - 1] == dohead) {
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ps.tos -= 2;
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goto again;
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}
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}
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}
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