Module Name: src
Committed By: rillig
Date: Tue Mar 9 18:21:01 UTC 2021
Modified Files:
src/usr.bin/indent: parse.c
Log Message:
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.
To generate a diff of this commit:
cvs rdiff -u -r1.15 -r1.16 src/usr.bin/indent/parse.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/usr.bin/indent/parse.c
diff -u src/usr.bin/indent/parse.c:1.15 src/usr.bin/indent/parse.c:1.16
--- src/usr.bin/indent/parse.c:1.15 Tue Mar 9 16:48:28 2021
+++ src/usr.bin/indent/parse.c Tue Mar 9 18:21:01 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: parse.c,v 1.15 2021/03/09 16:48:28 rillig Exp $ */
+/* $NetBSD: parse.c,v 1.16 2021/03/09 18:21:01 rillig Exp $ */
/*-
* SPDX-License-Identifier: BSD-4-Clause
@@ -232,116 +232,78 @@ parse(token_type tk) /* tk: the code fo
#endif
}
-/*
- * NAME: reduce
- *
- * FUNCTION: Implements the reduce part of the parsing algorithm
- *
- * ALGORITHM: The following reductions are done. Reductions are repeated
- * until no more are possible.
- *
- * Old TOS New TOS
- * <stmt> <stmt> <stmtl>
- * <stmtl> <stmt> <stmtl>
- * do <stmt> "dostmt"
- * if <stmt> "ifstmt"
- * switch <stmt> <stmt>
- * decl <stmt> <stmt>
- * "ifelse" <stmt> <stmt>
- * for <stmt> <stmt>
- * while <stmt> <stmt>
- * "dostmt" while <stmt>
- *
- * On each reduction, ps.i_l_follow (the indentation for the following line)
- * is set to the indentation level associated with the old TOS.
- *
- * PARAMETERS: None
- *
- * RETURNS: Nothing
- *
- * GLOBALS: ps.cstk ps.i_l_follow = ps.il ps.p_stack = ps.tos =
- *
- * CALLS: None
- *
- * CALLED BY: parse
- *
- * HISTORY: initial coding November 1976 D A Willcox of CAC
- *
- */
/*----------------------------------------------*\
| REDUCTION PHASE |
\*----------------------------------------------*/
-static void
-reduce(void)
-{
- int i;
- for (;;) { /* keep looping until there is nothing left to
- * reduce */
+/*
+ * Try to combine the statement on the top of the parse stack with the symbol
+ * directly below it, replacing these two symbols with a single symbol.
+ */
+static int
+reduce_stmt(void)
+{
+ switch (ps.p_stack[ps.tos - 1]) {
- switch (ps.p_stack[ps.tos]) {
+ case stmt: /* stmt stmt */
+ case stmtl: /* stmtl stmt */
+ ps.p_stack[--ps.tos] = stmtl;
+ return true;
+
+ case dolit: /* do <stmt> */
+ ps.p_stack[--ps.tos] = dohead;
+ ps.i_l_follow = ps.il[ps.tos];
+ return true;
+
+ case ifstmt: /* if (<expr>) <stmt> */
+ ps.p_stack[--ps.tos] = ifhead;
+ int i = ps.tos - 1;
+ while (ps.p_stack[i] != stmt &&
+ ps.p_stack[i] != stmtl &&
+ ps.p_stack[i] != lbrace)
+ --i;
+ ps.i_l_follow = ps.il[i];
+ /*
+ * for the time being, we will assume that there is no else on
+ * this if, and set the indentation level accordingly. If an
+ * else is scanned, it will be fixed up later
+ */
+ return true;
- case stmt:
- switch (ps.p_stack[ps.tos - 1]) {
-
- case stmt: /* stmt stmt */
- case stmtl: /* stmtl stmt */
- ps.p_stack[--ps.tos] = stmtl;
- break;
-
- case dolit: /* <do> <stmt> */
- ps.p_stack[--ps.tos] = dohead;
- ps.i_l_follow = ps.il[ps.tos];
- break;
-
- case ifstmt: /* <if> <stmt> */
- ps.p_stack[--ps.tos] = ifhead;
- for (i = ps.tos - 1;
- (
- ps.p_stack[i] != stmt
- &&
- ps.p_stack[i] != stmtl
- &&
- ps.p_stack[i] != lbrace
- );
- --i);
- ps.i_l_follow = ps.il[i];
- /*
- * for the time being, we will assume that there is no else on
- * this if, and set the indentation level accordingly. If an
- * else is scanned, it will be fixed up later
- */
- break;
-
- case swstmt: /* <switch> <stmt> */
- case_ind = ps.cstk[ps.tos - 1];
- /* FALLTHROUGH */
- case decl: /* finish of a declaration */
- case elsehead: /* <if> <stmt> else> <stmt> */
- case forstmt: /* <for> <stmt> */
- case whilestmt: /* <while> <stmt> */
- ps.p_stack[--ps.tos] = stmt;
- ps.i_l_follow = ps.il[ps.tos];
- break;
-
- default: /* <anything else> <stmt> */
- return;
-
- } /* end of section for <stmt> on top of stack */
- break;
-
- case whilestmt: /* while (...) on top */
- if (ps.p_stack[ps.tos - 1] == dohead) {
- /* it is termination of a do while */
- ps.tos -= 2;
- break;
- }
- else
- return;
+ case swstmt: /* switch (<expr>) <stmt> */
+ case_ind = ps.cstk[ps.tos - 1];
+ /* FALLTHROUGH */
+ case decl: /* finish of a declaration */
+ case elsehead: /* if (<expr>) <stmt> else <stmt> */
+ case forstmt: /* for (<...>) <stmt> */
+ case whilestmt: /* while (<expr>) <stmt> */
+ ps.p_stack[--ps.tos] = stmt;
+ ps.i_l_follow = ps.il[ps.tos];
+ return true;
- default: /* anything else on top */
- return;
+ default: /* <anything else> <stmt> */
+ return false;
+ }
+}
+/*
+ * Repeatedly try to reduce the top two symbols on the parse stack to a
+ * single symbol, until no more reductions are possible.
+ *
+ * On each reduction, ps.i_l_follow (the indentation for the following line)
+ * is set to the indentation level associated with the old TOS.
+ */
+static void
+reduce(void)
+{
+again:
+ if (ps.p_stack[ps.tos] == stmt) {
+ if (reduce_stmt())
+ goto again;
+ } else if (ps.p_stack[ps.tos] == whilestmt) {
+ if (ps.p_stack[ps.tos - 1] == dohead) {
+ ps.tos -= 2;
+ goto again;
}
}
}
