grep: move logic to compile header pattern into a separate helper

The callers should be queuing only GREP_PATTERN_HEAD elements to the
header_list queue; simplify the switch and guard it with an assert.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/grep.c b/grep.c
index 82fb349..718a3c2 100644 (file)
--- a/grep.c
+++ b/grep.c
@@ -189,29 +189,31 @@ static struct grep_expr *compile_pattern_expr(struct grep_pat **list)
        return compile_pattern_or(list);
 }
 
-void compile_grep_patterns(struct grep_opt *opt)
+static struct grep_expr *prep_header_patterns(struct grep_opt *opt)
 {
        struct grep_pat *p;
-       struct grep_expr *header_expr = NULL;
-
-       if (opt->header_list) {
-               p = opt->header_list;
-               header_expr = compile_pattern_expr(&p);
-               if (p)
-                       die("incomplete pattern expression: %s", p->pattern);
-               for (p = opt->header_list; p; p = p->next) {
-                       switch (p->token) {
-                       case GREP_PATTERN: /* atom */
-                       case GREP_PATTERN_HEAD:
-                       case GREP_PATTERN_BODY:
-                               compile_regexp(p, opt);
-                               break;
-                       default:
-                               opt->extended = 1;
-                               break;
-                       }
-               }
+       struct grep_expr *header_expr;
+
+       if (!opt->header_list)
+               return NULL;
+       p = opt->header_list;
+       header_expr = compile_pattern_expr(&p);
+       if (p)
+               die("incomplete pattern expression: %s", p->pattern);
+       for (p = opt->header_list; p; p = p->next) {
+               if (p->token != GREP_PATTERN_HEAD)
+                       die("bug: a non-header pattern in grep header list.");
+               if (p->field < 0 || GREP_HEADER_FIELD_MAX <= p->field)
+                       die("bug: unknown header field %d", p->field);
+               compile_regexp(p, opt);
        }
+       return header_expr;
+}
+
+void compile_grep_patterns(struct grep_opt *opt)
+{
+       struct grep_pat *p;
+       struct grep_expr *header_expr = prep_header_patterns(opt);
 
        for (p = opt->pattern_list; p; p = p->next) {
                switch (p->token) {
@@ -231,9 +233,6 @@ void compile_grep_patterns(struct grep_opt *opt)
        else if (!opt->extended)
                return;
 
-       /* Then bundle them up in an expression.
-        * A classic recursive descent parser would do.
-        */
        p = opt->pattern_list;
        if (p)
                opt->pattern_expression = compile_pattern_expr(&p);