grep.c: expose {,inverted} match column in match_line()

When calling match_line(), callers presently cannot determine the
relative offset of the match because match_line() discards the
'regmatch_t' that contains this information.

Instead, teach match_line() to take in two 'ssize_t's. Fill the first
with the offset of the match produced by the given expression. If
extended, fill the later with the offset of the match produced as if
--invert were given.

For instance, matching "--not -e x" on this line produces a columnar
offset of 0, (i.e., the whole line does not contain an x), but "--invert
--not -e -x" will fill the later ssize_t of the column containing an
"x", because this expression is semantically equivalent to "-e x".

To determine the column for the inverted and non-inverted case, do the
following:

- If matching an atom, the non-inverted column is as given from
match_one_pattern(), and the inverted column is unset.

- If matching a --not, the inverted column and non-inverted column
swap.

- If matching an --and, or --or, the non-inverted column is the
minimum of the two children.

Presently, the existing short-circuiting logic for AND and OR applies as
before. This will change in the following commit when we add options to
configure the --column flag. Taken together, this and the forthcoming
change will always yield the earlier column on a given line.

This patch will become useful when we later pick between the two new
results in order to display the column number of the first match on a
line with --column.

Co-authored-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/grep.c b/grep.c
index 45ec7e636c004dbd35d4e0d05c243bc1d1479d19..dedfe17f931f482d9e2c3723a93c6f44646053f8 100644 (file)
--- a/grep.c
+++ b/grep.c
@@ -1248,11 +1248,11 @@ static int match_one_pattern(struct grep_pat *p, char *bol, char *eol,
        return hit;
 }
 
-static int match_expr_eval(struct grep_expr *x, char *bol, char *eol,
-                          enum grep_context ctx, int collect_hits)
+static int match_expr_eval(struct grep_opt *opt, struct grep_expr *x, char *bol,
+                          char *eol, enum grep_context ctx, ssize_t *col,
+                          ssize_t *icol, int collect_hits)
 {
        int h = 0;
-       regmatch_t match;
 
        if (!x)
                die("Not a valid grep expression");
@@ -1261,25 +1261,39 @@ static int match_expr_eval(struct grep_expr *x, char *bol, char *eol,
                h = 1;
                break;
        case GREP_NODE_ATOM:
-               h = match_one_pattern(x->u.atom, bol, eol, ctx, &match, 0);
+               {
+                       regmatch_t tmp;
+                       h = match_one_pattern(x->u.atom, bol, eol, ctx,
+                                             &tmp, 0);
+                       if (h && (*col < 0 || tmp.rm_so < *col))
+                               *col = tmp.rm_so;
+               }
                break;
        case GREP_NODE_NOT:
-               h = !match_expr_eval(x->u.unary, bol, eol, ctx, 0);
+               /*
+                * Upon visiting a GREP_NODE_NOT, col and icol become swapped.
+                */
+               h = !match_expr_eval(opt, x->u.unary, bol, eol, ctx, icol, col,
+                                    0);
                break;
        case GREP_NODE_AND:
-               if (!match_expr_eval(x->u.binary.left, bol, eol, ctx, 0))
+               if (!match_expr_eval(opt, x->u.binary.left, bol, eol, ctx, col,
+                                    icol, 0))
                        return 0;
-               h = match_expr_eval(x->u.binary.right, bol, eol, ctx, 0);
+               h = match_expr_eval(opt, x->u.binary.right, bol, eol, ctx, col,
+                                   icol, 0);
                break;
        case GREP_NODE_OR:
                if (!collect_hits)
-                       return (match_expr_eval(x->u.binary.left,
-                                               bol, eol, ctx, 0) ||
-                               match_expr_eval(x->u.binary.right,
-                                               bol, eol, ctx, 0));
-               h = match_expr_eval(x->u.binary.left, bol, eol, ctx, 0);
+                       return (match_expr_eval(opt, x->u.binary.left, bol, eol,
+                                               ctx, col, icol, 0) ||
+                               match_expr_eval(opt, x->u.binary.right, bol,
+                                               eol, ctx, col, icol, 0));
+               h = match_expr_eval(opt, x->u.binary.left, bol, eol, ctx, col,
+                                   icol, 0);
                x->u.binary.left->hit |= h;
-               h |= match_expr_eval(x->u.binary.right, bol, eol, ctx, 1);
+               h |= match_expr_eval(opt, x->u.binary.right, bol, eol, ctx, col,
+                                    icol, 1);
                break;
        default:
                die("Unexpected node type (internal error) %d", x->node);
@@ -1290,25 +1304,30 @@ static int match_expr_eval(struct grep_expr *x, char *bol, char *eol,
 }
 
 static int match_expr(struct grep_opt *opt, char *bol, char *eol,
-                     enum grep_context ctx, int collect_hits)
+                     enum grep_context ctx, ssize_t *col,
+                     ssize_t *icol, int collect_hits)
 {
        struct grep_expr *x = opt->pattern_expression;
-       return match_expr_eval(x, bol, eol, ctx, collect_hits);
+       return match_expr_eval(opt, x, bol, eol, ctx, col, icol, collect_hits);
 }
 
 static int match_line(struct grep_opt *opt, char *bol, char *eol,
+                     ssize_t *col, ssize_t *icol,
                      enum grep_context ctx, int collect_hits)
 {
        struct grep_pat *p;
-       regmatch_t match;
 
        if (opt->extended)
-               return match_expr(opt, bol, eol, ctx, collect_hits);
+               return match_expr(opt, bol, eol, ctx, col, icol,
+                                 collect_hits);
 
        /* we do not call with collect_hits without being extended */
        for (p = opt->pattern_list; p; p = p->next) {
-               if (match_one_pattern(p, bol, eol, ctx, &match, 0))
+               regmatch_t tmp;
+               if (match_one_pattern(p, bol, eol, ctx, &tmp, 0)) {
+                       *col = tmp.rm_so;
                        return 1;
+               }
        }
        return 0;
 }
@@ -1763,6 +1782,7 @@ static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int colle
        while (left) {
                char *eol, ch;
                int hit;
+               ssize_t col = -1, icol = -1;
 
                /*
                 * look_ahead() skips quickly to the line that possibly
@@ -1786,7 +1806,7 @@ static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int colle
                if ((ctx == GREP_CONTEXT_HEAD) && (eol == bol))
                        ctx = GREP_CONTEXT_BODY;
 
-               hit = match_line(opt, bol, eol, ctx, collect_hits);
+               hit = match_line(opt, bol, eol, &col, &icol, ctx, collect_hits);
                *eol = ch;
 
                if (collect_hits)