sequencer: remove the 'arg' field from todo_item

The 'arg' field of todo_item used to store the address of the first byte
of the parameter of a command in a todo list.  It was associated with
the length of the parameter (the 'arg_len' field).

This replaces the 'arg' field by 'arg_offset'.  This new field does not
store the address of the parameter, but the position of the first
character of the parameter in the buffer.  todo_item_get_arg() is added
to return the address of the parameter of an item.

This will prevent todo_list_add_exec_commands() from having to do awful
pointer arithmetics when growing the todo list buffer.

Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 42 insertions, 31 deletions

diff --git a/sequencer.c b/sequencer.c
index 25cc7a9a91..c844a9b7f3 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1999,8 +1999,14 @@ static struct todo_item *append_new_todo(struct todo_list *todo_list)
 	return todo_list->items + todo_list->nr++;
 }
 
+const char *todo_item_get_arg(struct todo_list *todo_list,
+			      struct todo_item *item)
+{
+	return todo_list->buf.buf + item->arg_offset;
+}
+
 static int parse_insn_line(struct repository *r, struct todo_item *item,
-			   const char *bol, char *eol)
+			   const char *buf, const char *bol, char *eol)
 {
 	struct object_id commit_oid;
 	char *end_of_object_name;
@@ -2014,7 +2020,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 	if (bol == eol || *bol == '\r' || *bol == comment_line_char) {
 		item->command = TODO_COMMENT;
 		item->commit = NULL;
-		item->arg = bol;
+		item->arg_offset = bol - buf;
 		item->arg_len = eol - bol;
 		return 0;
 	}
@@ -2041,7 +2047,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 			return error(_("%s does not accept arguments: '%s'"),
 				     command_to_string(item->command), bol);
 		item->commit = NULL;
-		item->arg = bol;
+		item->arg_offset = bol - buf;
 		item->arg_len = eol - bol;
 		return 0;
 	}
@@ -2053,7 +2059,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 	if (item->command == TODO_EXEC || item->command == TODO_LABEL ||
 	    item->command == TODO_RESET) {
 		item->commit = NULL;
-		item->arg = bol;
+		item->arg_offset = bol - buf;
 		item->arg_len = (int)(eol - bol);
 		return 0;
 	}
@@ -2067,7 +2073,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 		} else {
 			item->flags |= TODO_EDIT_MERGE_MSG;
 			item->commit = NULL;
-			item->arg = bol;
+			item->arg_offset = bol - buf;
 			item->arg_len = (int)(eol - bol);
 			return 0;
 		}
@@ -2079,8 +2085,9 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 	status = get_oid(bol, &commit_oid);
 	*end_of_object_name = saved;
 
-	item->arg = end_of_object_name + strspn(end_of_object_name, " \t");
-	item->arg_len = (int)(eol - item->arg);
+	bol = end_of_object_name + strspn(end_of_object_name, " \t");
+	item->arg_offset = bol - buf;
+	item->arg_len = (int)(eol - bol);
 
 	if (status < 0)
 		return -1;
@@ -2108,11 +2115,11 @@ int todo_list_parse_insn_buffer(struct repository *r, char *buf,
 
 		item = append_new_todo(todo_list);
 		item->offset_in_buf = p - todo_list->buf.buf;
-		if (parse_insn_line(r, item, p, eol)) {
+		if (parse_insn_line(r, item, buf, p, eol)) {
 			res = error(_("invalid line %d: %.*s"),
 				i, (int)(eol - p), p);
 			item->command = TODO_COMMENT + 1;
-			item->arg = p;
+			item->arg_offset = p - buf;
 			item->arg_len = (int)(eol - p);
 			item->commit = NULL;
 		}
@@ -2452,7 +2459,7 @@ static int walk_revs_populate_todo(struct todo_list *todo_list,
 
 		item->command = command;
 		item->commit = commit;
-		item->arg = NULL;
+		item->arg_offset = 0;
 		item->arg_len = 0;
 		item->offset_in_buf = todo_list->buf.len;
 		subject_len = find_commit_subject(commit_buffer, &subject);
@@ -3491,6 +3498,8 @@ static int pick_commits(struct repository *r,
 
 	while (todo_list->current < todo_list->nr) {
 		struct todo_item *item = todo_list->items + todo_list->current;
+		const char *arg = todo_item_get_arg(todo_list, item);
+
 		if (save_todo(todo_list, opts))
 			return -1;
 		if (is_rebase_i(opts)) {
@@ -3542,10 +3551,9 @@ static int pick_commits(struct repository *r,
 					fprintf(stderr,
 						_("Stopped at %s...  %.*s\n"),
 						short_commit_name(commit),
-						item->arg_len, item->arg);
+						item->arg_len, arg);
 				return error_with_patch(r, commit,
-					item->arg, item->arg_len, opts, res,
-					!res);
+					arg, item->arg_len, opts, res, !res);
 			}
 			if (is_rebase_i(opts) && !res)
 				record_in_rewritten(&item->commit->object.oid,
@@ -3554,7 +3562,7 @@ static int pick_commits(struct repository *r,
 				if (res == 1)
 					intend_to_amend();
 				return error_failed_squash(r, item->commit, opts,
-					item->arg_len, item->arg);
+					item->arg_len, arg);
 			} else if (res && is_rebase_i(opts) && item->commit) {
 				int to_amend = 0;
 				struct object_id oid;
@@ -3573,16 +3581,16 @@ static int pick_commits(struct repository *r,
 					to_amend = 1;
 
 				return res | error_with_patch(r, item->commit,
-						item->arg, item->arg_len, opts,
+						arg, item->arg_len, opts,
 						res, to_amend);
 			}
 		} else if (item->command == TODO_EXEC) {
-			char *end_of_arg = (char *)(item->arg + item->arg_len);
+			char *end_of_arg = (char *)(arg + item->arg_len);
 			int saved = *end_of_arg;
 			struct stat st;
 
 			*end_of_arg = '\0';
-			res = do_exec(r, item->arg);
+			res = do_exec(r, arg);
 			*end_of_arg = saved;
 
 			/* Reread the todo file if it has changed. */
@@ -3599,14 +3607,14 @@ static int pick_commits(struct repository *r,
 				todo_list->current = -1;
 			}
 		} else if (item->command == TODO_LABEL) {
-			if ((res = do_label(r, item->arg, item->arg_len)))
+			if ((res = do_label(r, arg, item->arg_len)))
 				reschedule = 1;
 		} else if (item->command == TODO_RESET) {
-			if ((res = do_reset(r, item->arg, item->arg_len, opts)))
+			if ((res = do_reset(r, arg, item->arg_len, opts)))
 				reschedule = 1;
 		} else if (item->command == TODO_MERGE) {
 			if ((res = do_merge(r, item->commit,
-					    item->arg, item->arg_len,
+					    arg, item->arg_len,
 					    item->flags, opts)) < 0)
 				reschedule = 1;
 			else if (item->commit)
@@ -3615,9 +3623,8 @@ static int pick_commits(struct repository *r,
 			if (res > 0)
 				/* failed with merge conflicts */
 				return error_with_patch(r, item->commit,
-							item->arg,
-							item->arg_len, opts,
-							res, 0);
+							arg, item->arg_len,
+							opts, res, 0);
 		} else if (!is_noop(item->command))
 			return error(_("unknown command %d"), item->command);
 
@@ -3632,9 +3639,8 @@ static int pick_commits(struct repository *r,
 			if (item->commit)
 				return error_with_patch(r,
 							item->commit,
-							item->arg,
-							item->arg_len, opts,
-							res, 0);
+							arg, item->arg_len,
+							opts, res, 0);
 		}
 
 		todo_list->current++;
@@ -4575,7 +4581,8 @@ int transform_todos(struct repository *r, unsigned flags)
 	for (item = todo_list.items, i = 0; i < todo_list.nr; i++, item++) {
 		/* if the item is not a command write it and continue */
 		if (item->command >= TODO_COMMENT) {
-			strbuf_addf(&buf, "%.*s\n", item->arg_len, item->arg);
+			strbuf_addf(&buf, "%.*s\n", item->arg_len,
+				    todo_item_get_arg(&todo_list, item));
 			continue;
 		}
 
@@ -4605,7 +4612,8 @@ int transform_todos(struct repository *r, unsigned flags)
 		if (!item->arg_len)
 			strbuf_addch(&buf, '\n');
 		else
-			strbuf_addf(&buf, " %.*s\n", item->arg_len, item->arg);
+			strbuf_addf(&buf, " %.*s\n", item->arg_len,
+				    todo_item_get_arg(&todo_list, item));
 	}
 
 	i = write_message(buf.buf, buf.len, todo_file, 0);
@@ -4681,7 +4689,8 @@ int check_todo_list(struct repository *r)
 		if (commit && !*commit_seen_at(&commit_seen, commit)) {
 			strbuf_addf(&missing, " - %s %.*s\n",
 				    short_commit_name(commit),
-				    item->arg_len, item->arg);
+				    item->arg_len,
+				    todo_item_get_arg(&todo_list, item));
 			*commit_seen_at(&commit_seen, commit) = 1;
 		}
 	}
diff --git a/sequencer.h b/sequencer.h
index c6360bac66..50d552429c 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -104,9 +104,9 @@ struct todo_item {
 	enum todo_command command;
 	struct commit *commit;
 	unsigned int flags;
-	const char *arg;
 	int arg_len;
-	size_t offset_in_buf;
+	/* The offset of the command and its argument in the strbuf */
+	size_t offset_in_buf, arg_offset;
 };
 
 struct todo_list {
@@ -122,6 +122,8 @@ struct todo_list {
 int todo_list_parse_insn_buffer(struct repository *r, char *buf,
 				struct todo_list *todo_list);
 void todo_list_release(struct todo_list *todo_list);
+const char *todo_item_get_arg(struct todo_list *todo_list,
+			      struct todo_item *item);
 
 /* Call this to setup defaults before parsing command line options */
 void sequencer_init_config(struct replay_opts *opts);