1 files changed, 116 insertions, 0 deletions
diff --git a/tools/perf/util/help-unknown-cmd.c b/tools/perf/util/help-unknown-cmd.c
new file mode 100644
index 000000000..4f07a5ba5
--- /dev/null
+++ b/tools/perf/util/help-unknown-cmd.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "cache.h"
+#include "config.h"
+#include <poll.h>
+#include <stdio.h>
+#include <subcmd/help.h>
+#include "../builtin.h"
+#include "levenshtein.h"
+
+static int autocorrect;
+
+static int perf_unknown_cmd_config(const char *var, const char *value,
+				   void *cb __maybe_unused)
+{
+	if (!strcmp(var, "help.autocorrect"))
+		return perf_config_int(&autocorrect, var,value);
+
+	return 0;
+}
+
+static int levenshtein_compare(const void *p1, const void *p2)
+{
+	const struct cmdname *const *c1 = p1, *const *c2 = p2;
+	const char *s1 = (*c1)->name, *s2 = (*c2)->name;
+	int l1 = (*c1)->len;
+	int l2 = (*c2)->len;
+	return l1 != l2 ? l1 - l2 : strcmp(s1, s2);
+}
+
+static int add_cmd_list(struct cmdnames *cmds, struct cmdnames *old)
+{
+	unsigned int i, nr = cmds->cnt + old->cnt;
+	void *tmp;
+
+	if (nr > cmds->alloc) {
+		/* Choose bigger one to alloc */
+		if (alloc_nr(cmds->alloc) < nr)
+			cmds->alloc = nr;
+		else
+			cmds->alloc = alloc_nr(cmds->alloc);
+		tmp = realloc(cmds->names, cmds->alloc * sizeof(*cmds->names));
+		if (!tmp)
+			return -1;
+		cmds->names = tmp;
+	}
+	for (i = 0; i < old->cnt; i++)
+		cmds->names[cmds->cnt++] = old->names[i];
+	zfree(&old->names);
+	old->cnt = 0;
+	return 0;
+}
+
+const char *help_unknown_cmd(const char *cmd)
+{
+	unsigned int i, n = 0, best_similarity = 0;
+	struct cmdnames main_cmds, other_cmds;
+
+	memset(&main_cmds, 0, sizeof(main_cmds));
+	memset(&other_cmds, 0, sizeof(main_cmds));
+
+	perf_config(perf_unknown_cmd_config, NULL);
+
+	load_command_list("perf-", &main_cmds, &other_cmds);
+
+	if (add_cmd_list(&main_cmds, &other_cmds) < 0) {
+		fprintf(stderr, "ERROR: Failed to allocate command list for unknown command.\n");
+		goto end;
+	}
+	qsort(main_cmds.names, main_cmds.cnt,
+	      sizeof(main_cmds.names), cmdname_compare);
+	uniq(&main_cmds);
+
+	if (main_cmds.cnt) {
+		/* This reuses cmdname->len for similarity index */
+		for (i = 0; i < main_cmds.cnt; ++i)
+			main_cmds.names[i]->len =
+				levenshtein(cmd, main_cmds.names[i]->name, 0, 2, 1, 4);
+
+		qsort(main_cmds.names, main_cmds.cnt,
+		      sizeof(*main_cmds.names), levenshtein_compare);
+
+		best_similarity = main_cmds.names[0]->len;
+		n = 1;
+		while (n < main_cmds.cnt && best_similarity == main_cmds.names[n]->len)
+			++n;
+	}
+
+	if (autocorrect && n == 1) {
+		const char *assumed = main_cmds.names[0]->name;
+
+		main_cmds.names[0] = NULL;
+		clean_cmdnames(&main_cmds);
+		fprintf(stderr, "WARNING: You called a perf program named '%s', "
+			"which does not exist.\n"
+			"Continuing under the assumption that you meant '%s'\n",
+			cmd, assumed);
+		if (autocorrect > 0) {
+			fprintf(stderr, "in %0.1f seconds automatically...\n",
+				(float)autocorrect/10.0);
+			poll(NULL, 0, autocorrect * 100);
+		}
+		return assumed;
+	}
+
+	fprintf(stderr, "perf: '%s' is not a perf-command. See 'perf --help'.\n", cmd);
+
+	if (main_cmds.cnt && best_similarity < 6) {
+		fprintf(stderr, "\nDid you mean %s?\n",
+			n < 2 ? "this": "one of these");
+
+		for (i = 0; i < n; i++)
+			fprintf(stderr, "\t%s\n", main_cmds.names[i]->name);
+	}
+end:
+	exit(1);
+}