zircon/system/ulib/trace-test-utils/include/trace-test-utils/squelch.h

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#pragma once

#include <regex.h>

#include <memory>

// TODO(dje): Conversion to std::string needs to be done in conjunction with
// converting trace-reader.
#include <fbl/string.h>

namespace trace_testing {

// Squelcher is used to filter out elements of a trace record that may
// vary run to run or even within a run and are not germaine to determining
// correctness. The canonical example is record timestamps.
// The term "squelch" derives from radio circuitry used to remove noise.

class Squelcher {
public:
    // |regex_str| is a regular expression consistenting of one or more
    // subexpressions, the text in the parenthesis of each matching expressions
    // is replaced with '<>'.
    // Best illustration is an example. This example removes decimal numbers,
    // koids, timestamps ("ts"), and lowercase hex numbers.
    // const char regex[] = "([0-9]+/[0-9]+)"
    //   "|koid\\(([0-9]+)\\)"
    //   "|koid: ([0-9]+)"
    //   "|ts: ([0-9]+)"
    //   "|(0x[0-9a-f]+)";
    // So "ts: 123 42 mumble koid(456) foo koid: 789, bar 0xabcd"
    // becomes "ts: <> <> mumble koid(<>) foo koid: <>, bar <>".
    static std::unique_ptr<Squelcher> Create(const char* regex_str);

    ~Squelcher();

    fbl::String Squelch(const char* str);

private:
    Squelcher() = default;

    // The compiled regex.
    regex_t regex_;
};

}  // namespace trace_testing