Merge "Merge "aaudio: reduce glitching by improving sleep timing" into oc-dr1-dev am: d937a5cf85 am: f17f490519" into oc-mr1-dev-plus-aosp
am: fd26c7c157

Change-Id: I25961d07698078c6774c255ea382ead7807edaaa
diff --git a/media/libnbaio/include/media/nbaio/NBLog.h b/media/libnbaio/include/media/nbaio/NBLog.h
index 3e48ee1..3189e4e 100644
--- a/media/libnbaio/include/media/nbaio/NBLog.h
+++ b/media/libnbaio/include/media/nbaio/NBLog.h
@@ -37,234 +37,236 @@
 
 public:
 
-typedef uint64_t log_hash_t;
+    typedef uint64_t log_hash_t;
 
-// FIXME Everything needed for client (writer API and registration) should be isolated
-//       from the rest of the implementation.
-class Writer;
-class Reader;
+    // FIXME Everything needed for client (writer API and registration) should be isolated
+    //       from the rest of the implementation.
+    class Writer;
+    class Reader;
 
-enum Event : uint8_t {
-    EVENT_RESERVED,
-    EVENT_STRING,               // ASCII string, not NUL-terminated
-    // TODO: make timestamp optional
-    EVENT_TIMESTAMP,            // clock_gettime(CLOCK_MONOTONIC)
-    EVENT_INTEGER,              // integer value entry
-    EVENT_FLOAT,                // floating point value entry
-    EVENT_PID,                  // process ID and process name
-    EVENT_AUTHOR,               // author index (present in merged logs) tracks entry's original log
-    EVENT_START_FMT,            // logFormat start event: entry includes format string, following
-                                // entries contain format arguments
-    EVENT_HASH,                 // unique HASH of log origin, originates from hash of file name
-                                // and line number
-    EVENT_HISTOGRAM_ENTRY_TS,   // single datum for timestamp histogram
-    EVENT_AUDIO_STATE,          // audio on/off event: logged upon FastMixer::onStateChange() call
-    EVENT_END_FMT,              // end of logFormat argument list
+    enum Event : uint8_t {
+        EVENT_RESERVED,
+        EVENT_STRING,               // ASCII string, not NUL-terminated
+                                    // TODO: make timestamp optional
+        EVENT_TIMESTAMP,            // clock_gettime(CLOCK_MONOTONIC)
+        EVENT_INTEGER,              // integer value entry
+        EVENT_FLOAT,                // floating point value entry
+        EVENT_PID,                  // process ID and process name
+        EVENT_AUTHOR,               // author index (present in merged logs) tracks entry's
+                                    // original log
+        EVENT_START_FMT,            // logFormat start event: entry includes format string,
+                                    // following entries contain format arguments
+        EVENT_HASH,                 // unique HASH of log origin, originates from hash of file name
+                                    // and line number
+        EVENT_HISTOGRAM_ENTRY_TS,   // single datum for timestamp histogram
+        EVENT_AUDIO_STATE,          // audio on/off event: logged on FastMixer::onStateChange call
+        EVENT_END_FMT,              // end of logFormat argument list
 
-    EVENT_UPPER_BOUND,          // to check for invalid events
-};
+        EVENT_UPPER_BOUND,          // to check for invalid events
+    };
 
 private:
 
-// ---------------------------------------------------------------------------
-// API for handling format entry operations
+    // ---------------------------------------------------------------------------
+    // API for handling format entry operations
 
-// a formatted entry has the following structure:
-//    * START_FMT entry, containing the format string
-//    * TIMESTAMP entry
-//    * HASH entry
-//    * author entry of the thread that generated it (optional, present in merged log)
-//    * format arg1
-//    * format arg2
-//    * ...
-//    * END_FMT entry
+    // a formatted entry has the following structure:
+    //    * START_FMT entry, containing the format string
+    //    * TIMESTAMP entry
+    //    * HASH entry
+    //    * author entry of the thread that generated it (optional, present in merged log)
+    //    * format arg1
+    //    * format arg2
+    //    * ...
+    //    * END_FMT entry
 
-// entry representation in memory
-struct entry {
-    const uint8_t type;
-    const uint8_t length;
-    const uint8_t data[0];
-};
+    // entry representation in memory
+    struct entry {
+        const uint8_t type;
+        const uint8_t length;
+        const uint8_t data[0];
+    };
 
-// entry tail representation (after data)
-struct ending {
-    uint8_t length;
-    uint8_t next[0];
-};
+    // entry tail representation (after data)
+    struct ending {
+        uint8_t length;
+        uint8_t next[0];
+    };
 
-// entry iterator
-class EntryIterator {
-public:
-    EntryIterator();
-    explicit EntryIterator(const uint8_t *entry);
-    EntryIterator(const EntryIterator &other);
+    // entry iterator
+    class EntryIterator {
+    public:
+        EntryIterator();
+        explicit EntryIterator(const uint8_t *entry);
+        EntryIterator(const EntryIterator &other);
 
-    // dereference underlying entry
-    const entry&    operator*() const;
-    const entry*    operator->() const;
-    // advance to next entry
-    EntryIterator&       operator++(); // ++i
-    // back to previous entry
-    EntryIterator&       operator--(); // --i
-    EntryIterator        next() const;
-    EntryIterator        prev() const;
-    bool            operator!=(const EntryIterator &other) const;
-    int             operator-(const EntryIterator &other) const;
+        // dereference underlying entry
+        const entry&    operator*() const;
+        const entry*    operator->() const;
+        // advance to next entry
+        EntryIterator&       operator++(); // ++i
+        // back to previous entry
+        EntryIterator&       operator--(); // --i
+        EntryIterator        next() const;
+        EntryIterator        prev() const;
+        bool            operator!=(const EntryIterator &other) const;
+        int             operator-(const EntryIterator &other) const;
 
-    bool            hasConsistentLength() const;
-    void            copyTo(std::unique_ptr<audio_utils_fifo_writer> &dst) const;
-    void            copyData(uint8_t *dst) const;
+        bool            hasConsistentLength() const;
+        void            copyTo(std::unique_ptr<audio_utils_fifo_writer> &dst) const;
+        void            copyData(uint8_t *dst) const;
 
-    template<typename T>
-    inline const T& payload() {
-        return *reinterpret_cast<const T *>(ptr + offsetof(entry, data));
-    }
+        template<typename T>
+        inline const T& payload() {
+            return *reinterpret_cast<const T *>(ptr + offsetof(entry, data));
+        }
 
-    inline operator const uint8_t*() const {
-        return ptr;
-    }
+        inline operator const uint8_t*() const {
+            return ptr;
+        }
 
-private:
-    const uint8_t  *ptr;
-};
+    private:
+        const uint8_t  *ptr;
+    };
 
-class AbstractEntry {
-public:
+    class AbstractEntry {
+    public:
 
-    // Entry starting in the given pointer
-    explicit AbstractEntry(const uint8_t *entry);
-    virtual ~AbstractEntry() {}
+        // Entry starting in the given pointer
+        explicit AbstractEntry(const uint8_t *entry);
+        virtual ~AbstractEntry() {}
 
-    // build concrete entry of appropriate class from pointer
-    static std::unique_ptr<AbstractEntry> buildEntry(const uint8_t *ptr);
+        // build concrete entry of appropriate class from pointer
+        static std::unique_ptr<AbstractEntry> buildEntry(const uint8_t *ptr);
 
-    // get format entry timestamp
-    // TODO consider changing to uint64_t
-    virtual int64_t      timestamp() const = 0;
+        // get format entry timestamp
+        // TODO consider changing to uint64_t
+        virtual int64_t      timestamp() const = 0;
 
-    // get format entry's unique id
-    virtual log_hash_t   hash() const = 0;
+        // get format entry's unique id
+        virtual log_hash_t   hash() const = 0;
 
-    // entry's author index (-1 if none present)
-    // a Merger has a vector of Readers, author simply points to the index of the
-    // Reader that originated the entry
-    // TODO consider changing to uint32_t
-    virtual int          author() const = 0;
+        // entry's author index (-1 if none present)
+        // a Merger has a vector of Readers, author simply points to the index of the
+        // Reader that originated the entry
+        // TODO consider changing to uint32_t
+        virtual int          author() const = 0;
 
-    // copy entry, adding author before timestamp, returns iterator to end of entry
-    virtual EntryIterator    copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
-                                       int author) const = 0;
+        // copy entry, adding author before timestamp, returns iterator to end of entry
+        virtual EntryIterator    copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
+                                                int author) const = 0;
 
-protected:
-    // copies ordinary entry from src to dst, and returns length of entry
-    // size_t      copyEntry(audio_utils_fifo_writer *dst, const iterator &it);
-    const uint8_t  *mEntry;
-};
+    protected:
+        // copies ordinary entry from src to dst, and returns length of entry
+        // size_t      copyEntry(audio_utils_fifo_writer *dst, const iterator &it);
+        const uint8_t  *mEntry;
+    };
 
-class FormatEntry : public AbstractEntry {
-public:
-    // explicit FormatEntry(const EntryIterator &it);
-    explicit FormatEntry(const uint8_t *ptr) : AbstractEntry(ptr) {}
-    virtual ~FormatEntry() {}
+    class FormatEntry : public AbstractEntry {
+    public:
+        // explicit FormatEntry(const EntryIterator &it);
+        explicit FormatEntry(const uint8_t *ptr) : AbstractEntry(ptr) {}
+        virtual ~FormatEntry() {}
 
-    EntryIterator begin() const;
+        EntryIterator begin() const;
 
-    // Entry's format string
-    const   char* formatString() const;
+        // Entry's format string
+        const   char* formatString() const;
 
-    // Enrty's format string length
-            size_t      formatStringLength() const;
+        // Enrty's format string length
+        size_t      formatStringLength() const;
 
-    // Format arguments (excluding format string, timestamp and author)
-            EntryIterator    args() const;
+        // Format arguments (excluding format string, timestamp and author)
+        EntryIterator    args() const;
 
-    // get format entry timestamp
-    virtual int64_t     timestamp() const override;
+        // get format entry timestamp
+        virtual int64_t     timestamp() const override;
 
-    // get format entry's unique id
-    virtual log_hash_t  hash() const override;
+        // get format entry's unique id
+        virtual log_hash_t  hash() const override;
 
-    // entry's author index (-1 if none present)
-    // a Merger has a vector of Readers, author simply points to the index of the
-    // Reader that originated the entry
-    virtual int         author() const override;
+        // entry's author index (-1 if none present)
+        // a Merger has a vector of Readers, author simply points to the index of the
+        // Reader that originated the entry
+        virtual int         author() const override;
 
-    // copy entry, adding author before timestamp, returns size of original entry
-    virtual EntryIterator    copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
-                                       int author) const override;
+        // copy entry, adding author before timestamp, returns size of original entry
+        virtual EntryIterator    copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
+                                                int author) const override;
 
-};
+    };
 
-class HistogramEntry : public AbstractEntry {
-public:
-    explicit HistogramEntry(const uint8_t *ptr) : AbstractEntry(ptr) {
-    }
-    virtual ~HistogramEntry() {}
+    class HistogramEntry : public AbstractEntry {
+    public:
+        explicit HistogramEntry(const uint8_t *ptr) : AbstractEntry(ptr) {
+        }
+        virtual ~HistogramEntry() {}
 
-    virtual int64_t     timestamp() const override;
+        virtual int64_t     timestamp() const override;
 
-    virtual log_hash_t  hash() const override;
+        virtual log_hash_t  hash() const override;
 
-    virtual int         author() const override;
+        virtual int         author() const override;
 
-    virtual EntryIterator    copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
-                                       int author) const override;
+        virtual EntryIterator    copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
+                                                int author) const override;
 
-};
+    };
 
-// ---------------------------------------------------------------------------
+    // ---------------------------------------------------------------------------
 
-// representation of a single log entry in private memory
-struct Entry {
-    Entry(Event event, const void *data, size_t length)
-        : mEvent(event), mLength(length), mData(data) { }
-    /*virtual*/ ~Entry() { }
+    // representation of a single log entry in private memory
+    struct Entry {
+        Entry(Event event, const void *data, size_t length)
+            : mEvent(event), mLength(length), mData(data) { }
+        /*virtual*/ ~Entry() { }
 
-    // used during writing to format Entry information as follows: [type][length][data ... ][length]
-    int     copyEntryDataAt(size_t offset) const;
+        // used during writing to format Entry information as follows:
+        // [type][length][data ... ][length]
+        int     copyEntryDataAt(size_t offset) const;
 
-private:
-    friend class Writer;
-    Event       mEvent;     // event type
-    uint8_t     mLength;    // length of additional data, 0 <= mLength <= kMaxLength
-    const void *mData;      // event type-specific data
-    static const size_t kMaxLength = 255;
-public:
-    // mEvent, mLength, mData[...], duplicate mLength
-    static const size_t kOverhead = sizeof(entry) + sizeof(ending);
-    // endind length of previous entry
-    static const size_t kPreviousLengthOffset = - sizeof(ending) +
-                                                offsetof(ending, length);
-};
+    private:
+        friend class Writer;
+        Event       mEvent;     // event type
+        uint8_t     mLength;    // length of additional data, 0 <= mLength <= kMaxLength
+        const void *mData;      // event type-specific data
+        static const size_t kMaxLength = 255;
+    public:
+        // mEvent, mLength, mData[...], duplicate mLength
+        static const size_t kOverhead = sizeof(entry) + sizeof(ending);
+        // endind length of previous entry
+        static const size_t kPreviousLengthOffset = - sizeof(ending) +
+            offsetof(ending, length);
+    };
 
-struct HistTsEntry {
-    log_hash_t hash;
-    int64_t ts;
-}; //TODO __attribute__((packed));
+    struct HistTsEntry {
+        log_hash_t hash;
+        int64_t ts;
+    }; //TODO __attribute__((packed));
 
-struct HistTsEntryWithAuthor {
-    log_hash_t hash;
-    int64_t ts;
-    int author;
-}; //TODO __attribute__((packed));
+    struct HistTsEntryWithAuthor {
+        log_hash_t hash;
+        int64_t ts;
+        int author;
+    }; //TODO __attribute__((packed));
 
-using StateTsEntryWithAuthor = HistTsEntryWithAuthor;
+    using StateTsEntryWithAuthor = HistTsEntryWithAuthor;
 
-struct HistIntEntry {
-    log_hash_t hash;
-    int value;
-}; //TODO __attribute__((packed));
+    struct HistIntEntry {
+        log_hash_t hash;
+        int value;
+    }; //TODO __attribute__((packed));
 
-// representation of a single log entry in shared memory
-//  byte[0]             mEvent
-//  byte[1]             mLength
-//  byte[2]             mData[0]
-//  ...
-//  byte[2+i]           mData[i]
-//  ...
-//  byte[2+mLength-1]   mData[mLength-1]
-//  byte[2+mLength]     duplicate copy of mLength to permit reverse scan
-//  byte[3+mLength]     start of next log entry
+    // representation of a single log entry in shared memory
+    //  byte[0]             mEvent
+    //  byte[1]             mLength
+    //  byte[2]             mData[0]
+    //  ...
+    //  byte[2+i]           mData[i]
+    //  ...
+    //  byte[2+mLength-1]   mData[mLength-1]
+    //  byte[2+mLength]     duplicate copy of mLength to permit reverse scan
+    //  byte[3+mLength]     start of next log entry
 
     static void    appendInt(String8 *body, const void *data);
     static void    appendFloat(String8 *body, const void *data);
@@ -275,309 +277,311 @@
     static String8 bufferDump(const EntryIterator &it);
 public:
 
-// Located in shared memory, must be POD.
-// Exactly one process must explicitly call the constructor or use placement new.
-// Since this is a POD, the destructor is empty and unnecessary to call it explicitly.
-struct Shared {
-    Shared() /* mRear initialized via default constructor */ { }
-    /*virtual*/ ~Shared() { }
+    // Located in shared memory, must be POD.
+    // Exactly one process must explicitly call the constructor or use placement new.
+    // Since this is a POD, the destructor is empty and unnecessary to call it explicitly.
+    struct Shared {
+        Shared() /* mRear initialized via default constructor */ { }
+        /*virtual*/ ~Shared() { }
 
-    audio_utils_fifo_index  mRear;  // index one byte past the end of most recent Entry
-    char    mBuffer[0];             // circular buffer for entries
-};
-
-public:
-
-// ---------------------------------------------------------------------------
-
-// FIXME Timeline was intended to wrap Writer and Reader, but isn't actually used yet.
-// For now it is just a namespace for sharedSize().
-class Timeline : public RefBase {
-public:
-#if 0
-    Timeline(size_t size, void *shared = NULL);
-    virtual ~Timeline();
-#endif
-
-    // Input parameter 'size' is the desired size of the timeline in byte units.
-    // Returns the size rounded up to a power-of-2, plus the constant size overhead for indices.
-    static size_t sharedSize(size_t size);
-
-#if 0
-private:
-    friend class    Writer;
-    friend class    Reader;
-
-    const size_t    mSize;      // circular buffer size in bytes, must be a power of 2
-    bool            mOwn;       // whether I own the memory at mShared
-    Shared* const   mShared;    // pointer to shared memory
-#endif
-};
-
-// ---------------------------------------------------------------------------
-
-// Writer is thread-safe with respect to Reader, but not with respect to multiple threads
-// calling Writer methods.  If you need multi-thread safety for writing, use LockedWriter.
-class Writer : public RefBase {
-public:
-    Writer();                   // dummy nop implementation without shared memory
-
-    // Input parameter 'size' is the desired size of the timeline in byte units.
-    // The size of the shared memory must be at least Timeline::sharedSize(size).
-    Writer(void *shared, size_t size);
-    Writer(const sp<IMemory>& iMemory, size_t size);
-
-    virtual ~Writer();
-
-    // FIXME needs comments, and some should be private
-    virtual void    log(const char *string);
-    virtual void    logf(const char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
-    virtual void    logvf(const char *fmt, va_list ap);
-    virtual void    logTimestamp();
-    virtual void    logTimestamp(const int64_t ts);
-    virtual void    logInteger(const int x);
-    virtual void    logFloat(const float x);
-    virtual void    logPID();
-    virtual void    logFormat(const char *fmt, log_hash_t hash, ...);
-    virtual void    logVFormat(const char *fmt, log_hash_t hash, va_list ap);
-    virtual void    logStart(const char *fmt);
-    virtual void    logEnd();
-    virtual void    logHash(log_hash_t hash);
-    virtual void    logEventHistTs(Event event, log_hash_t hash);
-
-    virtual bool    isEnabled() const;
-
-    // return value for all of these is the previous isEnabled()
-    virtual bool    setEnabled(bool enabled);   // but won't enable if no shared memory
-            bool    enable()    { return setEnabled(true); }
-            bool    disable()   { return setEnabled(false); }
-
-    sp<IMemory>     getIMemory() const  { return mIMemory; }
-
-private:
-    // 0 <= length <= kMaxLength
-    // writes a single Entry to the FIFO
-    void    log(Event event, const void *data, size_t length);
-    // checks validity of an event before calling log above this one
-    void    log(const Entry *entry, bool trusted = false);
-
-    Shared* const   mShared;    // raw pointer to shared memory
-    sp<IMemory>     mIMemory;   // ref-counted version, initialized in constructor and then const
-    audio_utils_fifo * const mFifo;                 // FIFO itself,
-                                                    // non-NULL unless constructor fails
-    audio_utils_fifo_writer * const mFifoWriter;    // used to write to FIFO,
-                                                    // non-NULL unless dummy constructor used
-    bool            mEnabled;   // whether to actually log
-
-    // cached pid and process name to use in %p format specifier
-    // total tag length is mPidTagSize and process name is not zero terminated
-    char   *mPidTag;
-    size_t  mPidTagSize;
-};
-
-// ---------------------------------------------------------------------------
-
-// Similar to Writer, but safe for multiple threads to call concurrently
-class LockedWriter : public Writer {
-public:
-    LockedWriter();
-    LockedWriter(void *shared, size_t size);
-
-    virtual void    log(const char *string);
-    virtual void    logf(const char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
-    virtual void    logvf(const char *fmt, va_list ap);
-    virtual void    logTimestamp();
-    virtual void    logTimestamp(const int64_t ts);
-    virtual void    logInteger(const int x);
-    virtual void    logFloat(const float x);
-    virtual void    logPID();
-    virtual void    logStart(const char *fmt);
-    virtual void    logEnd();
-    virtual void    logHash(log_hash_t hash);
-
-    virtual bool    isEnabled() const;
-    virtual bool    setEnabled(bool enabled);
-
-private:
-    mutable Mutex   mLock;
-};
-
-// ---------------------------------------------------------------------------
-
-class Reader : public RefBase {
-public:
-
-    // A snapshot of a readers buffer
-    // This is raw data. No analysis has been done on it
-    class Snapshot {
-    public:
-        Snapshot() : mData(NULL), mLost(0) {}
-
-        Snapshot(size_t bufferSize) : mData(new uint8_t[bufferSize]) {}
-
-        ~Snapshot() { delete[] mData; }
-
-        // copy of the buffer
-        uint8_t *data() const { return mData; }
-
-        // amount of data lost (given by audio_utils_fifo_reader)
-        size_t   lost() const { return mLost; }
-
-        // iterator to beginning of readable segment of snapshot
-        // data between begin and end has valid entries
-        EntryIterator begin() { return mBegin; }
-
-        // iterator to end of readable segment of snapshot
-        EntryIterator end() { return mEnd; }
-
-    private:
-        friend class Reader;
-        uint8_t              *mData;
-        size_t                mLost;
-        EntryIterator mBegin;
-        EntryIterator mEnd;
+        audio_utils_fifo_index  mRear;  // index one byte past the end of most recent Entry
+        char    mBuffer[0];             // circular buffer for entries
     };
 
-    // Input parameter 'size' is the desired size of the timeline in byte units.
-    // The size of the shared memory must be at least Timeline::sharedSize(size).
-    Reader(const void *shared, size_t size);
-    Reader(const sp<IMemory>& iMemory, size_t size);
-
-    virtual ~Reader();
-
-    // get snapshot of readers fifo buffer, effectively consuming the buffer
-    std::unique_ptr<Snapshot> getSnapshot();
-    // dump a particular snapshot of the reader
-    // TODO: move dump to PerformanceAnalysis. Model/view/controller design
-    void     dump(int fd, size_t indent, Snapshot & snap);
-    // dump the current content of the reader's buffer (call getSnapshot() and previous dump())
-    void     dump(int fd, size_t indent = 0);
-    bool     isIMemory(const sp<IMemory>& iMemory) const;
-
-private:
-
-    static const std::set<Event> startingTypes;
-    static const std::set<Event> endingTypes;
-    /*const*/ Shared* const mShared;    // raw pointer to shared memory, actually const but not
-                                        // declared as const because audio_utils_fifo() constructor
-    sp<IMemory> mIMemory;       // ref-counted version, assigned only in constructor
-    int     mFd;                // file descriptor
-    int     mIndent;            // indentation level
-    audio_utils_fifo * const mFifo;                 // FIFO itself,
-                                                    // non-NULL unless constructor fails
-    audio_utils_fifo_reader * const mFifoReader;    // used to read from FIFO,
-                                                    // non-NULL unless constructor fails
-
-    // TODO: it might be clearer, instead of a direct map from source location to vector of
-    // timestamps, if we instead first mapped from source location to an object that
-    // represented that location. And one_of its fields would be a vector of timestamps.
-    // That would allow us to record other information about the source location beyond timestamps.
-    void    dumpLine(const String8& timestamp, String8& body);
-
-    EntryIterator   handleFormat(const FormatEntry &fmtEntry,
-                                         String8 *timestamp,
-                                         String8 *body);
-    // dummy method for handling absent author entry
-    virtual void handleAuthor(const AbstractEntry& /*fmtEntry*/, String8* /*body*/) {}
-
-    // Searches for the last entry of type <type> in the range [front, back)
-    // back has to be entry-aligned. Returns nullptr if none enconuntered.
-    static const uint8_t *findLastEntryOfTypes(const uint8_t *front, const uint8_t *back,
-                                         const std::set<Event> &types);
-
-    static const size_t kSquashTimestamp = 5; // squash this many or more adjacent timestamps
-};
-
-// Wrapper for a reader with a name. Contains a pointer to the reader and a pointer to the name
-class NamedReader {
 public:
-    NamedReader() { mName[0] = '\0'; } // for Vector
-    NamedReader(const sp<NBLog::Reader>& reader, const char *name) :
-        mReader(reader)
-        { strlcpy(mName, name, sizeof(mName)); }
-    ~NamedReader() { }
-    const sp<NBLog::Reader>&  reader() const { return mReader; }
-    const char*               name() const { return mName; }
 
-private:
-    sp<NBLog::Reader>   mReader;
-    static const size_t kMaxName = 32;
-    char                mName[kMaxName];
-};
+    // ---------------------------------------------------------------------------
 
-// ---------------------------------------------------------------------------
+    // FIXME Timeline was intended to wrap Writer and Reader, but isn't actually used yet.
+    // For now it is just a namespace for sharedSize().
+    class Timeline : public RefBase {
+    public:
+#if 0
+        Timeline(size_t size, void *shared = NULL);
+        virtual ~Timeline();
+#endif
 
-class Merger : public RefBase {
-public:
-    Merger(const void *shared, size_t size);
+        // Input parameter 'size' is the desired size of the timeline in byte units.
+        // Returns the size rounded up to a power-of-2, plus the constant size overhead for indices.
+        static size_t sharedSize(size_t size);
 
-    virtual ~Merger() {}
+#if 0
+    private:
+        friend class    Writer;
+        friend class    Reader;
 
-    void addReader(const NamedReader &reader);
-    // TODO add removeReader
-    void merge();
-    // FIXME This is returning a reference to a shared variable that needs a lock
-    const std::vector<NamedReader>& getNamedReaders() const;
-private:
-    // vector of the readers the merger is supposed to merge from.
-    // every reader reads from a writer's buffer
-    // FIXME Needs to be protected by a lock
-    std::vector<NamedReader> mNamedReaders;
+        const size_t    mSize;      // circular buffer size in bytes, must be a power of 2
+        bool            mOwn;       // whether I own the memory at mShared
+        Shared* const   mShared;    // pointer to shared memory
+#endif
+    };
 
-    // TODO Need comments on all of these
-    Shared * const mShared;
-    std::unique_ptr<audio_utils_fifo> mFifo;
-    std::unique_ptr<audio_utils_fifo_writer> mFifoWriter;
-};
+    // ---------------------------------------------------------------------------
 
-class MergeReader : public Reader {
-public:
-    MergeReader(const void *shared, size_t size, Merger &merger);
-private:
-    // FIXME Needs to be protected by a lock,
-    //       because even though our use of it is read-only there may be asynchronous updates
-    const std::vector<NamedReader>& mNamedReaders;
-    // handle author entry by looking up the author's name and appending it to the body
-    // returns number of bytes read from fmtEntry
-    void handleAuthor(const AbstractEntry &fmtEntry, String8 *body);
-};
+    // Writer is thread-safe with respect to Reader, but not with respect to multiple threads
+    // calling Writer methods.  If you need multi-thread safety for writing, use LockedWriter.
+    class Writer : public RefBase {
+    public:
+        Writer();                   // dummy nop implementation without shared memory
 
-// MergeThread is a thread that contains a Merger. It works as a retriggerable one-shot:
-// when triggered, it awakes for a lapse of time, during which it periodically merges; if
-// retriggered, the timeout is reset.
-// The thread is triggered on AudioFlinger binder activity.
-class MergeThread : public Thread {
-public:
-    MergeThread(Merger &merger);
-    virtual ~MergeThread() override;
+        // Input parameter 'size' is the desired size of the timeline in byte units.
+        // The size of the shared memory must be at least Timeline::sharedSize(size).
+        Writer(void *shared, size_t size);
+        Writer(const sp<IMemory>& iMemory, size_t size);
 
-    // Reset timeout and activate thread to merge periodically if it's idle
-    void wakeup();
+        virtual ~Writer();
 
-    // Set timeout period until the merging thread goes idle again
-    void setTimeoutUs(int time);
+        // FIXME needs comments, and some should be private
+        virtual void    log(const char *string);
+        virtual void    logf(const char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
+        virtual void    logvf(const char *fmt, va_list ap);
+        virtual void    logTimestamp();
+        virtual void    logTimestamp(const int64_t ts);
+        virtual void    logInteger(const int x);
+        virtual void    logFloat(const float x);
+        virtual void    logPID();
+        virtual void    logFormat(const char *fmt, log_hash_t hash, ...);
+        virtual void    logVFormat(const char *fmt, log_hash_t hash, va_list ap);
+        virtual void    logStart(const char *fmt);
+        virtual void    logEnd();
+        virtual void    logHash(log_hash_t hash);
+        virtual void    logEventHistTs(Event event, log_hash_t hash);
 
-private:
-    virtual bool threadLoop() override;
+        virtual bool    isEnabled() const;
 
-    // the merger who actually does the work of merging the logs
-    Merger&     mMerger;
+        // return value for all of these is the previous isEnabled()
+        virtual bool    setEnabled(bool enabled);   // but won't enable if no shared memory
+        bool    enable()    { return setEnabled(true); }
+        bool    disable()   { return setEnabled(false); }
 
-    // mutex for the condition variable
-    Mutex       mMutex;
+        sp<IMemory>     getIMemory() const  { return mIMemory; }
 
-    // condition variable to activate merging on timeout >= 0
-    Condition   mCond;
+    private:
+        // 0 <= length <= kMaxLength
+        // writes a single Entry to the FIFO
+        void    log(Event event, const void *data, size_t length);
+        // checks validity of an event before calling log above this one
+        void    log(const Entry *entry, bool trusted = false);
 
-    // time left until the thread blocks again (in microseconds)
-    int         mTimeoutUs;
+        Shared* const   mShared;    // raw pointer to shared memory
+        sp<IMemory>     mIMemory;   // ref-counted version, initialized in constructor
+                                    // and then const
+        audio_utils_fifo * const mFifo;                 // FIFO itself, non-NULL
+                                                        // unless constructor fails
+        audio_utils_fifo_writer * const mFifoWriter;    // used to write to FIFO, non-NULL
+                                                        // unless dummy constructor used
+        bool            mEnabled;   // whether to actually log
 
-    // merging period when the thread is awake
-    static const int  kThreadSleepPeriodUs = 1000000 /*1s*/;
+        // cached pid and process name to use in %p format specifier
+        // total tag length is mPidTagSize and process name is not zero terminated
+        char   *mPidTag;
+        size_t  mPidTagSize;
+    };
 
-    // initial timeout value when triggered
-    static const int  kThreadWakeupPeriodUs = 3000000 /*3s*/;
-};
+    // ---------------------------------------------------------------------------
+
+    // Similar to Writer, but safe for multiple threads to call concurrently
+    class LockedWriter : public Writer {
+    public:
+        LockedWriter();
+        LockedWriter(void *shared, size_t size);
+
+        virtual void    log(const char *string);
+        virtual void    logf(const char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
+        virtual void    logvf(const char *fmt, va_list ap);
+        virtual void    logTimestamp();
+        virtual void    logTimestamp(const int64_t ts);
+        virtual void    logInteger(const int x);
+        virtual void    logFloat(const float x);
+        virtual void    logPID();
+        virtual void    logStart(const char *fmt);
+        virtual void    logEnd();
+        virtual void    logHash(log_hash_t hash);
+
+        virtual bool    isEnabled() const;
+        virtual bool    setEnabled(bool enabled);
+
+    private:
+        mutable Mutex   mLock;
+    };
+
+    // ---------------------------------------------------------------------------
+
+    class Reader : public RefBase {
+    public:
+
+        // A snapshot of a readers buffer
+        // This is raw data. No analysis has been done on it
+        class Snapshot {
+        public:
+            Snapshot() : mData(NULL), mLost(0) {}
+
+            Snapshot(size_t bufferSize) : mData(new uint8_t[bufferSize]) {}
+
+            ~Snapshot() { delete[] mData; }
+
+            // copy of the buffer
+            uint8_t *data() const { return mData; }
+
+            // amount of data lost (given by audio_utils_fifo_reader)
+            size_t   lost() const { return mLost; }
+
+            // iterator to beginning of readable segment of snapshot
+            // data between begin and end has valid entries
+            EntryIterator begin() { return mBegin; }
+
+            // iterator to end of readable segment of snapshot
+            EntryIterator end() { return mEnd; }
+
+        private:
+            friend class Reader;
+            uint8_t              *mData;
+            size_t                mLost;
+            EntryIterator mBegin;
+            EntryIterator mEnd;
+        };
+
+        // Input parameter 'size' is the desired size of the timeline in byte units.
+        // The size of the shared memory must be at least Timeline::sharedSize(size).
+        Reader(const void *shared, size_t size);
+        Reader(const sp<IMemory>& iMemory, size_t size);
+
+        virtual ~Reader();
+
+        // get snapshot of readers fifo buffer, effectively consuming the buffer
+        std::unique_ptr<Snapshot> getSnapshot();
+        // dump a particular snapshot of the reader
+        // TODO: move dump to PerformanceAnalysis. Model/view/controller design
+        void     dump(int fd, size_t indent, Snapshot & snap);
+        // dump the current content of the reader's buffer (call getSnapshot() and previous dump())
+        void     dump(int fd, size_t indent = 0);
+        bool     isIMemory(const sp<IMemory>& iMemory) const;
+
+    private:
+
+        static const std::set<Event> startingTypes;
+        static const std::set<Event> endingTypes;
+        /*const*/ Shared* const mShared;    // raw pointer to shared memory, actually const but not
+        // declared as const because audio_utils_fifo() constructor
+        sp<IMemory> mIMemory;       // ref-counted version, assigned only in constructor
+        int     mFd;                // file descriptor
+        int     mIndent;            // indentation level
+        audio_utils_fifo * const mFifo;                 // FIFO itself,
+        // non-NULL unless constructor fails
+        audio_utils_fifo_reader * const mFifoReader;    // used to read from FIFO,
+        // non-NULL unless constructor fails
+
+        // TODO: it might be clearer, instead of a direct map from source location to vector of
+        // timestamps, if we instead first mapped from source location to an object that
+        // represented that location. And one_of its fields would be a vector of timestamps.
+        // That would allow us to record other information about the source location beyond
+        // timestamps.
+        void    dumpLine(const String8& timestamp, String8& body);
+
+        EntryIterator   handleFormat(const FormatEntry &fmtEntry,
+                                     String8 *timestamp,
+                                     String8 *body);
+        // dummy method for handling absent author entry
+        virtual void handleAuthor(const AbstractEntry& /*fmtEntry*/, String8* /*body*/) {}
+
+        // Searches for the last entry of type <type> in the range [front, back)
+        // back has to be entry-aligned. Returns nullptr if none enconuntered.
+        static const uint8_t *findLastEntryOfTypes(const uint8_t *front, const uint8_t *back,
+                                                   const std::set<Event> &types);
+
+        static const size_t kSquashTimestamp = 5; // squash this many or more adjacent timestamps
+    };
+
+    // Wrapper for a reader with a name. Contains a pointer to the reader and a pointer to the name
+    class NamedReader {
+    public:
+        NamedReader() { mName[0] = '\0'; } // for Vector
+        NamedReader(const sp<NBLog::Reader>& reader, const char *name) :
+            mReader(reader)
+            { strlcpy(mName, name, sizeof(mName)); }
+        ~NamedReader() { }
+        const sp<NBLog::Reader>&  reader() const { return mReader; }
+        const char*               name() const { return mName; }
+
+    private:
+        sp<NBLog::Reader>   mReader;
+        static const size_t kMaxName = 32;
+        char                mName[kMaxName];
+    };
+
+    // ---------------------------------------------------------------------------
+
+    class Merger : public RefBase {
+    public:
+        Merger(const void *shared, size_t size);
+
+        virtual ~Merger() {}
+
+        void addReader(const NamedReader &reader);
+        // TODO add removeReader
+        void merge();
+        // FIXME This is returning a reference to a shared variable that needs a lock
+        const std::vector<NamedReader>& getNamedReaders() const;
+    private:
+        // vector of the readers the merger is supposed to merge from.
+        // every reader reads from a writer's buffer
+        // FIXME Needs to be protected by a lock
+        std::vector<NamedReader> mNamedReaders;
+
+        // TODO Need comments on all of these
+        Shared * const mShared;
+        std::unique_ptr<audio_utils_fifo> mFifo;
+        std::unique_ptr<audio_utils_fifo_writer> mFifoWriter;
+    };
+
+    class MergeReader : public Reader {
+    public:
+        MergeReader(const void *shared, size_t size, Merger &merger);
+    private:
+        // FIXME Needs to be protected by a lock,
+        //       because even though our use of it is read-only there may be asynchronous updates
+        const std::vector<NamedReader>& mNamedReaders;
+        // handle author entry by looking up the author's name and appending it to the body
+        // returns number of bytes read from fmtEntry
+        void handleAuthor(const AbstractEntry &fmtEntry, String8 *body);
+    };
+
+    // MergeThread is a thread that contains a Merger. It works as a retriggerable one-shot:
+    // when triggered, it awakes for a lapse of time, during which it periodically merges; if
+    // retriggered, the timeout is reset.
+    // The thread is triggered on AudioFlinger binder activity.
+    class MergeThread : public Thread {
+    public:
+        MergeThread(Merger &merger);
+        virtual ~MergeThread() override;
+
+        // Reset timeout and activate thread to merge periodically if it's idle
+        void wakeup();
+
+        // Set timeout period until the merging thread goes idle again
+        void setTimeoutUs(int time);
+
+    private:
+        virtual bool threadLoop() override;
+
+        // the merger who actually does the work of merging the logs
+        Merger&     mMerger;
+
+        // mutex for the condition variable
+        Mutex       mMutex;
+
+        // condition variable to activate merging on timeout >= 0
+        Condition   mCond;
+
+        // time left until the thread blocks again (in microseconds)
+        int         mTimeoutUs;
+
+        // merging period when the thread is awake
+        static const int  kThreadSleepPeriodUs = 1000000 /*1s*/;
+
+        // initial timeout value when triggered
+        static const int  kThreadWakeupPeriodUs = 3000000 /*3s*/;
+    };
 
 };  // class NBLog