diff --git a/media/libnblog/Writer.cpp b/media/libnblog/Writer.cpp
new file mode 100644
index 0000000..da3bd52
--- /dev/null
+++ b/media/libnblog/Writer.cpp
@@ -0,0 +1,320 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "NBLog"
+//#define LOG_NDEBUG 0
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <sys/prctl.h>
+
+#include <audio_utils/fifo.h>
+#include <binder/IMemory.h>
+#include <media/nblog/Entry.h>
+#include <media/nblog/Events.h>
+#include <media/nblog/Timeline.h>
+#include <media/nblog/Writer.h>
+#include <utils/Log.h>
+#include <utils/Mutex.h>
+
+namespace android {
+namespace NBLog {
+
+Writer::Writer(void *shared, size_t size)
+    : mShared((Shared *) shared),
+      mFifo(mShared != NULL ?
+        new audio_utils_fifo(size, sizeof(uint8_t),
+            mShared->mBuffer, mShared->mRear, NULL /*throttlesFront*/) : NULL),
+      mFifoWriter(mFifo != NULL ? new audio_utils_fifo_writer(*mFifo) : NULL),
+      mEnabled(mFifoWriter != NULL)
+{
+    // caching pid and process name
+    pid_t id = ::getpid();
+    char procName[16];
+    int status = prctl(PR_GET_NAME, procName);
+    if (status) {  // error getting process name
+        procName[0] = '\0';
+    }
+    size_t length = strlen(procName);
+    mPidTagSize = length + sizeof(pid_t);
+    mPidTag = new char[mPidTagSize];
+    memcpy(mPidTag, &id, sizeof(pid_t));
+    memcpy(mPidTag + sizeof(pid_t), procName, length);
+}
+
+Writer::Writer(const sp<IMemory>& iMemory, size_t size)
+    : Writer(iMemory != 0 ? (Shared *) iMemory->pointer() : NULL, size)
+{
+    mIMemory = iMemory;
+}
+
+Writer::~Writer()
+{
+    delete mFifoWriter;
+    delete mFifo;
+    delete[] mPidTag;
+}
+
+void Writer::log(const char *string)
+{
+    if (!mEnabled) {
+        return;
+    }
+    LOG_ALWAYS_FATAL_IF(string == NULL, "Attempted to log NULL string");
+    size_t length = strlen(string);
+    if (length > Entry::kMaxLength) {
+        length = Entry::kMaxLength;
+    }
+    log(EVENT_STRING, string, length);
+}
+
+void Writer::logf(const char *fmt, ...)
+{
+    if (!mEnabled) {
+        return;
+    }
+    va_list ap;
+    va_start(ap, fmt);
+    Writer::logvf(fmt, ap);     // the Writer:: is needed to avoid virtual dispatch for LockedWriter
+    va_end(ap);
+}
+
+void Writer::logTimestamp()
+{
+    if (!mEnabled) {
+        return;
+    }
+    struct timespec ts;
+    if (!clock_gettime(CLOCK_MONOTONIC, &ts)) {
+        log(EVENT_TIMESTAMP, &ts, sizeof(ts));
+    }
+}
+
+void Writer::logFormat(const char *fmt, log_hash_t hash, ...)
+{
+    if (!mEnabled) {
+        return;
+    }
+    va_list ap;
+    va_start(ap, hash);
+    Writer::logVFormat(fmt, hash, ap);
+    va_end(ap);
+}
+
+void Writer::logEventHistTs(Event event, log_hash_t hash)
+{
+    if (!mEnabled) {
+        return;
+    }
+    HistTsEntry data;
+    data.hash = hash;
+    data.ts = systemTime();
+    if (data.ts > 0) {
+        log(event, &data, sizeof(data));
+    } else {
+        ALOGE("Failed to get timestamp");
+    }
+}
+
+bool Writer::isEnabled() const
+{
+    return mEnabled;
+}
+
+bool Writer::setEnabled(bool enabled)
+{
+    bool old = mEnabled;
+    mEnabled = enabled && mShared != NULL;
+    return old;
+}
+
+void Writer::log(const Entry &etr, bool trusted)
+{
+    if (!mEnabled) {
+        return;
+    }
+    if (!trusted) {
+        log(etr.mEvent, etr.mData, etr.mLength);
+        return;
+    }
+    const size_t need = etr.mLength + Entry::kOverhead; // mEvent, mLength, data[mLength], mLength
+                                                        // need = number of bytes written to FIFO
+
+    // FIXME optimize this using memcpy for the data part of the Entry.
+    // The Entry could have a method copyTo(ptr, offset, size) to optimize the copy.
+    // checks size of a single log Entry: type, length, data pointer and ending
+    uint8_t temp[Entry::kMaxLength + Entry::kOverhead];
+    // write this data to temp array
+    for (size_t i = 0; i < need; i++) {
+        temp[i] = etr.copyEntryDataAt(i);
+    }
+    // write to circular buffer
+    mFifoWriter->write(temp, need);
+}
+
+void Writer::log(Event event, const void *data, size_t length)
+{
+    if (!mEnabled) {
+        return;
+    }
+    if (data == NULL || length > Entry::kMaxLength) {
+        // TODO Perhaps it makes sense to display truncated data or at least a
+        //      message that the data is too long?  The current behavior can create
+        //      a confusion for a programmer debugging their code.
+        return;
+    }
+    // Ignore if invalid event
+    if (event == EVENT_RESERVED || event >= EVENT_UPPER_BOUND) {
+        return;
+    }
+    Entry etr(event, data, length);
+    log(etr, true /*trusted*/);
+}
+
+void Writer::logvf(const char *fmt, va_list ap)
+{
+    if (!mEnabled) {
+        return;
+    }
+    char buffer[Entry::kMaxLength + 1 /*NUL*/];
+    int length = vsnprintf(buffer, sizeof(buffer), fmt, ap);
+    if (length >= (int) sizeof(buffer)) {
+        length = sizeof(buffer) - 1;
+        // NUL termination is not required
+        // buffer[length] = '\0';
+    }
+    if (length >= 0) {
+        log(EVENT_STRING, buffer, length);
+    }
+}
+
+void Writer::logStart(const char *fmt)
+{
+    if (!mEnabled) {
+        return;
+    }
+    size_t length = strlen(fmt);
+    if (length > Entry::kMaxLength) {
+        length = Entry::kMaxLength;
+    }
+    log(EVENT_FMT_START, fmt, length);
+}
+
+void Writer::logTimestampFormat()
+{
+    if (!mEnabled) {
+        return;
+    }
+    const nsecs_t ts = systemTime();
+    if (ts > 0) {
+        log(EVENT_FMT_TIMESTAMP, &ts, sizeof(ts));
+    } else {
+        ALOGE("Failed to get timestamp");
+    }
+}
+
+void Writer::logVFormat(const char *fmt, log_hash_t hash, va_list argp)
+{
+    if (!mEnabled) {
+        return;
+    }
+    Writer::logStart(fmt);
+    int i;
+    double d;
+    float f;
+    char* s;
+    size_t length;
+    int64_t t;
+    Writer::logTimestampFormat();
+    log(EVENT_FMT_HASH, &hash, sizeof(hash));
+    for (const char *p = fmt; *p != '\0'; p++) {
+        // TODO: implement more complex formatting such as %.3f
+        if (*p != '%') {
+            continue;
+        }
+        switch(*++p) {
+        case 's': // string
+            s = va_arg(argp, char *);
+            length = strlen(s);
+            if (length > Entry::kMaxLength) {
+                length = Entry::kMaxLength;
+            }
+            log(EVENT_FMT_STRING, s, length);
+            break;
+
+        case 't': // timestamp
+            t = va_arg(argp, int64_t);
+            log(EVENT_FMT_TIMESTAMP, &t, sizeof(t));
+            break;
+
+        case 'd': // integer
+            i = va_arg(argp, int);
+            log(EVENT_FMT_INTEGER, &i, sizeof(i));
+            break;
+
+        case 'f': // float
+            d = va_arg(argp, double); // float arguments are promoted to double in vararg lists
+            f = (float)d;
+            log(EVENT_FMT_FLOAT, &f, sizeof(f));
+            break;
+
+        case 'p': // pid
+            log(EVENT_FMT_PID, mPidTag, mPidTagSize);
+            break;
+
+        // the "%\0" case finishes parsing
+        case '\0':
+            --p;
+            break;
+
+        case '%':
+            break;
+
+        default:
+            ALOGW("NBLog Writer parsed invalid format specifier: %c", *p);
+            break;
+        }
+    }
+    Entry etr(EVENT_FMT_END, nullptr, 0);
+    log(etr, true);
+}
+
+// ---------------------------------------------------------------------------
+
+LockedWriter::LockedWriter(void *shared, size_t size)
+    : Writer(shared, size)
+{
+}
+
+bool LockedWriter::isEnabled() const
+{
+    Mutex::Autolock _l(mLock);
+    return Writer::isEnabled();
+}
+
+bool LockedWriter::setEnabled(bool enabled)
+{
+    Mutex::Autolock _l(mLock);
+    return Writer::setEnabled(enabled);
+}
+
+void LockedWriter::log(const Entry &entry, bool trusted) {
+    Mutex::Autolock _l(mLock);
+    Writer::log(entry, trusted);
+}
+
+}   // namespace NBLog
+}   // namespace android