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/*
* Copyright (C) 2013 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.
*/
// Non-blocking event logger intended for safe communication between processes via shared memory
#ifndef ANDROID_MEDIA_NBLOG_H
#define ANDROID_MEDIA_NBLOG_H
#include <binder/IMemory.h>
#include <utils/Mutex.h>
#include <media/nbaio/roundup.h>
namespace android {
class NBLog {
public:
class Writer;
class Reader;
private:
enum Event {
EVENT_RESERVED,
EVENT_STRING, // ASCII string, not NUL-terminated
EVENT_TIMESTAMP, // clock_gettime(CLOCK_MONOTONIC)
};
// ---------------------------------------------------------------------------
// 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() { }
int readAt(size_t offset) const;
private:
friend class Writer;
Event mEvent; // event type
size_t mLength; // length of additional data, 0 <= mLength <= 255
const void *mData; // event type-specific data
};
// 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
// located in shared memory
struct Shared {
Shared() : mRear(0) { }
/*virtual*/ ~Shared() { }
volatile int32_t 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(size_t size, void *shared);
Writer(size_t size, const sp<IMemory>& iMemory);
virtual ~Writer() { }
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 struct timespec& ts);
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:
void log(Event event, const void *data, size_t length);
void log(const Entry *entry, bool trusted = false);
const size_t mSize; // circular buffer size in bytes, must be a power of 2
Shared* const mShared; // raw pointer to shared memory
const sp<IMemory> mIMemory; // ref-counted version
int32_t mRear; // my private copy of mShared->mRear
bool mEnabled; // whether to actually log
};
// ---------------------------------------------------------------------------
// Similar to Writer, but safe for multiple threads to call concurrently
class LockedWriter : public Writer {
public:
LockedWriter();
LockedWriter(size_t size, void *shared);
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 struct timespec& ts);
virtual bool isEnabled() const;
virtual bool setEnabled(bool enabled);
private:
mutable Mutex mLock;
};
// ---------------------------------------------------------------------------
class Reader : public RefBase {
public:
// 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(size_t size, const void *shared);
Reader(size_t size, const sp<IMemory>& iMemory);
virtual ~Reader() { }
void dump(int fd, size_t indent = 0);
bool isIMemory(const sp<IMemory>& iMemory) const;
private:
const size_t mSize; // circular buffer size in bytes, must be a power of 2
const Shared* const mShared; // raw pointer to shared memory
const sp<IMemory> mIMemory; // ref-counted version
int32_t mFront; // index of oldest acknowledged Entry
static const size_t kSquashTimestamp = 5; // squash this many or more adjacent timestamps
};
}; // class NBLog
} // namespace android
#endif // ANDROID_MEDIA_NBLOG_H
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