rpcs3/Utilities/MTRingbuffer.h

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#pragma once
//Simple non-resizable FIFO Ringbuffer that can be simultaneously be read from and written to
//if we ever get to use boost please replace this with boost::circular_buffer, there's no reason
//why we would have to keep this amateur attempt at such a fundamental data-structure around
template< typename T, unsigned int MAX_MTRINGBUFFER_BUFFER_SIZE>
class MTRingbuffer{
std::array<T, MAX_MTRINGBUFFER_BUFFER_SIZE> mBuffer;
//this is a recursive mutex because the get methods lock it but the only
//way to be sure that they do not block is to check the size and the only
//way to check the size and use get atomically is to lock this mutex,
//so it goes:
//lock get mutex-->check size-->call get-->lock get mutex-->unlock get mutex-->return from get-->unlock get mutex
std::recursive_mutex mMutGet;
std::mutex mMutPut;
size_t mGet;
size_t mPut;
size_t moveGet(size_t by = 1){ return (mGet + by) % MAX_MTRINGBUFFER_BUFFER_SIZE; }
size_t movePut(size_t by = 1){ return (mPut + by) % MAX_MTRINGBUFFER_BUFFER_SIZE; }
public:
MTRingbuffer() : mGet(0), mPut(0){}
//blocks until there's something to get, so check "spaceLeft()" if you want to avoid blocking
//also lock the get mutex around the spaceLeft() check and the pop if you want to avoid racing
T pop()
{
std::lock_guard<std::recursive_mutex> lock(mMutGet);
while (mGet == mPut)
{
//wait until there's actually something to get
//throwing an exception might be better, blocking here is a little awkward
2014-12-22 23:31:11 +00:00
std::this_thread::sleep_for(std::chrono::milliseconds(1)); // hack
}
size_t ret = mGet;
mGet = moveGet();
return mBuffer[ret];
}
//blocks if the buffer is full until there's enough room
void push(T &putEle)
{
std::lock_guard<std::mutex> lock(mMutPut);
while (movePut() == mGet)
{
//if this is reached a lot it's time to increase the buffer size
//or implement dynamic re-sizing
2014-12-22 23:31:11 +00:00
std::this_thread::sleep_for(std::chrono::milliseconds(1)); // hack
}
mBuffer[mPut] = std::forward(putEle);
mPut = movePut();
}
bool empty()
{
return mGet == mPut;
}
//returns the amount of free places, this is the amount of actual free spaces-1
//since mGet==mPut signals an empty buffer we can't actually use the last free
//space, so we shouldn't report it as free.
size_t spaceLeft() //apparently free() is a macro definition in msvc in some conditions
{
if (mGet < mPut)
{
return mBuffer.size() - (mPut - mGet) - 1;
}
else if (mGet > mPut)
{
return mGet - mPut - 1;
}
else
{
return mBuffer.size() - 1;
}
}
size_t size()
{
//the magic -1 is the same magic 1 that is explained in the spaceLeft() function
return mBuffer.size() - spaceLeft() - 1;
}
//takes random access iterator to T
template<typename IteratorType>
void pushRange(IteratorType from, IteratorType until)
{
std::lock_guard<std::mutex> lock(mMutPut);
size_t length = until - from;
//if whatever we're trying to store is greater than the entire buffer the following loop will be infinite
assert(mBuffer.size() > length);
while (spaceLeft() < length)
{
//if this is reached a lot it's time to increase the buffer size
//or implement dynamic re-sizing
2014-12-22 23:31:11 +00:00
std::this_thread::sleep_for(std::chrono::milliseconds(1)); // hack
}
if (mPut + length <= mBuffer.size())
{
std::copy(from, until, mBuffer.begin() + mPut);
}
else
{
size_t tillEnd = mBuffer.size() - mPut;
std::copy(from, from + tillEnd, mBuffer.begin() + mPut);
std::copy(from + tillEnd, until, mBuffer.begin());
}
mPut = movePut(length);
}
//takes output iterator to T
template<typename IteratorType>
void popN(IteratorType output, size_t n)
{
std::lock_guard<std::recursive_mutex> lock(mMutGet);
//make sure we're not trying to retrieve more than is in
assert(n <= size());
peekN<IteratorType>(output, n);
mGet = moveGet(n);
}
//takes output iterator to T
template<typename IteratorType>
void peekN(IteratorType output, size_t n)
{
size_t lGet = mGet;
if (lGet + n <= mBuffer.size())
{
std::copy_n(mBuffer.begin() + lGet, n, output);
}
else
{
auto next = std::copy(mBuffer.begin() + lGet, mBuffer.end(), output);
std::copy_n(mBuffer.begin(), n - (mBuffer.size() - lGet), next);
}
}
//well this is just asking for trouble
//but the comment above the declaration of mMutGet explains why it's there
//if there's a better way please remove this
void lockGet()
{
mMutGet.lock();
}
//well this is just asking for trouble
//but the comment above the declaration of mMutGet explains why it's there
//if there's a better way please remove this
void unlockGet()
{
mMutGet.unlock();
}
};