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// --------------------------------------------------------------------------
//
// File
// Name: RateLimitingStream.cpp
// Purpose: Rate-limiting write-only wrapper around IOStreams
// Created: 2011/01/11
//
// --------------------------------------------------------------------------
#include "Box.h"
#include "RateLimitingStream.h"
#include "CommonException.h"
#include <string.h>
#include "MemLeakFindOn.h"
// --------------------------------------------------------------------------
//
// Function
// Name: RateLimitingStream::RateLimitingStream(const char *, int, int)
// Purpose: Constructor, set up buffer
// Created: 2011/01/11
//
// --------------------------------------------------------------------------
RateLimitingStream::RateLimitingStream(IOStream& rSink, size_t targetBytesPerSecond)
: mrSink(rSink), mStartTime(GetCurrentBoxTime()), mTotalBytesRead(0),
mTargetBytesPerSecond(targetBytesPerSecond)
{ }
// --------------------------------------------------------------------------
//
// Function
// Name: RateLimitingStream::Read(void *pBuffer, int NBytes,
// int Timeout)
// Purpose: Reads bytes to the underlying stream at no more than
// a fixed rate
// Created: 2011/01/11
//
// --------------------------------------------------------------------------
int RateLimitingStream::Read(void *pBuffer, int NBytes, int Timeout)
{
if(NBytes > 0 && (size_t)NBytes > mTargetBytesPerSecond)
{
// Limit to one second's worth of data for performance
BOX_TRACE("Reducing read size from " << NBytes << " to " <<
mTargetBytesPerSecond << " to smooth upload rate");
NBytes = mTargetBytesPerSecond;
}
int bytesReadThisTime = mrSink.Read(pBuffer, NBytes, Timeout);
// How many bytes we will have written after this write finishes?
mTotalBytesRead += bytesReadThisTime;
// When should it be completed by?
box_time_t desiredFinishTime = mStartTime +
SecondsToBoxTime(mTotalBytesRead / mTargetBytesPerSecond);
// How long do we have to wait?
box_time_t currentTime = GetCurrentBoxTime();
int64_t waitTime = desiredFinishTime - currentTime;
// How are we doing so far? (for logging only)
box_time_t currentDuration = currentTime - mStartTime;
// in case our timer is not very accurate, don't divide by zero on first pass
if(currentDuration == 0)
{
BOX_TRACE("Current rate not yet known, sending immediately");
return bytesReadThisTime;
}
uint64_t effectiveRateSoFar = (mTotalBytesRead * MICRO_SEC_IN_SEC_LL)
/ currentDuration;
if(waitTime > 0)
{
BOX_TRACE("Current rate " << effectiveRateSoFar <<
" higher than desired rate " << mTargetBytesPerSecond <<
", sleeping for " << BoxTimeToMilliSeconds(waitTime) <<
" ms");
ShortSleep(waitTime, false);
}
else
{
BOX_TRACE("Current rate " << effectiveRateSoFar <<
" lower than desired rate " << mTargetBytesPerSecond <<
", sending immediately (would have sent " <<
(BoxTimeToMilliSeconds(-waitTime)) << " ms ago)");
}
return bytesReadThisTime;
}
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