gecko-dev/devtools/shared/heapsnapshot/ZeroCopyNSIOutputStream.cpp
Nicholas Nethercote 34dcc7b852 Bug 1299384 - Use MOZ_MUST_USE with NS_warn_if_impl(). r=erahm.
This change avoids lots of false positives for Coverity's CHECKED_RETURN
warning, caused by NS_WARN_IF's current use in both statement-style and
expression-style.

In the case where the code within the NS_WARN_IF has side-effects, I made the
following change.

> NS_WARN_IF(NS_FAILED(FunctionWithSideEffects()));
> -->
> Unused << NS_WARN_IF(NS_FAILED(FunctionWithSideEffects()));

In the case where the code within the NS_WARN_IF lacks side-effects, I made the
following change.

> NS_WARN_IF(!condWithoutSideEffects);
> -->
> NS_WARNING_ASSERTION(condWithoutSideEffects, "msg");

This has two improvements.
- The condition is not evaluated in non-debug builds.
- The sense of the condition is inverted to the familiar "this condition should
  be true" sense used in assertions.

A common variation on the side-effect-free case is the following.

> nsresult rv = Fn();
> NS_WARN_IF_(NS_FAILED(rv));
> -->
> DebugOnly<nsresult rv> = Fn();
> NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "Fn failed");

--HG--
extra : rebase_source : 58788245021096efa8372a9dc1d597a611d45611
2016-09-02 17:12:24 +10:00

101 lines
2.3 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "mozilla/devtools/ZeroCopyNSIOutputStream.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/Unused.h"
namespace mozilla {
namespace devtools {
ZeroCopyNSIOutputStream::ZeroCopyNSIOutputStream(nsCOMPtr<nsIOutputStream>& out)
: out(out)
, result_(NS_OK)
, amountUsed(0)
, writtenCount(0)
{
DebugOnly<bool> nonBlocking = false;
MOZ_ASSERT(out->IsNonBlocking(&nonBlocking) == NS_OK);
MOZ_ASSERT(!nonBlocking);
}
ZeroCopyNSIOutputStream::~ZeroCopyNSIOutputStream()
{
if (!failed())
Unused << NS_WARN_IF(NS_FAILED(writeBuffer()));
}
nsresult
ZeroCopyNSIOutputStream::writeBuffer()
{
if (failed())
return result_;
if (amountUsed == 0)
return NS_OK;
int32_t amountWritten = 0;
while (amountWritten < amountUsed) {
uint32_t justWritten = 0;
result_ = out->Write(buffer + amountWritten,
amountUsed - amountWritten,
&justWritten);
if (NS_WARN_IF(NS_FAILED(result_)))
return result_;
amountWritten += justWritten;
}
writtenCount += amountUsed;
amountUsed = 0;
return NS_OK;
}
// ZeroCopyOutputStream Interface
bool
ZeroCopyNSIOutputStream::Next(void** data, int* size)
{
MOZ_ASSERT(data != nullptr);
MOZ_ASSERT(size != nullptr);
if (failed())
return false;
if (amountUsed == BUFFER_SIZE) {
if (NS_FAILED(writeBuffer()))
return false;
}
*data = buffer + amountUsed;
*size = BUFFER_SIZE - amountUsed;
amountUsed = BUFFER_SIZE;
return true;
}
void
ZeroCopyNSIOutputStream::BackUp(int count)
{
MOZ_ASSERT(count >= 0,
"Cannot back up a negative amount of bytes.");
MOZ_ASSERT(amountUsed == BUFFER_SIZE,
"Can only call BackUp directly after calling Next.");
MOZ_ASSERT(count <= amountUsed,
"Can't back up further than we've given out.");
amountUsed -= count;
}
::google::protobuf::int64
ZeroCopyNSIOutputStream::ByteCount() const
{
return writtenCount + amountUsed;
}
} // namespace devtools
} // namespace mozilla