The Tor Browser: image/encoders/png/nsPNGEncoder.cpp@6474c204b198 (annotated)

image/encoders/png/nsPNGEncoder.cpp@6474c204b198 (annotated)

image/encoders/png/nsPNGEncoder.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- 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 "nsCRT.h"
 #include "nsPNGEncoder.h"
 #include "prprf.h"
 #include "nsString.h"
 #include "nsStreamUtils.h"
 using namespace mozilla;
 NS_IMPL_ISUPPORTS(nsPNGEncoder, imgIEncoder, nsIInputStream, nsIAsyncInputStream)
 nsPNGEncoder::nsPNGEncoder() : mPNG(nullptr), mPNGinfo(nullptr),
                                mIsAnimation(false),
                                mFinished(false),
                                mImageBuffer(nullptr), mImageBufferSize(0),
                                mImageBufferUsed(0), mImageBufferReadPoint(0),
                                mCallback(nullptr),
                                mCallbackTarget(nullptr), mNotifyThreshold(0),
                                mReentrantMonitor("nsPNGEncoder.mReentrantMonitor")
 {
 }
 nsPNGEncoder::~nsPNGEncoder()
 {
   if (mImageBuffer) {
     moz_free(mImageBuffer);
     mImageBuffer = nullptr;
   }
   // don't leak if EndImageEncode wasn't called
   if (mPNG)
     png_destroy_write_struct(&mPNG, &mPNGinfo);
 }
 // nsPNGEncoder::InitFromData
 //
 //    One output option is supported: "transparency=none" means that the
 //    output PNG will not have an alpha channel, even if the input does.
 //
 //    Based partially on gfx/cairo/cairo/src/cairo-png.c
 //    See also modules/libimg/png/libpng.txt
 NS_IMETHODIMP nsPNGEncoder::InitFromData(const uint8_t* aData,
                                          uint32_t aLength, // (unused,
                                                            // req'd by JS)
                                          uint32_t aWidth,
                                          uint32_t aHeight,
                                          uint32_t aStride,
                                          uint32_t aInputFormat,
                                          const nsAString& aOutputOptions)
 {
   NS_ENSURE_ARG(aData);
   nsresult rv;
   rv = StartImageEncode(aWidth, aHeight, aInputFormat, aOutputOptions);
   if (!NS_SUCCEEDED(rv))
     return rv;
   rv = AddImageFrame(aData, aLength, aWidth, aHeight, aStride,
                      aInputFormat, aOutputOptions);
   if (!NS_SUCCEEDED(rv))
     return rv;
   rv = EndImageEncode();
   return rv;
 }
 // nsPNGEncoder::StartImageEncode
 //
 //
 // See ::InitFromData for other info.
 NS_IMETHODIMP nsPNGEncoder::StartImageEncode(uint32_t aWidth,
                                              uint32_t aHeight,
                                              uint32_t aInputFormat,
                                              const nsAString& aOutputOptions)
 {
   bool useTransparency = true, skipFirstFrame = false;
   uint32_t numFrames = 1;
   uint32_t numPlays = 0; // For animations, 0 == forever
   // can't initialize more than once
   if (mImageBuffer != nullptr)
     return NS_ERROR_ALREADY_INITIALIZED;
   // validate input format
   if (aInputFormat != INPUT_FORMAT_RGB &&
       aInputFormat != INPUT_FORMAT_RGBA &&
       aInputFormat != INPUT_FORMAT_HOSTARGB)
     return NS_ERROR_INVALID_ARG;
   // parse and check any provided output options
   nsresult rv = ParseOptions(aOutputOptions, &useTransparency, &skipFirstFrame,
                              &numFrames, &numPlays, nullptr, nullptr,
                              nullptr, nullptr, nullptr);
   if (rv != NS_OK)
     return rv;
 #ifdef PNG_APNG_SUPPORTED
   if (numFrames > 1)
     mIsAnimation = true;
 #endif
   // initialize
   mPNG = png_create_write_struct(PNG_LIBPNG_VER_STRING,
                                  nullptr,
                                  ErrorCallback,
                                  WarningCallback);
   if (! mPNG)
     return NS_ERROR_OUT_OF_MEMORY;
   mPNGinfo = png_create_info_struct(mPNG);
   if (! mPNGinfo) {
     png_destroy_write_struct(&mPNG, nullptr);
     return NS_ERROR_FAILURE;
   }
   // libpng's error handler jumps back here upon an error.
   // Note: It's important that all png_* callers do this, or errors
   // will result in a corrupt time-warped stack.
   if (setjmp(png_jmpbuf(mPNG))) {
     png_destroy_write_struct(&mPNG, &mPNGinfo);
     return NS_ERROR_FAILURE;
   }
   // Set up to read the data into our image buffer, start out with an 8K
   // estimated size. Note: we don't have to worry about freeing this data
   // in this function. It will be freed on object destruction.
   mImageBufferSize = 8192;
   mImageBuffer = (uint8_t*)moz_malloc(mImageBufferSize);
   if (!mImageBuffer) {
     png_destroy_write_struct(&mPNG, &mPNGinfo);
     return NS_ERROR_OUT_OF_MEMORY;
   }
   mImageBufferUsed = 0;
   // set our callback for libpng to give us the data
   png_set_write_fn(mPNG, this, WriteCallback, nullptr);
   // include alpha?
   int colorType;
   if ((aInputFormat == INPUT_FORMAT_HOSTARGB ||
        aInputFormat == INPUT_FORMAT_RGBA)  &&
        useTransparency)
     colorType = PNG_COLOR_TYPE_RGB_ALPHA;
   else
     colorType = PNG_COLOR_TYPE_RGB;
   png_set_IHDR(mPNG, mPNGinfo, aWidth, aHeight, 8, colorType,
                PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
                PNG_FILTER_TYPE_DEFAULT);
 #ifdef PNG_APNG_SUPPORTED
   if (mIsAnimation) {
     png_set_first_frame_is_hidden(mPNG, mPNGinfo, skipFirstFrame);
     png_set_acTL(mPNG, mPNGinfo, numFrames, numPlays);
   }
 #endif
   // XXX: support PLTE, gAMA, tRNS, bKGD?
   png_write_info(mPNG, mPNGinfo);
   return NS_OK;
 }
 // Returns the number of bytes in the image buffer used.
 NS_IMETHODIMP nsPNGEncoder::GetImageBufferUsed(uint32_t *aOutputSize)
 {
   NS_ENSURE_ARG_POINTER(aOutputSize);
   *aOutputSize = mImageBufferUsed;
   return NS_OK;
 }
 // Returns a pointer to the start of the image buffer
 NS_IMETHODIMP nsPNGEncoder::GetImageBuffer(char **aOutputBuffer)
 {
   NS_ENSURE_ARG_POINTER(aOutputBuffer);
   *aOutputBuffer = reinterpret_cast<char*>(mImageBuffer);
   return NS_OK;
 }
 NS_IMETHODIMP nsPNGEncoder::AddImageFrame(const uint8_t* aData,
                                           uint32_t aLength, // (unused,
                                                             // req'd by JS)
                                           uint32_t aWidth,
                                           uint32_t aHeight,
                                           uint32_t aStride,
                                           uint32_t aInputFormat,
                                           const nsAString& aFrameOptions)
 {
   bool useTransparency= true;
   uint32_t delay_ms = 500;
 #ifdef PNG_APNG_SUPPORTED
   uint32_t dispose_op = PNG_DISPOSE_OP_NONE;
   uint32_t blend_op = PNG_BLEND_OP_SOURCE;
 #else
   uint32_t dispose_op;
   uint32_t blend_op;
 #endif
   uint32_t x_offset = 0, y_offset = 0;
   // must be initialized
   if (mImageBuffer == nullptr)
     return NS_ERROR_NOT_INITIALIZED;
   // EndImageEncode was done, or some error occurred earlier
   if (!mPNG)
     return NS_BASE_STREAM_CLOSED;
   // validate input format
   if (aInputFormat != INPUT_FORMAT_RGB &&
       aInputFormat != INPUT_FORMAT_RGBA &&
       aInputFormat != INPUT_FORMAT_HOSTARGB)
     return NS_ERROR_INVALID_ARG;
   // libpng's error handler jumps back here upon an error.
   if (setjmp(png_jmpbuf(mPNG))) {
     png_destroy_write_struct(&mPNG, &mPNGinfo);
     return NS_ERROR_FAILURE;
   }
   // parse and check any provided output options
   nsresult rv = ParseOptions(aFrameOptions, &useTransparency, nullptr,
                              nullptr, nullptr, &dispose_op, &blend_op,
                              &delay_ms, &x_offset, &y_offset);
   if (rv != NS_OK)
     return rv;
 #ifdef PNG_APNG_SUPPORTED
   if (mIsAnimation) {
     // XXX the row pointers arg (#3) is unused, can it be removed?
     png_write_frame_head(mPNG, mPNGinfo, nullptr,
                          aWidth, aHeight, x_offset, y_offset,
                          delay_ms, 1000, dispose_op, blend_op);
   }
 #endif
   // Stride is the padded width of each row, so it better be longer
   // (I'm afraid people will not understand what stride means, so
   // check it well)
   if ((aInputFormat == INPUT_FORMAT_RGB &&
       aStride < aWidth * 3) ||
       ((aInputFormat == INPUT_FORMAT_RGBA ||
       aInputFormat == INPUT_FORMAT_HOSTARGB) &&
       aStride < aWidth * 4)) {
     NS_WARNING("Invalid stride for InitFromData/AddImageFrame");
     return NS_ERROR_INVALID_ARG;
   }
 #ifdef PNG_WRITE_FILTER_SUPPORTED
   png_set_filter(mPNG, PNG_FILTER_TYPE_BASE, PNG_FILTER_VALUE_NONE);
 #endif
   // write each row: if we add more input formats, we may want to
   // generalize the conversions
   if (aInputFormat == INPUT_FORMAT_HOSTARGB) {
     // PNG requires RGBA with post-multiplied alpha, so we need to
     // convert
     uint8_t* row = new uint8_t[aWidth * 4];
     for (uint32_t y = 0; y < aHeight; y ++) {
       ConvertHostARGBRow(&aData[y * aStride], row, aWidth, useTransparency);
       png_write_row(mPNG, row);
     }
     delete[] row;
   } else if (aInputFormat == INPUT_FORMAT_RGBA && ! useTransparency) {
     // RBGA, but we need to strip the alpha
     uint8_t* row = new uint8_t[aWidth * 4];
     for (uint32_t y = 0; y < aHeight; y ++) {
       StripAlpha(&aData[y * aStride], row, aWidth);
       png_write_row(mPNG, row);
     }
     delete[] row;
   } else if (aInputFormat == INPUT_FORMAT_RGB ||
              aInputFormat == INPUT_FORMAT_RGBA) {
     // simple RBG(A), no conversion needed
     for (uint32_t y = 0; y < aHeight; y ++) {
       png_write_row(mPNG, (uint8_t*)&aData[y * aStride]);
     }
   } else {
     NS_NOTREACHED("Bad format type");
     return NS_ERROR_INVALID_ARG;
   }
 #ifdef PNG_APNG_SUPPORTED
   if (mIsAnimation) {
     png_write_frame_tail(mPNG, mPNGinfo);
   }
 #endif
   return NS_OK;
 }
 NS_IMETHODIMP nsPNGEncoder::EndImageEncode()
 {
   // must be initialized
   if (mImageBuffer == nullptr)
     return NS_ERROR_NOT_INITIALIZED;
   // EndImageEncode has already been called, or some error
   // occurred earlier
   if (!mPNG)
     return NS_BASE_STREAM_CLOSED;
   // libpng's error handler jumps back here upon an error.
   if (setjmp(png_jmpbuf(mPNG))) {
     png_destroy_write_struct(&mPNG, &mPNGinfo);
     return NS_ERROR_FAILURE;
   }
   png_write_end(mPNG, mPNGinfo);
   png_destroy_write_struct(&mPNG, &mPNGinfo);
   mFinished = true;
   NotifyListener();
   // if output callback can't get enough memory, it will free our buffer
   if (!mImageBuffer)
     return NS_ERROR_OUT_OF_MEMORY;
   return NS_OK;
 }
 nsresult
 nsPNGEncoder::ParseOptions(const nsAString& aOptions,
                            bool* useTransparency,
                            bool* skipFirstFrame,
                            uint32_t* numFrames,
                            uint32_t* numPlays,
                            uint32_t* frameDispose,
                            uint32_t* frameBlend,
                            uint32_t* frameDelay,
                            uint32_t* offsetX,
                            uint32_t* offsetY)
 {
 #ifdef PNG_APNG_SUPPORTED
   // Make a copy of aOptions, because strtok() will modify it.
   nsAutoCString optionsCopy;
   optionsCopy.Assign(NS_ConvertUTF16toUTF8(aOptions));
   char* options = optionsCopy.BeginWriting();
   while (char* token = nsCRT::strtok(options, ";", &options)) {
     // If there's an '=' character, split the token around it.
     char* equals = token, *value = nullptr;
     while(*equals != '=' && *equals) {
       ++equals;
     }
     if (*equals == '=')
       value = equals + 1;
     if (value)
       *equals = '\0'; // temporary null
     // transparency=[yes|no|none]
     if (nsCRT::strcmp(token, "transparency") == 0 && useTransparency) {
       if (!value)
         return NS_ERROR_INVALID_ARG;
       if (nsCRT::strcmp(value, "none") == 0 ||
           nsCRT::strcmp(value, "no") == 0) {
         *useTransparency = false;
       } else if (nsCRT::strcmp(value, "yes") == 0) {
         *useTransparency = true;
       } else {
         return NS_ERROR_INVALID_ARG;
       }
     // skipfirstframe=[yes|no]
     } else if (nsCRT::strcmp(token, "skipfirstframe") == 0 &&
                skipFirstFrame) {
       if (!value)
         return NS_ERROR_INVALID_ARG;
       if (nsCRT::strcmp(value, "no") == 0) {
         *skipFirstFrame = false;
       } else if (nsCRT::strcmp(value, "yes") == 0) {
         *skipFirstFrame = true;
       } else {
         return NS_ERROR_INVALID_ARG;
       }
     // frames=#
     } else if (nsCRT::strcmp(token, "frames") == 0 && numFrames) {
       if (!value)
         return NS_ERROR_INVALID_ARG;
       if (PR_sscanf(value, "%u", numFrames) != 1) {
         return NS_ERROR_INVALID_ARG;
       }
       // frames=0 is nonsense.
       if (*numFrames == 0)
         return NS_ERROR_INVALID_ARG;
     // plays=#
     } else if (nsCRT::strcmp(token, "plays") == 0 && numPlays) {
       if (!value)
         return NS_ERROR_INVALID_ARG;
       // plays=0 to loop forever, otherwise play sequence specified
       // number of times
       if (PR_sscanf(value, "%u", numPlays) != 1)
         return NS_ERROR_INVALID_ARG;
     // dispose=[none|background|previous]
     } else if (nsCRT::strcmp(token, "dispose") == 0 && frameDispose) {
       if (!value)
         return NS_ERROR_INVALID_ARG;
       if (nsCRT::strcmp(value, "none") == 0) {
         *frameDispose = PNG_DISPOSE_OP_NONE;
       } else if (nsCRT::strcmp(value, "background") == 0) {
         *frameDispose = PNG_DISPOSE_OP_BACKGROUND;
       } else if (nsCRT::strcmp(value, "previous") == 0) {
         *frameDispose = PNG_DISPOSE_OP_PREVIOUS;
       } else {
         return NS_ERROR_INVALID_ARG;
       }
     // blend=[source|over]
     } else if (nsCRT::strcmp(token, "blend") == 0 && frameBlend) {
       if (!value)
         return NS_ERROR_INVALID_ARG;
       if (nsCRT::strcmp(value, "source") == 0) {
         *frameBlend = PNG_BLEND_OP_SOURCE;
       } else if (nsCRT::strcmp(value, "over") == 0) {
         *frameBlend = PNG_BLEND_OP_OVER;
       } else {
         return NS_ERROR_INVALID_ARG;
       }
     // delay=# (in ms)
     } else if (nsCRT::strcmp(token, "delay") == 0 && frameDelay) {
       if (!value)
         return NS_ERROR_INVALID_ARG;
       if (PR_sscanf(value, "%u", frameDelay) != 1)
         return NS_ERROR_INVALID_ARG;
     // xoffset=#
     } else if (nsCRT::strcmp(token, "xoffset") == 0 && offsetX) {
       if (!value)
         return NS_ERROR_INVALID_ARG;
       if (PR_sscanf(value, "%u", offsetX) != 1)
         return NS_ERROR_INVALID_ARG;
     // yoffset=#
     } else if (nsCRT::strcmp(token, "yoffset") == 0 && offsetY) {
       if (!value)
         return NS_ERROR_INVALID_ARG;
       if (PR_sscanf(value, "%u", offsetY) != 1)
         return NS_ERROR_INVALID_ARG;
     // unknown token name
     } else
       return NS_ERROR_INVALID_ARG;
     if (value)
       *equals = '='; // restore '=' so strtok doesn't get lost
   }
 #endif
   return NS_OK;
 }
 /* void close (); */
 NS_IMETHODIMP nsPNGEncoder::Close()
 {
   if (mImageBuffer != nullptr) {
     moz_free(mImageBuffer);
     mImageBuffer = nullptr;
     mImageBufferSize = 0;
     mImageBufferUsed = 0;
     mImageBufferReadPoint = 0;
   }
   return NS_OK;
 }
 /* unsigned long available (); */
 NS_IMETHODIMP nsPNGEncoder::Available(uint64_t *_retval)
 {
   if (!mImageBuffer)
     return NS_BASE_STREAM_CLOSED;
   *_retval = mImageBufferUsed - mImageBufferReadPoint;
   return NS_OK;
 }
 /* [noscript] unsigned long read (in charPtr aBuf,
                                   in unsigned long aCount); */
 NS_IMETHODIMP nsPNGEncoder::Read(char * aBuf, uint32_t aCount,
                                  uint32_t *_retval)
 {
   return ReadSegments(NS_CopySegmentToBuffer, aBuf, aCount, _retval);
 }
 /* [noscript] unsigned long readSegments (in nsWriteSegmentFun aWriter,
                                           in voidPtr aClosure,
                                           in unsigned long aCount); */
 NS_IMETHODIMP nsPNGEncoder::ReadSegments(nsWriteSegmentFun aWriter,
                                          void *aClosure, uint32_t aCount,
                                          uint32_t *_retval)
 {
   // Avoid another thread reallocing the buffer underneath us
   ReentrantMonitorAutoEnter autoEnter(mReentrantMonitor);
   uint32_t maxCount = mImageBufferUsed - mImageBufferReadPoint;
   if (maxCount == 0) {
     *_retval = 0;
     return mFinished ? NS_OK : NS_BASE_STREAM_WOULD_BLOCK;
   }
   if (aCount > maxCount)
     aCount = maxCount;
   nsresult rv =
       aWriter(this, aClosure,
               reinterpret_cast<const char*>(mImageBuffer+mImageBufferReadPoint),
 , aCount, _retval);
   if (NS_SUCCEEDED(rv)) {
     NS_ASSERTION(*_retval <= aCount, "bad write count");
     mImageBufferReadPoint += *_retval;
   }
   // errors returned from the writer end here!
   return NS_OK;
 }
 /* boolean isNonBlocking (); */
 NS_IMETHODIMP nsPNGEncoder::IsNonBlocking(bool *_retval)
 {
   *_retval = true;
   return NS_OK;
 }
 NS_IMETHODIMP nsPNGEncoder::AsyncWait(nsIInputStreamCallback *aCallback,
                                       uint32_t aFlags,
                                       uint32_t aRequestedCount,
                                       nsIEventTarget *aTarget)
 {
   if (aFlags != 0)
     return NS_ERROR_NOT_IMPLEMENTED;
   if (mCallback || mCallbackTarget)
     return NS_ERROR_UNEXPECTED;
   mCallbackTarget = aTarget;
   // 0 means "any number of bytes except 0"
   mNotifyThreshold = aRequestedCount;
   if (!aRequestedCount)
     mNotifyThreshold = 1024; // We don't want to notify incessantly
   // We set the callback absolutely last, because NotifyListener uses it to
   // determine if someone needs to be notified.  If we don't set it last,
   // NotifyListener might try to fire off a notification to a null target
   // which will generally cause non-threadsafe objects to be used off the main thread
   mCallback = aCallback;
   // What we are being asked for may be present already
   NotifyListener();
   return NS_OK;
 }
 NS_IMETHODIMP nsPNGEncoder::CloseWithStatus(nsresult aStatus)
 {
   return Close();
 }
 // nsPNGEncoder::ConvertHostARGBRow
 //
 //    Our colors are stored with premultiplied alphas, but PNGs use
 //    post-multiplied alpha. This swaps to PNG-style alpha.
 //
 //    Copied from gfx/cairo/cairo/src/cairo-png.c
 void
 nsPNGEncoder::ConvertHostARGBRow(const uint8_t* aSrc, uint8_t* aDest,
                                  uint32_t aPixelWidth,
                                  bool aUseTransparency)
 {
   uint32_t pixelStride = aUseTransparency ? 4 : 3;
   for (uint32_t x = 0; x < aPixelWidth; x ++) {
     const uint32_t& pixelIn = ((const uint32_t*)(aSrc))[x];
     uint8_t *pixelOut = &aDest[x * pixelStride];
     uint8_t alpha = (pixelIn & 0xff000000) >> 24;
     if (alpha == 0) {
       pixelOut[0] = pixelOut[1] = pixelOut[2] = pixelOut[3] = 0;
     } else {
       pixelOut[0] = (((pixelIn & 0xff0000) >> 16) * 255 + alpha / 2) / alpha;
       pixelOut[1] = (((pixelIn & 0x00ff00) >>  8) * 255 + alpha / 2) / alpha;
       pixelOut[2] = (((pixelIn & 0x0000ff) >>  0) * 255 + alpha / 2) / alpha;
       if (aUseTransparency)
         pixelOut[3] = alpha;
     }
   }
 }
 // nsPNGEncoder::StripAlpha
 //
 //    Input is RGBA, output is RGB
 void
 nsPNGEncoder::StripAlpha(const uint8_t* aSrc, uint8_t* aDest,
                           uint32_t aPixelWidth)
 {
   for (uint32_t x = 0; x < aPixelWidth; x ++) {
     const uint8_t* pixelIn = &aSrc[x * 4];
     uint8_t* pixelOut = &aDest[x * 3];
     pixelOut[0] = pixelIn[0];
     pixelOut[1] = pixelIn[1];
     pixelOut[2] = pixelIn[2];
   }
 }
 // nsPNGEncoder::WarningCallback
 void // static
 nsPNGEncoder::WarningCallback(png_structp png_ptr,
                             png_const_charp warning_msg)
 {
 #ifdef DEBUG
 	// XXX: these messages are probably useful callers...
         // use nsIConsoleService?
 	PR_fprintf(PR_STDERR, "PNG Encoder: %s\n", warning_msg);;
 #endif
 }
 // nsPNGEncoder::ErrorCallback
 void // static
 nsPNGEncoder::ErrorCallback(png_structp png_ptr,
                             png_const_charp error_msg)
 {
 #ifdef DEBUG
 	// XXX: these messages are probably useful callers...
         // use nsIConsoleService?
 	PR_fprintf(PR_STDERR, "PNG Encoder: %s\n", error_msg);;
 #endif
 #if PNG_LIBPNG_VER < 10500
         longjmp(png_ptr->jmpbuf, 1);
 #else
         png_longjmp(png_ptr, 1);
 #endif
 }
 // nsPNGEncoder::WriteCallback
 void // static
 nsPNGEncoder::WriteCallback(png_structp png, png_bytep data,
                             png_size_t size)
 {
   nsPNGEncoder* that = static_cast<nsPNGEncoder*>(png_get_io_ptr(png));
   if (! that->mImageBuffer)
     return;
   if (that->mImageBufferUsed + size > that->mImageBufferSize) {
     // When we're reallocing the buffer we need to take the lock to ensure
     // that nobody is trying to read from the buffer we are destroying
     ReentrantMonitorAutoEnter autoEnter(that->mReentrantMonitor);
     // expand buffer, just double each time
     that->mImageBufferSize *= 2;
     uint8_t* newBuf = (uint8_t*)moz_realloc(that->mImageBuffer,
                                             that->mImageBufferSize);
     if (! newBuf) {
       // can't resize, just zero (this will keep us from writing more)
       moz_free(that->mImageBuffer);
       that->mImageBuffer = nullptr;
       that->mImageBufferSize = 0;
       that->mImageBufferUsed = 0;
       return;
     }
     that->mImageBuffer = newBuf;
   }
   memcpy(&that->mImageBuffer[that->mImageBufferUsed], data, size);
   that->mImageBufferUsed += size;
   that->NotifyListener();
 }
 void
 nsPNGEncoder::NotifyListener()
 {
   // We might call this function on multiple threads (any threads that call
   // AsyncWait and any that do encoding) so we lock to avoid notifying the
   // listener twice about the same data (which generally leads to a truncated
   // image).
   ReentrantMonitorAutoEnter autoEnter(mReentrantMonitor);
   if (mCallback &&
       (mImageBufferUsed - mImageBufferReadPoint >= mNotifyThreshold ||
        mFinished)) {
     nsCOMPtr<nsIInputStreamCallback> callback;
     if (mCallbackTarget) {
       callback = NS_NewInputStreamReadyEvent(mCallback, mCallbackTarget);
     } else {
       callback = mCallback;
     }
     NS_ASSERTION(callback, "Shouldn't fail to make the callback");
     // Null the callback first because OnInputStreamReady could reenter
     // AsyncWait
     mCallback = nullptr;
     mCallbackTarget = nullptr;
     mNotifyThreshold = 0;
     callback->OnInputStreamReady(this);
   }
 }

The Tor Browser / annotate

image/encoders/png/nsPNGEncoder.cpp@6474c204b198 (annotated)

image/encoders/png/nsPNGEncoder.cpp