fuzz/fuzz.cpp - platform/external/skia - Gitiles

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #include "Fuzz.h"
 #include "SkCanvas.h"
 #include "SkCodec.h"
 #include "SkCommandLineFlags.h"
 #include "SkData.h"
 #include "SkForceLinking.h"
 #include "SkImage.h"
 #include "SkImageEncoder.h"
 #include "SkMallocPixelRef.h"
 #include "SkPicture.h"
 #include "SkStream.h"

 #include <cmath>
 #include <signal.h>
 #include <stdlib.h>

 // TODO(kjlubick): Remove once http://crrev.com/1671193002 lands
 __SK_FORCE_IMAGE_DECODER_LINKING;

 DEFINE_string2(bytes, b, "", "A path to a file.  This can be the fuzz bytes or a binary to parse.");
 DEFINE_string2(name, n, "", "If --type is 'api', fuzz the API with this name.");

 DEFINE_string2(type, t, "api", "How to interpret --bytes, either 'image_scale', 'image_mode', 'skp', or 'api'.");
 DEFINE_string2(dump, d, "", "If not empty, dump 'image*' or 'skp' types as a PNG with this name.");

 static int printUsage(const char* name) {
     SkDebugf("Usage: %s -t <type> -b <path/to/file> [-n api-to-fuzz]\n", name);
     return 1;
 }
 static uint8_t calculate_option(SkData*);

 static int fuzz_api(SkData*);
 static int fuzz_img(SkData*, uint8_t, uint8_t);
 static int fuzz_skp(SkData*);

 int main(int argc, char** argv) {
     SkCommandLineFlags::Parse(argc, argv);

     const char* path = FLAGS_bytes.isEmpty() ? argv[0] : FLAGS_bytes[0];
     SkAutoTUnref<SkData> bytes(SkData::NewFromFileName(path));
     if (!bytes) {
         SkDebugf("Could not read %s\n", path);
         return 2;
     }

     uint8_t option = calculate_option(bytes);

     if (!FLAGS_type.isEmpty()) {
         switch (FLAGS_type[0][0]) {
             case 'a': return fuzz_api(bytes);

             case 'i':
                 // We only allow one degree of freedom to avoid a search space explosion for afl-fuzz.
                 if (FLAGS_type[0][6] == 's') { // image_scale
                     return fuzz_img(bytes, option, 0);
                 }
                 // image_mode
                 return fuzz_img(bytes, 0, option);
             case 's': return fuzz_skp(bytes);
         }
     }
     return printUsage(argv[0]);
 }

 // This adds up the first 1024 bytes and returns it as an 8 bit integer.  This allows afl-fuzz to
 // deterministically excercise different paths, or *options* (such as different scaling sizes or
 // different image modes) without needing to introduce a parameter.  This way we don't need a
 // image_scale1, image_scale2, image_scale4, etc fuzzer, we can just have a image_scale fuzzer.
 // Clients are expected to transform this number into a different range, e.g. with modulo (%).
 static uint8_t calculate_option(SkData* bytes) {
     uint8_t total = 0;
     const uint8_t* data = bytes->bytes();
     for (size_t i = 0; i < 1024 && i < bytes->size(); i++) {
         total += data[i];
     }
     return total;
 }

 int fuzz_api(SkData* bytes) {
     const char* name = FLAGS_name.isEmpty() ? "" : FLAGS_name[0];

     for (auto r = SkTRegistry<Fuzzable>::Head(); r; r = r->next()) {
         auto fuzzable = r->factory();
         if (0 == strcmp(name, fuzzable.name)) {
             SkDebugf("Fuzzing %s...\n", fuzzable.name);
             Fuzz fuzz(bytes);
             fuzzable.fn(&fuzz);
             SkDebugf("[terminated] Success!\n");
             return 0;
         }
     }

     SkDebugf("When using --type api, please choose an API to fuzz with --name/-n:\n");
     for (auto r = SkTRegistry<Fuzzable>::Head(); r; r = r->next()) {
         auto fuzzable = r->factory();
         SkDebugf("\t%s\n", fuzzable.name);
     }
     return 1;
 }

 static void dump_png(SkBitmap bitmap) {
     if (!FLAGS_dump.isEmpty()) {
         SkImageEncoder::EncodeFile(FLAGS_dump[0], bitmap, SkImageEncoder::kPNG_Type, 100);
         SkDebugf("Dumped to %s\n", FLAGS_dump[0]);
     }
 }

 int fuzz_img(SkData* bytes, uint8_t scale, uint8_t mode) {
     // We can scale 1x, 2x, 4x, 8x, 16x
     scale = scale % 5;
     float fscale = (float)pow(2.0f, scale);
     SkDebugf("Scaling factor: %f\n", fscale);

     // We have 4 different modes of decoding, just like DM.
     mode = mode % 4;
     SkDebugf("Mode: %d\n", mode);

     // This is mostly copied from DMSrcSink's CodecSrc::draw method.
     SkDebugf("Decoding\n");
     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromData(bytes));
     if (nullptr == codec.get()) {
         SkDebugf("[terminated] Couldn't create codec.\n");
         return 3;
     }

     SkImageInfo decodeInfo = codec->getInfo();

     SkISize size = codec->getScaledDimensions(fscale);
     decodeInfo = decodeInfo.makeWH(size.width(), size.height());

     // Construct a color table for the decode if necessary
     SkAutoTUnref<SkColorTable> colorTable(nullptr);
     SkPMColor* colorPtr = nullptr;
     int* colorCountPtr = nullptr;
     int maxColors = 256;
     if (kIndex_8_SkColorType == decodeInfo.colorType()) {
         SkPMColor colors[256];
         colorTable.reset(new SkColorTable(colors, maxColors));
         colorPtr = const_cast<SkPMColor*>(colorTable->readColors());
         colorCountPtr = &maxColors;
     }

     SkBitmap bitmap;
     SkMallocPixelRef::ZeroedPRFactory zeroFactory;
     SkCodec::Options options;
     options.fZeroInitialized = SkCodec::kYes_ZeroInitialized;

     if (!bitmap.tryAllocPixels(decodeInfo, &zeroFactory, colorTable.get())) {
         SkDebugf("[terminated] Could not allocate memory.  Image might be too large (%d x %d)",
                  decodeInfo.width(), decodeInfo.height());
         return 4;
     }

     switch (mode) {
         case 0: {//kCodecZeroInit_Mode, kCodec_Mode
             switch (codec->getPixels(decodeInfo, bitmap.getPixels(), bitmap.rowBytes(), &options,
                                      colorPtr, colorCountPtr)) {
                 case SkCodec::kSuccess:
                     SkDebugf("[terminated] Success!\n");
                     break;
                 case SkCodec::kIncompleteInput:
                     SkDebugf("[terminated] Partial Success\n");
                     break;
                 case SkCodec::kInvalidConversion:
                     SkDebugf("Incompatible colortype conversion\n");
                     // Crash to allow afl-fuzz to know this was a bug.
                     raise(SIGSEGV);
                 default:
                     SkDebugf("[terminated] Couldn't getPixels.\n");
                     return 6;
             }
             break;
         }
         case 1: {//kScanline_Mode
             if (SkCodec::kSuccess != codec->startScanlineDecode(decodeInfo, NULL, colorPtr,
                                                                 colorCountPtr)) {
                     SkDebugf("[terminated] Could not start scanline decoder\n");
                     return 7;
                 }

             void* dst = bitmap.getAddr(0, 0);
             size_t rowBytes = bitmap.rowBytes();
             uint32_t height = decodeInfo.height();
             switch (codec->getScanlineOrder()) {
                 case SkCodec::kTopDown_SkScanlineOrder:
                 case SkCodec::kBottomUp_SkScanlineOrder:
                 case SkCodec::kNone_SkScanlineOrder:
                     // We do not need to check the return value.  On an incomplete
                     // image, memory will be filled with a default value.
                     codec->getScanlines(dst, height, rowBytes);
                     break;
                 case SkCodec::kOutOfOrder_SkScanlineOrder: {
                     for (int y = 0; y < decodeInfo.height(); y++) {
                         int dstY = codec->outputScanline(y);
                         void* dstPtr = bitmap.getAddr(0, dstY);
                         // We complete the loop, even if this call begins to fail
                         // due to an incomplete image.  This ensures any uninitialized
                         // memory will be filled with the proper value.
                         codec->getScanlines(dstPtr, 1, bitmap.rowBytes());
                     }
                     break;
                 }
             }
             SkDebugf("[terminated] Success!\n");
             break;
         }
         case 2: { //kStripe_Mode
             const int height = decodeInfo.height();
             // This value is chosen arbitrarily.  We exercise more cases by choosing a value that
             // does not align with image blocks.
             const int stripeHeight = 37;
             const int numStripes = (height + stripeHeight - 1) / stripeHeight;

             // Decode odd stripes
             if (SkCodec::kSuccess != codec->startScanlineDecode(decodeInfo, NULL, colorPtr,
                                                                 colorCountPtr)
                     || SkCodec::kTopDown_SkScanlineOrder != codec->getScanlineOrder()) {
                 // This mode was designed to test the new skip scanlines API in libjpeg-turbo.
                 // Jpegs have kTopDown_SkScanlineOrder, and at this time, it is not interesting
                 // to run this test for image types that do not have this scanline ordering.
                 SkDebugf("[terminated] Could not start top-down scanline decoder\n");
                 return 8;
             }

             for (int i = 0; i < numStripes; i += 2) {
                 // Skip a stripe
                 const int linesToSkip = SkTMin(stripeHeight, height - i * stripeHeight);
                 codec->skipScanlines(linesToSkip);

                 // Read a stripe
                 const int startY = (i + 1) * stripeHeight;
                 const int linesToRead = SkTMin(stripeHeight, height - startY);
                 if (linesToRead > 0) {
                     codec->getScanlines(bitmap.getAddr(0, startY), linesToRead, bitmap.rowBytes());
                 }
             }

             // Decode even stripes
             const SkCodec::Result startResult = codec->startScanlineDecode(decodeInfo, nullptr,
                     colorPtr, colorCountPtr);
             if (SkCodec::kSuccess != startResult) {
                 SkDebugf("[terminated] Failed to restart scanline decoder with same parameters.\n");
                 return 9;
             }
             for (int i = 0; i < numStripes; i += 2) {
                 // Read a stripe
                 const int startY = i * stripeHeight;
                 const int linesToRead = SkTMin(stripeHeight, height - startY);
                 codec->getScanlines(bitmap.getAddr(0, startY), linesToRead, bitmap.rowBytes());

                 // Skip a stripe
                 const int linesToSkip = SkTMin(stripeHeight, height - (i + 1) * stripeHeight);
                 if (linesToSkip > 0) {
                     codec->skipScanlines(linesToSkip);
                 }
             }
             SkDebugf("[terminated] Success!\n");
             break;
         }
         case 3: { //kSubset_Mode
             // Arbitrarily choose a divisor.
             int divisor = 2;
             // Total width/height of the image.
             const int W = codec->getInfo().width();
             const int H = codec->getInfo().height();
             if (divisor > W || divisor > H) {
                 SkDebugf("[terminated] Cannot codec subset: divisor %d is too big "
                          "with dimensions (%d x %d)\n", divisor, W, H);
                 return 10;
             }
             // subset dimensions
             // SkWebpCodec, the only one that supports subsets, requires even top/left boundaries.
             const int w = SkAlign2(W / divisor);
             const int h = SkAlign2(H / divisor);
             SkIRect subset;
             SkCodec::Options opts;
             opts.fSubset = &subset;
             SkBitmap subsetBm;
             // We will reuse pixel memory from bitmap.
             void* pixels = bitmap.getPixels();
             // Keep track of left and top (for drawing subsetBm into canvas). We could use
             // fscale * x and fscale * y, but we want integers such that the next subset will start
             // where the last one ended. So we'll add decodeInfo.width() and height().
             int left = 0;
             for (int x = 0; x < W; x += w) {
                 int top = 0;
                 for (int y = 0; y < H; y+= h) {
                     // Do not make the subset go off the edge of the image.
                     const int preScaleW = SkTMin(w, W - x);
                     const int preScaleH = SkTMin(h, H - y);
                     subset.setXYWH(x, y, preScaleW, preScaleH);
                     // And fscale
                     // FIXME: Should we have a version of getScaledDimensions that takes a subset
                     // into account?
                     decodeInfo = decodeInfo.makeWH(
                             SkTMax(1, SkScalarRoundToInt(preScaleW * fscale)),
                             SkTMax(1, SkScalarRoundToInt(preScaleH * fscale)));
                     size_t rowBytes = decodeInfo.minRowBytes();
                     if (!subsetBm.installPixels(decodeInfo, pixels, rowBytes, colorTable.get(),
                                                 nullptr, nullptr)) {
                         SkDebugf("[terminated] Could not install pixels.\n");
                         return 11;
                     }
                     const SkCodec::Result result = codec->getPixels(decodeInfo, pixels, rowBytes,
                             &opts, colorPtr, colorCountPtr);
                     switch (result) {
                         case SkCodec::kSuccess:
                         case SkCodec::kIncompleteInput:
                             SkDebugf("okay\n");
                             break;
                         case SkCodec::kInvalidConversion:
                             if (0 == (x|y)) {
                                 // First subset is okay to return unimplemented.
                                 SkDebugf("[terminated] Incompatible colortype conversion\n");
                                 return 12;
                             }
                             // If the first subset succeeded, a later one should not fail.
                             // fall through to failure
                         case SkCodec::kUnimplemented:
                             if (0 == (x|y)) {
                                 // First subset is okay to return unimplemented.
                                 SkDebugf("[terminated] subset codec not supported\n");
                                 return 13;
                             }
                             // If the first subset succeeded, why would a later one fail?
                             // fall through to failure
                         default:
                             SkDebugf("[terminated] subset codec failed to decode (%d, %d, %d, %d) "
                                                   "with dimensions (%d x %d)\t error %d\n",
                                                   x, y, decodeInfo.width(), decodeInfo.height(),
                                                   W, H, result);
                             return 14;
                     }
                     // translate by the scaled height.
                     top += decodeInfo.height();
                 }
                 // translate by the scaled width.
                 left += decodeInfo.width();
             }
             SkDebugf("[terminated] Success!\n");
             break;
         }
         default:
             SkDebugf("[terminated] Mode not implemented yet\n");
     }

     dump_png(bitmap);
     return 0;
 }

 int fuzz_skp(SkData* bytes) {
     SkMemoryStream stream(bytes);
     SkDebugf("Decoding\n");
     sk_sp<SkPicture> pic(SkPicture::MakeFromStream(&stream));
     if (!pic) {
         SkDebugf("[terminated] Couldn't decode as a picture.\n");
         return 3;
     }
     SkDebugf("Rendering\n");
     SkBitmap bitmap;
     if (!FLAGS_dump.isEmpty()) {
         SkIRect size = pic->cullRect().roundOut();
         bitmap.allocN32Pixels(size.width(), size.height());
     }
     SkCanvas canvas(bitmap);
     canvas.drawPicture(pic);
     SkDebugf("[terminated] Success! Decoded and rendered an SkPicture!\n");
     dump_png(bitmap);
     return 0;
 }

 Fuzz::Fuzz(SkData* bytes) : fBytes(SkSafeRef(bytes)), fNextByte(0) {}

 void Fuzz::signalBug   () { SkDebugf("Signal bug\n"); raise(SIGSEGV); }
 void Fuzz::signalBoring() { SkDebugf("Signal boring\n"); exit(0); }

 template <typename T>
 T Fuzz::nextT() {
     if (fNextByte + sizeof(T) > fBytes->size()) {
         this->signalBoring();
     }

     T val;
     memcpy(&val, fBytes->bytes() + fNextByte, sizeof(T));
     fNextByte += sizeof(T);
     return val;
 }

 uint8_t  Fuzz::nextB() { return this->nextT<uint8_t >(); }
 bool  Fuzz::nextBool() { return nextB()&1; }
 uint32_t Fuzz::nextU() { return this->nextT<uint32_t>(); }
 float    Fuzz::nextF() { return this->nextT<float   >(); }

 float    Fuzz::nextF1() {
     // This is the same code as is in SkRandom's nextF()
     unsigned int floatint = 0x3f800000 | (this->nextU() >> 9);
     float f = SkBits2Float(floatint) - 1.0f;
     return f;
 }

 uint32_t Fuzz::nextRangeU(uint32_t min, uint32_t max) {
     if (min > max) {
         SkDebugf("Check mins and maxes (%d, %d)\n", min, max);
         this->signalBoring();
     }
     uint32_t range = max - min + 1;
     if (0 == range) {
         return this->nextU();
     } else {
         return min + this->nextU() % range;
     }
 }
 float Fuzz::nextRangeF(float min, float max) {
     if (min > max) {
         SkDebugf("Check mins and maxes (%f, %f)\n", min, max);
         this->signalBoring();
     }
     float f = std::abs(this->nextF());
     if (!std::isnormal(f) && f != 0.0) {
         this->signalBoring();
     }
     return min + fmod(f, (max - min + 1));
 }
	/*
	* Copyright 2016 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#include "Fuzz.h"
	#include "SkCanvas.h"
	#include "SkCodec.h"
	#include "SkCommandLineFlags.h"
	#include "SkData.h"
	#include "SkForceLinking.h"
	#include "SkImage.h"
	#include "SkImageEncoder.h"
	#include "SkMallocPixelRef.h"
	#include "SkPicture.h"
	#include "SkStream.h"

	#include <cmath>
	#include <signal.h>
	#include <stdlib.h>

	// TODO(kjlubick): Remove once http://crrev.com/1671193002 lands
	__SK_FORCE_IMAGE_DECODER_LINKING;

	DEFINE_string2(bytes, b, "", "A path to a file. This can be the fuzz bytes or a binary to parse.");
	DEFINE_string2(name, n, "", "If --type is 'api', fuzz the API with this name.");

	DEFINE_string2(type, t, "api", "How to interpret --bytes, either 'image_scale', 'image_mode', 'skp', or 'api'.");
	DEFINE_string2(dump, d, "", "If not empty, dump 'image*' or 'skp' types as a PNG with this name.");

	static int printUsage(const char* name) {
	SkDebugf("Usage: %s -t <type> -b <path/to/file> [-n api-to-fuzz]\n", name);
	return 1;
	}
	static uint8_t calculate_option(SkData*);

	static int fuzz_api(SkData*);
	static int fuzz_img(SkData*, uint8_t, uint8_t);
	static int fuzz_skp(SkData*);

	int main(int argc, char** argv) {
	SkCommandLineFlags::Parse(argc, argv);

	const char* path = FLAGS_bytes.isEmpty() ? argv[0] : FLAGS_bytes[0];
	SkAutoTUnref<SkData> bytes(SkData::NewFromFileName(path));
	if (!bytes) {
	SkDebugf("Could not read %s\n", path);
	return 2;
	}

	uint8_t option = calculate_option(bytes);

	if (!FLAGS_type.isEmpty()) {
	switch (FLAGS_type[0][0]) {
	case 'a': return fuzz_api(bytes);

	case 'i':
	// We only allow one degree of freedom to avoid a search space explosion for afl-fuzz.
	if (FLAGS_type[0][6] == 's') { // image_scale
	return fuzz_img(bytes, option, 0);
	}
	// image_mode
	return fuzz_img(bytes, 0, option);
	case 's': return fuzz_skp(bytes);
	}
	}
	return printUsage(argv[0]);
	}

	// This adds up the first 1024 bytes and returns it as an 8 bit integer. This allows afl-fuzz to
	// deterministically excercise different paths, or options (such as different scaling sizes or
	// different image modes) without needing to introduce a parameter. This way we don't need a
	// image_scale1, image_scale2, image_scale4, etc fuzzer, we can just have a image_scale fuzzer.
	// Clients are expected to transform this number into a different range, e.g. with modulo (%).
	static uint8_t calculate_option(SkData* bytes) {
	uint8_t total = 0;
	const uint8_t* data = bytes->bytes();
	for (size_t i = 0; i < 1024 && i < bytes->size(); i++) {
	total += data[i];
	}
	return total;
	}

	int fuzz_api(SkData* bytes) {
	const char* name = FLAGS_name.isEmpty() ? "" : FLAGS_name[0];

	for (auto r = SkTRegistry<Fuzzable>::Head(); r; r = r->next()) {
	auto fuzzable = r->factory();
	if (0 == strcmp(name, fuzzable.name)) {
	SkDebugf("Fuzzing %s...\n", fuzzable.name);
	Fuzz fuzz(bytes);
	fuzzable.fn(&fuzz);
	SkDebugf("[terminated] Success!\n");
	return 0;
	}
	}

	SkDebugf("When using --type api, please choose an API to fuzz with --name/-n:\n");
	for (auto r = SkTRegistry<Fuzzable>::Head(); r; r = r->next()) {
	auto fuzzable = r->factory();
	SkDebugf("\t%s\n", fuzzable.name);
	}
	return 1;
	}

	static void dump_png(SkBitmap bitmap) {
	if (!FLAGS_dump.isEmpty()) {
	SkImageEncoder::EncodeFile(FLAGS_dump[0], bitmap, SkImageEncoder::kPNG_Type, 100);
	SkDebugf("Dumped to %s\n", FLAGS_dump[0]);
	}
	}

	int fuzz_img(SkData* bytes, uint8_t scale, uint8_t mode) {
	// We can scale 1x, 2x, 4x, 8x, 16x
	scale = scale % 5;
	float fscale = (float)pow(2.0f, scale);
	SkDebugf("Scaling factor: %f\n", fscale);

	// We have 4 different modes of decoding, just like DM.
	mode = mode % 4;
	SkDebugf("Mode: %d\n", mode);

	// This is mostly copied from DMSrcSink's CodecSrc::draw method.
	SkDebugf("Decoding\n");
	SkAutoTDelete<SkCodec> codec(SkCodec::NewFromData(bytes));
	if (nullptr == codec.get()) {
	SkDebugf("[terminated] Couldn't create codec.\n");
	return 3;
	}

	SkImageInfo decodeInfo = codec->getInfo();

	SkISize size = codec->getScaledDimensions(fscale);
	decodeInfo = decodeInfo.makeWH(size.width(), size.height());

	// Construct a color table for the decode if necessary
	SkAutoTUnref<SkColorTable> colorTable(nullptr);
	SkPMColor* colorPtr = nullptr;
	int* colorCountPtr = nullptr;
	int maxColors = 256;
	if (kIndex_8_SkColorType == decodeInfo.colorType()) {
	SkPMColor colors[256];
	colorTable.reset(new SkColorTable(colors, maxColors));
	colorPtr = const_cast<SkPMColor*>(colorTable->readColors());
	colorCountPtr = &maxColors;
	}

	SkBitmap bitmap;
	SkMallocPixelRef::ZeroedPRFactory zeroFactory;
	SkCodec::Options options;
	options.fZeroInitialized = SkCodec::kYes_ZeroInitialized;

	if (!bitmap.tryAllocPixels(decodeInfo, &zeroFactory, colorTable.get())) {
	SkDebugf("[terminated] Could not allocate memory. Image might be too large (%d x %d)",
	decodeInfo.width(), decodeInfo.height());
	return 4;
	}

	switch (mode) {
	case 0: {//kCodecZeroInit_Mode, kCodec_Mode
	switch (codec->getPixels(decodeInfo, bitmap.getPixels(), bitmap.rowBytes(), &options,
	colorPtr, colorCountPtr)) {
	case SkCodec::kSuccess:
	SkDebugf("[terminated] Success!\n");
	break;
	case SkCodec::kIncompleteInput:
	SkDebugf("[terminated] Partial Success\n");
	break;
	case SkCodec::kInvalidConversion:
	SkDebugf("Incompatible colortype conversion\n");
	// Crash to allow afl-fuzz to know this was a bug.
	raise(SIGSEGV);
	default:
	SkDebugf("[terminated] Couldn't getPixels.\n");
	return 6;
	}
	break;
	}
	case 1: {//kScanline_Mode
	if (SkCodec::kSuccess != codec->startScanlineDecode(decodeInfo, NULL, colorPtr,
	colorCountPtr)) {
	SkDebugf("[terminated] Could not start scanline decoder\n");
	return 7;
	}

	void* dst = bitmap.getAddr(0, 0);
	size_t rowBytes = bitmap.rowBytes();
	uint32_t height = decodeInfo.height();
	switch (codec->getScanlineOrder()) {
	case SkCodec::kTopDown_SkScanlineOrder:
	case SkCodec::kBottomUp_SkScanlineOrder:
	case SkCodec::kNone_SkScanlineOrder:
	// We do not need to check the return value. On an incomplete
	// image, memory will be filled with a default value.
	codec->getScanlines(dst, height, rowBytes);
	break;
	case SkCodec::kOutOfOrder_SkScanlineOrder: {
	for (int y = 0; y < decodeInfo.height(); y++) {
	int dstY = codec->outputScanline(y);
	void* dstPtr = bitmap.getAddr(0, dstY);
	// We complete the loop, even if this call begins to fail
	// due to an incomplete image. This ensures any uninitialized
	// memory will be filled with the proper value.
	codec->getScanlines(dstPtr, 1, bitmap.rowBytes());
	}
	break;
	}
	}
	SkDebugf("[terminated] Success!\n");
	break;
	}
	case 2: { //kStripe_Mode
	const int height = decodeInfo.height();
	// This value is chosen arbitrarily. We exercise more cases by choosing a value that
	// does not align with image blocks.
	const int stripeHeight = 37;
	const int numStripes = (height + stripeHeight - 1) / stripeHeight;

	// Decode odd stripes
	if (SkCodec::kSuccess != codec->startScanlineDecode(decodeInfo, NULL, colorPtr,
	colorCountPtr)
	\|\| SkCodec::kTopDown_SkScanlineOrder != codec->getScanlineOrder()) {
	// This mode was designed to test the new skip scanlines API in libjpeg-turbo.
	// Jpegs have kTopDown_SkScanlineOrder, and at this time, it is not interesting
	// to run this test for image types that do not have this scanline ordering.
	SkDebugf("[terminated] Could not start top-down scanline decoder\n");
	return 8;
	}

	for (int i = 0; i < numStripes; i += 2) {
	// Skip a stripe
	const int linesToSkip = SkTMin(stripeHeight, height - i * stripeHeight);
	codec->skipScanlines(linesToSkip);

	// Read a stripe
	const int startY = (i + 1) * stripeHeight;
	const int linesToRead = SkTMin(stripeHeight, height - startY);
	if (linesToRead > 0) {
	codec->getScanlines(bitmap.getAddr(0, startY), linesToRead, bitmap.rowBytes());
	}
	}

	// Decode even stripes
	const SkCodec::Result startResult = codec->startScanlineDecode(decodeInfo, nullptr,
	colorPtr, colorCountPtr);
	if (SkCodec::kSuccess != startResult) {
	SkDebugf("[terminated] Failed to restart scanline decoder with same parameters.\n");
	return 9;
	}
	for (int i = 0; i < numStripes; i += 2) {
	// Read a stripe
	const int startY = i * stripeHeight;
	const int linesToRead = SkTMin(stripeHeight, height - startY);
	codec->getScanlines(bitmap.getAddr(0, startY), linesToRead, bitmap.rowBytes());

	// Skip a stripe
	const int linesToSkip = SkTMin(stripeHeight, height - (i + 1) * stripeHeight);
	if (linesToSkip > 0) {
	codec->skipScanlines(linesToSkip);
	}
	}
	SkDebugf("[terminated] Success!\n");
	break;
	}
	case 3: { //kSubset_Mode
	// Arbitrarily choose a divisor.
	int divisor = 2;
	// Total width/height of the image.
	const int W = codec->getInfo().width();
	const int H = codec->getInfo().height();
	if (divisor > W \|\| divisor > H) {
	SkDebugf("[terminated] Cannot codec subset: divisor %d is too big "
	"with dimensions (%d x %d)\n", divisor, W, H);
	return 10;
	}
	// subset dimensions
	// SkWebpCodec, the only one that supports subsets, requires even top/left boundaries.
	const int w = SkAlign2(W / divisor);
	const int h = SkAlign2(H / divisor);
	SkIRect subset;
	SkCodec::Options opts;
	opts.fSubset = &subset;
	SkBitmap subsetBm;
	// We will reuse pixel memory from bitmap.
	void* pixels = bitmap.getPixels();
	// Keep track of left and top (for drawing subsetBm into canvas). We could use
	// fscale * x and fscale * y, but we want integers such that the next subset will start
	// where the last one ended. So we'll add decodeInfo.width() and height().
	int left = 0;
	for (int x = 0; x < W; x += w) {
	int top = 0;
	for (int y = 0; y < H; y+= h) {
	// Do not make the subset go off the edge of the image.
	const int preScaleW = SkTMin(w, W - x);
	const int preScaleH = SkTMin(h, H - y);
	subset.setXYWH(x, y, preScaleW, preScaleH);
	// And fscale
	// FIXME: Should we have a version of getScaledDimensions that takes a subset
	// into account?
	decodeInfo = decodeInfo.makeWH(
	SkTMax(1, SkScalarRoundToInt(preScaleW * fscale)),
	SkTMax(1, SkScalarRoundToInt(preScaleH * fscale)));
	size_t rowBytes = decodeInfo.minRowBytes();
	if (!subsetBm.installPixels(decodeInfo, pixels, rowBytes, colorTable.get(),
	nullptr, nullptr)) {
	SkDebugf("[terminated] Could not install pixels.\n");
	return 11;
	}
	const SkCodec::Result result = codec->getPixels(decodeInfo, pixels, rowBytes,
	&opts, colorPtr, colorCountPtr);
	switch (result) {
	case SkCodec::kSuccess:
	case SkCodec::kIncompleteInput:
	SkDebugf("okay\n");
	break;
	case SkCodec::kInvalidConversion:
	if (0 == (x\|y)) {
	// First subset is okay to return unimplemented.
	SkDebugf("[terminated] Incompatible colortype conversion\n");
	return 12;
	}
	// If the first subset succeeded, a later one should not fail.
	// fall through to failure
	case SkCodec::kUnimplemented:
	if (0 == (x\|y)) {
	// First subset is okay to return unimplemented.
	SkDebugf("[terminated] subset codec not supported\n");
	return 13;
	}
	// If the first subset succeeded, why would a later one fail?
	// fall through to failure
	default:
	SkDebugf("[terminated] subset codec failed to decode (%d, %d, %d, %d) "
	"with dimensions (%d x %d)\t error %d\n",
	x, y, decodeInfo.width(), decodeInfo.height(),
	W, H, result);
	return 14;
	}
	// translate by the scaled height.
	top += decodeInfo.height();
	}
	// translate by the scaled width.
	left += decodeInfo.width();
	}
	SkDebugf("[terminated] Success!\n");
	break;
	}
	default:
	SkDebugf("[terminated] Mode not implemented yet\n");
	}

	dump_png(bitmap);
	return 0;
	}

	int fuzz_skp(SkData* bytes) {
	SkMemoryStream stream(bytes);
	SkDebugf("Decoding\n");
	sk_sp<SkPicture> pic(SkPicture::MakeFromStream(&stream));
	if (!pic) {
	SkDebugf("[terminated] Couldn't decode as a picture.\n");
	return 3;
	}
	SkDebugf("Rendering\n");
	SkBitmap bitmap;
	if (!FLAGS_dump.isEmpty()) {
	SkIRect size = pic->cullRect().roundOut();
	bitmap.allocN32Pixels(size.width(), size.height());
	}
	SkCanvas canvas(bitmap);
	canvas.drawPicture(pic);
	SkDebugf("[terminated] Success! Decoded and rendered an SkPicture!\n");
	dump_png(bitmap);
	return 0;
	}

	Fuzz::Fuzz(SkData* bytes) : fBytes(SkSafeRef(bytes)), fNextByte(0) {}

	void Fuzz::signalBug () { SkDebugf("Signal bug\n"); raise(SIGSEGV); }
	void Fuzz::signalBoring() { SkDebugf("Signal boring\n"); exit(0); }

	template <typename T>
	T Fuzz::nextT() {
	if (fNextByte + sizeof(T) > fBytes->size()) {
	this->signalBoring();
	}

	T val;
	memcpy(&val, fBytes->bytes() + fNextByte, sizeof(T));
	fNextByte += sizeof(T);
	return val;
	}

	uint8_t Fuzz::nextB() { return this->nextT<uint8_t >(); }
	bool Fuzz::nextBool() { return nextB()&1; }
	uint32_t Fuzz::nextU() { return this->nextT<uint32_t>(); }
	float Fuzz::nextF() { return this->nextT<float >(); }

	float Fuzz::nextF1() {
	// This is the same code as is in SkRandom's nextF()
	unsigned int floatint = 0x3f800000 \| (this->nextU() >> 9);
	float f = SkBits2Float(floatint) - 1.0f;
	return f;
	}

	uint32_t Fuzz::nextRangeU(uint32_t min, uint32_t max) {
	if (min > max) {
	SkDebugf("Check mins and maxes (%d, %d)\n", min, max);
	this->signalBoring();
	}
	uint32_t range = max - min + 1;
	if (0 == range) {
	return this->nextU();
	} else {
	return min + this->nextU() % range;
	}
	}
	float Fuzz::nextRangeF(float min, float max) {
	if (min > max) {
	SkDebugf("Check mins and maxes (%f, %f)\n", min, max);
	this->signalBoring();
	}
	float f = std::abs(this->nextF());
	if (!std::isnormal(f) && f != 0.0) {
	this->signalBoring();
	}
	return min + fmod(f, (max - min + 1));
	}