Initial error handling code

src/core/SkValidatingReadBuffer.cpp

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkBitmap.h"
+#include "SkErrorInternals.h"
+#include "SkValidatingReadBuffer.h"
+#include "SkStream.h"
+#include "SkTypeface.h"
+
+SkValidatingReadBuffer::SkValidatingReadBuffer(const void* data, size_t size) {
+    this->setMemory(data, size);
+    fError = false;
+
+    this->setFlags(SkFlattenableReadBuffer::kValidation_Flag);
+}
+
+SkValidatingReadBuffer::~SkValidatingReadBuffer() {
+}
+
+void SkValidatingReadBuffer::setMemory(const void* data, size_t size) {
+    fError = fError || !IsPtrAlign4(data) || (SkAlign4(size) != size);
+    if (!fError) {
+        fReader.setMemory(data, size);
+    }
+}
+
+const void* SkValidatingReadBuffer::skip(size_t size) {
+    size_t inc = SkAlign4(size);
+    const void* addr = fReader.peek();
+    fError = fError || !IsPtrAlign4(addr) || !fReader.isAvailable(inc);
+    if (!fError) {
+        fReader.skip(size);
+    }
+    return addr;
+}
+
+// All the methods in this file funnel down into either readInt(), readScalar() or skip(),
+// followed by a memcpy. So we've got all our validation in readInt(), readScalar() and skip();
+// if they fail they'll return a zero value or skip nothing, respectively, and set fError to
+// true, which the caller should check to see if an error occurred during the read operation.
+
+bool SkValidatingReadBuffer::readBool() {
+    return this->readInt() != 0;
+}
+
+SkColor SkValidatingReadBuffer::readColor() {
+    return this->readInt();
+}
+
+SkFixed SkValidatingReadBuffer::readFixed() {
+    return this->readInt();
+}
+
+int32_t SkValidatingReadBuffer::readInt() {
+    const size_t inc = sizeof(int32_t);
+    fError = fError || !IsPtrAlign4(fReader.peek()) || !fReader.isAvailable(inc);
+    return fError ? 0 : fReader.readInt();
+}
+
+SkScalar SkValidatingReadBuffer::readScalar() {
+    const size_t inc = sizeof(SkScalar);
+    fError = fError || !IsPtrAlign4(fReader.peek()) || !fReader.isAvailable(inc);
+    return fError ? 0 : fReader.readScalar();
+}
+
+uint32_t SkValidatingReadBuffer::readUInt() {
+    return this->readInt();
+}
+
+int32_t SkValidatingReadBuffer::read32() {
+    return this->readInt();
+}
+
+void SkValidatingReadBuffer::readString(SkString* string) {
+    const size_t len = this->readInt();
+    const void* ptr = fReader.peek();
+    const char* cptr = (const char*)ptr;
+
+    // skip over the string + '\0' and then pad to a multiple of 4
+    const size_t alignedSize = SkAlign4(len + 1);
+    this->skip(alignedSize);
+    fError = fError || (cptr[len] != '\0');
+    if (!fError) {
+        string->set(cptr, len);
+    }
+}
+
+void* SkValidatingReadBuffer::readEncodedString(size_t* length, SkPaint::TextEncoding encoding) {
+    const int32_t encodingType = fReader.readInt();
+    fError = fError || (encodingType != encoding);
+    *length = this->readInt();
+    const void* ptr = this->skip(SkAlign4(*length));
+    void* data = NULL;
+    if (!fError) {
+        data = sk_malloc_throw(*length);
+        memcpy(data, ptr, *length);
+    }
+    return data;
+}
+
+void SkValidatingReadBuffer::readPoint(SkPoint* point) {
+    point->fX = fReader.readScalar();
+    point->fY = fReader.readScalar();
+}
+
+void SkValidatingReadBuffer::readMatrix(SkMatrix* matrix) {
+    const size_t size = matrix->readFromMemory(fReader.peek());
+    fError = fError || (SkAlign4(size) != size);
+    if (!fError) {
+        (void)this->skip(size);
+    }
+}
+
+void SkValidatingReadBuffer::readIRect(SkIRect* rect) {
+    const void* ptr = this->skip(sizeof(SkIRect));
+    if (!fError) {
+        memcpy(rect, ptr, sizeof(SkIRect));
+    }
+}
+
+void SkValidatingReadBuffer::readRect(SkRect* rect) {
+    const void* ptr = this->skip(sizeof(SkRect));
+    if (!fError) {
+        memcpy(rect, ptr, sizeof(SkRect));
+    }
+}
+
+void SkValidatingReadBuffer::readRegion(SkRegion* region) {
+    const size_t size = region->readFromMemory(fReader.peek());
+    fError = fError || (SkAlign4(size) != size);
+    if (!fError) {
+        (void)this->skip(size);
+    }
+}
+
+void SkValidatingReadBuffer::readPath(SkPath* path) {
+    const size_t size = path->readFromMemory(fReader.peek());
+    fError = fError || (SkAlign4(size) != size);
+    if (!fError) {
+        (void)this->skip(size);
+    }
+}
+
+uint32_t SkValidatingReadBuffer::readByteArray(void* value) {
+    const uint32_t length = this->readUInt();
+    const void* ptr = this->skip(SkAlign4(length));
+    if (!fError) {
+        memcpy(value, ptr, length);
+        return length;
+    }
+    return 0;
+}
+
+uint32_t SkValidatingReadBuffer::readColorArray(SkColor* colors) {
+    const uint32_t count = this->readUInt();
+    const uint32_t byteLength = count * sizeof(SkColor);
+    const void* ptr = this->skip(SkAlign4(byteLength));
+    if (!fError) {
+        memcpy(colors, ptr, byteLength);
+        return count;
+    }
+    return 0;
+}
+
+uint32_t SkValidatingReadBuffer::readIntArray(int32_t* values) {
+    const uint32_t count = this->readUInt();
+    const uint32_t byteLength = count * sizeof(int32_t);
+    const void* ptr = this->skip(SkAlign4(byteLength));
+    if (!fError) {
+        memcpy(values, ptr, byteLength);
+        return count;
+    }
+    return 0;
+}
+
+uint32_t SkValidatingReadBuffer::readPointArray(SkPoint* points) {
+    const uint32_t count = this->readUInt();
+    const uint32_t byteLength = count * sizeof(SkPoint);
+    const void* ptr = this->skip(SkAlign4(byteLength));
+    if (!fError) {
+        memcpy(points, ptr, byteLength);
+        return count;
+    }
+    return 0;
+}
+
+uint32_t SkValidatingReadBuffer::readScalarArray(SkScalar* values) {
+    const uint32_t count = this->readUInt();
+    const uint32_t byteLength = count * sizeof(SkScalar);
+    const void* ptr = this->skip(SkAlign4(byteLength));
+    if (!fError) {
+        memcpy(values, ptr, byteLength);
+        return count;
+    }
+    return 0;
+}
+
+uint32_t SkValidatingReadBuffer::getArrayCount() {
+    return *(uint32_t*)fReader.peek();
+}
+
+void SkValidatingReadBuffer::readBitmap(SkBitmap* bitmap) {
+    const int width = this->readInt();
+    const int height = this->readInt();
+    const size_t length = this->readUInt();
+    // A size of zero means the SkBitmap was simply flattened.
+    fError = fError || (length != 0);
+    if (fError) {
+        return;
+    }
+    bitmap->unflatten(*this);
+    fError = fError || (bitmap->width() != width) || (bitmap->height() != height);
+}
+
+SkFlattenable* SkValidatingReadBuffer::readFlattenable(SkFlattenable::Type type) {
+    SkString name;
+    this->readString(&name);
+    if (fError) {
+        return NULL;
+    }
+
+    // Is this the type we wanted ?
+    const char* cname = name.c_str();
+    SkFlattenable::Type baseType;
+    if (!SkFlattenable::NameToType(cname, &baseType) || (baseType != type)) {
+        return NULL;
+    }
+
+    SkFlattenable::Factory factory = SkFlattenable::NameToFactory(cname);
+    if (NULL == factory) {
+        return NULL; // writer failed to give us the flattenable
+    }
+
+    // if we get here, factory may still be null, but if that is the case, the
+    // failure was ours, not the writer.
+    SkFlattenable* obj = NULL;
+    uint32_t sizeRecorded = this->readUInt();
+    if (factory) {
+        uint32_t offset = fReader.offset();
+        obj = (*factory)(*this);
+        // check that we read the amount we expected
+        uint32_t sizeRead = fReader.offset() - offset;
+        fError = fError || (sizeRecorded != sizeRead);
+        if (fError) {
+            // we could try to fix up the offset...
+            delete obj;
+            obj = NULL;
+        }
+    } else {
+        // we must skip the remaining data
+        this->skip(sizeRecorded);
+        SkASSERT(false);
+    }
+    return obj;
+}