Initial error handling code

src/core/SkSecureReader32.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 "SkSecureReader32.h"
+#include "SkString.h"
+
+SkSecureReader32::SkSecureReader32() : fCurr(NULL), fStop(NULL), fBase(NULL), fError(false) {
+}
+
+SkSecureReader32::SkSecureReader32(const void* data, size_t size) : fError(false) {
+    this->setMemory(data, size);
+}
+
+void SkSecureReader32::setMemory(const void* data, size_t size) {
+    fError |= (!ptr_align_4(data) || (SkAlign4(size) != size));
+    SkASSERT(!fError);
+
+    fBase = fCurr = (const char*)data;
+    fStop = (const char*)data + size;
+}
+
+uint32_t SkSecureReader32::size() const {
+    return SkToU32(fStop - fBase);
+}
+
+uint32_t SkSecureReader32::offset() const {
+    return SkToU32(fCurr - fBase);
+}
+
+bool SkSecureReader32::eof() const {
+    return fCurr >= fStop;
+}
+
+const void* SkSecureReader32::base() const {
+    return fBase;
+}
+
+const void* SkSecureReader32::peek() const {
+    return fCurr;
+}
+
+bool SkSecureReader32::isAvailable(uint32_t size) const {
+    return fCurr + size <= fStop;
+}
+
+bool SkSecureReader32::readBool() {
+    return this->readInt() != 0;
+}
+
+int32_t SkSecureReader32::readInt() {
+    int32_t value = 0;
+    size_t inc = sizeof(value);
+    fError |= !ptr_align_4(fCurr) || !this->isAvailable(inc);
+    if (!fError) {
+        value = *(const int32_t*)fCurr;
+        fCurr += inc;
+    }
+    return value;
+}
+
+SkScalar SkSecureReader32::readScalar() {
+    SkScalar value = 0;
+    size_t inc = sizeof(value);
+    fError |= !ptr_align_4(fCurr) || !this->isAvailable(inc);
+    if (!fError) {
+        value = *(const SkScalar*)fCurr;
+        fCurr += inc;
+    }
+    return value;
+}
+
+const void* SkSecureReader32::skip(size_t size) {
+    size_t inc = SkAlign4(size);
+    fError |= !ptr_align_4(fCurr) || !this->isAvailable(inc);
+    const void* addr = fCurr;
+    if (!fError) {
+        fCurr += inc;
+    }
+    return addr;
+}
+
+int32_t SkSecureReader32::readS32() {
+    return this->readInt();
+}
+
+uint32_t SkSecureReader32::readU32() {
+    return this->readInt();
+}
+
+void SkSecureReader32::readPath(SkPath* path) {
+    size_t size = path->readFromMemory(this->peek());
+    fError |= (SkAlign4(size) != size);
+    if (!fError) {
+        (void)this->skip(size);
+    }
+}
+
+void SkSecureReader32::readMatrix(SkMatrix* matrix) {
+    size_t size = matrix->readFromMemory(this->peek());
+    fError |= (SkAlign4(size) != size);
+    if (!fError) {
+        (void)this->skip(size);
+    }
+}
+
+void SkSecureReader32::readRegion(SkRegion* rgn) {
+    size_t size = rgn->readFromMemory(this->peek());
+    fError |= (SkAlign4(size) != size);
+    if (!fError) {
+        (void)this->skip(size);
+    }
+}
+
+/*
+ *  Strings are stored as: length[4-bytes] + string_data + '\0' + pad_to_mul_4
+ */
+
+const char* SkSecureReader32::readString(size_t* outLen) {
+    size_t len = this->readInt();
+    const void* ptr = this->peek();
+
+    // skip over the string + '\0' and then pad to a multiple of 4
+    size_t alignedSize = SkAlign4(len + 1);
+    this->skip(alignedSize);
+
+    if (outLen) {
+        *outLen = fError ? 0 : len;
+    }
+    return fError ? NULL : (const char*)ptr;
+}