handle odd-index-count in encode/decode

Bug: skia:
Change-Id: Iffb123001a77049c6581f63bbc69c62f241a87f8
Reviewed-on: https://skia-review.googlesource.com/11405
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Eric Boren <borenet@google.com>

2 files changed, 8 insertions, 5 deletions

diff --git a/src/core/SkVertices.cpp b/src/core/SkVertices.cpp
index f9cd39cf93..8dadad056b 100644
--- a/src/core/SkVertices.cpp
+++ b/src/core/SkVertices.cpp
@@ -169,7 +169,8 @@ sk_sp<SkData> SkVertices::encode() const {
 
     Sizes sizes(fVertexCnt, fIndexCnt, this->hasTexCoords(), this->hasColors());
     SkASSERT(sizes.isValid());
-    const size_t size = kHeaderSize + sizes.fArrays;
+    // need to force alignment to 4 for SkWriter32 -- will pad w/ 0s as needed
+    const size_t size = SkAlign4(kHeaderSize + sizes.fArrays);
 
     sk_sp<SkData> data = SkData::MakeUninitialized(size);
     SkWriter32 writer(data->writable_data(), data->size());
@@ -180,7 +181,8 @@ sk_sp<SkData> SkVertices::encode() const {
     writer.write(fPositions, sizes.fVSize);
     writer.write(fTexs, sizes.fTSize);
     writer.write(fColors, sizes.fCSize);
-    writer.write(fIndices, sizes.fISize);
+    // if index-count is odd, we won't be 4-bytes aligned, so we call the pad version
+    writer.writePad(fIndices, sizes.fISize);
 
     return data;
 }
@@ -203,7 +205,8 @@ sk_sp<SkVertices> SkVertices::Decode(const void* data, size_t length) {
     if (!sizes.isValid()) {
         return nullptr;
     }
-    if (kHeaderSize + sizes.fArrays != length) {
+    // logically we can be only 2-byte aligned, but our buffer is always 4-byte aligned
+    if (SkAlign4(kHeaderSize + sizes.fArrays) != length) {
         return nullptr;
     }
 
diff --git a/tests/VerticesTest.cpp b/tests/VerticesTest.cpp
index 5c5c6af41d..399aba2f21 100644
--- a/tests/VerticesTest.cpp
+++ b/tests/VerticesTest.cpp
@@ -50,8 +50,8 @@ static bool equal(const SkVertices* v0, const SkVertices* v1) {
 }
 
 DEF_TEST(Vertices, reporter) {
-    int vCount = 4;
-    int iCount = 6;
+    int vCount = 5;
+    int iCount = 9; // odd value exercises padding logic in encode()
 
     const uint32_t texFlags[] = { 0, SkVertices::kHasTexCoords_BuilderFlag };
     const uint32_t colFlags[] = { 0, SkVertices::kHasColors_BuilderFlag };