SkUTF16_CountUnichars to error instead of assert.

Update SkUTF16_CountUnichars to return -1 on invalid input instead of
simply asserting in debug. This also removes the unneeded checks for
zero length input. This also updates SkPaintPriv::ValidCountText and its
documentation to reflect the reality that it returns -1 on invalid data.

Bug: skia:8156
Change-Id: Ief227b7dec9d1e823b93e9061558f8412791fc09
Reviewed-on: https://skia-review.googlesource.com/142168
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>

1 files changed, 4 insertions, 7 deletions

diff --git a/src/core/SkPaintPriv.cpp b/src/core/SkPaintPriv.cpp
index 9cd5e4708d..3be1ebeafa 100644
--- a/src/core/SkPaintPriv.cpp
+++ b/src/core/SkPaintPriv.cpp
@@ -91,19 +91,16 @@ bool SkPaintPriv::ShouldDither(const SkPaint& p, SkColorType dstCT) {
 }
 
 int SkPaintPriv::ValidCountText(const void* text, size_t length, SkPaint::TextEncoding encoding) {
-    if (length == 0) {
-        return 0;
-    }
     switch (encoding) {
         case SkPaint::kUTF8_TextEncoding: return SkUTF8_CountUnichars(text, length);
         case SkPaint::kUTF16_TextEncoding: return SkUTF16_CountUnichars(text, length);
         case SkPaint::kUTF32_TextEncoding: return SkUTF32_CountUnichars(text, length);
         case SkPaint::kGlyphID_TextEncoding:
-            if (SkIsAlign2(intptr_t(text)) && SkIsAlign2(length)) {
-                return length >> 1;
+            if (!SkIsAlign2(intptr_t(text)) || !SkIsAlign2(length)) {
+                return -1;
             }
-            break;
+            return length >> 1;
     }
-    return 0;
+    return -1;
 }