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>

3 files changed, 8 insertions, 19 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;
 }
 
diff --git a/src/core/SkPaintPriv.h b/src/core/SkPaintPriv.h
index dbac69beb0..a5ee9a5e59 100644
--- a/src/core/SkPaintPriv.h
+++ b/src/core/SkPaintPriv.h
@@ -68,7 +68,7 @@ public:
 
     static bool ShouldDither(const SkPaint&, SkColorType);
 
-    // returns 0 if buffer is invalid for specified encoding
+    // returns -1 if buffer is invalid for specified encoding
     static int ValidCountText(const void* text, size_t length, SkPaint::TextEncoding);
 
     static SkTypeface* GetTypefaceOrDefault(const SkPaint& paint) {
diff --git a/src/core/SkUtils.cpp b/src/core/SkUtils.cpp
index c12bac50ff..f0c1f60a09 100644
--- a/src/core/SkUtils.cpp
+++ b/src/core/SkUtils.cpp
@@ -86,10 +86,6 @@ int SkUTF8_CountUnichars(const char utf8[]) {
 int SkUTF8_CountUnichars(const void* text, size_t byteLength) {
     SkASSERT(text);
     const char* utf8 = static_cast<const char*>(text);
-    if (byteLength == 0) {
-        return 0;
-    }
-
     int         count = 0;
     const char* stop = utf8 + byteLength;
 
@@ -262,9 +258,6 @@ int SkUTF16_CountUnichars(const uint16_t src[]) {
 // returns -1 on error
 int SkUTF16_CountUnichars(const void* text, size_t byteLength) {
     SkASSERT(text);
-    if (byteLength == 0) {
-        return 0;
-    }
     if (!SkIsAlign2(intptr_t(text)) || !SkIsAlign2(byteLength)) {
         return -1;
     }
@@ -274,7 +267,9 @@ int SkUTF16_CountUnichars(const void* text, size_t byteLength) {
     int count = 0;
     while (src < stop) {
         unsigned c = *src++;
-        SkASSERT(!SkUTF16_IsLowSurrogate(c));
+        if (SkUTF16_IsLowSurrogate(c)) {
+            return -1;
+        }
         if (SkUTF16_IsHighSurrogate(c)) {
             if (src >= stop) {
                 return -1;
@@ -405,9 +400,6 @@ size_t SkUTF16_ToUTF8(const uint16_t utf16[], int numberOf16BitValues,
 
 // returns -1 on error
 int SkUTF32_CountUnichars(const void* text, size_t byteLength) {
-    if (byteLength == 0) {
-        return 0;
-    }
     if (!SkIsAlign4(intptr_t(text)) || !SkIsAlign4(byteLength)) {
         return -1;
     }