Add String16#contains and strstr16 methods.

These are needed for aapt to find javadoc comments that contain
"@removed" in order to skip them when printing styleable docs.

Bug: 28663748
Change-Id: I8866d2167c41e11d6c2586da369560d5815fd13e

include/utils/String16.h

@@ -90,7 +90,9 @@ public:
 
             bool                startsWith(const String16& prefix) const;
             bool                startsWith(const char16_t* prefix) const;
-            
+
+            bool                contains(const char16_t* chrs) const;
+
             status_t            makeLower();
 
             status_t            replaceAll(char16_t replaceThis,

include/utils/Unicode.h

@@ -29,6 +29,7 @@ size_t strlen16(const char16_t *);
 size_t strnlen16(const char16_t *, size_t);
 char16_t *strcpy16(char16_t *, const char16_t *);
 char16_t *strncpy16(char16_t *, const char16_t *, size_t);
+char16_t *strstr16(const char16_t*, const char16_t*);
 
 // Version of comparison that supports embedded nulls.
 // This is different than strncmp() because we don't stop

libutils/String16.cpp

@@ -345,6 +345,11 @@ bool String16::startsWith(const char16_t* prefix) const
     return strncmp16(mString, prefix, ps) == 0;
 }
 
+bool String16::contains(const char16_t* chrs) const
+{
+    return strstr16(mString, chrs) != nullptr;
+}
+
 status_t String16::makeLower()
 {
     const size_t N = size();

libutils/Unicode.cpp

@@ -222,12 +222,17 @@ int strncmp16(const char16_t *s1, const char16_t *s2, size_t n)
   char16_t ch;
   int d = 0;
 
-  while ( n-- ) {
-    d = (int)(ch = *s1++) - (int)*s2++;
-    if ( d || !ch )
-      break;
+  if (n == 0) {
+    return 0;
   }
 
+  do {
+    d = (int)(ch = *s1++) - (int)*s2++;
+    if ( d || !ch ) {
+      break;
+    }
+  } while (--n);
+
   return d;
 }
 
@@ -284,6 +289,24 @@ size_t strnlen16(const char16_t *s, size_t maxlen)
   return ss-s;
 }
 
+char16_t* strstr16(const char16_t* src, const char16_t* target)
+{
+    const char16_t needle = *target++;
+    if (needle != '\0') {
+      do {
+        do {
+          if (*src == '\0') {
+            return nullptr;
+          }
+        } while (*src++ != needle);
+      } while (strcmp16(src, target) != 0);
+      src--;
+    }
+
+    return (char16_t*)src;
+}
+
+
 int strzcmp16(const char16_t *s1, size_t n1, const char16_t *s2, size_t n2)
 {
     const char16_t* e1 = s1+n1;

libutils/tests/Unicode_test.cpp

@@ -29,6 +29,8 @@ protected:
 
     virtual void TearDown() {
     }
+
+    char16_t const * const kSearchString = u"I am a leaf on the wind.";
 };
 
 TEST_F(UnicodeTest, UTF8toUTF16ZeroLength) {
@@ -112,4 +114,37 @@ TEST_F(UnicodeTest, UTF8toUTF16Normal) {
             << "should be NULL terminated";
 }
 
+TEST_F(UnicodeTest, strstr16EmptyTarget) {
+    EXPECT_EQ(strstr16(kSearchString, u""), kSearchString)
+            << "should return the original pointer";
+}
+
+TEST_F(UnicodeTest, strstr16SameString) {
+    const char16_t* result = strstr16(kSearchString, kSearchString);
+    EXPECT_EQ(kSearchString, result)
+            << "should return the original pointer";
+}
+
+TEST_F(UnicodeTest, strstr16TargetStartOfString) {
+    const char16_t* result = strstr16(kSearchString, u"I am");
+    EXPECT_EQ(kSearchString, result)
+            << "should return the original pointer";
+}
+
+
+TEST_F(UnicodeTest, strstr16TargetEndOfString) {
+    const char16_t* result = strstr16(kSearchString, u"wind.");
+    EXPECT_EQ(kSearchString+19, result);
+}
+
+TEST_F(UnicodeTest, strstr16TargetWithinString) {
+    const char16_t* result = strstr16(kSearchString, u"leaf");
+    EXPECT_EQ(kSearchString+7, result);
+}
+
+TEST_F(UnicodeTest, strstr16TargetNotPresent) {
+    const char16_t* result = strstr16(kSearchString, u"soar");
+    EXPECT_EQ(nullptr, result);
+}
+
 }