Add a couple of useful string functions. (DO NOT MERGE)

Change-Id: I158f69917bab5f15482dd8f2b66b36a4cc0f11ad
(cherry picked from commit 5ee915afe1)

include/utils/String8.h

@@ -130,11 +130,19 @@ public:
             // start, or -1 if not found
             ssize_t             find(const char* other, size_t start = 0) const;
 
+            // return true if this string contains the specified substring
+    inline  bool                contains(const char* other) const;
+
+            // removes all occurrence of the specified substring
+            // returns true if any were found and removed
+            bool                removeAll(const char* other);
+
             void                toLower();
             void                toLower(size_t start, size_t numChars);
             void                toUpper();
             void                toUpper(size_t start, size_t numChars);
 
+
     /*
      * These methods operate on the string as if it were a path name.
      */
@@ -280,6 +288,11 @@ inline const SharedBuffer* String8::sharedBuffer() const
     return SharedBuffer::bufferFromData(mString);
 }
 
+inline bool String8::contains(const char* other) const
+{
+    return find(other) >= 0;
+}
+
 inline String8& String8::operator=(const String8& other)
 {
     setTo(other);

libutils/String8.cpp

@@ -408,6 +408,30 @@ ssize_t String8::find(const char* other, size_t start) const
     return p ? p-mString : -1;
 }
 
+bool String8::removeAll(const char* other) {
+    ssize_t index = find(other);
+    if (index < 0) return false;
+
+    char* buf = lockBuffer(size());
+    if (!buf) return false; // out of memory
+
+    size_t skip = strlen(other);
+    size_t len = size();
+    size_t tail = index;
+    while (size_t(index) < len) {
+        ssize_t next = find(other, index + skip);
+        if (next < 0) {
+            next = len;
+        }
+
+        memcpy(buf + tail, buf + index + skip, next - index - skip);
+        tail += next - index - skip;
+        index = next;
+    }
+    unlockBuffer(tail);
+    return true;
+}
+
 void String8::toLower()
 {
     toLower(0, size());