Revert "Drop all path-related methods from android::String8"

This reverts commit b9dc1c2991de9ca87bdbf00c413b7f2bb4477fe2.

Reason for revert: http://b/299624573

Change-Id: I0d5993295df65ec31c180b6b5a76fbe939891f45
diff --git a/libutils/String8.cpp b/libutils/String8.cpp
index a2cfc08..2b72847 100644
--- a/libutils/String8.cpp
+++ b/libutils/String8.cpp
@@ -430,6 +430,31 @@
 // ---------------------------------------------------------------------------
 // Path functions
 
+static void setPathName(String8& s, const char* name) {
+    size_t len = strlen(name);
+    char* buf = s.lockBuffer(len);
+
+    memcpy(buf, name, len);
+
+    // remove trailing path separator, if present
+    if (len > 0 && buf[len - 1] == OS_PATH_SEPARATOR) len--;
+    buf[len] = '\0';
+
+    s.unlockBuffer(len);
+}
+
+String8 String8::getPathLeaf(void) const
+{
+    const char* cp;
+    const char*const buf = mString;
+
+    cp = strrchr(buf, OS_PATH_SEPARATOR);
+    if (cp == nullptr)
+        return String8(*this);
+    else
+        return String8(cp+1);
+}
+
 String8 String8::getPathDir(void) const
 {
     const char* cp;
@@ -442,4 +467,115 @@
         return String8(str, cp - str);
 }
 
+String8 String8::walkPath(String8* outRemains) const
+{
+    const char* cp;
+    const char*const str = mString;
+    const char* buf = str;
+
+    cp = strchr(buf, OS_PATH_SEPARATOR);
+    if (cp == buf) {
+        // don't include a leading '/'.
+        buf = buf+1;
+        cp = strchr(buf, OS_PATH_SEPARATOR);
+    }
+
+    if (cp == nullptr) {
+        String8 res = buf != str ? String8(buf) : *this;
+        if (outRemains) *outRemains = String8("");
+        return res;
+    }
+
+    String8 res(buf, cp-buf);
+    if (outRemains) *outRemains = String8(cp+1);
+    return res;
+}
+
+/*
+ * Helper function for finding the start of an extension in a pathname.
+ *
+ * Returns a pointer inside mString, or NULL if no extension was found.
+ */
+char* String8::find_extension(void) const
+{
+    const char* lastSlash;
+    const char* lastDot;
+    const char* const str = mString;
+
+    // only look at the filename
+    lastSlash = strrchr(str, OS_PATH_SEPARATOR);
+    if (lastSlash == nullptr)
+        lastSlash = str;
+    else
+        lastSlash++;
+
+    // find the last dot
+    lastDot = strrchr(lastSlash, '.');
+    if (lastDot == nullptr)
+        return nullptr;
+
+    // looks good, ship it
+    return const_cast<char*>(lastDot);
+}
+
+String8 String8::getPathExtension(void) const
+{
+    char* ext;
+
+    ext = find_extension();
+    if (ext != nullptr)
+        return String8(ext);
+    else
+        return String8("");
+}
+
+String8 String8::getBasePath(void) const
+{
+    char* ext;
+    const char* const str = mString;
+
+    ext = find_extension();
+    if (ext == nullptr)
+        return String8(*this);
+    else
+        return String8(str, ext - str);
+}
+
+String8& String8::appendPath(const char* name)
+{
+    // TODO: The test below will fail for Win32 paths. Fix later or ignore.
+    if (name[0] != OS_PATH_SEPARATOR) {
+        if (*name == '\0') {
+            // nothing to do
+            return *this;
+        }
+
+        size_t len = length();
+        if (len == 0) {
+            // no existing filename, just use the new one
+            setPathName(*this, name);
+            return *this;
+        }
+
+        // make room for oldPath + '/' + newPath
+        int newlen = strlen(name);
+
+        char* buf = lockBuffer(len+1+newlen);
+
+        // insert a '/' if needed
+        if (buf[len-1] != OS_PATH_SEPARATOR)
+            buf[len++] = OS_PATH_SEPARATOR;
+
+        memcpy(buf+len, name, newlen+1);
+        len += newlen;
+
+        unlockBuffer(len);
+
+        return *this;
+    } else {
+        setPathName(*this, name);
+        return *this;
+    }
+}
+
 }; // namespace android