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

This reverts commit 4b6a7c3940bc6d5e89e15179d8d49600e6dd4857.

Reason for revert: b/299695302, b/299694769

Change-Id: I89c6719d23446f2f9ce24e5b75d321538b580431
diff --git a/libutils/String8.cpp b/libutils/String8.cpp
index 4301f0e..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;
@@ -442,14 +467,40 @@
         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.
  */
-static const char* find_extension(const char* str) {
+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);
@@ -464,16 +515,67 @@
         return nullptr;
 
     // looks good, ship it
-    return lastDot;
+    return const_cast<char*>(lastDot);
 }
 
 String8 String8::getPathExtension(void) const
 {
-    auto ext = find_extension(mString);
+    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