Generate NDK headers and a new public library libicu

Symbol selection
- Expose the C symbols listed in libicu_export.txt
- Currently, we focus on exposing the symbols used by the ART mainline
  module, and selecting a logical set of symbols from uchar.h,
  ustring.h, uloc.h, uversion.h and utypes.h.
- The symbols are further filtered by checking whether we have
  provided the same functionality in Java by ICU4J/ICU4C via
  android.icu.*/java.* classes. The Java APIs are reviewed/proved useful
  and it could reduce the maintenance cost since ICU4J mostly mirrors
  the behavior of ICU4C and code changes/bug fixes are often applied
  in both places. But here is the exception:
  1. uloc_setDefault
    Many places in libcore assumes Locale, ULocale, and ICU4C has the same
    default locale. App setting a different default locale in ICU4C will
    likely break things.
  2. uloc_getDefault
    We could expose uloc_getDefault, but since uloc_setDefault is not
    exposed, uloc_getDefault becomes a shortcut function to obtain
    the default Locale from ULocale.getDefault or even framework's
    getResources().getConfiguration().locale. Such behavior is not
    well-documented in uloc_getDefault. Also, without ART managed
    runtime, e.g. standalone executable binary, the behavior could be
    undefined. Probably Android should provide JNI interop method/other
    C API to get the Android system default locale, but not via
    uloc_getDefault.
- Other symbols excluded from the above headers
    u_UCharsToChars
    u_austrcpy
    u_austrncpy
    u_charsToUChars
    u_getFC_NFKC_Closure
    u_strCompareIter
    u_strFromJavaModifiedUTF8WithSub
    u_strFromWCS
    u_strToJavaModifiedUTF8
    u_strToWCS
    u_uastrcpy
    u_uastrncpy
    u_unescape
    u_unescapeAt
    u_versionFromString
    u_versionFromUString
    uloc_acceptLanguageFromHTTP
    uloc_getLCID
    uloc_getLocaleForLCID
    uloc_getParent

Symbol name
- libicu.so will have symbols for the exact same functionality
  as the symbols in libicuuc.so and libicui18n.so,
  e.g. u_isalpha and u_isalpha_66. The ICU-version-specific symbol
  u_isalpha_66 is kept for app compatability because many app has been
  using it even though the version number increases for every platform
  release. u_isalpha is implemented as a shim of u_isalpha_66 in
  shim.cpp.

Code transformation
- shim.cpp, libicu.map.txt and the headers are generated by running
  the new generate_ndk.py script

Test
- CTS will be in the next CL.

Bug: 160350521
Test: ./generate_ndk.py
Test: m droid
Change-Id: I2eb6d5a0968c72bb6922221a971414de20273041

1 files changed, 3 insertions, 0 deletions

diff --git a/android_icu4c/Android.bp b/android_icu4c/Android.bp
index 98fd89faa..2bf2721f2 100644
--- a/android_icu4c/Android.bp
+++ b/android_icu4c/Android.bp
@@ -11,6 +11,9 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+package {
+    default_visibility: ["//external/icu:__subpackages__"],
+}
 
 // Android repo only headers for icu4c
 // The header should mainly contain config for C preprocessor,