[core] Safeguard ICU UChar usage

2 files changed, 25 insertions, 7 deletions

diff --git a/include/mbgl/util/traits.hpp b/include/mbgl/util/traits.hpp
index 9d6f947cd2..5b9401aad7 100644
--- a/include/mbgl/util/traits.hpp
+++ b/include/mbgl/util/traits.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <cstdint>
 #include <type_traits>
 
 namespace mbgl {
@@ -9,4 +10,19 @@ constexpr auto underlying_type(T t) -> typename std::underlying_type_t<T> {
     return typename std::underlying_type_t<T>(t);
 }
 
+template <typename T> struct is_utf16char_like: std::false_type {};
+template <typename T> struct is_utf16char_like<const T>: is_utf16char_like<T> {};
+template <> struct is_utf16char_like<char16_t>: std::true_type {};
+template <> struct is_utf16char_like<wchar_t>: std::true_type {};
+template <> struct is_utf16char_like<uint16_t>: std::true_type {};
+
+template <typename T> using is_utf16char_like_pointer = std::integral_constant<bool, std::is_pointer<T>::value
+                                                                                     && is_utf16char_like<typename std::remove_pointer<T>::type>::value>;
+
+template <class OutPointer, class InChar>
+typename std::enable_if<is_utf16char_like<InChar>::value && is_utf16char_like_pointer<OutPointer>::value, OutPointer>::type utf16char_cast(InChar *in)
+{
+    return reinterpret_cast<OutPointer>(in);
+}
+
 } // namespace mbgl
diff --git a/platform/default/bidi.cpp b/platform/default/bidi.cpp
index 25b4dbe3a7..59df6dd6df 100644
--- a/platform/default/bidi.cpp
+++ b/platform/default/bidi.cpp
@@ -1,9 +1,11 @@
-#include <memory>
-
 #include <mbgl/text/bidi.hpp>
+#include <mbgl/util/traits.hpp>
+
 #include <unicode/ubidi.h>
 #include <unicode/ushape.h>
 
+#include <memory>
+
 namespace mbgl {
 
 class BiDiImpl {
@@ -28,7 +30,7 @@ std::u16string applyArabicShaping(const std::u16string& input) {
     UErrorCode errorCode = U_ZERO_ERROR;
 
     const int32_t outputLength =
-        u_shapeArabic(input.c_str(), static_cast<int32_t>(input.size()), NULL, 0,
+        u_shapeArabic(mbgl::utf16char_cast<const UChar*>(input.c_str()), static_cast<int32_t>(input.size()), NULL, 0,
                       (U_SHAPE_LETTERS_SHAPE & U_SHAPE_LETTERS_MASK) |
                           (U_SHAPE_TEXT_DIRECTION_LOGICAL & U_SHAPE_TEXT_DIRECTION_MASK),
                       &errorCode);
@@ -37,7 +39,7 @@ std::u16string applyArabicShaping(const std::u16string& input) {
     errorCode = U_ZERO_ERROR;
 
     auto outputText = std::make_unique<UChar[]>(outputLength);
-    u_shapeArabic(input.c_str(), static_cast<int32_t>(input.size()), outputText.get(), outputLength,
+    u_shapeArabic(mbgl::utf16char_cast<const UChar*>(input.c_str()), static_cast<int32_t>(input.size()), outputText.get(), outputLength,
                   (U_SHAPE_LETTERS_SHAPE & U_SHAPE_LETTERS_MASK) |
                       (U_SHAPE_TEXT_DIRECTION_LOGICAL & U_SHAPE_TEXT_DIRECTION_MASK),
                   &errorCode);
@@ -46,7 +48,7 @@ std::u16string applyArabicShaping(const std::u16string& input) {
     if (U_FAILURE(errorCode))
         return input;
 
-    return std::u16string(outputText.get(), outputLength);
+    return std::u16string(mbgl::utf16char_cast<const char16_t*>(outputText.get()), outputLength);
 }
 
 void BiDi::mergeParagraphLineBreaks(std::set<size_t>& lineBreakPoints) {
@@ -86,7 +88,7 @@ std::vector<std::u16string> BiDi::processText(const std::u16string& input,
                                               std::set<std::size_t> lineBreakPoints) {
     UErrorCode errorCode = U_ZERO_ERROR;
 
-    ubidi_setPara(impl->bidiText, input.c_str(), static_cast<int32_t>(input.size()),
+    ubidi_setPara(impl->bidiText, mbgl::utf16char_cast<const UChar*>(input.c_str()), static_cast<int32_t>(input.size()),
                   UBIDI_DEFAULT_LTR, NULL, &errorCode);
 
     if (U_FAILURE(errorCode)) {
@@ -121,7 +123,7 @@ std::u16string BiDi::getLine(std::size_t start, std::size_t end) {
                                  u_errorName(errorCode));
     }
 
-    return std::u16string(outputText.get(), outputLength);
+    return std::u16string(mbgl::utf16char_cast<const char16_t*>(outputText.get()), outputLength);
 }
 
 } // end namespace mbgl