1 files changed, 155 insertions, 0 deletions
diff --git a/intl/components/src/MeasureUnit.h b/intl/components/src/MeasureUnit.h
new file mode 100644
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+++ b/intl/components/src/MeasureUnit.h
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef intl_components_MeasureUnit_h_
+#define intl_components_MeasureUnit_h_
+
+#include "mozilla/Assertions.h"
+#include "mozilla/intl/ICU4CGlue.h"
+#include "mozilla/intl/ICUError.h"
+#include "mozilla/Result.h"
+#include "mozilla/Span.h"
+#include "mozilla/UniquePtr.h"
+
+#include <iterator>
+#include <stddef.h>
+#include <stdint.h>
+#include <utility>
+
+struct UResourceBundle;
+
+namespace mozilla::intl {
+
+/**
+ * This component is a Mozilla-focused API for working with measurement units in
+ * internationalization code. It is used in coordination with other operations
+ * such as number formatting.
+ */
+class MeasureUnit final {
+  class UResourceBundleDeleter {
+   public:
+    void operator()(UResourceBundle* aPtr);
+  };
+
+  using UniqueUResourceBundle =
+      UniquePtr<UResourceBundle, UResourceBundleDeleter>;
+
+ public:
+  MeasureUnit() = delete;
+
+  class Enumeration final {
+    // Resource bundle for the root locale.
+    UniqueUResourceBundle mRootLocale = nullptr;
+
+    // Resource bundle for the root locale's "units" resource table.
+    UniqueUResourceBundle mUnits = nullptr;
+
+    // The overall amount of available units.
+    int32_t mUnitsSize = 0;
+
+   public:
+    Enumeration(UniqueUResourceBundle aRootLocale,
+                UniqueUResourceBundle aUnits);
+
+    class Iterator {
+     public:
+      // std::iterator traits.
+      using iterator_category = std::input_iterator_tag;
+      using value_type = SpanResult<char>;
+      using difference_type = ptrdiff_t;
+      using pointer = value_type*;
+      using reference = value_type&;
+
+     private:
+      const Enumeration& mEnumeration;
+
+      // Resource bundle to a measurement type within the "units" table.
+      //
+      // Measurement types describe various categories, like "area", "length",
+      // or "mass".
+      UniqueUResourceBundle mType = nullptr;
+
+      // Resource bundle to a specific subtype within the type table.
+      //
+      // Measurement subtypes describe concrete measure units, like "acre",
+      // "meter", or "kilogram".
+      UniqueUResourceBundle mSubtype = nullptr;
+
+      // The next position within the "units" table.
+      int32_t mUnitsPos = 0;
+
+      // The overall amount of types within the |mType| table.
+      int32_t mTypeSize = 0;
+
+      // The next position within the |mType| table.
+      int32_t mTypePos = 0;
+
+      // Flag set when an ICU error has occurred. All further operations on this
+      // iterator will return an error result when this flag is set.
+      bool mHasError = false;
+
+      void advance();
+
+     public:
+      Iterator(const Enumeration& aEnumeration, int32_t aUnitsPos)
+          : mEnumeration(aEnumeration), mUnitsPos(aUnitsPos) {
+        advance();
+      }
+
+      Iterator& operator++() {
+        advance();
+        return *this;
+      }
+
+      // The post-increment operator would return an invalid iterator, so it's
+      // not implemented.
+      Iterator operator++(int) = delete;
+
+      bool operator==(const Iterator& aOther) const {
+        // It's an error to compare an iterator against an iterator from a
+        // different enumeration.
+        MOZ_ASSERT(&mEnumeration == &aOther.mEnumeration);
+
+        return mUnitsPos == aOther.mUnitsPos && mTypeSize == aOther.mTypeSize &&
+               mTypePos == aOther.mTypePos && mHasError == aOther.mHasError;
+      }
+
+      bool operator!=(const Iterator& aOther) const {
+        return !(*this == aOther);
+      }
+
+      value_type operator*() const;
+    };
+
+    friend class Iterator;
+
+    // std::iterator begin() and end() methods.
+
+    /**
+     * Return an iterator pointing to the start of the "units" table.
+     */
+    Iterator begin() { return Iterator(*this, 0); }
+
+    /**
+     * Return an iterator pointing to the end of the "units" table.
+     */
+    Iterator end() { return Iterator(*this, mUnitsSize); }
+
+    /**
+     * Create a new measurement unit enumeration.
+     */
+    static Result<Enumeration, ICUError> TryCreate();
+  };
+
+  /**
+   * Return an enumeration over all available measurement units.
+   */
+  static Result<Enumeration, ICUError> GetAvailable() {
+    return Enumeration::TryCreate();
+  }
+};
+
+}  // namespace mozilla::intl
+
+#endif