1 files changed, 60 insertions, 0 deletions
diff --git a/xpcom/ds/Tokenizer.h b/xpcom/ds/Tokenizer.h
index 713b63f269..6a4ec89d51 100644
--- a/xpcom/ds/Tokenizer.h
+++ b/xpcom/ds/Tokenizer.h
@@ -439,6 +439,66 @@ class TTokenizer : public TokenizerBase<TChar> {
   }
 
   /**
+   * This is an hexadecimal read helper.  It returns false and doesn't move the
+   * read cursor when any of the following happens:
+   *  - the token at the read cursor is not 0, and it's not followed by x
+   *  - the token(s) that follow don't make a valid hexadecimal number
+   *  - the final number doesn't fit the T type
+   * Otherwise true is returned, aValue is filled with the integral number
+   * and the cursor is moved forward.
+   */
+  template <typename T>
+  [[nodiscard]] bool ReadHexadecimal(T* aValue, bool aPrefixed = true) {
+    MOZ_RELEASE_ASSERT(aValue);
+
+    typename base::TAString::const_char_iterator rollback = mRollback;
+    typename base::TAString::const_char_iterator cursor = base::mCursor;
+    auto revert = MakeScopeExit([&] {
+      // Move to a state as if Check() call has failed
+      mRollback = rollback;
+      base::mCursor = cursor;
+      base::mHasFailed = true;
+    });
+
+    if (aPrefixed) {
+      typename base::Token t;
+      if (!Check(base::TOKEN_INTEGER, t) && t.AsInteger() != 0) {
+        return false;
+      }
+
+      if (!CheckChar([](const TChar aChar) { return aChar == 'x'; })) {
+        return false;
+      }
+    }
+
+    TChar c = 'z';
+    mozilla::CheckedInt<T> resultingNumber = 0;
+    while (ReadChar(
+        [](const TChar aChar) {
+          return (aChar >= '0' && aChar <= '9') ||
+                 (aChar >= 'A' && aChar <= 'F') ||
+                 (aChar >= 'a' && aChar <= 'f');
+        },
+        &c)) {
+      resultingNumber *= 16;
+      if (c <= '9') {
+        resultingNumber += static_cast<uint64_t>(c - '0');
+      } else if (c <= 'F') {
+        resultingNumber += static_cast<uint64_t>(c - 'A') + 0xa;
+      } else {
+        resultingNumber += static_cast<uint64_t>(c - 'a') + 0xa;
+      }
+    }
+    if (c == 'z' || !resultingNumber.isValid()) {
+      return false;
+    }
+
+    *aValue = resultingNumber.value();
+    revert.release();
+    return true;
+  }
+
+  /**
    * Returns the read cursor position back as it was before the last call of any
    * parsing method of TTokenizer (Next, Check*, Skip*, Read*) so that the last
    * operation can be repeated. Rollback cannot be used multiple times, it only