1 files changed, 78 insertions, 0 deletions
diff --git a/src/PercentEncodedCharacterDecoder.cpp b/src/PercentEncodedCharacterDecoder.cpp
new file mode 100644
index 0000000..d3bc0d9
--- /dev/null
+++ b/src/PercentEncodedCharacterDecoder.cpp
@@ -0,0 +1,78 @@
+/**
+ * @file PercentEncodedCharacterDecoder.cpp
+ *
+ * This module contains the implementation of the
+ * Uri::PercentEncodedCharacterDecoder class.
+ *
+ * © 2018 by Richard Walters
+ */
+
+#include "IsCharacterInSet.hpp"
+#include "PercentEncodedCharacterDecoder.hpp"
+
+namespace Uri {
+
+    struct PercentEncodedCharacterDecoder::Impl {
+        /**
+         * This is the decoded character.
+         */
+        int decodedCharacter = 0;
+
+        /**
+         * This is the current state of the decoder's state machine.
+         * - 0: we haven't yet received the first hex digit.
+         * - 1: we received the first hex digit but not the second.
+         * - 2: we received both hex digits
+         */
+        size_t decoderState = 0;
+    };
+
+    PercentEncodedCharacterDecoder::~PercentEncodedCharacterDecoder() = default;
+    PercentEncodedCharacterDecoder::PercentEncodedCharacterDecoder(PercentEncodedCharacterDecoder&&) = default;
+    PercentEncodedCharacterDecoder& PercentEncodedCharacterDecoder::operator=(PercentEncodedCharacterDecoder&&) = default;
+
+    PercentEncodedCharacterDecoder::PercentEncodedCharacterDecoder()
+        : impl_(new Impl)
+    {
+    }
+
+    bool PercentEncodedCharacterDecoder::NextEncodedCharacter(char c) {
+        switch(impl_->decoderState) {
+            case 0: { // % ...
+                impl_->decoderState = 1;
+                impl_->decodedCharacter <<= 4;
+                if (IsCharacterInSet(c, {'0','9'})) {
+                    impl_->decodedCharacter += (int)(c - '0');
+                } else if (IsCharacterInSet(c, {'A','F'})) {
+                    impl_->decodedCharacter += (int)(c - 'A') + 10;
+                } else {
+                    return false;
+                }
+            } break;
+
+            case 1: { // %[0-9A-F] ...
+                impl_->decoderState = 2;
+                impl_->decodedCharacter <<= 4;
+                if (IsCharacterInSet(c, {'0','9'})) {
+                    impl_->decodedCharacter += (int)(c - '0');
+                } else if (IsCharacterInSet(c, {'A','F'})) {
+                    impl_->decodedCharacter += (int)(c - 'A') + 10;
+                } else {
+                    return false;
+                }
+            } break;
+
+            default: break;
+        }
+        return true;
+    }
+
+    bool PercentEncodedCharacterDecoder::Done() const {
+        return (impl_->decoderState == 2);
+    }
+
+    char PercentEncodedCharacterDecoder::GetDecodedCharacter() const {
+        return (char)impl_->decodedCharacter;
+    }
+
+}