Refactor embedder and extractor

src/kyut/watermarker/FunctionOrderingWatermarker.cpp

@@ -14,34 +14,19 @@ namespace kyut::watermarker {
         constexpr auto factorialBitLengthTable = std::array<std::size_t, 21>{
             0, 0, 1, 2, 4, 6, 9, 12, 15, 18, 21, 25, 28, 32, 36, 40, 44, 48, 52, 56, 61,
         };
-    } // namespace
-
-    std::size_t embedFunctionOrdering(wasm::Module &module, CircularBitStreamReader &stream, std::size_t maxChunkSize) {
-        assert(2 <= maxChunkSize && maxChunkSize < 21 && "because 21! > 2^64");
-
-        // Number of bits embedded in the module
-        std::size_t numBits = 0;
-
-        // Split according to the function in the module has body or not
-        // [begin, start) has no body, and [start, end) has
-        const auto start = std::partition(
-            std::begin(module.functions), std::end(module.functions), [](const auto &f) { return f->body == nullptr; });
 
-        const size_t count = std::distance(start, std::end(module.functions));
-
-        for (size_t i = 0; i < count; i += maxChunkSize) {
-            const auto chunkSize = (std::min)(maxChunkSize, count - i);
-            const auto chunkBegin = start + i;
-            const auto chunkEnd = chunkBegin + chunkSize;
+        template <typename Iterator>
+        std::size_t embedIntoChunk(Iterator chunkBegin, Iterator chunkEnd, CircularBitStreamReader &stream) {
+            const auto chunkSize = std::distance(chunkBegin, chunkEnd);
 
             // Number of bits that can be embedded in the chunk
-            const auto numBitsEmbeddedInChunk = factorialBitLengthTable[chunkSize];
+            const auto numBits = factorialBitLengthTable[chunkSize];
 
             // Sort functions in the chunk
             std::sort(chunkBegin, chunkEnd, [](const auto &a, const auto &b) { return a->name < b->name; });
 
             // A watermark to embed in the chunk
-            auto watermark = stream.read<std::uint64_t>(numBitsEmbeddedInChunk);
+            auto watermark = stream.read<std::uint64_t>(numBits);
 
             // Reorder the functions
             for (auto it = chunkBegin; it != chunkEnd; ++it) {
@@ -52,32 +37,15 @@ namespace kyut::watermarker {
                 std::swap(*it, *(it + n));
             }
 
-            numBits += numBitsEmbeddedInChunk;
-        }
-
             return numBits;
         }
 
-    std::size_t extractFunctionOrdering(wasm::Module &module, BitStreamWriter &stream, std::size_t maxChunkSize) {
-        assert(2 <= maxChunkSize && maxChunkSize < 21 && "because 21! > 2^64");
-
-        // Number of bits extracted in the module
-        std::size_t numBits = 0;
-
-        // Split according to the function in the module has body or not
-        // [begin, start) has no body, and [start, end) has
-        const auto start = std::partition(
-            std::begin(module.functions), std::end(module.functions), [](const auto &f) { return f->body == nullptr; });
-
-        const size_t count = std::distance(start, std::end(module.functions));
-
-        for (size_t i = 0; i < count; i += maxChunkSize) {
-            const auto chunkSize = (std::min)(maxChunkSize, count - i);
-            const auto chunkBegin = start + i;
-            const auto chunkEnd = chunkBegin + chunkSize;
+        template <typename Iterator>
+        std::size_t extractFromChunk(Iterator chunkBegin, Iterator chunkEnd, BitStreamWriter &stream) {
+            const auto chunkSize = std::distance(chunkBegin, chunkEnd);
 
             // Number of bits embedded in the chunk
-            const auto numBitsEmbeddedInChunk = factorialBitLengthTable[chunkSize];
+            const auto numBits = factorialBitLengthTable[chunkSize];
 
             // Extract watermarks from the chunk
             std::vector<wasm::Function *> functions;
@@ -95,9 +63,7 @@ namespace kyut::watermarker {
             auto funcBegin = std::begin(functions);
             const auto funcEnd = std::end(functions);
 
-            for (auto it = chunkBegin; it != chunkEnd; ++it) {
-                assert(std::distance(it, chunkEnd) == std::distance(funcBegin, funcEnd));
-
+            for (auto it = chunkBegin; it != chunkEnd; ++it, ++funcBegin) {
                 // Get index of the function `*it`
                 const auto pos = std::find_if(funcBegin, funcEnd, [it](const auto &f) { return f == it->get(); });
                 assert(pos != funcEnd);
@@ -109,12 +75,59 @@ namespace kyut::watermarker {
 
                 // Remove the function found in this step
                 std::swap(*funcBegin, *pos);
-                ++funcBegin;
             }
 
-            stream.write(watermark, numBitsEmbeddedInChunk);
+            stream.write(watermark, numBits);
+
+            return numBits;
+        }
+    } // namespace
 
-            numBits += numBitsEmbeddedInChunk;
+    std::size_t embedFunctionOrdering(wasm::Module &module, CircularBitStreamReader &stream, std::size_t maxChunkSize) {
+        assert(2 <= maxChunkSize && maxChunkSize < 21 && "because 21! > 2^64");
+
+        // Number of bits embedded in the module
+        std::size_t numBits = 0;
+
+        // Split according to the function in the module has body or not
+        // [begin, start) has no body, and [start, end) has
+        const auto start = std::partition(
+            std::begin(module.functions), std::end(module.functions), [](const auto &f) { return f->body == nullptr; });
+
+        const size_t count = std::distance(start, std::end(module.functions));
+
+        for (size_t i = 0; i < count; i += maxChunkSize) {
+            const auto chunkSize = (std::min)(maxChunkSize, count - i);
+            const auto chunkBegin = start + i;
+            const auto chunkEnd = chunkBegin + chunkSize;
+
+            // Embed watermarks into the chunk
+            numBits += embedIntoChunk(chunkBegin, chunkEnd, stream);
+        }
+
+        return numBits;
+    }
+
+    std::size_t extractFunctionOrdering(wasm::Module &module, BitStreamWriter &stream, std::size_t maxChunkSize) {
+        assert(2 <= maxChunkSize && maxChunkSize < 21 && "because 21! > 2^64");
+
+        // Number of bits extracted in the module
+        std::size_t numBits = 0;
+
+        // Split according to the function in the module has body or not
+        // [begin, start) has no body, and [start, end) has
+        const auto start = std::partition(
+            std::begin(module.functions), std::end(module.functions), [](const auto &f) { return f->body == nullptr; });
+
+        const size_t count = std::distance(start, std::end(module.functions));
+
+        for (size_t i = 0; i < count; i += maxChunkSize) {
+            const auto chunkSize = (std::min)(maxChunkSize, count - i);
+            const auto chunkBegin = start + i;
+            const auto chunkEnd = chunkBegin + chunkSize;
+
+            // Extract watermarks from the chunk
+            numBits += extractFromChunk(chunkBegin, chunkEnd, stream);
         }
 
         return numBits;