Support chunked transfer-encoding in fast path

src/HttpParser.h

@@ -152,8 +152,107 @@ private:
     std::string fallback;
     unsigned int remainingStreamingBytes = 0;
 
+    /* This guy should be encoded in remainingStreamingBytes as highest bit */
+    //bool chunked = false;
+
+    /* We do not support any trailer other than empty ones for now */
+    unsigned int consumeTrailer(char *data, unsigned int length) {
+        if (length >= 2) {
+            if (data[0] == '\r' && data[1] == '\n') {
+                return 2;
+            }
+        }
+        return 0;
+    }
+
+    /* Returns [bytes consumed, chunk to emit, isFin] */
+    std::tuple<unsigned int, std::string_view, bool> consumeChunked(char *data, unsigned int length) { 
+        char *start = data;
+        char *end = data + length;
+        
+        /* Can't consume nothing */
+        if (!length) {
+            return {0, std::string_view(), false};
+        }
+
+        /* If first byte is CR, then skip two bytes */
+        if (data[0] == '\r') {
+            if (length > 2) {
+                data += 2;
+            } else {
+                /* We must have at least 3 bytes */
+                return {0, std::string_view(), false};
+            }
+        }
+
+        /* Find next \r */
+        char *numberEnd = data;
+        while (numberEnd < end && *numberEnd != '\r') numberEnd++;
+        /* Break if we cannot find \r */
+        if (numberEnd == end) {
+            return {0, std::string_view(), false};
+        }
+
+        unsigned int toEmit = 0;
+        if (&numberEnd[1] != end && numberEnd[1] == '\n') {
+            /* The following cannot fail */
+            toEmit = toUnsignedIntegerHex(std::string_view(data, (unsigned int)(numberEnd - data)));
+            data = numberEnd + 2;
+
+            /* Skip reading data if we got the null chunk */
+            if (toEmit == 0) {
+                /* Consume trailer then as well */
+                data += consumeTrailer(data, (unsigned int)(end - data));
+
+                /* Emit the empty chunk with fin = true */
+                return {data - start, std::string_view(nullptr, 0), true};
+            }
+
+            /* We cannot emit everything and must return what we have without knowing if it is fin or not */
+            if (data + toEmit >= end) {
+                // todo: set remainingBytesStream and chunked
+                // todo: emit what we can and enter slow path
+                return {0, std::string_view(), false};
+            }
+
+            /* Emit everything now */
+            std::string_view emittableChunk(data, toEmit);
+            data += toEmit;
+            bool fin = false;
+
+            /* Consume the two \r\n following the whole chunk */
+            data += 2;
+            if (data >= end) {
+                /* We could emit the data still here, only without knowing if it is fin */
+                return {0, std::string_view(), false};
+            }
+
+            /* Check if this is fin */
+            if ((data + 3 < end) && !memcmp(data, "0\r\n", 3)) {
+                fin = true;
+                data += 3;
+
+                /* Consume trailer then as well */
+                data += consumeTrailer(data, (unsigned int)(end - data));
+            }
+
+            /* Finally emit this chunk */
+            return {data - start, emittableChunk, fin};
+        }
+
+        return {0, std::string_view(), false};
+    }
+
     const size_t MAX_FALLBACK_SIZE = 1024 * 4;
 
+    static unsigned int toUnsignedIntegerHex(std::string_view str) {
+        unsigned int unsignedIntegerValue = 0;
+        for (char c : str) {
+            unsignedIntegerValue = unsignedIntegerValue * 16u + ((unsigned int) c - (unsigned int) '0');
+        }
+        return unsignedIntegerValue;
+    }
+
     static unsigned int toUnsignedInteger(std::string_view str) {
         unsigned int unsignedIntegerValue = 0;
         for (char c : str) {
@@ -287,20 +386,42 @@ private:
                 return {consumedTotal, returnedUser};
             }
 
-            // todo: do not check this for GET (get should not have a body)
-            // todo: also support reading chunked streams
-            std::string_view contentLengthString = req->getHeader("content-length");
-            if (contentLengthString.length()) {
-                remainingStreamingBytes = toUnsignedInteger(contentLengthString);
+            
+            if (req->getMethod() != "get") {
+                std::string_view contentLengthString = req->getHeader("content-length");
+                if (contentLengthString.length()) {
+                    remainingStreamingBytes = toUnsignedInteger(contentLengthString);
 
-                if (!CONSUME_MINIMALLY) {
-                    unsigned int emittable = std::min<unsigned int>(remainingStreamingBytes, length);
-                    dataHandler(user, std::string_view(data, emittable), emittable == remainingStreamingBytes);
-                    remainingStreamingBytes -= emittable;
+                    if (!CONSUME_MINIMALLY) {
+                        unsigned int emittable = std::min<unsigned int>(remainingStreamingBytes, length);
+                        dataHandler(user, std::string_view(data, emittable), emittable == remainingStreamingBytes);
+                        remainingStreamingBytes -= emittable;
 
-                    data += emittable;
-                    length -= emittable;
-                    consumedTotal += emittable;
+                        data += emittable;
+                        length -= emittable;
+                        consumedTotal += emittable;
+                    }
+                } else {
+                    /* We are not GET and we have no content-length, so assume transfer-encoding: chunked */
+                    /* Todo: care about consume minimally */
+                    while (true) {
+                        auto [consumed, chunk, fin] = consumeChunked(data, length);
+                        if (!consumed) {
+                            break;
+                        }
+                        /* If we consumed something and we either have fin to report, or a chunk, then emit to app */
+                        if (consumed && (chunk.length() || fin)) {
+                            dataHandler(user, chunk, fin);
+                        }
+
+                        data += consumed;
+                        length -= consumed;
+                        consumedTotal += consumed;
+
+                        if (fin) {
+                            break;
+                        }
+                    }
                 }
             } else {
                 /* Still emit an empty data chunk to signal no data */