Initial implementation

Author: bblanchon

extras/test/ChunkDecodingStreamTest.cpp

@@ -13,9 +13,21 @@ TEST_CASE("ChunkDecodingStream") {
   StringStream upstream;
   ChunkDecodingStream stream{upstream};
 
-  WHEN("upstream is empty") {
-    THEN("available() should return 0") {
-      CHECK(stream.available() == 0);
-    }
+  SUBCASE("empty stream") {
+    CHECK(stream.available() == 0);
+    CHECK(stream.peek() == -1);
+    CHECK(stream.read() == -1);
+    CHECK(stream.readString() == "");
+  }
+
+  SUBCASE("one chunk, no extension") {
+    upstream.print("3\r\nABC");
+    CHECK(stream.available() == 3);
+    CHECK(stream.peek() == 'A');
+    CHECK(stream.available() == 3);
+    CHECK(stream.read() == 'A');
+    CHECK(stream.available() == 2);
+    CHECK(stream.readString() == "BC");
+    CHECK(stream.available() == 0);
   }
 }

src/StreamUtils/Policies/ChunkDecodingPolicy.hpp

@@ -0,0 +1,112 @@
+// StreamUtils - github.com/bblanchon/ArduinoStreamUtils
+// Copyright Benoit Blanchon 2019-2024
+// MIT License
+
+#pragma once
+
+#include <Client.h>
+#include <assert.h>
+
+namespace StreamUtils {
+
+class ChunkDecodingPolicy {
+  enum class State {
+    Size,
+    Extensions,
+    StartCrLf,
+    Body,
+    Error,
+  };
+
+ public:
+  int available(Stream &target) {
+    if (!isInChunkBody(target))
+      return 0;
+    return min(target.available(), remaining_);
+  }
+
+  int read(Stream &target) {
+    if (!isInChunkBody(target))
+      return -1;
+    int c = target.read();
+    if (c >= 0)
+      remaining_--;
+    return c;
+  }
+
+  int peek(Stream &target) {
+    if (!isInChunkBody(target))
+      return -1;
+    return target.peek();
+  }
+
+  size_t readBytes(Stream &target, char *buffer, size_t size) {
+    if (!isInChunkBody(target))
+      return 0;
+    size_t n = target.readBytes(buffer, min(size, remaining_));
+    remaining_ -= n;
+    return n;
+  }
+
+  int read(Client &target, uint8_t *buffer, size_t size) {
+    return readBytes(target, reinterpret_cast<char *>(buffer), size);
+  }
+
+ private:
+  bool isInChunkBody(Stream &target) {
+    while (state_ != State::Error && state_ != State::Body &&
+           target.available()) {
+      state_ = injestNext(target);
+    }
+    return state_ == State::Body;
+  }
+
+  State injestNext(Stream &target) {
+    int c = target.read();
+    switch (state_) {
+      case State::Size:
+        if (c >= '0' && c <= '9')
+          return appendSizeHexDigit(c - '0');
+        else if (c >= 'A' && c <= 'F')
+          return appendSizeHexDigit(c - 'A' + 10);
+        else if (c >= 'a' && c <= 'f')
+          return appendSizeHexDigit(c - 'a' + 10);
+        else if (c == '\r')
+          return State::StartCrLf;
+        else if (c == ' ' || c == '\t' || c == ';')
+          return State::Extensions;
+        else
+          return State::Error;
+
+      case State::Extensions:
+        if (c == '\r')
+          return State::StartCrLf;
+        else
+          return State::Extensions;
+
+      case State::StartCrLf:
+        if (c == '\n')
+          return State::Body;
+        else
+          return State::Error;
+
+      default:
+        assert(false);
+        return State::Error;
+    }
+  }
+
+  State appendSizeHexDigit(uint8_t digit) {
+    remaining_ = remaining_ * 16 + digit;
+    return State::Size;
+  }
+
+  size_t min(size_t a, size_t b) {
+    return a < b ? a : b;
+  }
+
+  size_t remaining_ = 0;
+  State state_ = State::Size;
+};
+
+}  // namespace StreamUtils

src/StreamUtils/Streams/ChunkDecodingStream.hpp

@@ -4,17 +4,17 @@
 
 #pragma once
 
-#include "StreamUtils/Policies/ReadForwardingPolicy.hpp"
+#include "StreamUtils/Policies/ChunkDecodingPolicy.hpp"
 #include "StreamUtils/Policies/WriteForwardingPolicy.hpp"
 
 #include "StreamProxy.hpp"
 
 namespace StreamUtils {
 
 struct ChunkDecodingStream
-    : StreamProxy<ReadForwardingPolicy, WriteForwardingPolicy> {
+    : StreamProxy<ChunkDecodingPolicy, WriteForwardingPolicy> {
   ChunkDecodingStream(Stream &target)
-      : StreamProxy<ReadForwardingPolicy, WriteForwardingPolicy>(target) {}
+      : StreamProxy<ChunkDecodingPolicy, WriteForwardingPolicy>(target) {}
 };
 
 }  // namespace StreamUtils