Fix infinite loop when transmission cuts mid-chunk

Fixes #37

Author: bblanchon

CHANGELOG.md

@@ -1,6 +1,11 @@
 StreamUtils - Change log
 ========================
 
+HEAD
+----
+
+* Fix infinite loop in `ChunkDecodingPolicy` when transmission cuts mid-chunk (issue #37)
+
 1.9.0 (2024/07/10)
 -----
 

extras/test/ChunkDecodingStreamTest.cpp

@@ -298,7 +298,7 @@ TEST_CASE("ChunkDecodingStream") {
   }
 
 #if STREAMUTILS_STREAM_READBYTES_IS_VIRTUAL
-  SUBCASE("readBytes() waits timeout") {
+  SUBCASE("readBytes() waits timeout if transmission cuts before final chunk") {
     char buffer[32];
 
     upstream.print(
@@ -308,7 +308,7 @@ TEST_CASE("ChunkDecodingStream") {
     REQUIRE(buffer[0] == 'X');
 
     REQUIRE(log.str() ==
-            "readBytes(1) -> 1"  // 1
+            "readBytes(1) -> 1"  // 4
             "readBytes(1) -> 1"  // \r
             "readBytes(1) -> 1"  // \n
             "readBytes(4) -> 4"  // XXXX
@@ -317,6 +317,23 @@ TEST_CASE("ChunkDecodingStream") {
             "readBytes(1) -> 0 [timeout]");
   }
 
+  // Issue #37
+  SUBCASE("readBytes() waits timeout if transmission cuts mid-chunk") {
+    char buffer[32];
+
+    upstream.print(
+        "4\r\n"
+        "XX");
+    REQUIRE(stream.readBytes(buffer, 32) == 2);
+    REQUIRE(buffer[0] == 'X');
+
+    REQUIRE(log.str() ==
+            "readBytes(1) -> 1"  // 4
+            "readBytes(1) -> 1"  // \r
+            "readBytes(1) -> 1"  // \n
+            "readBytes(4) -> 2 [timeout]");
+  }
+
   SUBCASE("readBytes() doen't wait if final chunk received") {
     char buffer[32];
 

src/StreamUtils/Policies/ChunkDecodingPolicy.hpp

@@ -70,11 +70,14 @@ class ChunkDecodingPolicy {
   size_t doReadBytes(TTarget &target, char *buffer, size_t size) {
     size_t result = 0;
     while (size > 0 && !error() && !ended() && goToChunkBody(target, true)) {
-      size_t n = readOrReadBytes(target, buffer, min_(size, remaining_));
-      decreaseRemaining(n);
-      result += n;
-      size -= n;
-      buffer += n;
+      size_t requestedBytes = min_(size, remaining_);
+      size_t returnedBytes = readOrReadBytes(target, buffer, requestedBytes);
+      decreaseRemaining(returnedBytes);
+      result += returnedBytes;
+      size -= returnedBytes;
+      buffer += returnedBytes;
+      if (returnedBytes < requestedBytes)
+        break;  // no more data available right now
     }
     return result;
   }