diff --git a/lib/cpp/src/protocol/TDenseProtocol.cpp b/lib/cpp/src/protocol/TDenseProtocol.cpp
index e79d4f1..55f3902 100644
--- a/lib/cpp/src/protocol/TDenseProtocol.cpp
+++ b/lib/cpp/src/protocol/TDenseProtocol.cpp
@@ -180,12 +180,13 @@
   uint32_t used = 0;
   uint64_t val = 0;
   uint8_t buf[10];  // 64 bits / (7 bits/byte) = 10 bytes.
-  bool borrowed = trans_->borrow(buf, sizeof(buf));
+  uint32_t buf_size = sizeof(buf);
+  const uint8_t* borrowed = trans_->borrow(buf, &buf_size);
 
   // Fast path.  TODO(dreiss): Make it faster.
-  if (borrowed) {
+  if (borrowed != NULL) {
     while (true) {
-      uint8_t byte = buf[used];
+      uint8_t byte = borrowed[used];
       used++;
       val = (val << 7) | (byte & 0x7f);
       if (!(byte & 0x80)) {
diff --git a/lib/cpp/src/transport/TTransport.h b/lib/cpp/src/transport/TTransport.h
index b3d8820..4e3c218 100644
--- a/lib/cpp/src/transport/TTransport.h
+++ b/lib/cpp/src/transport/TTransport.h
@@ -139,21 +139,31 @@
   virtual void flush() {}
 
   /**
-   * Attempts to copy len bytes from the transport into buf.  Does not consume
-   * the bytes read (i.e.: a later read will return the same data).  This
-   * method is meant to support protocols that need to read variable-length
-   * fields.  They can attempt to borrow the maximum amount of data that they
-   * will need, then consume (see next method) what they actually use.  Some
-   * transports will not support this method and others will fail occasionally,
-   * so protocols must be prepared to use read if borrow fails.
+   * Attempts to return a pointer to \c len bytes, possibly copied into \c buf.
+   * Does not consume the bytes read (i.e.: a later read will return the same
+   * data).  This method is meant to support protocols that need to read
+   * variable-length fields.  They can attempt to borrow the maximum amount of
+   * data that they will need, then consume (see next method) what they
+   * actually use.  Some transports will not support this method and others
+   * will fail occasionally, so protocols must be prepared to use read if
+   * borrow fails.
    *
-   * @oaram buf  The buffer to store the data
-   * @param len  How much data to borrow
-   * @return true if the requested data has been borrowed, false otherwise
+   * @oaram buf  A buffer where the data can be stored if needed.
+   *             If borrow doesn't return buf, then the contents of
+   *             buf after the call are undefined.
+   * @param len  *len should initially contain the number of bytes to borrow.
+   *             If borrow succeeds, *len will contain the number of bytes
+   *             available in the returned pointer.  This will be at least
+   *             what was requested, but may be more if borrow returns
+   *             a pointer to an internal buffer, rather than buf.
+   *             If borrow fails, the contents of *len are undefined.
+   * @return If the borrow succeeds, return a pointer to the borrowed data.
+   *         This might be equal to \c buf, or it might be a pointer into
+   *         the transport's internal buffers.
    * @throws TTransportException if an error occurs
    */
-  virtual bool borrow(uint8_t* buf, uint32_t len) {
-    return false;
+  virtual const uint8_t* borrow(uint8_t* buf, uint32_t* len) {
+    return NULL;
   }
 
   /**
diff --git a/lib/cpp/src/transport/TTransportUtils.cpp b/lib/cpp/src/transport/TTransportUtils.cpp
index b10958c..b5e7fa8 100644
--- a/lib/cpp/src/transport/TTransportUtils.cpp
+++ b/lib/cpp/src/transport/TTransportUtils.cpp
@@ -59,15 +59,15 @@
   }
 }
 
-bool TBufferedTransport::borrow(uint8_t* buf, uint32_t len) {
+const uint8_t* TBufferedTransport::borrow(uint8_t* buf, uint32_t* len) {
   // Don't try to be clever with shifting buffers.
-  // If we have enough data, give it, otherwise
-  // let the protcol use its slow path.
-  if (rLen_-rPos_ >= len) {
-    memcpy(buf, rBuf_+rPos_, len);
-    return true;
+  // If we have enough data, give a pointer to it,
+  // otherwise let the protcol use its slow path.
+  if (rLen_-rPos_ >= *len) {
+    *len = rLen_-rPos_;
+    return rBuf_+rPos_;
   }
-  return false;
+  return NULL;
 }
 
 void TBufferedTransport::consume(uint32_t len) {
@@ -203,15 +203,15 @@
   transport_->flush();
 }
 
-bool TFramedTransport::borrow(uint8_t* buf, uint32_t len) {
+const uint8_t* TFramedTransport::borrow(uint8_t* buf, uint32_t* len) {
   // Don't try to be clever with shifting buffers.
-  // If we have enough data, give it, otherwise
-  // let the protcol use its slow path.
-  if (read_ && (rLen_-rPos_ >= len)) {
-    memcpy(buf, rBuf_+rPos_, len);
-    return true;
+  // If we have enough data, give a pointer to it,
+  // otherwise let the protcol use its slow path.
+  if (read_ && (rLen_-rPos_ >= *len)) {
+    *len = rLen_-rPos_;
+    return rBuf_+rPos_;
   }
-  return false;
+  return NULL;
 }
 
 void TFramedTransport::consume(uint32_t len) {
@@ -293,15 +293,12 @@
   wPos_ += len;
 }
 
-bool TMemoryBuffer::borrow(uint8_t* buf, uint32_t len) {
-  // Don't try to be clever with shifting buffers.
-  // If we have enough data, give it, otherwise
-  // let the protcol use its slow path.
-  if (wPos_-rPos_ >= len) {
-    memcpy(buf, buffer_ + rPos_, len);
-    return true;
+const uint8_t* TMemoryBuffer::borrow(uint8_t* buf, uint32_t* len) {
+  if (wPos_-rPos_ >= *len) {
+    *len = wPos_-rPos_;
+    return buffer_ + rPos_;
   }
-  return false;
+  return NULL;
 }
 
 void TMemoryBuffer::consume(uint32_t len) {
diff --git a/lib/cpp/src/transport/TTransportUtils.h b/lib/cpp/src/transport/TTransportUtils.h
index 38d2787..ed64dec 100644
--- a/lib/cpp/src/transport/TTransportUtils.h
+++ b/lib/cpp/src/transport/TTransportUtils.h
@@ -106,7 +106,7 @@
 
   void flush();
 
-  bool borrow(uint8_t* buf, uint32_t len);
+  const uint8_t* borrow(uint8_t* buf, uint32_t* len);
 
   void consume(uint32_t len);
 
@@ -225,7 +225,7 @@
 
   void flush();
 
-  bool borrow(uint8_t* buf, uint32_t len);
+  const uint8_t* borrow(uint8_t* buf, uint32_t* len);
 
   void consume(uint32_t len);
 
@@ -424,7 +424,7 @@
     return wPos_ - rPos_;
   }
 
-  bool borrow(uint8_t* buf, uint32_t len);
+  const uint8_t* borrow(uint8_t* buf, uint32_t* len);
 
   void consume(uint32_t len);
 
diff --git a/lib/cpp/src/transport/TZlibTransport.cpp b/lib/cpp/src/transport/TZlibTransport.cpp
index 59e3a36..ea0b0a4 100644
--- a/lib/cpp/src/transport/TZlibTransport.cpp
+++ b/lib/cpp/src/transport/TZlibTransport.cpp
@@ -234,15 +234,15 @@
   }
 }
 
-bool TZlibTransport::borrow(uint8_t* buf, uint32_t len) {
+const uint8_t* TZlibTransport::borrow(uint8_t* buf, uint32_t* len) {
   // Don't try to be clever with shifting buffers.
-  // If we have enough data, give it, otherwise
-  // let the protcol use its slow path.
+  // If we have enough data, give a pointer to it,
+  // otherwise let the protcol use its slow path.
   if (readAvail() >= (int)len) {
-    memcpy(buf, urbuf_ + urpos_, len);
-    return true;
+    *len = (uint32_t)readAvail();
+    return urbuf_ + urpos_;
   }
-  return false;
+  return NULL;
 }
 
 void TZlibTransport::consume(uint32_t len) {
diff --git a/lib/cpp/src/transport/TZlibTransport.h b/lib/cpp/src/transport/TZlibTransport.h
index cc2522d..dd8ae2f 100644
--- a/lib/cpp/src/transport/TZlibTransport.h
+++ b/lib/cpp/src/transport/TZlibTransport.h
@@ -150,7 +150,7 @@
 
   void flush();
 
-  bool borrow(uint8_t* buf, uint32_t len);
+  const uint8_t* borrow(uint8_t* buf, uint32_t* len);
 
   void consume(uint32_t len);