Rebased PNaCl localmods in LLVM to 223109

tools/pnacl-llc/SRPCStreamer.h

+//===-- SRPCStreamer.h - Stream bitcode over SRPC  ------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#ifndef SRPCSTREAMER_H
+#define SRPCSTREAMER_H
+
+#include <pthread.h>
+#include <cassert>
+#include <cstdio>
+#include <cstring>
+#include <vector>
+#include "llvm/Support/DataStream.h"
+
+// Implements LLVM's interface for fetching data from a stream source.
+// Bitcode bytes from the RPC thread are placed here with PutBytes and buffered
+// until the bitcode reader calls GetBytes to remove them.
+// The blocking behavior of GetBytes and PutBytes means that if the
+// compilation happens faster than the bytes come in from the browser, the
+// whole pipeline can block waiting for the RPC thread to put more bytes.
+
+class QueueStreamer : public llvm::DataStreamer {
+ public:
+ QueueStreamer() : Done(false), Prod(0), Cons(0) {
+    pthread_mutex_init(&Mutex, NULL);
+    pthread_cond_init(&Cond, NULL);
+    Bytes.resize(64 * 1024);
+  }
+
+  // Called by the compilation thread. Copy len bytes from the queue into
+  // buf. If there are less than len bytes available, copy as many as
+  // there are, signal the RPC thread, and block to wait for the rest.
+  // If all bytes have been received from the browser and there are
+  // fewer than len bytes available, copy all remaining bytes.
+  // Return the number of bytes copied.
+  virtual size_t GetBytes(unsigned char *buf, size_t len);
+
+  // Called by the RPC thread. Copy len bytes from buf into the queue.
+  // If there is not enough space in the queue, copy as many bytes as
+  // will fit, signal the compilation thread, and block until there is
+  // enough space for the rest.
+  // Return the number of bytes copied.
+  size_t PutBytes(unsigned char *buf, size_t len);
+
+  // Called by the RPC thread. Signal that all bytes have been received,
+  // so the last call to GetBytes will return the remaining bytes rather
+  // than waiting for the entire requested amound.
+  void SetDone();
+
+ private:
+  bool Done;
+  pthread_mutex_t Mutex;
+  pthread_cond_t Cond;
+  // Maximum size of the queue. The limitation on the queue size means that
+  // if the compilation happens slower than bytes arrive from the network,
+  // the queue will fill up, the RPC thread will be blocked most of the time,
+  // the RPC thread on the browser side will be waiting for the SRPC to return,
+  // and the buffer on the browser side will grow unboundedly until the
+  // whole bitcode file arrives (which is better than having the queue on
+  // the untrusted side consume all that memory).
+  // The partial-copying behavior of GetBytes and PutBytes prevents deadlock
+  // even if the requested number of bytes is greater than the size limit
+  // (although it will of course be less efficient).
+  // The initial size of the queue is expected to be smaller than this, but
+  // if not, it will simply never be resized.
+  const static size_t queuesize_limit_ = 256 * 1024;
+
+  // Variables and functions to manage the circular queue
+  std::vector<unsigned char> Bytes;
+  size_t Prod; // Queue producer index
+  size_t Cons; // Queue consumer index
+  size_t queueSize() {
+    return Prod >= Cons ? Prod - Cons : Bytes.size() - (Cons - Prod);
+  }
+  size_t capacityRemaining() {
+    return (Prod >= Cons ? Bytes.size() - (Prod - Cons) : (Cons - Prod)) - 1;
+  }
+  void queueResize();
+  void queuePut(unsigned char *buf, size_t len);
+  void queueGet(unsigned char *buf, size_t len);
+};
+
+// Class to manage the compliation thread and serve as the interface from
+// the SRPC thread
+class SRPCStreamer  {
+public:
+  SRPCStreamer() : Error(false) {}
+  // Initialize streamer, create a new thread running Callback, and
+  // return a pointer to the DataStreamer the threads will use to
+  // synchronize. On error, return NULL and fill in the ErrorMsg string
+  llvm::DataStreamer *init(void *(*Callback)(void *),
+                           void *arg, std::string *ErrMsg);
+  // Called by the RPC thread. Copy len bytes from buf. Return bytes copied.
+  size_t gotChunk(unsigned char *bytes, size_t len);
+  // Called by the RPC thread. Wait for the compilation thread to finish.
+  int streamEnd(std::string *ErrMsg);
+  // Called by the compilation thread. Set the error condition and also
+  // terminate the thread.
+  void setFatalError(const std::string& message);
+private:
+  int Error;
+  std::string ErrorMessage;
+  QueueStreamer Q;
+  pthread_t CompileThread;
+};
+
+
+
+#endif  // SRPCSTREAMER_H