[NaCl SDK] Support non blocking TCP/UDP

native_client_sdk/src/libraries/nacl_io/fifo_char.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "nacl_io/fifo_char.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <algorithm>
+
+namespace nacl_io {
+
+FIFOChar::FIFOChar(size_t size)
+    : buffer_(NULL),
+      size_(size),
+      avail_(0),
+      tail_(0) {
+  if (size) {
+    buffer_ = new char[size];

[binji, 2013/09/12 01:47:57]

use a std::vector instead of an array?

[noelallen1, 2013/09/12 23:19:03]

Since this is a circular buffer, the resize case get's uglier.  I would first
need to move possibly across the edge, then shrink.

+  } else {
+    buffer_ = NULL;
+  }
+}
+
+FIFOChar::~FIFOChar() {
+  delete[] buffer_;
+}
+
+bool FIFOChar::IsEmpty() {
+  return avail_ == 0;
+}
+
+bool FIFOChar::IsFull() {
+  return avail_ >= size_;
+}
+
+bool FIFOChar::Resize(size_t len) {
+  // Can not resize smaller than the current size
+  if (len < avail_)
+    return false;
+
+  // Read current data into new buffer
+  char* data = new char[len];
+  avail_ = Read(data, avail_);
+
+  // Replace buffer
+  delete[] buffer_;
+  buffer_ = data;
+  size_ = len;
+  return true;
+}
+
+
+size_t FIFOChar::ReadAvailable() {
+  return avail_;
+}
+
+size_t FIFOChar::WriteAvailable() {
+  return size_ - avail_;
+}
+
+size_t FIFOChar::Peek(char* buf, size_t len) {
+  size_t out = 0;
+  len = std::min(len, avail_);
+
+  size_t offs = tail_;
+  while (len > 0) {

[binji, 2013/09/12 01:47:57]

Seems unnecessary: You only need to do one or two iterations, and a memcpy of
zero bytes is a no-op.

How about:

size_t count = /* num available bytes */;
size_t end_count = /* num bytes at the end, before wrapping */
size_t begin_count = /* rest of bytes, maybe 0 */
memcpy(&buf[0], &buffer_[tail_], end_count);
memcpy(&buf[end_count], &buffer_[0], begin_count);

+    size_t read_len = std::min(len, size_ - offs);
+    memcpy(buf, &buffer_[offs], read_len);
+
+    buf += read_len;
+    offs += read_len;
+    if (static_cast<size_t>(offs) == size_)
+      offs = 0;
+
+    out += read_len;
+    len -= read_len;
+  }
+
+  return out;
+}
+
+size_t FIFOChar::Read(char* buf, size_t len) {
+  size_t read_len = Peek(buf, len);
+  if (read_len > 0) {
+    avail_ -= read_len;
+    tail_ = (tail_ + read_len) % size_;
+  }
+  return read_len;
+}
+
+size_t FIFOChar::Write(const char* buf, size_t len) {

[binji, 2013/09/12 01:47:57]

tests for this class?

+  size_t out = 0;
+  size_t room = size_ - avail_;
+  len = std::min(len, room);
+
+  size_t offs = tail_ + avail_;
+  while (len > 0) {
+    size_t write_len = std::min(len, size_ - offs);
+    memcpy(&buffer_[offs], buf, write_len);
+
+    buf += write_len;
+    offs += write_len;
+    if (offs == size_)
+      offs = 0;
+
+    out += write_len;
+    len -= write_len;
+  }
+
+  avail_ += out;
+  return out;
+}
+
+
+}  // namespace nacl_io