From 6a67632af10abbed2fc8cb681ea64be1561a8c54 Mon Sep 17 00:00:00 2001
From: "Dr. Chat" <arkolbed@gmail.com>
Date: Sun, 24 Jan 2016 22:39:05 -0600
Subject: [PATCH] Update RingBuffer - Add immediate read/write and some error
 checking asserts.

---
 src/xenia/base/ring_buffer.cc | 36 +++++++++++++++++++++++++++++++++++
 src/xenia/base/ring_buffer.h  | 27 ++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/src/xenia/base/ring_buffer.cc b/src/xenia/base/ring_buffer.cc
index 9638d1301..b4e1013f8 100644
--- a/src/xenia/base/ring_buffer.cc
+++ b/src/xenia/base/ring_buffer.cc
@@ -17,6 +17,26 @@ namespace xe {
 RingBuffer::RingBuffer(uint8_t* buffer, size_t capacity)
     : buffer_(buffer), capacity_(capacity) {}
 
+void RingBuffer::AdvanceRead(size_t count) {
+  if (read_offset_ + count < capacity_) {
+    read_offset_ += count;
+  } else {
+    size_t left_half = capacity_ - read_offset_;
+    size_t right_half = count - left_half;
+    read_offset_ = right_half;
+  }
+}
+
+void RingBuffer::AdvanceWrite(size_t count) {
+  if (write_offset_ + count < capacity_) {
+    write_offset_ += count;
+  } else {
+    size_t left_half = capacity_ - write_offset_;
+    size_t right_half = count - left_half;
+    write_offset_ = right_half;
+  }
+}
+
 RingBuffer::ReadRange RingBuffer::BeginRead(size_t count) {
   count = std::min(count, capacity_);
   if (!count) {
@@ -45,6 +65,14 @@ size_t RingBuffer::Read(uint8_t* buffer, size_t count) {
     return 0;
   }
 
+  // Sanity check: Make sure we don't read over the write offset.
+  if (read_offset_ < write_offset_) {
+    assert_true(read_offset_ + count <= write_offset_);
+  } else if (read_offset_ + count >= capacity_) {
+    size_t left_half = capacity_ - read_offset_;
+    assert_true(count - left_half <= write_offset_);
+  }
+
   if (read_offset_ + count < capacity_) {
     std::memcpy(buffer, buffer_ + read_offset_, count);
     read_offset_ += count;
@@ -65,6 +93,14 @@ size_t RingBuffer::Write(const uint8_t* buffer, size_t count) {
     return 0;
   }
 
+  // Sanity check: Make sure we don't write over the read offset.
+  if (write_offset_ < read_offset_) {
+    assert_true(write_offset_ + count <= read_offset_);
+  } else if (write_offset_ + count >= capacity_) {
+    size_t left_half = capacity_ - write_offset_;
+    assert_true(count - left_half <= read_offset_);
+  }
+
   if (write_offset_ + count < capacity_) {
     std::memcpy(buffer_ + write_offset_, buffer, count);
     write_offset_ += count;
diff --git a/src/xenia/base/ring_buffer.h b/src/xenia/base/ring_buffer.h
index 9628c9c0c..b52f6afd0 100644
--- a/src/xenia/base/ring_buffer.h
+++ b/src/xenia/base/ring_buffer.h
@@ -14,6 +14,9 @@
 #include <string>
 #include <vector>
 
+#include "xenia/base/assert.h"
+#include "xenia/base/byte_order.h"
+
 namespace xe {
 
 class RingBuffer {
@@ -25,6 +28,7 @@ class RingBuffer {
   bool empty() const { return read_offset_ == write_offset_; }
 
   size_t read_offset() const { return read_offset_; }
+  uintptr_t read_ptr() const { return uintptr_t(buffer_) + read_offset_; }
   void set_read_offset(size_t offset) { read_offset_ = offset % capacity_; }
   size_t read_count() const {
     if (read_offset_ == write_offset_) {
@@ -37,6 +41,7 @@ class RingBuffer {
   }
 
   size_t write_offset() const { return write_offset_; }
+  uintptr_t write_ptr() const { return uintptr_t(buffer_) + write_offset_; }
   void set_write_offset(size_t offset) { write_offset_ = offset % capacity_; }
   size_t write_count() const {
     if (read_offset_ == write_offset_) {
@@ -48,6 +53,9 @@ class RingBuffer {
     }
   }
 
+  void AdvanceRead(size_t count);
+  void AdvanceWrite(size_t count);
+
   struct ReadRange {
     const uint8_t* first;
     size_t first_length;
@@ -63,12 +71,31 @@ class RingBuffer {
     return Read(reinterpret_cast<uint8_t*>(buffer), count);
   }
 
+  template <typename T>
+  T Read(bool swap = false) {
+    static_assert(sizeof(T) <= 8, "Immediate read only supports basic types!");
+
+    T imm;
+    size_t read = Read(reinterpret_cast<uint8_t*>(&imm), sizeof(T));
+    assert_true(read == sizeof(T));
+    if (swap) {
+      imm = xe::byte_swap(imm);
+    }
+
+    return imm;
+  }
+
   size_t Write(const uint8_t* buffer, size_t count);
   template <typename T>
   size_t Write(const T* buffer, size_t count) {
     return Write(reinterpret_cast<const uint8_t*>(buffer), count);
   }
 
+  template <typename T>
+  size_t Write(T& data) {
+    return Write(reinterpret_cast<const uint8_t*>(&data), sizeof(T));
+  }
+
  private:
   uint8_t* buffer_ = nullptr;
   size_t capacity_ = 0;