Allow gpu ringbuffer to wrap around.

gpu/command_buffer/client/ring_buffer.cc

Index: gpu/command_buffer/client/ring_buffer.cc
diff --git a/gpu/command_buffer/client/ring_buffer.cc b/gpu/command_buffer/client/ring_buffer.cc
index 835f430d3df62e7ffdfb3b0c6df58c175dd7536e..201c15354fa1c19d5e5f42175d18b8c06e2253e8 100644
--- a/gpu/command_buffer/client/ring_buffer.cc
+++ b/gpu/command_buffer/client/ring_buffer.cc
@@ -29,8 +29,11 @@ RingBuffer::~RingBuffer() {
 void RingBuffer::FreeOldestBlock() {
   GPU_DCHECK(!blocks_.empty()) << "no free blocks";
   Block& block = blocks_.front();
-  GPU_DCHECK(block.valid) << "attempt to allocate more than maximum memory";
-  helper_->WaitForToken(block.token);
+  GPU_DCHECK(block.state != IN_USE)
+      << "attempt to allocate more than maximum memory";
+  if (block.state == FREE_PENDING_TOKEN) {
+    helper_->WaitForToken(block.token);
+  }
   in_use_offset_ += block.size;
   if (in_use_offset_ == size_) {
     in_use_offset_ = 0;
@@ -45,7 +48,7 @@ void RingBuffer::FreeOldestBlock() {
 
 RingBuffer::Offset RingBuffer::Alloc(unsigned int size) {
   GPU_DCHECK_LE(size, size_) << "attempt to allocate more than maximum memory";
-  GPU_DCHECK(blocks_.empty() || blocks_.back().valid)
+  GPU_DCHECK(blocks_.empty() || blocks_.back().state != IN_USE)
       << "Attempt to alloc another block before freeing the previous.";
   // Similarly to malloc, an allocation of 0 allocates at least 1 byte, to
   // return different pointers every time.
@@ -56,8 +59,14 @@ RingBuffer::Offset RingBuffer::Alloc(unsigned int size) {
     FreeOldestBlock();
   }
 
+  if (size + free_offset_ > size_) {
+    //Add padding to fill space before wrapping around

[piman, 2011/05/03 16:30:20]

1 space after //

+    blocks_.push_back(Block(free_offset_, size_ - free_offset_, PADDING));
+    free_offset_ = 0;
+  }
+
   Offset offset = free_offset_;
-  blocks_.push_back(Block(offset, size));
+  blocks_.push_back(Block(offset, size, IN_USE));
   free_offset_ += size;
   if (free_offset_ == size_) {
     free_offset_ = 0;
@@ -74,10 +83,10 @@ void RingBuffer::FreePendingToken(RingBuffer::Offset offset,
         ++it) {
     Block& block = *it;
     if (block.offset == offset) {
-      GPU_DCHECK(!block.valid)
+      GPU_DCHECK(block.state == IN_USE)
           << "block that corresponds to offset already freed";
       block.token = token;
-      block.valid = true;
+      block.state = FREE_PENDING_TOKEN;
       return;
     }
   }
@@ -97,8 +106,8 @@ unsigned int RingBuffer::GetLargestFreeSizeNoWaiting() {
       return 0;
     }
   } else if (free_offset_ > in_use_offset_) {
-    // It's free from free_offset_ to size_
-    return size_ - free_offset_;
+    // It's free from free_offset_ to size_ and from 0 to in_use_offset_
+    return std::max(size_ - free_offset_, in_use_offset_);
   } else {
     // It's free from free_offset_ -> in_use_offset_;
     return in_use_offset_ - free_offset_;