1 files changed, 91 insertions, 4 deletions
diff --git a/gpu/command_buffer/service/buffer_manager.cc b/gpu/command_buffer/service/buffer_manager.cc
index 2dfbc15..9b58e42 100644
--- a/gpu/command_buffer/service/buffer_manager.cc
+++ b/gpu/command_buffer/service/buffer_manager.cc
@@ -4,6 +4,7 @@
 
 #include "gpu/command_buffer/service/buffer_manager.h"
 #include "base/logging.h"
+#include "gpu/command_buffer/common/gles2_cmd_utils.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 namespace gpu {
@@ -31,10 +32,96 @@ void BufferManager::RemoveBufferInfo(GLuint buffer_id) {
   }
 }
 
-GLuint BufferManager::BufferInfo::GetMaxValueForRange(
-    GLuint offset, GLsizei count, GLenum type) {
-  // TODO(gman): Scan the values in the given range and cache their results.
-  return 0u;
+void BufferManager::BufferInfo::SetSize(GLsizeiptr size) {
+  DCHECK(!IsDeleted());
+  if (size != size_) {
+    size_ = size;
+    ClearCache();
+    if (target_ == GL_ELEMENT_ARRAY_BUFFER) {
+      shadow_.reset(new int8[size]);
+      memset(shadow_.get(), 0, size);
+    }
+  }
+}
+
+bool BufferManager::BufferInfo::SetRange(
+    GLintptr offset, GLsizeiptr size, const GLvoid * data) {
+  DCHECK(!IsDeleted());
+  if (offset + size < offset ||
+        offset + size > size_) {
+    return false;
+  }
+  if (target_ == GL_ELEMENT_ARRAY_BUFFER) {
+    memcpy(shadow_.get() + offset, data, size);
+    ClearCache();
+  }
+  return true;
+}
+
+void BufferManager::BufferInfo::ClearCache() {
+  range_set_.clear();
+}
+
+template <typename T>
+GLuint GetMaxValue(const void* data, GLuint offset, GLsizei count) {
+  GLuint max_value = 0;
+  const T* element = reinterpret_cast<const T*>(
+      static_cast<const int8*>(data) + offset);
+  const T* end = element + count;
+  for (; element < end; ++element) {
+    if (*element > max_value) {
+      max_value = *element;
+    }
+  }
+  return max_value;
+}
+
+bool BufferManager::BufferInfo::GetMaxValueForRange(
+    GLuint offset, GLsizei count, GLenum type, GLuint* max_value) {
+  DCHECK_EQ(target_, static_cast<GLenum>(GL_ELEMENT_ARRAY_BUFFER));
+  DCHECK(!IsDeleted());
+  Range range(offset, count, type);
+  RangeToMaxValueMap::iterator it = range_set_.find(range);
+  if (it != range_set_.end()) {
+    *max_value = it->second;
+    return true;
+  }
+
+  uint32 size;
+  if (!SafeMultiplyUint32(
+      count, GLES2Util::GetGLTypeSizeForTexturesAndBuffers(type), &size)) {
+    return false;
+  }
+
+  if (!SafeAddUint32(offset, size, &size)) {
+    return false;
+  }
+
+  if (size > static_cast<uint32>(size_)) {
+    return false;
+  }
+
+  // Scan the range for the max value and store
+  GLuint max_v = 0;
+  switch (type) {
+    case GL_UNSIGNED_BYTE:
+      max_v = GetMaxValue<uint8>(shadow_.get(), offset, count);
+      break;
+    case GL_UNSIGNED_SHORT:
+      // Check we are not accessing an odd byte for a 2 byte value.
+      if ((offset & 1) != 0) {
+        return false;
+      }
+      max_v = GetMaxValue<uint16>(shadow_.get(), offset, count);
+      break;
+    default:
+      NOTREACHED();  // should never get here by validation.
+      break;
+  }
+  std::pair<RangeToMaxValueMap::iterator, bool> result =
+      range_set_.insert(std::make_pair(range, max_v));
+  *max_value = max_v;
+  return true;
 }
 
 }  // namespace gles2