O(1) SkPictureUtils::ApproxBytesUsed()

src/core/SkVarAlloc.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkVarAlloc.h"
 
 // We use non-standard malloc diagnostic methods to make sure our allocations are sized well.
 #if defined(SK_BUILD_FOR_MAC)
     #include <malloc/malloc.h>
 #elif defined(SK_BUILD_FOR_UNIX) || defined(SK_BUILD_FOR_WIN32)
     #include <malloc.h>
 #endif
 
 struct SkVarAlloc::Block {
     Block* prev;
     char* data() { return (char*)(this + 1); }
 
     static Block* Alloc(Block* prev, size_t size, unsigned flags) {
         SkASSERT(size >= sizeof(Block));
         Block* b = (Block*)sk_malloc_flags(size, flags);
         b->prev = prev;
         return b;
     }
 };
 
 SkVarAlloc::SkVarAlloc(size_t minLgSize)
-    : fByte(NULL)
+    : fBytesAllocated(0)
+    , fByte(NULL)
     , fRemaining(0)
     , fLgSize(minLgSize)
     , fBlock(NULL) {}
 
 SkVarAlloc::SkVarAlloc(size_t minLgSize, char* storage, size_t len)
-    : fByte(storage)
+    : fBytesAllocated(0)
+    , fByte(storage)
     , fRemaining(len)
     , fLgSize(minLgSize)
     , fBlock(NULL) {}
 
 SkVarAlloc::~SkVarAlloc() {
     Block* b = fBlock;
     while (b) {
         Block* prev = b->prev;
         sk_free(b);
         b = prev;
     }
 }
 
 void SkVarAlloc::makeSpace(size_t bytes, unsigned flags) {
     SkASSERT(SkIsAlignPtr(bytes));
 
     size_t alloc = 1<<fLgSize++;
     while (alloc < bytes + sizeof(Block)) {
         alloc *= 2;
     }
+    fBytesAllocated += alloc;
     fBlock = Block::Alloc(fBlock, alloc, flags);
     fByte = fBlock->data();
     fRemaining = alloc - sizeof(Block);
 
 #if defined(SK_BUILD_FOR_MAC)
     SkASSERT(alloc == malloc_good_size(alloc));
 #elif defined(SK_BUILD_FOR_UNIX) && !defined(__UCLIBC__)
     // TODO(mtklein): tune so we can assert something like this
     //SkASSERT(alloc == malloc_usable_size(fBlock));
 #endif
 }
-
-static size_t heap_size(void* p) {
-#if defined(SK_BUILD_FOR_MAC)
-    return malloc_size(p);
-#elif defined(SK_BUILD_FOR_UNIX) && !defined(__UCLIBC__)
-    return malloc_usable_size(p);
-#elif defined(SK_BUILD_FOR_WIN32)
-    return _msize(p);
-#else
-    return 0;  // Tough luck.
-#endif
-}
-
-size_t SkVarAlloc::approxBytesAllocated() const {
-    size_t sum = 0;
-    for (Block* b = fBlock; b; b = b->prev) {
-        sum += heap_size(b);
-    }
-    return sum;
-}