Update re2

third_party/re2/util/arena.cc

-// Copyright 2000 The RE2 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 "util/util.h"
-
-namespace re2 {
-
-// ----------------------------------------------------------------------
-// UnsafeArena::UnsafeArena()
-// UnsafeArena::~UnsafeArena()
-//    Destroying the arena automatically calls Reset()
-// ----------------------------------------------------------------------
-
-
-UnsafeArena::UnsafeArena(const size_t block_size)
-  : block_size_(block_size),
-    freestart_(NULL),                   // set for real in Reset()
-    last_alloc_(NULL),
-    remaining_(0),
-    blocks_alloced_(1),
-    overflow_blocks_(NULL) {
-  assert(block_size > kDefaultAlignment);
-
-  first_blocks_[0].mem = reinterpret_cast<char*>(malloc(block_size_));
-  first_blocks_[0].size = block_size_;
-
-  Reset();
-}
-
-UnsafeArena::~UnsafeArena() {
-  FreeBlocks();
-  assert(overflow_blocks_ == NULL);    // FreeBlocks() should do that
-  // The first X blocks stay allocated always by default.  Delete them now.
-  for (int i = 0; i < blocks_alloced_; i++)
-    free(first_blocks_[i].mem);
-}
-
-// ----------------------------------------------------------------------
-// UnsafeArena::Reset()
-//    Clears all the memory an arena is using.
-// ----------------------------------------------------------------------
-
-void UnsafeArena::Reset() {
-  FreeBlocks();
-  freestart_ = first_blocks_[0].mem;
-  remaining_ = first_blocks_[0].size;
-  last_alloc_ = NULL;
-
-  // We do not know for sure whether or not the first block is aligned,
-  // so we fix that right now.
-  const int overage = reinterpret_cast<uintptr_t>(freestart_) &
-                      (kDefaultAlignment-1);
-  if (overage > 0) {
-    const int waste = kDefaultAlignment - overage;
-    freestart_ += waste;
-    remaining_ -= waste;
-  }
-  freestart_when_empty_ = freestart_;
-  assert(!(reinterpret_cast<uintptr_t>(freestart_)&(kDefaultAlignment-1)));
-}
-
-// -------------------------------------------------------------
-// UnsafeArena::AllocNewBlock()
-//    Adds and returns an AllocatedBlock.
-//    The returned AllocatedBlock* is valid until the next call
-//    to AllocNewBlock or Reset.  (i.e. anything that might
-//    affect overflow_blocks_).
-// -------------------------------------------------------------
-
-UnsafeArena::AllocatedBlock* UnsafeArena::AllocNewBlock(const size_t block_size) {
-  AllocatedBlock *block;
-  // Find the next block.
-  if ( blocks_alloced_ < arraysize(first_blocks_) ) {
-    // Use one of the pre-allocated blocks
-    block = &first_blocks_[blocks_alloced_++];
-  } else {                   // oops, out of space, move to the vector
-    if (overflow_blocks_ == NULL) overflow_blocks_ = new vector<AllocatedBlock>;
-    // Adds another block to the vector.
-    overflow_blocks_->resize(overflow_blocks_->size()+1);
-    // block points to the last block of the vector.
-    block = &overflow_blocks_->back();
-  }
-
-  block->mem = reinterpret_cast<char*>(malloc(block_size));
-  block->size = block_size;
-
-  return block;
-}
-
-// ----------------------------------------------------------------------
-// UnsafeArena::GetMemoryFallback()
-//    We take memory out of our pool, aligned on the byte boundary
-//    requested.  If we don't have space in our current pool, we
-//    allocate a new block (wasting the remaining space in the
-//    current block) and give you that.  If your memory needs are
-//    too big for a single block, we make a special your-memory-only
-//    allocation -- this is equivalent to not using the arena at all.
-// ----------------------------------------------------------------------
-
-void* UnsafeArena::GetMemoryFallback(const size_t size, const int align) {
-  if (size == 0)
-    return NULL;             // stl/stl_alloc.h says this is okay
-
-  assert(align > 0 && 0 == (align & (align - 1)));  // must be power of 2
-
-  // If the object is more than a quarter of the block size, allocate
-  // it separately to avoid wasting too much space in leftover bytes
-  if (block_size_ == 0 || size > block_size_/4) {
-    // then it gets its own block in the arena
-    assert(align <= kDefaultAlignment);   // because that's what new gives us
-    // This block stays separate from the rest of the world; in particular
-    // we don't update last_alloc_ so you can't reclaim space on this block.
-    return AllocNewBlock(size)->mem;
-  }
-
-  const int overage =
-    (reinterpret_cast<uintptr_t>(freestart_) & (align-1));
-  if (overage) {
-    const int waste = align - overage;
-    freestart_ += waste;
-    if (waste < remaining_) {
-      remaining_ -= waste;
-    } else {
-      remaining_ = 0;
-    }
-  }
-  if (size > remaining_) {
-    AllocatedBlock *block = AllocNewBlock(block_size_);
-    freestart_ = block->mem;
-    remaining_ = block->size;
-  }
-  remaining_ -= size;
-  last_alloc_ = freestart_;
-  freestart_ += size;
-  assert((reinterpret_cast<uintptr_t>(last_alloc_) & (align-1)) == 0);
-  return reinterpret_cast<void*>(last_alloc_);
-}
-
-// ----------------------------------------------------------------------
-// UnsafeArena::FreeBlocks()
-//    Unlike GetMemory(), which does actual work, ReturnMemory() is a
-//    no-op: we don't "free" memory until Reset() is called.  We do
-//    update some stats, though.  Note we do no checking that the
-//    pointer you pass in was actually allocated by us, or that it
-//    was allocated for the size you say, so be careful here!
-//       FreeBlocks() does the work for Reset(), actually freeing all
-//    memory allocated in one fell swoop.
-// ----------------------------------------------------------------------
-
-void UnsafeArena::FreeBlocks() {
-  for ( int i = 1; i < blocks_alloced_; ++i ) {  // keep first block alloced
-    free(first_blocks_[i].mem);
-    first_blocks_[i].mem = NULL;
-    first_blocks_[i].size = 0;
-  }
-  blocks_alloced_ = 1;
-  if (overflow_blocks_ != NULL) {
-    vector<AllocatedBlock>::iterator it;
-    for (it = overflow_blocks_->begin(); it != overflow_blocks_->end(); ++it) {
-      free(it->mem);
-    }
-    delete overflow_blocks_;             // These should be used very rarely
-    overflow_blocks_ = NULL;
-  }
-}
-
-}  // namespace re2