Include RE2 library

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