cpp

// mycpp/bump_leak_heap.cc: Leaky Bump Allocator

#include "mycpp/bump_leak_heap.h"

#include <inttypes.h>  // PRId64

#include <stddef.h>

#include <stdio.h>

#include <string.h>  // memcpy

#include <unistd.h>  // STDERR_FILENO

#include "mycpp/common.h"  // aligned

// We need this #ifdef because we don't want the global var in other binaries

#ifdef BUMP_LEAK

char gMemory[MiB(2000)];  // some benchmarks take more than 1 GiB

// This type is for "layout"; it's not instantiated

struct LayoutBlock {

  size_t num_bytes;

  char data[1];  // flexible array

};

// offsetof() accounts for possible padding, but it should equal sizeof(size_t)

const int kHeaderSize = offsetof(LayoutBlock, data);

// Allocate() bumps a pointer

void* BumpLeakHeap::Allocate(size_t num_bytes) {

  char* p = &(gMemory[mem_pos_]);

  LayoutBlock* block = reinterpret_cast<LayoutBlock*>(p);

  block->num_bytes = num_bytes;  // record size for Reallocate()

  mem_pos_ += aligned(kHeaderSize + num_bytes);

  // Update stats

  num_allocated_++;

  bytes_allocated_ += num_bytes;

  // log("Allocate() -> %p", block->data);

  return block->data;  // pointer user can write to

}

// Reallocate() calls Allocate() and then copies the old data

void* BumpLeakHeap::Reallocate(void* old_data, size_t num_bytes) {

  // log("");

  // log("Reallocate(%d) got %p", num_bytes, old_data);

  char* new_data = reinterpret_cast<char*>(Allocate(num_bytes));

  char* p_old = reinterpret_cast<char*>(old_data) - kHeaderSize;

  LayoutBlock* old_block = reinterpret_cast<LayoutBlock*>(p_old);

  memcpy(new_data, old_block->data, old_block->num_bytes);

  return new_data;

}

void BumpLeakHeap::PrintStats(int fd) {

  dprintf(fd, "[BumpLeakHeap]");

  dprintf(fd, "  num allocated = %10d\n", num_allocated_);

  dprintf(fd, "bytes allocated = %10" PRId64 "\n", bytes_allocated_);

  dprintf(fd, "  mem pos       = %10d\n", mem_pos_);

}

void BumpLeakHeap::CleanProcessExit() {

  PrintStats(STDERR_FILENO);

}

void BumpLeakHeap::FastProcessExit() {

  PrintStats(STDERR_FILENO);

}

BumpLeakHeap gHeap;

#endif