//===-- DWARFDebugRanges.cpp ----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "DWARFDebugRanges.h"
#include "DWARFUnit.h"

using namespace lldb_private;

static dw_addr_t GetBaseAddressMarker(uint32_t addr_size) {
  switch(addr_size) {
    case 2:
      return 0xffff;
    case 4:
      return 0xffffffff;
    case 8:
      return 0xffffffffffffffff;
  }
  llvm_unreachable("GetBaseAddressMarker unsupported address size.");
}

DWARFDebugRanges::DWARFDebugRanges() : m_range_map() {}

void DWARFDebugRanges::Extract(DWARFContext &context) {
  DWARFRangeList range_list;
  lldb::offset_t offset = 0;
  dw_offset_t debug_ranges_offset = offset;
  while (Extract(context, &offset, range_list)) {
    range_list.Sort();
    m_range_map[debug_ranges_offset] = range_list;
    debug_ranges_offset = offset;
  }
}

bool DWARFDebugRanges::Extract(DWARFContext &context,
                               lldb::offset_t *offset_ptr,
                               DWARFRangeList &range_list) {
  range_list.Clear();

  lldb::offset_t range_offset = *offset_ptr;
  const DWARFDataExtractor &debug_ranges_data = context.getOrLoadRangesData();
  uint32_t addr_size = debug_ranges_data.GetAddressByteSize();
  dw_addr_t base_addr = 0;
  dw_addr_t base_addr_marker = GetBaseAddressMarker(addr_size);

  while (
      debug_ranges_data.ValidOffsetForDataOfSize(*offset_ptr, 2 * addr_size)) {
    dw_addr_t begin = debug_ranges_data.GetMaxU64(offset_ptr, addr_size);
    dw_addr_t end = debug_ranges_data.GetMaxU64(offset_ptr, addr_size);

    if (!begin && !end) {
      // End of range list
      break;
    }

    if (begin == base_addr_marker) {
      base_addr = end;
      continue;
    }

    // Filter out empty ranges
    if (begin < end)
      range_list.Append(DWARFRangeList::Entry(begin + base_addr, end - begin));
  }

  // Make sure we consumed at least something
  return range_offset != *offset_ptr;
}

DWARFRangeList
DWARFDebugRanges::FindRanges(const DWARFUnit *cu,
                             dw_offset_t debug_ranges_offset) const {
  dw_addr_t debug_ranges_address = cu->GetRangesBase() + debug_ranges_offset;
  auto pos = m_range_map.find(debug_ranges_address);
  DWARFRangeList ans =
      pos == m_range_map.end() ? DWARFRangeList() : pos->second;

  // All DW_AT_ranges are relative to the base address of the compile
  // unit. We add the compile unit base address to make sure all the
  // addresses are properly fixed up.
  ans.Slide(cu->GetBaseAddress());
  return ans;
}