// SPDX-FileCopyrightText: 2019-2024 Connor McLaughlin <stenzek@gmail.com>
// SPDX-License-Identifier: (GPL-3.0 OR PolyForm-Strict-1.0.0)

#include "small_string.h"
#include "assert.h"
#include "string_util.h"

#include <algorithm>
#include <cctype>
#include <cstdio>
#include <cstring>

#ifdef _WIN32
#include "windows_headers.h"
#endif

SmallStringBase::SmallStringBase() = default;

SmallStringBase::SmallStringBase(const SmallStringBase& copy)
{
  assign(copy.m_buffer, copy.m_length);
}

SmallStringBase::SmallStringBase(const char* str)
{
  assign(str);
}

SmallStringBase::SmallStringBase(const char* str, u32 count)
{
  assign(str, count);
}

SmallStringBase::SmallStringBase(SmallStringBase&& move)
{
  assign(std::move(move));
}

SmallStringBase::SmallStringBase(const std::string_view sv)
{
  assign(sv);
}

SmallStringBase::SmallStringBase(const std::string& str)
{
  assign(str);
}

SmallStringBase::~SmallStringBase()
{
  if (m_on_heap)
    std::free(m_buffer);
}

void SmallStringBase::reserve(u32 new_reserve)
{
  const u32 real_reserve = new_reserve + 1;
  if (m_buffer_size >= real_reserve)
    return;

  if (m_on_heap)
  {
    char* new_ptr = static_cast<char*>(std::realloc(m_buffer, real_reserve));
    if (!new_ptr)
      Panic("Memory allocation failed.");

#ifdef _DEBUG
    std::memset(new_ptr + m_length, 0, real_reserve - m_length);
#endif
    m_buffer = new_ptr;
  }
  else
  {
    char* new_ptr = static_cast<char*>(std::malloc(real_reserve));
    if (!new_ptr)
      Panic("Memory allocation failed.");

    if (m_length > 0)
      std::memcpy(new_ptr, m_buffer, m_length);
#ifdef _DEBUG
    std::memset(new_ptr + m_length, 0, real_reserve - m_length);
#else
    new_ptr[m_length] = 0;
#endif
    m_buffer = new_ptr;
    m_on_heap = true;
  }

  m_buffer_size = new_reserve;
}

void SmallStringBase::shrink_to_fit()
{
  const u32 buffer_size = (m_length + 1);
  if (!m_on_heap || buffer_size == m_buffer_size)
    return;

  if (m_length == 0)
  {
    std::free(m_buffer);
    m_buffer = nullptr;
    m_buffer_size = 0;
    return;
  }

  char* new_ptr = static_cast<char*>(std::realloc(m_buffer, buffer_size));
  if (!new_ptr)
    Panic("Memory allocation failed.");

  m_buffer = new_ptr;
  m_buffer_size = buffer_size;
}

std::string_view SmallStringBase::view() const
{
  return (m_length == 0) ? std::string_view() : std::string_view(m_buffer, m_length);
}

SmallStringBase& SmallStringBase::operator=(SmallStringBase&& move)
{
  assign(move);
  return *this;
}

SmallStringBase& SmallStringBase::operator=(const std::string_view str)
{
  assign(str);
  return *this;
}

SmallStringBase& SmallStringBase::operator=(const std::string& str)
{
  assign(str);
  return *this;
}

SmallStringBase& SmallStringBase::operator=(const char* str)
{
  assign(str);
  return *this;
}

SmallStringBase& SmallStringBase::operator=(const SmallStringBase& copy)
{
  assign(copy);
  return *this;
}

void SmallStringBase::make_room_for(u32 space)
{
  const u32 required_size = m_length + space + 1;
  if (m_buffer_size >= required_size)
    return;

  reserve(std::max(required_size, m_buffer_size * 2));
}

void SmallStringBase::append(const char* str, u32 length)
{
  if (length == 0)
    return;

  make_room_for(length);

  DebugAssert((length + m_length) < m_buffer_size);

  std::memcpy(m_buffer + m_length, str, length);
  m_length += length;
  m_buffer[m_length] = 0;
}

void SmallStringBase::append_hex(const void* data, size_t len)
{
  if (len == 0)
    return;

  make_room_for(static_cast<u32>(len) * 4);
  const u8* bytes = static_cast<const u8*>(data);
  append_format("{:02X}", bytes[0]);
  for (size_t i = 1; i < len; i++)
    append_format(", {:02X}", bytes[i]);
}

void SmallStringBase::prepend(const char* str, u32 length)
{
  if (length == 0)
    return;

  make_room_for(length);

  DebugAssert((length + m_length) < m_buffer_size);

  std::memmove(m_buffer + length, m_buffer, m_length);
  std::memcpy(m_buffer, str, length);
  m_length += length;
  m_buffer[m_length] = 0;
}

void SmallStringBase::append(char c)
{
  append(&c, 1);
}

void SmallStringBase::append(const SmallStringBase& str)
{
  append(str.m_buffer, str.m_length);
}

void SmallStringBase::append(const char* str)
{
  append(str, static_cast<u32>(std::strlen(str)));
}

void SmallStringBase::append(const std::string& str)
{
  append(str.c_str(), static_cast<u32>(str.length()));
}

void SmallStringBase::append(const std::string_view str)
{
  append(str.data(), static_cast<u32>(str.length()));
}

void SmallStringBase::append_sprintf(const char* format, ...)
{
  std::va_list ap;
  va_start(ap, format);
  append_vsprintf(format, ap);
  va_end(ap);
}

void SmallStringBase::append_vsprintf(const char* format, va_list ap)
{
  // We have a 1KB byte buffer on the stack here. If this is too little, we'll grow it via the heap,
  // but 1KB should be enough for most strings.
  char stack_buffer[1024];
  char* heap_buffer = nullptr;
  char* buffer = stack_buffer;
  u32 buffer_size = static_cast<u32>(std::size(stack_buffer));
  u32 written;

  for (;;)
  {
    std::va_list ap_copy;
    va_copy(ap_copy, ap);
    const int ret = std::vsnprintf(buffer, buffer_size, format, ap_copy);
    va_end(ap_copy);
    if (ret < 0 || (static_cast<u32>(ret) >= (buffer_size - 1)))
    {
      buffer_size *= 2;
      buffer = heap_buffer = reinterpret_cast<char*>(std::realloc(heap_buffer, buffer_size));
      if (!buffer) [[unlikely]]
        Panic("Memory allocation failed.");
      continue;
    }

    written = static_cast<u32>(ret);
    break;
  }

  append(buffer, written);

  if (heap_buffer)
    std::free(heap_buffer);
}

void SmallStringBase::prepend(char c)
{
  prepend(&c, 1);
}

void SmallStringBase::prepend(const SmallStringBase& str)
{
  prepend(str.m_buffer, str.m_length);
}

void SmallStringBase::prepend(const char* str)
{
  prepend(str, static_cast<u32>(std::strlen(str)));
}

void SmallStringBase::prepend(const std::string& str)
{
  prepend(str.c_str(), static_cast<u32>(str.length()));
}

void SmallStringBase::prepend(const std::string_view str)
{
  prepend(str.data(), static_cast<u32>(str.length()));
}

void SmallStringBase::prepend_sprintf(const char* format, ...)
{
  va_list ap;
  va_start(ap, format);
  prepend_vsprintf(format, ap);
  va_end(ap);
}

void SmallStringBase::prepend_vsprintf(const char* format, va_list ArgPtr)
{
  // We have a 1KB byte buffer on the stack here. If this is too little, we'll grow it via the heap,
  // but 1KB should be enough for most strings.
  char stack_buffer[1024];
  char* heap_buffer = nullptr;
  char* buffer = stack_buffer;
  u32 buffer_size = static_cast<u32>(std::size(stack_buffer));
  u32 written;

  for (;;)
  {
    int ret = std::vsnprintf(buffer, buffer_size, format, ArgPtr);
    if (ret < 0 || (static_cast<u32>(ret) >= (buffer_size - 1)))
    {
      buffer_size *= 2;
      buffer = heap_buffer = reinterpret_cast<char*>(std::realloc(heap_buffer, buffer_size));
      if (!buffer) [[unlikely]]
        Panic("Memory allocation failed.");
      continue;
    }

    written = static_cast<u32>(ret);
    break;
  }

  prepend(buffer, written);

  if (heap_buffer)
    std::free(heap_buffer);
}

void SmallStringBase::insert(s32 offset, const char* str)
{
  insert(offset, str, static_cast<u32>(std::strlen(str)));
}

void SmallStringBase::insert(s32 offset, const SmallStringBase& str)
{
  insert(offset, str, str.m_length);
}

void SmallStringBase::insert(s32 offset, const char* str, u32 length)
{
  if (length == 0)
    return;

  make_room_for(length);

  // calc real offset
  u32 real_offset;
  if (offset < 0)
    real_offset = static_cast<u32>(std::max<s32>(0, static_cast<s32>(m_length) + offset));
  else
    real_offset = std::min(static_cast<u32>(offset), m_length);

  // determine number of characters after offset
  DebugAssert(real_offset <= m_length);
  const u32 chars_after_offset = m_length - real_offset;
  if (chars_after_offset > 0)
    std::memmove(m_buffer + offset + length, m_buffer + offset, chars_after_offset);

  // insert the string
  std::memcpy(m_buffer + real_offset, str, length);
  m_length += length;

  // ensure null termination
  m_buffer[m_length] = 0;
}

void SmallStringBase::insert(s32 offset, const std::string& str)
{
  insert(offset, str.c_str(), static_cast<u32>(str.size()));
}

void SmallStringBase::insert(s32 offset, const std::string_view str)
{
  insert(offset, str.data(), static_cast<u32>(str.size()));
}

void SmallStringBase::sprintf(const char* format, ...)
{
  va_list ap;
  va_start(ap, format);
  vsprintf(format, ap);
  va_end(ap);
}

void SmallStringBase::vsprintf(const char* format, va_list ap)
{
  clear();
  append_vsprintf(format, ap);
}

void SmallStringBase::assign(const SmallStringBase& copy)
{
  assign(copy.c_str(), copy.length());
}

void SmallStringBase::assign(const char* str)
{
  assign(str, static_cast<u32>(std::strlen(str)));
}

void SmallStringBase::assign(const char* str, u32 length)
{
  clear();
  if (length > 0)
    append(str, length);
}

void SmallStringBase::assign(SmallStringBase&& move)
{
  if (move.m_on_heap)
  {
    if (m_on_heap)
      std::free(m_buffer);
    m_buffer = move.m_buffer;
    m_buffer_size = move.m_buffer_size;
    m_length = move.m_length;
    m_on_heap = true;
    move.m_buffer = nullptr;
    move.m_buffer_size = 0;
    move.m_length = 0;
  }
  else
  {
    assign(move.m_buffer, move.m_buffer_size);
  }
}

void SmallStringBase::assign(const std::string& str)
{
  clear();
  append(str.data(), static_cast<u32>(str.size()));
}

void SmallStringBase::assign(const std::string_view str)
{
  clear();
  append(str.data(), static_cast<u32>(str.size()));
}

#ifdef _WIN32

void SmallStringBase::assign(const std::wstring_view wstr)
{
  int mblen =
    WideCharToMultiByte(CP_UTF8, 0, wstr.data(), static_cast<int>(wstr.length()), nullptr, 0, nullptr, nullptr);
  if (mblen < 0)
  {
    clear();
    return;
  }

  reserve(static_cast<u32>(mblen));
  if (mblen > 0 && WideCharToMultiByte(CP_UTF8, 0, wstr.data(), static_cast<int>(wstr.length()), m_buffer, mblen,
                                       nullptr, nullptr) < 0)
  {
    clear();
    return;
  }

  m_length = static_cast<u32>(mblen);
}

std::wstring SmallStringBase::wstring() const
{
  return StringUtil::UTF8StringToWideString(view());
}

#endif

void SmallStringBase::vformat(fmt::string_view fmt, fmt::format_args args)
{
  clear();
  fmt::vformat_to(std::back_inserter(*this), fmt, args);
}

bool SmallStringBase::equals(const char* str) const
{
  if (m_length == 0)
    return (std::strlen(str) == 0);
  else
    return (std::strcmp(m_buffer, str) == 0);
}

bool SmallStringBase::equals(const SmallStringBase& str) const
{
  return (m_length == str.m_length && (m_length == 0 || std::strcmp(m_buffer, str.m_buffer) == 0));
}

bool SmallStringBase::equals(const std::string_view str) const
{
  return (m_length == static_cast<u32>(str.length()) &&
          (m_length == 0 || std::memcmp(m_buffer, str.data(), m_length) == 0));
}

bool SmallStringBase::equals(const std::string& str) const
{
  return (m_length == static_cast<u32>(str.length()) &&
          (m_length == 0 || std::memcmp(m_buffer, str.data(), m_length) == 0));
}

bool SmallStringBase::iequals(const char* otherText) const
{
  if (m_length == 0)
    return (std::strlen(otherText) == 0);
  else
    return StringUtil::EqualNoCase(view(), otherText);
}

bool SmallStringBase::iequals(const SmallStringBase& str) const
{
  return (m_length == str.m_length && (m_length == 0 || std::strcmp(m_buffer, str.m_buffer) == 0));
}

bool SmallStringBase::iequals(const std::string_view str) const
{
  return (m_length == static_cast<u32>(str.length()) &&
          (m_length == 0 || StringUtil::Strncasecmp(m_buffer, str.data(), m_length) == 0));
}

bool SmallStringBase::iequals(const std::string& str) const
{
  return (m_length == static_cast<u32>(str.length()) &&
          (m_length == 0 || StringUtil::Strncasecmp(m_buffer, str.data(), m_length) == 0));
}

int SmallStringBase::compare(const char* otherText) const
{
  return compare(std::string_view(otherText));
}

int SmallStringBase::compare(const SmallStringBase& str) const
{
  if (m_length == 0)
    return (str.m_length == 0) ? 0 : -1;
  else if (str.m_length == 0)
    return 1;

  const int res = std::strncmp(m_buffer, str.m_buffer, std::min(m_length, str.m_length));
  if (m_length == str.m_length || res != 0)
    return res;
  else
    return (m_length > str.m_length) ? 1 : -1;
}

int SmallStringBase::compare(const std::string_view str) const
{
  const u32 slength = static_cast<u32>(str.length());
  if (m_length == 0)
    return (slength == 0) ? 0 : -1;
  else if (slength == 0)
    return 1;

  const int res = std::strncmp(m_buffer, str.data(), std::min(m_length, slength));
  if (m_length == slength || res != 0)
    return res;
  else
    return (m_length > slength) ? 1 : -1;
}

int SmallStringBase::compare(const std::string& str) const
{
  const u32 slength = static_cast<u32>(str.length());
  if (m_length == 0)
    return (slength == 0) ? 0 : -1;
  else if (slength == 0)
    return 1;

  const int res = std::strncmp(m_buffer, str.data(), std::min(m_length, slength));
  if (m_length == slength || res != 0)
    return res;
  else
    return (m_length > slength) ? 1 : -1;
}

int SmallStringBase::icompare(const char* otherText) const
{
  return icompare(std::string_view(otherText));
}

int SmallStringBase::icompare(const SmallStringBase& str) const
{
  if (m_length == 0)
    return (str.m_length == 0) ? 0 : -1;
  else if (str.m_length == 0)
    return 1;

  const int res = StringUtil::Strncasecmp(m_buffer, str.m_buffer, std::min(m_length, str.m_length));
  if (m_length == str.m_length || res != 0)
    return res;
  else
    return (m_length > str.m_length) ? 1 : -1;
}

int SmallStringBase::icompare(const std::string_view str) const
{
  const u32 slength = static_cast<u32>(str.length());
  if (m_length == 0)
    return (slength == 0) ? 0 : -1;
  else if (slength == 0)
    return 1;

  const int res = StringUtil::Strncasecmp(m_buffer, str.data(), std::min(m_length, slength));
  if (m_length == slength || res != 0)
    return res;
  else
    return (m_length > slength) ? 1 : -1;
}

int SmallStringBase::icompare(const std::string& str) const
{
  const u32 slength = static_cast<u32>(str.length());
  if (m_length == 0)
    return (slength == 0) ? 0 : -1;
  else if (slength == 0)
    return 1;

  const int res = StringUtil::Strncasecmp(m_buffer, str.data(), std::min(m_length, slength));
  if (m_length == slength || res != 0)
    return res;
  else
    return (m_length > slength) ? 1 : -1;
}

bool SmallStringBase::starts_with(const char* str, bool case_sensitive) const
{
  const u32 other_length = static_cast<u32>(std::strlen(str));
  if (other_length > m_length)
    return false;

  return (case_sensitive) ? (std::strncmp(str, m_buffer, other_length) == 0) :
                            (StringUtil::Strncasecmp(str, m_buffer, other_length) == 0);
}

bool SmallStringBase::starts_with(const SmallStringBase& str, bool case_sensitive) const
{
  const u32 other_length = str.m_length;
  if (other_length > m_length)
    return false;

  return (case_sensitive) ? (std::strncmp(str.m_buffer, m_buffer, other_length) == 0) :
                            (StringUtil::Strncasecmp(str.m_buffer, m_buffer, other_length) == 0);
}

bool SmallStringBase::starts_with(const std::string_view str, bool case_sensitive) const
{
  const u32 other_length = static_cast<u32>(str.length());
  if (other_length > m_length)
    return false;

  return (case_sensitive) ? (std::strncmp(str.data(), m_buffer, other_length) == 0) :
                            (StringUtil::Strncasecmp(str.data(), m_buffer, other_length) == 0);
}

bool SmallStringBase::starts_with(const std::string& str, bool case_sensitive) const
{
  const u32 other_length = static_cast<u32>(str.length());
  if (other_length > m_length)
    return false;

  return (case_sensitive) ? (std::strncmp(str.data(), m_buffer, other_length) == 0) :
                            (StringUtil::Strncasecmp(str.data(), m_buffer, other_length) == 0);
}

bool SmallStringBase::ends_with(const char* str, bool case_sensitive) const
{
  const u32 other_length = static_cast<u32>(std::strlen(str));
  if (other_length > m_length)
    return false;

  u32 start_offset = m_length - other_length;
  return (case_sensitive) ? (std::strncmp(str, m_buffer + start_offset, other_length) == 0) :
                            (StringUtil::Strncasecmp(str, m_buffer + start_offset, other_length) == 0);
}

bool SmallStringBase::ends_with(const SmallStringBase& str, bool case_sensitive) const
{
  const u32 other_length = str.m_length;
  if (other_length > m_length)
    return false;

  const u32 start_offset = m_length - other_length;
  return (case_sensitive) ? (std::strncmp(str.m_buffer, m_buffer + start_offset, other_length) == 0) :
                            (StringUtil::Strncasecmp(str.m_buffer, m_buffer + start_offset, other_length) == 0);
}

bool SmallStringBase::ends_with(const std::string_view str, bool case_sensitive) const
{
  const u32 other_length = static_cast<u32>(str.length());
  if (other_length > m_length)
    return false;

  const u32 start_offset = m_length - other_length;
  return (case_sensitive) ? (std::strncmp(str.data(), m_buffer + start_offset, other_length) == 0) :
                            (StringUtil::Strncasecmp(str.data(), m_buffer + start_offset, other_length) == 0);
}

bool SmallStringBase::ends_with(const std::string& str, bool case_sensitive) const
{
  const u32 other_length = static_cast<u32>(str.length());
  if (other_length > m_length)
    return false;

  const u32 start_offset = m_length - other_length;
  return (case_sensitive) ? (std::strncmp(str.data(), m_buffer + start_offset, other_length) == 0) :
                            (StringUtil::Strncasecmp(str.data(), m_buffer + start_offset, other_length) == 0);
}

void SmallStringBase::clear()
{
  // in debug, zero whole string, in release, zero only the first character
#if _DEBUG
  std::memset(m_buffer, 0, m_buffer_size);
#else
  m_buffer[0] = '\0';
#endif
  m_length = 0;
}

s32 SmallStringBase::find(char c, u32 offset) const
{
  if (m_length == 0)
    return -1;

  DebugAssert(offset <= m_length);
  const char* at = std::strchr(m_buffer + offset, c);
  return at ? static_cast<s32>(at - m_buffer) : -1;
}

s32 SmallStringBase::rfind(char c, u32 offset) const
{
  if (m_length == 0)
    return -1;

  DebugAssert(offset <= m_length);
  const char* at = std::strrchr(m_buffer + offset, c);
  return at ? static_cast<s32>(at - m_buffer) : -1;
}

s32 SmallStringBase::find(const char* str, u32 offset) const
{
  if (m_length == 0)
    return -1;

  DebugAssert(offset <= m_length);
  const char* at = std::strstr(m_buffer + offset, str);
  return at ? static_cast<s32>(at - m_buffer) : -1;
}

u32 SmallStringBase::count(char ch) const
{
  const char* ptr = m_buffer;
  const char* end = ptr + m_length;
  u32 count = 0;
  while (ptr != end)
    count += static_cast<u32>(*(ptr++) == ch);
  return count;
}

u32 SmallStringBase::replace(const char* search, const char* replacement)
{
  const u32 search_length = static_cast<u32>(std::strlen(search));
  const u32 replacement_length = static_cast<u32>(std::strlen(replacement));

  s32 offset = 0;
  u32 count = 0;
  for (;;)
  {
    offset = find(search, static_cast<u32>(offset));
    if (offset < 0)
      break;

    const u32 new_length = m_length - search_length + replacement_length;
    reserve(new_length);
    m_length = new_length;

    const u32 chars_after_offset = (m_length - static_cast<u32>(offset));
    DebugAssert(chars_after_offset >= search_length);
    if (chars_after_offset > search_length)
    {
      std::memmove(&m_buffer[static_cast<u32>(offset) + replacement_length],
                   &m_buffer[static_cast<u32>(offset) + search_length], chars_after_offset - search_length);
      std::memcpy(&m_buffer[static_cast<u32>(offset)], replacement, replacement_length);
    }
    else
    {
      // at end of string
      std::memcpy(&m_buffer[static_cast<u32>(offset)], replacement, replacement_length);
      m_buffer[static_cast<u32>(offset) + replacement_length] = '\0';
    }

    offset += replacement_length;
    count++;
  }

  return count;
}

void SmallStringBase::resize(u32 new_size, char fill, bool shrink_if_smaller)
{
  // if going larger, or we don't own the buffer, realloc
  if (new_size >= m_buffer_size)
  {
    reserve(new_size);

    if (m_length < new_size)
    {
      std::memset(m_buffer + m_length, fill, m_buffer_size - m_length - 1);
    }

    m_length = new_size;
  }
  else
  {
    // update length and terminator
#if _DEBUG
    std::memset(m_buffer + new_size, 0, m_buffer_size - new_size);
#else
    m_buffer[new_size] = 0;
#endif
    m_length = new_size;

    // shrink if requested
    if (shrink_if_smaller)
      shrink_to_fit();
  }
}

void SmallStringBase::update_size()
{
  m_length = static_cast<u32>(std::strlen(m_buffer));
}

std::string_view SmallStringBase::substr(s32 offset, s32 count) const
{
  // calc real offset
  u32 real_offset;
  if (offset < 0)
    real_offset = static_cast<u32>(std::max<s32>(0, static_cast<s32>(m_length + offset)));
  else
    real_offset = std::min((u32)offset, m_length);

  // calc real count
  u32 real_count;
  if (count < 0)
  {
    real_count =
      std::min(m_length - real_offset, static_cast<u32>(std::max<s32>(0, static_cast<s32>(m_length) + count)));
  }
  else
  {
    real_count = std::min(m_length - real_offset, static_cast<u32>(count));
  }

  return (real_count > 0) ? std::string_view(m_buffer + real_offset, real_count) : std::string_view();
}

void SmallStringBase::erase(s32 offset, s32 count)
{
  // calc real offset
  u32 real_offset;
  if (offset < 0)
    real_offset = static_cast<u32>(std::max<s32>(0, static_cast<s32>(m_length + offset)));
  else
    real_offset = std::min((u32)offset, m_length);

  // calc real count
  u32 real_count;
  if (count < 0)
  {
    real_count =
      std::min(m_length - real_offset, static_cast<u32>(std::max<s32>(0, static_cast<s32>(m_length) + count)));
  }
  else
  {
    real_count = std::min(m_length - real_offset, static_cast<u32>(count));
  }

  // Fastpath: offset == 0, count < 0, wipe whole string.
  if (real_offset == 0 && real_count == m_length)
  {
    clear();
    return;
  }

  // Fastpath: offset >= 0, count < 0, wipe everything after offset + count
  if ((real_offset + real_count) == m_length)
  {
    m_length -= real_count;
#ifdef _DEBUG
    std::memset(m_buffer + m_length, 0, m_buffer_size - m_length);
#else
    m_buffer[m_length] = 0;
#endif
  }
  // Slowpath: offset >= 0, count < length
  else
  {
    const u32 after_erase_block = m_length - real_offset - real_count;
    DebugAssert(after_erase_block > 0);

    std::memmove(m_buffer + offset, m_buffer + real_offset + real_count, after_erase_block);
    m_length = m_length - real_count;

#ifdef _DEBUG
    std::memset(m_buffer + m_length, 0, m_buffer_size - m_length);
#else
    m_buffer[m_length] = 0;
#endif
  }
}
