本文分享一个纯C语言编写的7Z解压缩代码库，本代码库的主要目的是在嵌入式环境下使用7z解压缩文件，可以将升级包通过7z进行压缩，然后发送给设备，减小和设备传输过程中的文件大小，进而达到传输大文件的目的。

下载链接 提取码pi4t

这个库使用的是19版本的库，

这个库是单线程的，移除了多线程代码，因为多线程依赖其他库。我只需要一个独立版本。

已经通过编译。

库的目录结构如下：

#ifdef USE_WINDOWS_FILE
static WRes File_OpenW(CSzFile *p, const WCHAR *name, int writeMode)
{
  p->handle = CreateFileW(name,
      writeMode ? GENERIC_WRITE : GENERIC_READ,
      FILE_SHARE_READ, NULL,
      writeMode ? CREATE_ALWAYS : OPEN_EXISTING,
      FILE_ATTRIBUTE_NORMAL, NULL);
  return (p->handle != INVALID_HANDLE_VALUE) ? 0 : GetLastError();
}
WRes InFile_OpenW(CSzFile *p, const WCHAR *name) { return File_OpenW(p, name, 0); }
WRes OutFile_OpenW(CSzFile *p, const WCHAR *name) { return File_OpenW(p, name, 1); }
#endif

WRes File_Close(CSzFile *p)
{
  #ifdef USE_WINDOWS_FILE
  if (p->handle != INVALID_HANDLE_VALUE)
  {
    if (!CloseHandle(p->handle))
      return GetLastError();
    p->handle = INVALID_HANDLE_VALUE;
  }
  #else
  if (p->file != NULL)
  {
    int res = fclose(p->file);
    if (res != 0)
      return res;
    p->file = NULL;
  }
  #endif
  return 0;
}

WRes File_Read(CSzFile *p, void *data, size_t *size)
{
  size_t originalSize = *size;
  if (originalSize == 0)
    return 0;

  #ifdef USE_WINDOWS_FILE

  *size = 0;
  do
  {
    DWORD curSize = (originalSize > kChunkSizeMax) ? kChunkSizeMax : (DWORD)originalSize;
    DWORD processed = 0;
    BOOL res = ReadFile(p->handle, data, curSize, &processed, NULL);
    data = (void *)((Byte *)data + processed);
    originalSize -= processed;
    *size += processed;
    if (!res)
      return GetLastError();
    if (processed == 0)
      break;
  }
  while (originalSize > 0);
  return 0;

  #else
  
  *size = fread(data, 1, originalSize, p->file);
  if (*size == originalSize)
    return 0;
  return ferror(p->file);
  
  #endif
}

static SRes SzDecodePpmd(const Byte *props, unsigned propsSize, UInt64 inSize, const ILookInStream *inStream,
    Byte *outBuffer, SizeT outSize, ISzAllocPtr allocMain)
{
  CPpmd7 ppmd;
  CByteInToLook s;
  SRes res = SZ_OK;

  s.vt.Read = ReadByte;
  s.inStream = inStream;
  s.begin = s.end = s.cur = NULL;
  s.extra = False;
  s.res = SZ_OK;
  s.processed = 0;

  if (propsSize != 5)
    return SZ_ERROR_UNSUPPORTED;

  {
    unsigned order = props[0];
    UInt32 memSize = GetUi32(props + 1);
    if (order < PPMD7_MIN_ORDER ||
        order > PPMD7_MAX_ORDER ||
        memSize < PPMD7_MIN_MEM_SIZE ||
        memSize > PPMD7_MAX_MEM_SIZE)
      return SZ_ERROR_UNSUPPORTED;
    Ppmd7_Construct(&ppmd);
    if (!Ppmd7_Alloc(&ppmd, memSize, allocMain))
      return SZ_ERROR_MEM;
    Ppmd7_Init(&ppmd, order);
  }
  {
    CPpmd7z_RangeDec rc;
    Ppmd7z_RangeDec_CreateVTable(&rc);
    rc.Stream = &s.vt;
    if (!Ppmd7z_RangeDec_Init(&rc))
      res = SZ_ERROR_DATA;
    else if (s.extra)
      res = (s.res != SZ_OK ? s.res : SZ_ERROR_DATA);
    else
    {
      SizeT i;
      for (i = 0; i < outSize; i++)
      {
        int sym = Ppmd7_DecodeSymbol(&ppmd, &rc.vt);
        if (s.extra || sym < 0)
          break;
        outBuffer[i] = (Byte)sym;
      }
      if (i != outSize)
        res = (s.res != SZ_OK ? s.res : SZ_ERROR_DATA);
      else if (s.processed + (s.cur - s.begin) != inSize || !Ppmd7z_RangeDec_IsFinishedOK(&rc))
        res = SZ_ERROR_DATA;
    }
  }
  Ppmd7_Free(&ppmd, allocMain);
  return res;
}

#endif


static SRes SzDecodeLzma(const Byte *props, unsigned propsSize, UInt64 inSize, ILookInStream *inStream,
    Byte *outBuffer, SizeT outSize, ISzAllocPtr allocMain)
{
  CLzmaDec state;
  SRes res = SZ_OK;

  LzmaDec_Construct(&state);
  RINOK(LzmaDec_AllocateProbs(&state, props, propsSize, allocMain));
  state.dic = outBuffer;
  state.dicBufSize = outSize;
  LzmaDec_Init(&state);

  for (;;)
  {
    const void *inBuf = NULL;
    size_t lookahead = (1 << 18);
    if (lookahead > inSize)
      lookahead = (size_t)inSize;
    res = ILookInStream_Look(inStream, &inBuf, &lookahead);
    if (res != SZ_OK)
      break;

    {
      SizeT inProcessed = (SizeT)lookahead, dicPos = state.dicPos;
      ELzmaStatus status;
      res = LzmaDec_DecodeToDic(&state, outSize, (const Byte *)inBuf, &inProcessed, LZMA_FINISH_END, &status);
      lookahead -= inProcessed;
      inSize -= inProcessed;
      if (res != SZ_OK)
        break;

      if (status == LZMA_STATUS_FINISHED_WITH_MARK)
      {
        if (outSize != state.dicPos || inSize != 0)
          res = SZ_ERROR_DATA;
        break;
      }

      if (outSize == state.dicPos && inSize == 0 && status == LZMA_STATUS_MAYBE_FINISHED_WITHOUT_MARK)
        break;

      if (inProcessed == 0 && dicPos == state.dicPos)
      {
        res = SZ_ERROR_DATA;
        break;
      }

      res = ILookInStream_Skip(inStream, inProcessed);
      if (res != SZ_OK)
        break;
    }
  }

  LzmaDec_FreeProbs(&state, allocMain);
  return res;
}

链接: https://pan.baidu.com/s/1ldjyd3l4zyC9AOw8-ox67g 提取码: pi4t

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