c++ - zlib compress2 返回 Z_STREAM_ERROR

Question

char buffer[12] = {"Testing! 12"};

unsigned long compressedSize;
char* compressed = compress(buffer, 12, &compressedSize);

...

char* compress(char* buffer, unsigned long size, unsigned long* compressedSize)
{
    Bytef* inBuffer = reinterpret_cast<Bytef*>(buffer);
    uLong inSize = static_cast<uLong>(size);

    Bytef* outBuffer = 0;
    uLong outBufferSize = compressBound(inSize);

    int error = compress2(outBuffer, &outBufferSize, inBuffer, inSize, 6);

    if(error != Z_OK)
    {
        switch(error)
        {
            case Z_MEM_ERROR:
                std::cerr << "Memory error!" << std::endl;
                break;

            case Z_BUF_ERROR:
                std::cerr << "Buffer error!" << std::endl;
                break;

            default:
                std::cerr << "Unknown error: " << error << std::endl;
                break;
        }

        return 0;
    }

    *compressedSize = static_cast<unsigned long>(outBufferSize);

    return reinterpret_cast<char*>(outBuffer);
}

我点击了“未知错误:-2”，结果是 ZLIB_STREAM_ERROR。我无法弄清楚问题所在。所有变量似乎都是正确的。

Answer 1

您的 outBuffer 是一个 NULL 指针。您不能将 NULL 指针作为输出缓冲区传递给 compress2 ，compress2 需要一些空间来存储压缩数据，因此分配一个 compressBound(inSize) 大的缓冲区。从 compression2 的原型(prototype)可以明显看出，您不能让 compress2 分配并“返回”这样的缓冲区给您。

编辑，因为此时的实际错误是 Z_STREAM_ERROR ，这是因为您传入了一个无效级别。

compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR if there was not enough room in the output buffer, Z_STREAM_ERROR if the level parameter is invalid.

您应该使用以下级别之一:

#define Z_NO_COMPRESSION         0
#define Z_BEST_SPEED             1
#define Z_BEST_COMPRESSION       9
#define Z_DEFAULT_COMPRESSION  (-1)