用C++lzma对大流量进行分段压缩和解压缩

我需要动态地进行lzma压缩和解压缩。我通过Qt中的qnetworkmanager收到一个大文件，我需要在下载数据流时对其进行解压缩。

当我收到部分数据流时，我需要解压缩它，附加到文件中，然后在这个过程中释放任何使用过的内存。最好的方法是什么？

现在我正在尝试xz-utils，纯c api，也许有人可以提出更好的方法？

以下代码基于此示例

UPD2:

extern "C" void *lz_alloc(void *opaque, size_t nmemb, size_t size)
{
void *p = NULL;
try{
    p = new char [size];
}
catch(std::bad_alloc &ba)
{
    p = NULL;
}
return p;
}
extern "C" void lz_free(void *opaque, void *ptr)
{
delete [] (char*)ptr;
}

QByteArray lzCompress(QByteArray data)
{
QByteArray arr;
lzma_check check = LZMA_CHECK_CRC64;
lzma_stream strm = LZMA_STREAM_INIT; /* alloc and init lzma_stream struct */
lzma_allocator al;
al.alloc = lz_alloc;
al.free = lz_free;
strm.allocator = &al;
byte *in_buf;
byte out_buf [OUT_BUF_MAX];
size_t in_len;  /* length of useful data in in_buf */
size_t out_len; /* length of useful data in out_buf */
lzma_ret ret_xz;
/* initialize xz encoder */
ret_xz = lzma_easy_encoder (&strm, 9 | LZMA_PRESET_EXTREME, check);
if (ret_xz != LZMA_OK) {
    return QByteArray();
}
in_len = data.size();
in_buf = (byte*)data.data();
strm.next_in = in_buf;
strm.avail_in = in_len;
do {
    strm.next_out = out_buf;
    strm.avail_out = OUT_BUF_MAX;
    ret_xz = lzma_code (&strm, LZMA_FINISH);
    out_len = OUT_BUF_MAX - strm.avail_out;
    arr.append((char*)out_buf, out_len);
    out_buf[0] = 0;
} while (strm.avail_out == 0);
lzma_end (&strm);
return arr;
}

我睡了几个小时，现在我想得更清楚了，修复了我的错误代码，更新了它（它的行为就像qCompress一样）

UPD3:

解压缩代码（类似qUncompress的行为）

QByteArray lzUncompress(QByteArray data)
{
lzma_stream strm = LZMA_STREAM_INIT; /* alloc and init lzma_stream struct */
const uint32_t flags = LZMA_TELL_UNSUPPORTED_CHECK | LZMA_CONCATENATED;
const uint64_t memory_limit = UINT64_MAX; /* no memory limit */
byte *in_buf;
uint8_t out_buf [OUT_BUF_MAX];
size_t in_len;  /* length of useful data in in_buf */
size_t out_len; /* length of useful data in out_buf */
lzma_ret ret_xz;
QByteArray arr;
ret_xz = lzma_stream_decoder (&strm, memory_limit, flags);
if (ret_xz != LZMA_OK) {
    return QByteArray();
}
in_len = data.size();
in_buf = (byte*)data.data();
strm.next_in = in_buf;
strm.avail_in = in_len;
do {
    strm.next_out = out_buf;
    strm.avail_out = OUT_BUF_MAX;
    ret_xz = lzma_code (&strm, LZMA_FINISH);
    out_len = OUT_BUF_MAX - strm.avail_out;
    arr.append((char*)out_buf, out_len);
    out_buf[0] = 0;
} while (strm.avail_out == 0);
lzma_end (&strm);
return arr;
}

UPD4:

基本的流解压缩类，下面的代码只是动态解压缩从http服务器下载的xz流，这正是我所需要的：

class lz_stream_decompressor : public QObject
{
Q_OBJECT
public:
lz_stream_decompressor(QNetworkReply *r, QNetworkAccessManager *q, const QString &str, unsigned long sz): flags(LZMA_TELL_UNSUPPORTED_CHECK | LZMA_CONCATENATED), memory_limit(UINT64_MAX), state(0), total_upd_size(sz)
{
    repl = r;
    qnm = q;
    path = str;
    strm.next_in = NULL;
    strm.avail_in = 0;
    strm.total_in = 0;
    strm.next_out = NULL;
    strm.avail_out = 0;
    strm.total_out = 0;
    strm.allocator = NULL;
    strm.internal = NULL;
    strm.reserved_ptr1 = NULL;
    strm.reserved_ptr2 = NULL;
    strm.reserved_ptr3 = NULL;
    strm.reserved_ptr4 = NULL;
    strm.reserved_int1 = 0;
    strm.reserved_int2 = 0;
    strm.reserved_int3 = 0;
    strm.reserved_int4 = 0;
    strm.reserved_enum1 = LZMA_RESERVED_ENUM;
    strm.reserved_enum2 = LZMA_RESERVED_ENUM;
    ret_xz = lzma_stream_decoder (&strm, memory_limit, flags);
    if (ret_xz != LZMA_OK)
    {
        state = -1;
        repl->abort();
    }
    else
    {
        connect(repl, SIGNAL(downloadProgress(qint64,qint64)), SLOT(handle_new_data(qint64,qint64)));
        connect(q, SIGNAL(finished(QNetworkReply*)), SLOT(compressed_file_request_finished(QNetworkReply*)));
        QFile(path).rename(path + ".tmp");
    }
}
~lz_stream_decompressor()
{
/*        if(repl)
        delete repl; */
    lzma_end (&strm);
}
const short get_state()
{
    return state;
}
signals:
void finished();
public slots:
void handle_new_data(qint64 bytesReceived, qint64 bytesTotal);
void compressed_file_request_finished(QNetworkReply*);
private:
QNetworkReply *repl;
QNetworkAccessManager *qnm;
lzma_stream strm;
const uint32_t flags;
const uint64_t memory_limit; /* no memory limit */
short state;
byte *in_buf;
byte out_buf [OUT_BUF_MAX];
size_t in_len;  /* length of useful data in in_buf */
size_t out_len; /* length of useful data in out_buf */
lzma_ret ret_xz;
QString path;
unsigned long &total_upd_size;
};

和实现：

void lz_stream_decompressor::handle_new_data(qint64 bytesReceived, qint64 bytesTotal)
{
if(repl->error() != QNetworkReply::NoError)
{//TODO: handle error here
    QFile(path).remove();
    QFile(path + ".tmp").rename(path);
    return;
}
total_upd_size -= repl->bytesAvailable();
QByteArray data = repl->readAll();
in_len = data.size();
in_buf = (byte*)data.data();
strm.next_in = in_buf;
strm.avail_in = in_len;
do {
    strm.next_out = out_buf;
    strm.avail_out = OUT_BUF_MAX;
    ret_xz = lzma_code (&strm, LZMA_RUN);
    out_len = OUT_BUF_MAX - strm.avail_out;
    QFile file(path);
    if(file.open(QIODevice::WriteOnly | QIODevice::Append))
    {
        file.write(QByteArray((char*)out_buf, (int)out_len));
        file.close();
    }
    out_buf[0] = 0;
} while (strm.avail_out == 0);
}
void lz_stream_decompressor::compressed_file_request_finished(QNetworkReply* repl)
{
if(repl->error() != QNetworkReply::NoError)
{//TODO: handle error here
    QFile(path).remove();
    QFile(path + ".tmp").rename(path);
    emit finished();
    return;
}
total_upd_size -= repl->bytesAvailable();
QByteArray data = repl->readAll();
in_len = data.size();
in_buf = (byte*)data.data();
strm.next_in = in_buf;
strm.avail_in = in_len;
do {
    strm.next_out = out_buf;
    strm.avail_out = OUT_BUF_MAX;
    ret_xz = lzma_code (&strm, LZMA_FINISH);
    out_len = OUT_BUF_MAX - strm.avail_out;
    QFile file(path);
    if(file.open(QIODevice::WriteOnly | QIODevice::Append))
    {
        file.write(QByteArray((char*)out_buf, (int)out_len));
        file.close();
    }
    out_buf[0] = 0;
} while (strm.avail_out == 0);
repl->deleteLater();
QFile(path + ".tmp").remove();
emit finished();
}

所有这些都基于第一个链接中的示例，您需要用代码替换注释的代码部分，以便对未压缩的数据进行处理。

我想看看对这个代码有什么建议

您还需要将"compressed_file_request_finished"插槽连接到qnetworkmanager的finished信号，以完成未压缩的数据。

UPD5:

修复了lzCompress和lzUncompress，现在看起来工作得很好，不确定是否在handle_new_data中使用LZMA_FULL_FLUSH，因为我读到这是我需要的，但仍然不确定，现在我调整现有代码以使用它。。。

UPD6:

你还需要这样的东西：

/* read/write buffer sizes */
#define IN_BUF_MAX  409600
#define OUT_BUF_MAX 409600
/* analogous to xz CLI options: -0 to -9 */
#define COMPRESSION_LEVEL 7
/* boolean setting, analogous to xz CLI option: -e */
#define COMPRESSION_EXTREME true

在可见范围内，此代码才能工作。

UPD7:

更新的代码，所有的测试和工作，我发现liblzma不是完全线程安全的，我试图对filelist进行多线程压缩。而且它经常崩溃。