FileFd: avoid further writing if file failed

[apt.git] / apt-pkg / contrib / fileutl.cc

diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index 99c0a34170923ca71d8ba9b6d2ad764e008cbeac..9990b753ab365bccf4ec4861b44919a3eb5e5ea0 100644 (file)
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -63,6 +63,9 @@
 #ifdef HAVE_LZMA
        #include <lzma.h>
 #endif
 #ifdef HAVE_LZMA
        #include <lzma.h>
 #endif

+#ifdef HAVE_LZ4
+       #include <lz4frame.h>
+#endif

 #include <endian.h>
 #include <stdint.h>
 
 #include <endian.h>
 #include <stdint.h>
 


@@ -75,6 +78,9 @@
 
 using namespace std;
 
 
 using namespace std;
 

+/* Should be a multiple of the common page size (4096) */
+static constexpr unsigned long long APT_BUFFER_SIZE = 64 * 1024;
+

 // RunScripts - Run a set of scripts from a configuration subtree      /*{{{*/
 // ---------------------------------------------------------------------
 /* */
 // RunScripts - Run a set of scripts from a configuration subtree      /*{{{*/
 // ---------------------------------------------------------------------
 /* */


@@ -160,7 +166,7 @@ bool CopyFile(FileFd &From,FileFd &To)
       return false;
 
    // Buffered copy between fds
       return false;
 
    // Buffered copy between fds

-   constexpr size_t BufSize = 64000;
+   constexpr size_t BufSize = APT_BUFFER_SIZE;

    std::unique_ptr<unsigned char[]> Buf(new unsigned char[BufSize]);
    unsigned long long ToRead = 0;
    do {
    std::unique_ptr<unsigned char[]> Buf(new unsigned char[BufSize]);
    unsigned long long ToRead = 0;
    do {


@@ -920,16 +926,35 @@ bool ChangeOwnerAndPermissionOfFile(char const * const requester, char const * c
                                                                        /*}}}*/
 
 struct APT_HIDDEN simple_buffer {                                                      /*{{{*/
                                                                        /*}}}*/
 
 struct APT_HIDDEN simple_buffer {                                                      /*{{{*/

-   static constexpr size_t buffersize_max = 4096;
+   size_t buffersize_max = 0;

    unsigned long long bufferstart = 0;
    unsigned long long bufferend = 0;
    unsigned long long bufferstart = 0;
    unsigned long long bufferend = 0;

-   char buffer[buffersize_max];
+   char *buffer = nullptr;
+
+   simple_buffer() {
+      reset(4096);
+   }
+   ~simple_buffer() {
+      delete[] buffer;
+   }

 
    const char *get() const { return buffer + bufferstart; }
    char *get() { return buffer + bufferstart; }
 
    const char *get() const { return buffer + bufferstart; }
    char *get() { return buffer + bufferstart; }

+   const char *getend() const { return buffer + bufferend; }
+   char *getend() { return buffer + bufferend; }

    bool empty() const { return bufferend <= bufferstart; }
    bool full() const { return bufferend == buffersize_max; }
    bool empty() const { return bufferend <= bufferstart; }
    bool full() const { return bufferend == buffersize_max; }

+   unsigned long long free() const { return buffersize_max - bufferend; }

    unsigned long long size() const { return bufferend-bufferstart; }
    unsigned long long size() const { return bufferend-bufferstart; }

+   void reset(size_t size)
+   {
+      if (size > buffersize_max) {
+        delete[] buffer;
+        buffersize_max = size;
+        buffer = new char[size];
+      }
+      reset();
+   }

    void reset() { bufferend = bufferstart = 0; }
    ssize_t read(void *to, unsigned long long requested_size) APT_MUSTCHECK
    {
    void reset() { bufferend = bufferstart = 0; }
    ssize_t read(void *to, unsigned long long requested_size) APT_MUSTCHECK
    {


@@ -943,9 +968,9 @@ struct APT_HIDDEN simple_buffer {                                                   /*{{{*/
    }
    ssize_t write(const void *from, unsigned long long requested_size) APT_MUSTCHECK
    {
    }
    ssize_t write(const void *from, unsigned long long requested_size) APT_MUSTCHECK
    {

-      if (buffersize_max - size() < requested_size)
-        requested_size = buffersize_max - size();
-      memcpy(buffer + bufferend, from, requested_size);
+      if (free() < requested_size)
+        requested_size = free();
+      memcpy(getend(), from, requested_size);

       bufferend += requested_size;
       if (bufferstart == bufferend)
         bufferstart = bufferend = 0;
       bufferend += requested_size;
       if (bufferstart == bufferend)
         bufferstart = bufferend = 0;


@@ -955,19 +980,53 @@ struct APT_HIDDEN simple_buffer {                                                 /*{{{*/
                                                                        /*}}}*/
 
 class APT_HIDDEN FileFdPrivate {                                                       /*{{{*/
                                                                        /*}}}*/
 
 class APT_HIDDEN FileFdPrivate {                                                       /*{{{*/

+   friend class BufferedWriteFileFdPrivate;

 protected:
    FileFd * const filefd;
    simple_buffer buffer;
 protected:
    FileFd * const filefd;
    simple_buffer buffer;

-public:

    int compressed_fd;
    pid_t compressor_pid;
    bool is_pipe;
    APT::Configuration::Compressor compressor;
    unsigned int openmode;
    unsigned long long seekpos;
    int compressed_fd;
    pid_t compressor_pid;
    bool is_pipe;
    APT::Configuration::Compressor compressor;
    unsigned int openmode;
    unsigned long long seekpos;

+public:
+

    explicit FileFdPrivate(FileFd * const pfilefd) : filefd(pfilefd),
       compressed_fd(-1), compressor_pid(-1), is_pipe(false),
       openmode(0), seekpos(0) {};
    explicit FileFdPrivate(FileFd * const pfilefd) : filefd(pfilefd),
       compressed_fd(-1), compressor_pid(-1), is_pipe(false),
       openmode(0), seekpos(0) {};

+   virtual APT::Configuration::Compressor get_compressor() const
+   {
+      return compressor;
+   }
+   virtual void set_compressor(APT::Configuration::Compressor const &compressor)
+   {
+      this->compressor = compressor;
+   }
+   virtual unsigned int get_openmode() const
+   {
+      return openmode;
+   }
+   virtual void set_openmode(unsigned int openmode)
+   {
+      this->openmode = openmode;
+   }
+   virtual bool get_is_pipe() const
+   {
+      return is_pipe;
+   }
+   virtual void set_is_pipe(bool is_pipe)
+   {
+      this->is_pipe = is_pipe;
+   }
+   virtual unsigned long long get_seekpos() const
+   {
+      return seekpos;
+   }
+   virtual void set_seekpos(unsigned long long seekpos)
+   {
+      this->seekpos = seekpos;
+   }

 
    virtual bool InternalOpen(int const iFd, unsigned int const Mode) = 0;
    ssize_t InternalRead(void * To, unsigned long long Size)
 
    virtual bool InternalOpen(int const iFd, unsigned int const Mode) = 0;
    ssize_t InternalRead(void * To, unsigned long long Size)


@@ -995,7 +1054,7 @@ public:
         {
            buffer.reset();
            unsigned long long actualread = 0;
         {
            buffer.reset();
            unsigned long long actualread = 0;

-           if (filefd->Read(buffer.get(), buffer.buffersize_max, &actualread) == false)
+           if (filefd->Read(buffer.getend(), buffer.free(), &actualread) == false)

               return nullptr;
            buffer.bufferend = actualread;
            if (buffer.size() == 0)
               return nullptr;
            buffer.bufferend = actualread;
            if (buffer.size() == 0)


@@ -1022,6 +1081,10 @@ public:
       *To = '\0';
       return InitialTo;
    }
       *To = '\0';
       return InitialTo;
    }

+   virtual bool InternalFlush()
+   {
+      return true;
+   }

    virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) = 0;
    virtual bool InternalWriteError() { return filefd->FileFdErrno("write",_("Write error")); }
    virtual bool InternalSeek(unsigned long long const To)
    virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) = 0;
    virtual bool InternalWriteError() { return filefd->FileFdErrno("write",_("Write error")); }
    virtual bool InternalSeek(unsigned long long const To)


@@ -1056,6 +1119,7 @@ public:
         return filefd->FileFdError("Seek on file %s because it couldn't be reopened", filefd->FileName.c_str());
 
       buffer.reset();
         return filefd->FileFdError("Seek on file %s because it couldn't be reopened", filefd->FileName.c_str());
 
       buffer.reset();

+      set_seekpos(0);

       if (To != 0)
         return filefd->Skip(To);
 
       if (To != 0)
         return filefd->Skip(To);
 


@@ -1112,11 +1176,157 @@ public:
    virtual ~FileFdPrivate() {}
 };
                                                                        /*}}}*/
    virtual ~FileFdPrivate() {}
 };
                                                                        /*}}}*/

+class APT_HIDDEN BufferedWriteFileFdPrivate : public FileFdPrivate {   /*{{{*/
+protected:
+   FileFdPrivate *wrapped;
+   simple_buffer writebuffer;
+
+public:
+
+   explicit BufferedWriteFileFdPrivate(FileFdPrivate *Priv) :
+      FileFdPrivate(Priv->filefd), wrapped(Priv) {};
+
+   virtual APT::Configuration::Compressor get_compressor() const APT_OVERRIDE
+   {
+      return wrapped->get_compressor();
+   }
+   virtual void set_compressor(APT::Configuration::Compressor const &compressor)  APT_OVERRIDE
+   {
+      return wrapped->set_compressor(compressor);
+   }
+   virtual unsigned int get_openmode() const  APT_OVERRIDE
+   {
+      return wrapped->get_openmode();
+   }
+   virtual void set_openmode(unsigned int openmode)  APT_OVERRIDE
+   {
+      return wrapped->set_openmode(openmode);
+   }
+   virtual bool get_is_pipe() const  APT_OVERRIDE
+   {
+      return wrapped->get_is_pipe();
+   }
+   virtual void set_is_pipe(bool is_pipe) APT_OVERRIDE
+   {
+      FileFdPrivate::set_is_pipe(is_pipe);
+      wrapped->set_is_pipe(is_pipe);
+   }
+   virtual unsigned long long get_seekpos() const APT_OVERRIDE
+   {
+      return wrapped->get_seekpos();
+   }
+   virtual void set_seekpos(unsigned long long seekpos) APT_OVERRIDE
+   {
+      return wrapped->set_seekpos(seekpos);
+   }
+   virtual bool InternalOpen(int const iFd, unsigned int const Mode) APT_OVERRIDE
+   {
+      if (InternalFlush() == false)
+        return false;
+      return wrapped->InternalOpen(iFd, Mode);
+   }
+   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) APT_OVERRIDE
+   {
+      if (InternalFlush() == false)
+        return -1;
+      return wrapped->InternalUnbufferedRead(To, Size);
+
+   }
+   virtual bool InternalReadError() APT_OVERRIDE
+   {
+      return wrapped->InternalReadError();
+   }
+   virtual char * InternalReadLine(char * To, unsigned long long Size) APT_OVERRIDE
+   {
+      if (InternalFlush() == false)
+        return nullptr;
+      return wrapped->InternalReadLine(To, Size);
+   }
+   virtual bool InternalFlush() APT_OVERRIDE
+   {
+      while (writebuffer.empty() == false) {
+        auto written = wrapped->InternalWrite(writebuffer.get(),
+                                              writebuffer.size());
+        // Ignore interrupted syscalls
+        if (written < 0 && errno == EINTR)
+           continue;
+        if (written < 0)
+           return wrapped->InternalWriteError();
+
+        writebuffer.bufferstart += written;
+      }
+
+      writebuffer.reset();
+      return true;
+   }
+   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) APT_OVERRIDE
+   {
+      // Optimisation: If the buffer is empty and we have more to write than
+      // would fit in the buffer (or equal number of bytes), write directly.
+      if (writebuffer.empty() == true && Size >= writebuffer.free())
+        return wrapped->InternalWrite(From, Size);
+
+      // Write as much into the buffer as possible and then flush if needed
+      auto written = writebuffer.write(From, Size);
+
+      if (writebuffer.full() && InternalFlush() == false)
+        return -1;
+
+      return written;
+   }
+   virtual bool InternalWriteError() APT_OVERRIDE
+   {
+      return wrapped->InternalWriteError();
+   }
+   virtual bool InternalSeek(unsigned long long const To) APT_OVERRIDE
+   {
+      if (InternalFlush() == false)
+        return false;
+      return wrapped->InternalSeek(To);
+   }
+   virtual bool InternalSkip(unsigned long long Over) APT_OVERRIDE
+   {
+      if (InternalFlush() == false)
+        return false;
+      return wrapped->InternalSkip(Over);
+   }
+   virtual bool InternalTruncate(unsigned long long const Size) APT_OVERRIDE
+   {
+      if (InternalFlush() == false)
+        return false;
+      return wrapped->InternalTruncate(Size);
+   }
+   virtual unsigned long long InternalTell() APT_OVERRIDE
+   {
+      if (InternalFlush() == false)
+        return -1;
+      return wrapped->InternalTell();
+   }
+   virtual unsigned long long InternalSize() APT_OVERRIDE
+   {
+      if (InternalFlush() == false)
+        return -1;
+      return wrapped->InternalSize();
+   }
+   virtual bool InternalClose(std::string const &FileName) APT_OVERRIDE
+   {
+      return wrapped->InternalClose(FileName);
+   }
+   virtual bool InternalAlwaysAutoClose() const APT_OVERRIDE
+   {
+      return wrapped->InternalAlwaysAutoClose();
+   }
+   virtual ~BufferedWriteFileFdPrivate()
+   {
+      delete wrapped;
+   }
+};
+                                                                       /*}}}*/

 class APT_HIDDEN GzipFileFdPrivate: public FileFdPrivate {                             /*{{{*/
 #ifdef HAVE_ZLIB
 public:
    gzFile gz;
 class APT_HIDDEN GzipFileFdPrivate: public FileFdPrivate {                             /*{{{*/
 #ifdef HAVE_ZLIB
 public:
    gzFile gz;

-   virtual bool InternalOpen(int const iFd, unsigned int const Mode) override
+   virtual bool InternalOpen(int const iFd, unsigned int const Mode) APT_OVERRIDE

    {
       if ((Mode & FileFd::ReadWrite) == FileFd::ReadWrite)
         gz = gzdopen(iFd, "r+");
    {
       if ((Mode & FileFd::ReadWrite) == FileFd::ReadWrite)
         gz = gzdopen(iFd, "r+");


@@ -1127,11 +1337,11 @@ public:
       filefd->Flags |= FileFd::Compressed;
       return gz != nullptr;
    }
       filefd->Flags |= FileFd::Compressed;
       return gz != nullptr;
    }

-   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) override
+   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) APT_OVERRIDE

    {
       return gzread(gz, To, Size);
    }
    {
       return gzread(gz, To, Size);
    }

-   virtual bool InternalReadError() override
+   virtual bool InternalReadError() APT_OVERRIDE

    {
       int err;
       char const * const errmsg = gzerror(gz, &err);
    {
       int err;
       char const * const errmsg = gzerror(gz, &err);


@@ -1139,15 +1349,15 @@ public:
         return filefd->FileFdError("gzread: %s (%d: %s)", _("Read error"), err, errmsg);
       return FileFdPrivate::InternalReadError();
    }
         return filefd->FileFdError("gzread: %s (%d: %s)", _("Read error"), err, errmsg);
       return FileFdPrivate::InternalReadError();
    }

-   virtual char * InternalReadLine(char * To, unsigned long long Size) override
+   virtual char * InternalReadLine(char * To, unsigned long long Size) APT_OVERRIDE

    {
       return gzgets(gz, To, Size);
    }
    {
       return gzgets(gz, To, Size);
    }

-   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) override
+   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) APT_OVERRIDE

    {
       return gzwrite(gz,From,Size);
    }
    {
       return gzwrite(gz,From,Size);
    }

-   virtual bool InternalWriteError() override
+   virtual bool InternalWriteError() APT_OVERRIDE

    {
       int err;
       char const * const errmsg = gzerror(gz, &err);
    {
       int err;
       char const * const errmsg = gzerror(gz, &err);


@@ -1155,7 +1365,7 @@ public:
         return filefd->FileFdError("gzwrite: %s (%d: %s)", _("Write error"), err, errmsg);
       return FileFdPrivate::InternalWriteError();
    }
         return filefd->FileFdError("gzwrite: %s (%d: %s)", _("Write error"), err, errmsg);
       return FileFdPrivate::InternalWriteError();
    }

-   virtual bool InternalSeek(unsigned long long const To) override
+   virtual bool InternalSeek(unsigned long long const To) APT_OVERRIDE

    {
       off_t const res = gzseek(gz, To, SEEK_SET);
       if (res != (off_t)To)
    {
       off_t const res = gzseek(gz, To, SEEK_SET);
       if (res != (off_t)To)


@@ -1164,7 +1374,7 @@ public:
       buffer.reset();
       return true;
    }
       buffer.reset();
       return true;
    }

-   virtual bool InternalSkip(unsigned long long Over) override
+   virtual bool InternalSkip(unsigned long long Over) APT_OVERRIDE

    {
       if (Over >= buffer.size())
       {
    {
       if (Over >= buffer.size())
       {


@@ -1184,11 +1394,11 @@ public:
       seekpos = res;
       return true;
    }
       seekpos = res;
       return true;
    }

-   virtual unsigned long long InternalTell() override
+   virtual unsigned long long InternalTell() APT_OVERRIDE

    {
       return gztell(gz) - buffer.size();
    }
    {
       return gztell(gz) - buffer.size();
    }

-   virtual unsigned long long InternalSize() override
+   virtual unsigned long long InternalSize() APT_OVERRIDE

    {
       unsigned long long filesize = FileFdPrivate::InternalSize();
       // only check gzsize if we are actually a gzip file, just checking for
    {
       unsigned long long filesize = FileFdPrivate::InternalSize();
       // only check gzsize if we are actually a gzip file, just checking for


@@ -1222,7 +1432,7 @@ public:
       }
       return size;
    }
       }
       return size;
    }

-   virtual bool InternalClose(std::string const &FileName) override
+   virtual bool InternalClose(std::string const &FileName) APT_OVERRIDE

    {
       if (gz == nullptr)
         return true;
    {
       if (gz == nullptr)
         return true;


@@ -1243,7 +1453,7 @@ class APT_HIDDEN Bz2FileFdPrivate: public FileFdPrivate {                         /*{{{*/
 #ifdef HAVE_BZ2
    BZFILE* bz2;
 public:
 #ifdef HAVE_BZ2
    BZFILE* bz2;
 public:

-   virtual bool InternalOpen(int const iFd, unsigned int const Mode) override
+   virtual bool InternalOpen(int const iFd, unsigned int const Mode) APT_OVERRIDE

    {
       if ((Mode & FileFd::ReadWrite) == FileFd::ReadWrite)
         bz2 = BZ2_bzdopen(iFd, "r+");
    {
       if ((Mode & FileFd::ReadWrite) == FileFd::ReadWrite)
         bz2 = BZ2_bzdopen(iFd, "r+");


@@ -1254,11 +1464,11 @@ public:
       filefd->Flags |= FileFd::Compressed;
       return bz2 != nullptr;
    }
       filefd->Flags |= FileFd::Compressed;
       return bz2 != nullptr;
    }

-   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) override
+   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) APT_OVERRIDE

    {
       return BZ2_bzread(bz2, To, Size);
    }
    {
       return BZ2_bzread(bz2, To, Size);
    }

-   virtual bool InternalReadError() override
+   virtual bool InternalReadError() APT_OVERRIDE

    {
       int err;
       char const * const errmsg = BZ2_bzerror(bz2, &err);
    {
       int err;
       char const * const errmsg = BZ2_bzerror(bz2, &err);


@@ -1266,11 +1476,11 @@ public:
         return filefd->FileFdError("BZ2_bzread: %s %s (%d: %s)", filefd->FileName.c_str(), _("Read error"), err, errmsg);
       return FileFdPrivate::InternalReadError();
    }
         return filefd->FileFdError("BZ2_bzread: %s %s (%d: %s)", filefd->FileName.c_str(), _("Read error"), err, errmsg);
       return FileFdPrivate::InternalReadError();
    }

-   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) override
+   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) APT_OVERRIDE

    {
       return BZ2_bzwrite(bz2, (void*)From, Size);
    }
    {
       return BZ2_bzwrite(bz2, (void*)From, Size);
    }

-   virtual bool InternalWriteError() override
+   virtual bool InternalWriteError() APT_OVERRIDE

    {
       int err;
       char const * const errmsg = BZ2_bzerror(bz2, &err);
    {
       int err;
       char const * const errmsg = BZ2_bzerror(bz2, &err);


@@ -1278,8 +1488,8 @@ public:
         return filefd->FileFdError("BZ2_bzwrite: %s %s (%d: %s)", filefd->FileName.c_str(), _("Write error"), err, errmsg);
       return FileFdPrivate::InternalWriteError();
    }
         return filefd->FileFdError("BZ2_bzwrite: %s %s (%d: %s)", filefd->FileName.c_str(), _("Write error"), err, errmsg);
       return FileFdPrivate::InternalWriteError();
    }

-   virtual bool InternalStream() const override { return true; }
-   virtual bool InternalClose(std::string const &) override
+   virtual bool InternalStream() const APT_OVERRIDE { return true; }
+   virtual bool InternalClose(std::string const &) APT_OVERRIDE

    {
       if (bz2 == nullptr)
         return true;
    {
       if (bz2 == nullptr)
         return true;


@@ -1291,22 +1501,177 @@ public:
    explicit Bz2FileFdPrivate(FileFd * const filefd) : FileFdPrivate(filefd), bz2(nullptr) {}
    virtual ~Bz2FileFdPrivate() { InternalClose(""); }
 #endif
    explicit Bz2FileFdPrivate(FileFd * const filefd) : FileFdPrivate(filefd), bz2(nullptr) {}
    virtual ~Bz2FileFdPrivate() { InternalClose(""); }
 #endif

+};
+                                                                       /*}}}*/
+class APT_HIDDEN Lz4FileFdPrivate: public FileFdPrivate {                              /*{{{*/
+   static constexpr unsigned long long LZ4_HEADER_SIZE = 19;
+   static constexpr unsigned long long LZ4_FOOTER_SIZE = 4;
+#ifdef HAVE_LZ4
+   LZ4F_decompressionContext_t dctx;
+   LZ4F_compressionContext_t cctx;
+   LZ4F_errorCode_t res;
+   FileFd backend;
+   simple_buffer lz4_buffer;
+   // Count of bytes that the decompressor expects to read next, or buffer size.
+   size_t next_to_load = APT_BUFFER_SIZE;
+public:
+   virtual bool InternalOpen(int const iFd, unsigned int const Mode) APT_OVERRIDE
+   {
+      if ((Mode & FileFd::ReadWrite) == FileFd::ReadWrite)
+        return _error->Error("lz4 only supports write or read mode");
+
+      if ((Mode & FileFd::WriteOnly) == FileFd::WriteOnly) {
+        res = LZ4F_createCompressionContext(&cctx, LZ4F_VERSION);
+        lz4_buffer.reset(LZ4F_compressBound(APT_BUFFER_SIZE, nullptr)
+                         + LZ4_HEADER_SIZE + LZ4_FOOTER_SIZE);
+      } else {
+        res = LZ4F_createDecompressionContext(&dctx, LZ4F_VERSION);
+        lz4_buffer.reset(APT_BUFFER_SIZE);
+      }
+
+      filefd->Flags |= FileFd::Compressed;
+
+      if (LZ4F_isError(res))
+        return false;
+
+      unsigned int flags = (Mode & (FileFd::WriteOnly|FileFd::ReadOnly));
+      if (backend.OpenDescriptor(iFd, flags) == false)
+        return false;
+
+      // Write the file header
+      if ((Mode & FileFd::WriteOnly) == FileFd::WriteOnly)
+      {
+        res = LZ4F_compressBegin(cctx, lz4_buffer.buffer, lz4_buffer.buffersize_max, nullptr);
+        if (LZ4F_isError(res) || backend.Write(lz4_buffer.buffer, res) == false)
+           return false;
+      }
+
+      return true;
+   }
+   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) APT_OVERRIDE
+   {
+      /* Keep reading as long as the compressor still wants to read */
+      while (next_to_load) {
+        // Fill compressed buffer;
+        if (lz4_buffer.empty()) {
+           unsigned long long read;
+           /* Reset - if LZ4 decompressor wants to read more, allocate more */
+           lz4_buffer.reset(next_to_load);
+           if (backend.Read(lz4_buffer.getend(), lz4_buffer.free(), &read) == false)
+              return -1;
+           lz4_buffer.bufferend += read;
+
+           /* Expected EOF */
+           if (read == 0) {
+              res = -1;
+              return filefd->FileFdError("LZ4F: %s %s",
+                                         filefd->FileName.c_str(),
+                                         _("Unexpected end of file")), -1;
+           }
+        }
+        // Drain compressed buffer as far as possible.
+        size_t in = lz4_buffer.size();
+        size_t out = Size;
+
+        res = LZ4F_decompress(dctx, To, &out, lz4_buffer.get(), &in, nullptr);
+        if (LZ4F_isError(res))
+              return -1;
+
+        next_to_load = res;
+        lz4_buffer.bufferstart += in;
+
+        if (out != 0)
+           return out;
+      }
+
+      return 0;
+   }
+   virtual bool InternalReadError() APT_OVERRIDE
+   {
+      char const * const errmsg = LZ4F_getErrorName(res);
+
+      return filefd->FileFdError("LZ4F: %s %s (%zu: %s)", filefd->FileName.c_str(), _("Read error"), res, errmsg);
+   }
+   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) APT_OVERRIDE
+   {
+      unsigned long long const towrite = std::min(APT_BUFFER_SIZE, Size);
+
+      res = LZ4F_compressUpdate(cctx,
+                               lz4_buffer.buffer, lz4_buffer.buffersize_max,
+                               From, towrite, nullptr);
+
+      if (LZ4F_isError(res) || backend.Write(lz4_buffer.buffer, res) == false)
+        return -1;
+
+      return towrite;
+   }
+   virtual bool InternalWriteError() APT_OVERRIDE
+   {
+      char const * const errmsg = LZ4F_getErrorName(res);
+
+      return filefd->FileFdError("LZ4F: %s %s (%zu: %s)", filefd->FileName.c_str(), _("Write error"), res, errmsg);
+   }
+   virtual bool InternalStream() const APT_OVERRIDE { return true; }
+
+   virtual bool InternalFlush() APT_OVERRIDE
+   {
+      return backend.Flush();
+   }
+
+   virtual bool InternalClose(std::string const &) APT_OVERRIDE
+   {
+      /* Reset variables */
+      res = 0;
+      next_to_load = APT_BUFFER_SIZE;
+
+      if (cctx != nullptr)
+      {
+        if (filefd->Failed() == false)
+        {
+           res = LZ4F_compressEnd(cctx, lz4_buffer.buffer, lz4_buffer.buffersize_max, nullptr);
+           if (LZ4F_isError(res) || backend.Write(lz4_buffer.buffer, res) == false)
+              return false;
+           if (!backend.Flush())
+              return false;
+        }
+        if (!backend.Close())
+           return false;
+
+        res = LZ4F_freeCompressionContext(cctx);
+        cctx = nullptr;
+      }
+
+      if (dctx != nullptr)
+      {
+        res = LZ4F_freeDecompressionContext(dctx);
+        dctx = nullptr;
+      }
+
+      return LZ4F_isError(res) == false;
+   }
+
+   explicit Lz4FileFdPrivate(FileFd * const filefd) : FileFdPrivate(filefd), dctx(nullptr), cctx(nullptr) {}
+   virtual ~Lz4FileFdPrivate() {
+      InternalClose("");
+   }
+#endif

 };
                                                                        /*}}}*/
 class APT_HIDDEN LzmaFileFdPrivate: public FileFdPrivate {                             /*{{{*/
 #ifdef HAVE_LZMA
    struct LZMAFILE {
       FILE* file;
 };
                                                                        /*}}}*/
 class APT_HIDDEN LzmaFileFdPrivate: public FileFdPrivate {                             /*{{{*/
 #ifdef HAVE_LZMA
    struct LZMAFILE {
       FILE* file;

+      FileFd * const filefd;

       uint8_t buffer[4096];
       lzma_stream stream;
       lzma_ret err;
       bool eof;
       bool compressing;
 
       uint8_t buffer[4096];
       lzma_stream stream;
       lzma_ret err;
       bool eof;
       bool compressing;
 

-      LZMAFILE() : file(nullptr), eof(false), compressing(false) { buffer[0] = '\0'; }
+      LZMAFILE(FileFd * const fd) : file(nullptr), filefd(fd), eof(false), compressing(false) { buffer[0] = '\0'; }

       ~LZMAFILE()
       {
       ~LZMAFILE()
       {

-        if (compressing == true)
+        if (compressing == true && filefd->Failed() == false)

         {
            size_t constexpr buffersize = sizeof(buffer)/sizeof(buffer[0]);
            while(true)
         {
            size_t constexpr buffersize = sizeof(buffer)/sizeof(buffer[0]);
            while(true)


@@ -1361,13 +1726,13 @@ class APT_HIDDEN LzmaFileFdPrivate: public FileFdPrivate {                              /*{{{*/
       return 6;
    }
 public:
       return 6;
    }
 public:

-   virtual bool InternalOpen(int const iFd, unsigned int const Mode) override
+   virtual bool InternalOpen(int const iFd, unsigned int const Mode) APT_OVERRIDE

    {
       if ((Mode & FileFd::ReadWrite) == FileFd::ReadWrite)
         return filefd->FileFdError("ReadWrite mode is not supported for lzma/xz files %s", filefd->FileName.c_str());
 
       if (lzma == nullptr)
    {
       if ((Mode & FileFd::ReadWrite) == FileFd::ReadWrite)
         return filefd->FileFdError("ReadWrite mode is not supported for lzma/xz files %s", filefd->FileName.c_str());
 
       if (lzma == nullptr)

-        lzma = new LzmaFileFdPrivate::LZMAFILE;
+        lzma = new LzmaFileFdPrivate::LZMAFILE(filefd);

       if ((Mode & FileFd::WriteOnly) == FileFd::WriteOnly)
         lzma->file = fdopen(iFd, "w");
       else
       if ((Mode & FileFd::WriteOnly) == FileFd::WriteOnly)
         lzma->file = fdopen(iFd, "w");
       else


@@ -1413,7 +1778,7 @@ public:
       }
       return true;
    }
       }
       return true;
    }

-   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) override
+   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) APT_OVERRIDE

    {
       ssize_t Res;
       if (lzma->eof == true)
    {
       ssize_t Res;
       if (lzma->eof == true)


@@ -1449,12 +1814,13 @@ public:
       }
       return Res;
    }
       }
       return Res;
    }

-   virtual bool InternalReadError() override
+   virtual bool InternalReadError() APT_OVERRIDE

    {
       return filefd->FileFdError("lzma_read: %s (%d)", _("Read error"), lzma->err);
    }
    {
       return filefd->FileFdError("lzma_read: %s (%d)", _("Read error"), lzma->err);
    }

-   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) override
+   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) APT_OVERRIDE

    {
    {

+      ssize_t Res;

       lzma->stream.next_in = (uint8_t *)From;
       lzma->stream.avail_in = Size;
       lzma->stream.next_out = lzma->buffer;
       lzma->stream.next_in = (uint8_t *)From;
       lzma->stream.avail_in = Size;
       lzma->stream.next_out = lzma->buffer;


@@ -1465,16 +1831,28 @@ public:
       size_t const n = sizeof(lzma->buffer)/sizeof(lzma->buffer[0]) - lzma->stream.avail_out;
       size_t const m = (n == 0) ? 0 : fwrite(lzma->buffer, 1, n, lzma->file);
       if (m != n)
       size_t const n = sizeof(lzma->buffer)/sizeof(lzma->buffer[0]) - lzma->stream.avail_out;
       size_t const m = (n == 0) ? 0 : fwrite(lzma->buffer, 1, n, lzma->file);
       if (m != n)

-        return -1;
+      {
+        Res = -1;
+        errno = 0;
+      }

       else
       else

-        return Size - lzma->stream.avail_in;
+      {
+        Res = Size - lzma->stream.avail_in;
+        if (Res == 0)
+        {
+           // lzma run was okay, but produced no output…
+           Res = -1;
+           errno = EINTR;
+        }
+      }
+      return Res;

    }
    }

-   virtual bool InternalWriteError() override
+   virtual bool InternalWriteError() APT_OVERRIDE

    {
       return filefd->FileFdError("lzma_write: %s (%d)", _("Write error"), lzma->err);
    }
    {
       return filefd->FileFdError("lzma_write: %s (%d)", _("Write error"), lzma->err);
    }

-   virtual bool InternalStream() const override { return true; }
-   virtual bool InternalClose(std::string const &) override
+   virtual bool InternalStream() const APT_OVERRIDE { return true; }
+   virtual bool InternalClose(std::string const &) APT_OVERRIDE

    {
       delete lzma;
       lzma = nullptr;
    {
       delete lzma;
       lzma = nullptr;


@@ -1491,7 +1869,7 @@ class APT_HIDDEN PipedFileFdPrivate: public FileFdPrivate                         /*{{{*/
    by executing a specified binary and pipe in/out what we need */
 {
 public:
    by executing a specified binary and pipe in/out what we need */
 {
 public:

-   virtual bool InternalOpen(int const, unsigned int const Mode) override
+   virtual bool InternalOpen(int const, unsigned int const Mode) APT_OVERRIDE

    {
       // collect zombies here in case we reopen
       if (compressor_pid > 0)
    {
       // collect zombies here in case we reopen
       if (compressor_pid > 0)


@@ -1526,7 +1904,7 @@ public:
         SetCloseExec(Pipe[J],true);
 
       compressed_fd = filefd->iFd;
         SetCloseExec(Pipe[J],true);
 
       compressed_fd = filefd->iFd;

-      is_pipe = true;
+      set_is_pipe(true);

 
       if (Comp == true)
         filefd->iFd = Pipe[1];
 
       if (Comp == true)
         filefd->iFd = Pipe[1];


@@ -1589,15 +1967,15 @@ public:
 
       return true;
    }
 
       return true;
    }

-   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) override
+   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) APT_OVERRIDE

    {
       return read(filefd->iFd, To, Size);
    }
    {
       return read(filefd->iFd, To, Size);
    }

-   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) override
+   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) APT_OVERRIDE

    {
       return write(filefd->iFd, From, Size);
    }
    {
       return write(filefd->iFd, From, Size);
    }

-   virtual bool InternalClose(std::string const &) override
+   virtual bool InternalClose(std::string const &) APT_OVERRIDE

    {
       bool Ret = true;
       if (compressor_pid > 0)
    {
       bool Ret = true;
       if (compressor_pid > 0)


@@ -1612,12 +1990,12 @@ public:
 class APT_HIDDEN DirectFileFdPrivate: public FileFdPrivate                             /*{{{*/
 {
 public:
 class APT_HIDDEN DirectFileFdPrivate: public FileFdPrivate                             /*{{{*/
 {
 public:

-   virtual bool InternalOpen(int const, unsigned int const) override { return true; }
-   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) override
+   virtual bool InternalOpen(int const, unsigned int const) APT_OVERRIDE { return true; }
+   virtual ssize_t InternalUnbufferedRead(void * const To, unsigned long long const Size) APT_OVERRIDE

    {
       return read(filefd->iFd, To, Size);
    }
    {
       return read(filefd->iFd, To, Size);
    }

-   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) override
+   virtual ssize_t InternalWrite(void const * const From, unsigned long long const Size) APT_OVERRIDE

    {
       // files opened read+write are strange and only really "supported" for direct files
       if (buffer.size() != 0)
    {
       // files opened read+write are strange and only really "supported" for direct files
       if (buffer.size() != 0)


@@ -1627,7 +2005,7 @@ public:
       }
       return write(filefd->iFd, From, Size);
    }
       }
       return write(filefd->iFd, From, Size);
    }

-   virtual bool InternalSeek(unsigned long long const To) override
+   virtual bool InternalSeek(unsigned long long const To) APT_OVERRIDE

    {
       off_t const res = lseek(filefd->iFd, To, SEEK_SET);
       if (res != (off_t)To)
    {
       off_t const res = lseek(filefd->iFd, To, SEEK_SET);
       if (res != (off_t)To)


@@ -1636,7 +2014,7 @@ public:
       buffer.reset();
       return true;
    }
       buffer.reset();
       return true;
    }

-   virtual bool InternalSkip(unsigned long long Over) override
+   virtual bool InternalSkip(unsigned long long Over) APT_OVERRIDE

    {
       if (Over >= buffer.size())
       {
    {
       if (Over >= buffer.size())
       {


@@ -1656,7 +2034,7 @@ public:
       seekpos = res;
       return true;
    }
       seekpos = res;
       return true;
    }

-   virtual bool InternalTruncate(unsigned long long const To) override
+   virtual bool InternalTruncate(unsigned long long const To) APT_OVERRIDE

    {
       if (buffer.size() != 0)
       {
    {
       if (buffer.size() != 0)
       {


@@ -1672,16 +2050,16 @@ public:
         return filefd->FileFdError("Unable to truncate to %llu",To);
       return true;
    }
         return filefd->FileFdError("Unable to truncate to %llu",To);
       return true;
    }

-   virtual unsigned long long InternalTell() override
+   virtual unsigned long long InternalTell() APT_OVERRIDE

    {
       return lseek(filefd->iFd,0,SEEK_CUR) - buffer.size();
    }
    {
       return lseek(filefd->iFd,0,SEEK_CUR) - buffer.size();
    }

-   virtual unsigned long long InternalSize() override
+   virtual unsigned long long InternalSize() APT_OVERRIDE

    {
       return filefd->FileSize();
    }
    {
       return filefd->FileSize();
    }

-   virtual bool InternalClose(std::string const &) override { return true; }
-   virtual bool InternalAlwaysAutoClose() const override { return false; }
+   virtual bool InternalClose(std::string const &) APT_OVERRIDE { return true; }
+   virtual bool InternalAlwaysAutoClose() const APT_OVERRIDE { return false; }

 
    explicit DirectFileFdPrivate(FileFd * const filefd) : FileFdPrivate(filefd) {}
    virtual ~DirectFileFdPrivate() { InternalClose(""); }
 
    explicit DirectFileFdPrivate(FileFd * const filefd) : FileFdPrivate(filefd) {}
    virtual ~DirectFileFdPrivate() { InternalClose(""); }


@@ -1765,6 +2143,7 @@ bool FileFd::Open(string FileName,unsigned int const Mode,CompressMode Compress,
       case Bzip2: name = "bzip2"; break;
       case Lzma: name = "lzma"; break;
       case Xz: name = "xz"; break;
       case Bzip2: name = "bzip2"; break;
       case Lzma: name = "lzma"; break;
       case Xz: name = "xz"; break;

+      case Lz4: name = "lz4"; break;

       case Auto:
       case Extension:
         // Unreachable
       case Auto:
       case Extension:
         // Unreachable


@@ -1881,6 +2260,7 @@ bool FileFd::OpenDescriptor(int Fd, unsigned int const Mode, CompressMode Compre
    case Bzip2: name = "bzip2"; break;
    case Lzma: name = "lzma"; break;
    case Xz: name = "xz"; break;
    case Bzip2: name = "bzip2"; break;
    case Lzma: name = "lzma"; break;
    case Xz: name = "xz"; break;

+   case Lz4: name = "lz4"; break;

    case Auto:
    case Extension:
       if (AutoClose == true && Fd != -1)
    case Auto:
    case Extension:
       if (AutoClose == true && Fd != -1)


@@ -1942,14 +2322,20 @@ bool FileFd::OpenInternDescriptor(unsigned int const Mode, APT::Configuration::C
       APT_COMPRESS_INIT("xz", LzmaFileFdPrivate);
       APT_COMPRESS_INIT("lzma", LzmaFileFdPrivate);
 #endif
       APT_COMPRESS_INIT("xz", LzmaFileFdPrivate);
       APT_COMPRESS_INIT("lzma", LzmaFileFdPrivate);
 #endif

+#ifdef HAVE_LZ4
+      APT_COMPRESS_INIT("lz4", Lz4FileFdPrivate);
+#endif

 #undef APT_COMPRESS_INIT
       else if (compressor.Name == "." || compressor.Binary.empty() == true)
         d = new DirectFileFdPrivate(this);
       else
         d = new PipedFileFdPrivate(this);
 
 #undef APT_COMPRESS_INIT
       else if (compressor.Name == "." || compressor.Binary.empty() == true)
         d = new DirectFileFdPrivate(this);
       else
         d = new PipedFileFdPrivate(this);
 

-      d->openmode = Mode;
-      d->compressor = compressor;
+      if (Mode & BufferedWrite)
+        d = new BufferedWriteFileFdPrivate(d);
+
+      d->set_openmode(Mode);
+      d->set_compressor(compressor);

       if ((Flags & AutoClose) != AutoClose && d->InternalAlwaysAutoClose())
       {
         // Need to duplicate fd here or gz/bz2 close for cleanup will close the fd as well
       if ((Flags & AutoClose) != AutoClose && d->InternalAlwaysAutoClose())
       {
         // Need to duplicate fd here or gz/bz2 close for cleanup will close the fd as well


@@ -2007,7 +2393,7 @@ bool FileFd::Read(void *To,unsigned long long Size,unsigned long long *Actual)
       To = (char *)To + Res;
       Size -= Res;
       if (d != NULL)
       To = (char *)To + Res;
       Size -= Res;
       if (d != NULL)

-        d->seekpos += Res;
+        d->set_seekpos(d->get_seekpos() + Res);

       if (Actual != 0)
         *Actual += Res;
    }
       if (Actual != 0)
         *Actual += Res;
    }


@@ -2037,6 +2423,15 @@ char* FileFd::ReadLine(char *To, unsigned long long const Size)
    return d->InternalReadLine(To, Size);
 }
                                                                        /*}}}*/
    return d->InternalReadLine(To, Size);
 }
                                                                        /*}}}*/

+// FileFd::Flush - Flush the file                                      /*{{{*/
+bool FileFd::Flush()
+{
+   if (d == nullptr)
+      return true;
+
+   return d->InternalFlush();
+}
+                                                                       /*}}}*/

 // FileFd::Write - Write to the file                                   /*{{{*/
 bool FileFd::Write(const void *From,unsigned long long Size)
 {
 // FileFd::Write - Write to the file                                   /*{{{*/
 bool FileFd::Write(const void *From,unsigned long long Size)
 {


@@ -2047,15 +2442,23 @@ bool FileFd::Write(const void *From,unsigned long long Size)
    while (Res > 0 && Size > 0)
    {
       Res = d->InternalWrite(From, Size);
    while (Res > 0 && Size > 0)
    {
       Res = d->InternalWrite(From, Size);

-      if (Res < 0 && errno == EINTR)
-        continue;
+

       if (Res < 0)
       if (Res < 0)

+      {
+        if (errno == EINTR)
+        {
+           // trick the while-loop into running again
+           Res = 1;
+           errno = 0;
+           continue;
+        }

         return d->InternalWriteError();
         return d->InternalWriteError();

+      }

 
       From = (char const *)From + Res;
       Size -= Res;
       if (d != NULL)
 
       From = (char const *)From + Res;
       Size -= Res;
       if (d != NULL)

-        d->seekpos += Res;
+        d->set_seekpos(d->get_seekpos() + Res);

    }
 
    if (Size == 0)
    }
 
    if (Size == 0)


@@ -2123,13 +2526,13 @@ unsigned long long FileFd::Tell()
    off_t const Res = d->InternalTell();
    if (Res == (off_t)-1)
       FileFdErrno("lseek","Failed to determine the current file position");
    off_t const Res = d->InternalTell();
    if (Res == (off_t)-1)
       FileFdErrno("lseek","Failed to determine the current file position");

-   d->seekpos = Res;
+   d->set_seekpos(Res);

    return Res;
 }
                                                                        /*}}}*/
 static bool StatFileFd(char const * const msg, int const iFd, std::string const &FileName, struct stat &Buf, FileFdPrivate * const d) /*{{{*/
 {
    return Res;
 }
                                                                        /*}}}*/
 static bool StatFileFd(char const * const msg, int const iFd, std::string const &FileName, struct stat &Buf, FileFdPrivate * const d) /*{{{*/
 {

-   bool ispipe = (d != NULL && d->is_pipe == true);
+   bool ispipe = (d != NULL && d->get_is_pipe() == true);

    if (ispipe == false)
    {
       if (fstat(iFd,&Buf) != 0)
    if (ispipe == false)
    {
       if (fstat(iFd,&Buf) != 0)


@@ -2146,7 +2549,7 @@ static bool StatFileFd(char const * const msg, int const iFd, std::string const
       // we set it here, too, as we get the info here for free
       // in theory the Open-methods should take care of it already
       if (d != NULL)
       // we set it here, too, as we get the info here for free
       // in theory the Open-methods should take care of it already
       if (d != NULL)

-        d->is_pipe = true;
+        d->set_is_pipe(true);

       if (stat(FileName.c_str(), &Buf) != 0)
         return _error->Errno("fstat", "Unable to determine %s for file %s", msg, FileName.c_str());
    }
       if (stat(FileName.c_str(), &Buf) != 0)
         return _error->Errno("fstat", "Unable to determine %s for file %s", msg, FileName.c_str());
    }


@@ -2190,6 +2593,8 @@ unsigned long long FileFd::Size()
 /* */
 bool FileFd::Close()
 {
 /* */
 bool FileFd::Close()
 {

+   if (Failed() == false && Flush() == false)
+      return false;

    if (iFd == -1)
       return true;
 
    if (iFd == -1)
       return true;