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Commit a100c02b authored by Christopher Tate's avatar Christopher Tate
Browse files

Compress the backup output stream 

Zlib compression, with a full flush between each application's
data.  Encryption will be performed on the already-compressed data
once that's implemented.

On restore, the streamed data is similarly uncompressed on the fly.

Change-Id: I19b65c88e759a66527d10913d18fffa9df0bc011
parent 15a99db8

libs/utils/BackupHelpers.cpp

+12 −4
Original line number Diff line number Diff line
@@ -481,6 +481,14 @@ static int write_pax_header_entry(char* buf, const char* key, const char* value) 
    return sprintf(buf, "%d %s=%s\n", len, key, value);

}



// Wire format to the backup manager service is chunked:  each chunk is prefixed by

// a 4-byte count of its size.  A chunk size of zero (four zero bytes) indicates EOD.

void send_tarfile_chunk(BackupDataWriter* writer, const char* buffer, size_t size) {

    uint32_t chunk_size_no = htonl(size);

    writer->WriteEntityData(&chunk_size_no, 4);

    if (size != 0) writer->WriteEntityData(buffer, size);

}



int write_tarfile(const String8& packageName, const String8& domain,

        const String8& rootpath, const String8& filepath, BackupDataWriter* writer)

{
@@ -660,16 +668,16 @@ int write_tarfile(const String8& packageName, const String8& domain, 


        // Checksum and write the pax block header

        calc_tar_checksum(paxHeader);

        writer->WriteEntityData(paxHeader, 512);

        send_tarfile_chunk(writer, paxHeader, 512);



        // Now write the pax data itself

        int paxblocks = (paxLen + 511) / 512;

        writer->WriteEntityData(paxData, 512 * paxblocks);

        send_tarfile_chunk(writer, paxData, 512 * paxblocks);

    }



    // Checksum and write the 512-byte ustar file header block to the output

    calc_tar_checksum(buf);

    writer->WriteEntityData(buf, 512);

    send_tarfile_chunk(writer, buf, 512);



    // Now write the file data itself, for real files.  We honor tar's convention that

    // only full 512-byte blocks are sent to write().
@@ -699,7 +707,7 @@ int write_tarfile(const String8& packageName, const String8& domain, 
                memset(buf + nRead, 0, remainder);

                nRead += remainder;

            }

            writer->WriteEntityData(buf, nRead);

            send_tarfile_chunk(writer, buf, nRead);

            toWrite -= nRead;

        }

    }