Module: Pocolog::Format::V2

Defined in:
lib/pocolog/format/v2.rb

Defined Under Namespace

Classes: IndexStreamInfo

Constant Summary

MAGIC =

The magic code present at the beginning of each pocolog file

'POCOSIM'
VERSION =

Format version ID. Increment this when the file format changes in a non-backward-compatible way

2
PROLOGUE_SIZE =

The size of the file's prologue

MAGIC.size + 9
INDEX_MAGIC =

The magic code at the beginning of a pocolog index

'POCOSIM_INDEX'
INDEX_VERSION =

The current index version. Unlike with the format version, a changing index version will only cause rebuilding the index

(i.e. this can change without changing the overall format version)

3
INDEX_PROLOGUE_SIZE =

Size of the index prologue

INDEX_MAGIC.size + 20
INDEX_STREAM_DESCRIPTION_SIZE =

Size of a stream description in the index

8 * 8
INDEX_STREAM_ENTRY_SIZE =

Size of an entry in the index table

8 * 3
BLOCK_HEADER_SIZE =

The size of the generic block header

8
TIME_SIZE =

The size of a time in a block header

8
DATA_BLOCK_HEADER_SIZE =

The size of a data header, excluding the generic block header

TIME_SIZE * 2 + 5
STREAM_BLOCK_DECLARATION_HEADER_SIZE_MIN =

The size of a stream block declaration header

Stream declarations contain variable-length strings, we can only have a min

9

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.index_contents_from_stream(stream_info, index_data_pos) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Helper method that prepares index contents for a given stream



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# File 'lib/pocolog/format/v2.rb', line 359

def self.index_contents_from_stream(stream_info, index_data_pos)
    interval_rt = stream_info.interval_rt.dup
    interval_lg = stream_info.interval_lg.dup
    base_time   = stream_info.index.base_time
    index_stream_info = [
        stream_info.declaration_blocks.first,
        index_data_pos,
        base_time || 0,
        stream_info.size,
        interval_rt[0] || 0, interval_rt[1] || 0,
        interval_lg[0] || 0, interval_lg[1] || 0
    ]

    [index_stream_info, stream_info.index.index_map.flatten]
end

.index_file_valid?(index_path, file_path) ⇒ Boolean

Tests whether the index whose path is given is valid for the given log file

Returns:

  • (Boolean) 


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# File 'lib/pocolog/format/v2.rb', line 209

def self.index_file_valid?(index_path, file_path)
    stat = file_path.stat
    begin
        File.open(index_path) do |index_io|
            read_index_stream_info(index_io, expected_file_size: stat.size)
        end
        true
    rescue Errno::ENOENT
        false
    end
rescue InvalidIndex
    false
end

.read_index(index_io, expected_file_size: nil, expected_mtime: nil) ⇒ Array<StreamInfo>

Read the information contained in a file index

Returns:

  • (Array<StreamInfo>) —

    the information contained in the index file



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# File 'lib/pocolog/format/v2.rb', line 168

def self.read_index(index_io, expected_file_size: nil, expected_mtime: nil)
    minimal_stream_info = read_index_stream_info(
        index_io,
        expected_file_size: expected_file_size,
        expected_mtime: expected_mtime
    )

    minimal_stream_info.map do |info|
        index_size = info.stream_size * INDEX_STREAM_ENTRY_SIZE
        index_io.seek(info.index_pos)
        index_data = index_io.read(index_size)
        if index_data.size != index_size
            raise InvalidIndex, 'not enough or too much data in index'
        end

        index_data = index_data.unpack('Q>*')
                               .each_slice(3).to_a
        StreamInfo.from_raw_data(
            info.declaration_pos, info.interval_rt, info.base_time,
            index_data
        )
    end
end

.read_index_prologue(index_io, validate_version: true, expected_mtime: nil, expected_file_size: nil) ⇒ Integer

Read the prologue of an index file

Parameters:

  • validate_version (Boolean) —

    if true, the method will raise if the file version does not match INDEX_VERSION

Returns:

  • (Integer) —

    the index file version



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# File 'lib/pocolog/format/v2.rb', line 104

def self.read_index_prologue(
    index_io, validate_version: true,
    expected_mtime: nil, expected_file_size: nil
)
    if index_io.size < INDEX_PROLOGUE_SIZE
        raise InvalidIndex, 'index file too small to contain a valid index'
    end

    header = index_io.read(INDEX_MAGIC.size + 4)
    magic = header[0, INDEX_MAGIC.size]
    if magic != INDEX_MAGIC
        message =
            if magic
                "wrong index magic in #{index_io.path}, "\
                'probably an old index'
            else
                "#{index_io.path} is empty"
            end

        raise MissingIndexPrologue, message
    end

    index_version = Integer(header[INDEX_MAGIC.size, 4].unpack('L>').first)
    if validate_version
        if index_version < INDEX_VERSION
            raise ObsoleteIndexVersion,
                  "old format #{index_version}, "\
                  "current format is #{INDEX_VERSION}"
        elsif index_version > INDEX_VERSION
            raise InvalidIndex,
                  "old format #{index_version}, "\
                  "current format is #{INDEX_VERSION}"
        end
    end

    index_size, index_mtime = index_io.read(16).unpack('Q>Q>')
    if expected_file_size && expected_file_size != index_size
        raise InvalidIndex,
              "file size in index (#{index_size}) and actual file "\
              "size (#{expected_file_size}) mismatch"
    end
    if expected_mtime
        expected_mtime_i = StreamIndex.time_to_internal(expected_mtime, 0)
        if expected_mtime_i != index_mtime
            raise InvalidIndex,
                  "mtime in index (#{index_mtime}) and actual mtime "\
                  "(#{expected_mtime_i}) mismatch"
        end
    end
    [index_version, index_size,
     StreamIndex.time_from_internal(index_mtime, 0)]
end

.read_index_stream_info(index_io, expected_file_size: nil, expected_mtime: nil) ⇒ Array<IndexStreamInfo>

Read basic stream information from an index file

Parameters:

  • index_io (IO) —

    the index IO

Returns:



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# File 'lib/pocolog/format/v2.rb', line 228

def self.read_index_stream_info(index_io,
                                expected_file_size: nil,
                                expected_mtime: nil)
    read_index_prologue(index_io,
                        validate_version: true,
                        expected_mtime: expected_mtime,
                        expected_file_size: expected_file_size)

    index_size = index_io.size
    if index_size < INDEX_PROLOGUE_SIZE + 8
        raise InvalidIndex, 'index file too small'
    end

    stream_count = index_io.read(8).unpack('Q>').first
    minimum_index_size = INDEX_PROLOGUE_SIZE + 8 +
                         INDEX_STREAM_DESCRIPTION_SIZE * stream_count
    if index_size < minimum_index_size
        raise InvalidIndex, 'index file too small'
    end

    expected_file_size = []

    streams = []
    stream_count.times do
        values = index_io.read(INDEX_STREAM_DESCRIPTION_SIZE).unpack('Q>*')
        # This is (declaration_pos, index_pos, stream_size)
        declaration_pos, index_pos, base_time, stream_size,
            interval_rt_min, interval_rt_max,
            interval_lg_min, interval_lg_max = *values

        index_size = stream_size * INDEX_STREAM_ENTRY_SIZE
        expected_file_size << index_size + index_pos

        if stream_size == 0
            base_time = nil
            interval_rt = []
            interval_lg = []
        else
            interval_rt = [interval_rt_min, interval_rt_max]
            interval_lg = [interval_lg_min, interval_lg_max]
        end

        streams << IndexStreamInfo.new(
            declaration_pos, index_pos, base_time,
            stream_size, interval_rt, interval_lg
        )
    end
    expected_file_size = expected_file_size.max
    if index_io.size != expected_file_size
        raise InvalidIndex,
              "index file should be of size #{expected_file_size} "\
              "but is of size #{index_io.size}"
    end

    streams
end

.read_minimal_stream_info(index_io, file_io) ⇒ Array<(BlockStream::StreamBlock,IndexStreamInfo)>

Read the stream information, but not the actual block index, from an index file

Returns:



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# File 'lib/pocolog/format/v2.rb', line 289

def self.read_minimal_stream_info(index_io, file_io)
    index_stream_info = read_index_stream_info(
        index_io,
        expected_file_size: file_io.size
    )

    index_stream_info.map do |info|
        file_io.seek(info.declaration_pos)
        block_stream = BlockStream.new(file_io)
        block_stream.read_next_block_header
        stream_block = block_stream.read_stream_block
        [stream_block, info]
    end
end

.read_prologue(io, validate_version: true) ⇒ (Integer,Boolean)

Read a file's prologue

Parameters:

  • io (IO) —

    the file from which to read the prologue

  • validate_version (Boolean) —

    if true, the method will raise if the file version does not match INDEX_VERSION

Returns:

  • ((Integer,Boolean)) —

    the file format version and a flag that tells whether the file's data is encoded as big or little endian



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# File 'lib/pocolog/format/v2.rb', line 48

def self.read_prologue(io, validate_version: true)
    header = io.read(PROLOGUE_SIZE) || ''
    if !header || (header.size < PROLOGUE_SIZE)
        raise MissingPrologue, "#{io.path} too small"
    end

    magic = header[0, MAGIC.size]
    if magic != MAGIC
        raise MissingPrologue,
              "#{io.path} is not a pocolog log file. "\
              "Got #{magic} at #{io.tell}, but was expecting #{MAGIC}"
    end

    format_version, big_endian = header[MAGIC.size, 9].unpack('xVV')
    validate_version(format_version) if validate_version
    [format_version, big_endian]
end

.rebuild_index_file(io, index_path) ⇒ Array<StreamInfo,nil>

Rebuild a pocolog file's index and saves it to file

Parameters:

  • io (File) —

    the pocolog file IO

  • index_path (String) —

    the path into which the index should be saved

Returns:



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# File 'lib/pocolog/format/v2.rb', line 310

def self.rebuild_index_file(io, index_path)
    block_stream = BlockStream.new(io)
    block_stream.read_prologue
    stream_info = Pocolog.file_index_builder(block_stream)
    FileUtils.mkdir_p(File.dirname(index_path))
    File.open(index_path, 'w') do |index_io|
        write_index(index_io, io, stream_info)
    end
    stream_info
end

.valid_file?(file) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pocolog/format/v2.rb', line 84

def self.valid_file?(file)
    File.open(file) do |io|
        read_prologue(io)
        true
    end
rescue InvalidFile
    false
end

.validate_version(version) ⇒ Object

Verify that the given version is compatible with this format version

Raises:

  • ObsoleteVersion if the version is older than VERSION and cannot be loaded by this code

  • InvalidFile if the version is newer than VERSION



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# File 'lib/pocolog/format/v2.rb', line 71

def self.validate_version(version)
    if version < VERSION
        raise ObsoleteVersion,
              "old format #{version}, current format "\
              "is #{VERSION}. Convert it using the "\
              '--to-new-format of pocolog'
    elsif version > VERSION
        raise InvalidFile,
              "this file is in v#{version} which is "\
              "newer that the one we know #{VERSION}. Update pocolog"
    end
end

.write_index(index_io, file_io, streams, version: INDEX_VERSION) ⇒ Object

Write an index file for a given file

Parameters:

  • file_io (File) —

    the file that is being indexed. It cannot be a IOSequence

  • index_io (File) —

    the file into which the index should be written

  • streams (Array<StreamInfo>) —

    the stream information that should be stored



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# File 'lib/pocolog/format/v2.rb', line 329

def self.write_index(index_io, file_io, streams, version: INDEX_VERSION)
    if index_io.path == file_io.path
        raise ArgumentError, 'attempting to overwrite the file by its index'
    end

    write_index_prologue(index_io, file_io.stat.size, file_io.stat.mtime,
                         version: version)
    index_io.write([streams.size].pack('Q>'))

    index_list_pos = index_io.tell
    index_data_pos = INDEX_STREAM_DESCRIPTION_SIZE * streams.size +
                     index_list_pos

    streams.each do |stream_info|
        index_stream_info, index_data =
            index_contents_from_stream(stream_info, index_data_pos)

        index_io.seek(index_list_pos)
        index_io.write(index_stream_info.pack('Q>*'))
        index_io.seek(index_data_pos)
        index_io.write(index_data.pack('Q>*'))

        index_list_pos += INDEX_STREAM_DESCRIPTION_SIZE
        index_data_pos += index_data.size * 8
    end
end

.write_index_prologue(index_io, size, mtime, version: INDEX_VERSION) ⇒ Object

Write a prologue on an index file



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# File 'lib/pocolog/format/v2.rb', line 158

def self.write_index_prologue(index_io, size, mtime, version: INDEX_VERSION)
    index_io.write(INDEX_MAGIC)
    data = [version, size, StreamIndex.time_to_internal(mtime, 0)]
    index_io.write(data.pack('L>Q>Q>'))
end

.write_prologue(io, big_endian = Pocolog.big_endian?) ⇒ Object

Write a v2 file prologue



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# File 'lib/pocolog/format/v2.rb', line 94

def self.write_prologue(io, big_endian = Pocolog.big_endian?)
    io.write(MAGIC)
    io.write(*[VERSION, big_endian ? 1 : 0].pack('xVV'))
end

Instance Method Details

#declaration_pos ⇒ Integer

Returns the position in the pocolog file of the stream declaration block

Returns:

  • (Integer) —

    the position in the pocolog file of the stream declaration block



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# File 'lib/pocolog/format/v2.rb', line 202

IndexStreamInfo = Struct.new(
    :declaration_pos, :index_pos, :base_time, :stream_size,
    :interval_rt, :interval_lg
)

#index_pos ⇒ Integer

Returns the position in the index file of the stream index data

Returns:

  • (Integer) —

    the position in the index file of the stream index data



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# File 'lib/pocolog/format/v2.rb', line 202

IndexStreamInfo = Struct.new(
    :declaration_pos, :index_pos, :base_time, :stream_size,
    :interval_rt, :interval_lg
)

#stream_size ⇒ Integer

Returns the number of samples in the stream

Returns:

  • (Integer) —

    the number of samples in the stream



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# File 'lib/pocolog/format/v2.rb', line 202

IndexStreamInfo = Struct.new(
    :declaration_pos, :index_pos, :base_time, :stream_size,
    :interval_rt, :interval_lg
)