Sha256: 78e161a8b1406132d6c47e914c58a9a4e70be37374382b226eeff4b9fbcba8cd
Contents?: true
Size: 1.8 KB
Versions: 11
Compression:
Stored size: 1.8 KB
Contents
# frozen_string_literal: true
# A simple stateful class for keeping track of a CRC32 value through multiple writes
class ZipTricks::StreamCRC32
STRINGS_HAVE_CAPACITY_SUPPORT = begin
String.new('', capacity: 1)
true
rescue ArgumentError
false
end
CRC_BUF_SIZE = 1024 * 512
private_constant :STRINGS_HAVE_CAPACITY_SUPPORT, :CRC_BUF_SIZE
# Compute a CRC32 value from an IO object. The object should respond to `read` and `eof?`
#
# @param io[IO] the IO to read the data from
# @return [Fixnum] the computed CRC32 value
def self.from_io(io)
# If we can specify the string capacity upfront we will not have to resize
# the string during operation. This saves time but is only available on
# recent Ruby 2.x versions.
blob = STRINGS_HAVE_CAPACITY_SUPPORT ? String.new('', capacity: CRC_BUF_SIZE) : String.new('')
crc = new
crc << io.read(CRC_BUF_SIZE, blob) until io.eof?
crc.to_i
end
# Creates a new streaming CRC32 calculator
def initialize
@crc = Zlib.crc32('')
end
# Append data to the CRC32. Updates the contained CRC32 value in place.
#
# @param blob[String] the string to compute the CRC32 from
# @return [self]
def <<(blob)
@crc = Zlib.crc32_combine(@crc, Zlib.crc32(blob), blob.bytesize)
self
end
# Returns the CRC32 value computed so far
#
# @return [Fixnum] the updated CRC32 value for all the blobs so far
def to_i
@crc
end
# Appends a known CRC32 value to the current one, and combines the
# contained CRC32 value in-place.
#
# @param crc32[Fixnum] the CRC32 value to append
# @param blob_size[Fixnum] the size of the daata the `crc32` is computed from
# @return [Fixnum] the updated CRC32 value for all the blobs so far
def append(crc32, blob_size)
@crc = Zlib.crc32_combine(@crc, crc32, blob_size)
end
end
Version data entries
11 entries across 11 versions & 1 rubygems