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file.cr
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file.cr
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require "./file_info"
# Provides random read access to zip file entries stores inside
# a `File` or an `IO::Memory`.
#
# ### Example
#
# ```
# require "compress/zip"
#
# Compress::Zip::File.open("./file.zip") do |file|
# # Iterate through all entries printing their filename and contents
# file.entries.each do |entry|
# p entry.filename
# entry.open do |io|
# p io.gets_to_end
# end
# end
#
# # Random access to entries by filename is also provided
# entry = file["some_file.txt"]
# entry.open do |io|
# p io.gets_to_end
# end
# end
# ```
class Compress::Zip::File
# Returns all entries inside this zip file.
getter entries : Array(Entry)
# Returns `true` if this zip file is closed.
getter? closed = false
# Returns the zip file comment.
getter comment = ""
# Opens a `Zip::File` for reading from the given *io*.
def initialize(@io : IO, @sync_close = false)
directory_end_offset = find_directory_end_offset
entries_size, directory_offset = read_directory_end(directory_end_offset)
@entries = Array(Entry).new(entries_size)
@entries_by_filename = {} of String => Entry
read_entries(directory_offset, entries_size)
end
# Opens a `Zip::File` for reading from the given *filename*.
def self.new(filename : String)
new(::File.new(filename), sync_close: true)
end
# Opens a `Zip::File` for reading from the given *io*, yields
# it to the given block, and closes it at the end.
def self.open(io : IO, sync_close = false)
zip = new io, sync_close
yield zip ensure zip.close
end
# Opens a `Zip::File` for reading from the given *filename*, yields
# it to the given block, and closes it at the end.
def self.open(filename : String)
zip = new filename
yield zip ensure zip.close
end
# Returns the entry that has the given filename, or
# raises `KeyError` if no such entry exists.
def [](filename : String) : Entry
self[filename]? || raise(KeyError.new("Missing zip entry: #{filename}"))
end
# Returns the entry that has the given filename, or
# `nil` if no such entry exists.
def []?(filename : String) : Entry?
@entries_by_filename[filename]?
end
# Closes this zip file.
def close
return if @closed
@closed = true
if @sync_close
@io.close
end
end
# Tries to find the directory end offset (by searching its signature)
# in the last 64, 1024 and 65K bytes (in that order)
private def find_directory_end_offset
find_directory_end_offset(64) ||
find_directory_end_offset(1024) ||
find_directory_end_offset(65 * 1024) ||
raise Compress::Zip::Error.new("Couldn't find directory end signature in the last 65KB")
end
private def find_directory_end_offset(buf_size)
@io.seek(0, IO::Seek::End)
size = @io.pos
buf_size = Math.min(buf_size, size)
@io.pos = size - buf_size
buf = Bytes.new(buf_size)
@io.read_fully(buf)
i = buf_size - 1 - 4
while i >= 0
# These are the bytes the make up the directory end signature,
# according to the spec
break if buf[i] == 0x50 && buf[i + 1] == 0x4b && buf[i + 2] == 0x05 && buf[i + 3] == 0x06
i -= 1
end
i == -1 ? nil : size - buf_size + i
end
private def read_directory_end(directory_end_offset)
@io.pos = directory_end_offset
signature = read UInt32
if signature != Zip::END_OF_CENTRAL_DIRECTORY_HEADER_SIGNATURE
raise Error.new("Expected end of central directory header signature, not 0x#{signature.to_s(16)}")
end
read Int16 # number of this disk
read Int16 # disk start
read Int16 # number of entries in disk
entries_size = read Int16 # number of total entries
read UInt32 # size of the central directory
directory_offset = read UInt32 # offset of central directory
comment_length = read UInt16 # comment length
if comment_length != 0
@comment = @io.read_string(comment_length)
end
{entries_size, directory_offset}
end
private def read_entries(directory_offset, entries_size)
@io.pos = directory_offset
entries_size.times do
signature = read UInt32
if signature != Zip::CENTRAL_DIRECTORY_HEADER_SIGNATURE
raise Error.new("Expected directory header signature, not 0x#{signature.to_s(16)}")
end
entry = Entry.new(@io)
@entries << entry
@entries_by_filename[entry.filename] = entry
end
end
private def read(type)
@io.read_bytes(type, IO::ByteFormat::LittleEndian)
end
# An entry inside a `Zip::File`.
#
# Use the `open` method to read from it.
class Entry
include FileInfo
# :nodoc:
def initialize(@io : IO)
super(at_central_directory_header: io)
end
# Yields an `IO` to read this entry's contents.
# Multiple entries can be opened and read concurrently.
def open
@io.read_at(data_offset.to_i32, compressed_size.to_i32) do |io|
io = decompressor_for(io, is_sized: true)
checksum_reader = ChecksumReader.new(io, filename, verify: crc32)
yield checksum_reader
end
end
private getter(data_offset : UInt32) do
# Apparently a zip entry might have different extra bytes
# in the local file header and central directory header,
# so to know the data offset we must read them again.
#
# The bytes inside a local file header, from the signature
# and up to the extra length field, sum up 30 bytes.
#
# This 30 and 22 constants are burned inside the zip spec and
# will never change.
@io.read_at(offset.to_i32, 30) do |io|
# at least check that the signature is OK (these are 4 bytes)
signature = read(io, UInt32)
if signature != FileInfo::SIGNATURE
raise Compress::Zip::Error.new("Wrong local file header signature (expected 0x#{FileInfo::SIGNATURE.to_s(16)}, got 0x#{signature.to_s(16)})")
end
# Skip most of the headers except filename length and extra length
# (skip 22, so we already read 26 bytes)
io.skip(22)
# With these two we read 4 bytes more, so we are at 30 bytes
filename_length = read(io, UInt16)
extra_length = read(io, UInt16)
# The data of this entry comes at the local file header offset
# plus 30 bytes (the ones we just skipped) plus skipping the
# filename's bytes plus skipping the extra bytes.
@offset + 30 + filename_length + extra_length
end
end
end
end