/
zoneinfo_timezone_info.rb
516 lines (433 loc) · 21.6 KB
/
zoneinfo_timezone_info.rb
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module TZInfo
# An InvalidZoneinfoFile exception is raised if an attempt is made to load an
# invalid zoneinfo file.
class InvalidZoneinfoFile < StandardError
end
# Represents a timezone defined by a compiled zoneinfo TZif (\0, 2 or 3) file.
#
# @private
class ZoneinfoTimezoneInfo < TransitionDataTimezoneInfo #:nodoc:
# The year to generate transitions up to.
#
# @private
GENERATE_UP_TO = RubyCoreSupport.time_supports_64bit ? Time.now.utc.year + 100 : 2037
# Minimum supported timestamp (inclusive).
#
# Time.utc(1700, 1, 1).to_i
MIN_TIMESTAMP = -8520336000
# Maximum supported timestamp (exclusive).
#
# Time.utc(2500, 1, 1).to_i
MAX_TIMESTAMP = 16725225600
# Constructs the new ZoneinfoTimezoneInfo with an identifier, path
# to the file and parser to use to parse the POSIX-like TZ string.
def initialize(identifier, file_path, posix_tz_parser)
super(identifier)
File.open(file_path, 'rb') do |file|
parse(file, posix_tz_parser)
end
end
private
# Unpack will return unsigned 32-bit integers. Translate to
# signed 32-bit.
def make_signed_int32(long)
long >= 0x80000000 ? long - 0x100000000 : long
end
# Unpack will return a 64-bit integer as two unsigned 32-bit integers
# (most significant first). Translate to signed 64-bit
def make_signed_int64(high, low)
unsigned = (high << 32) | low
unsigned >= 0x8000000000000000 ? unsigned - 0x10000000000000000 : unsigned
end
# Read bytes from file and check that the correct number of bytes could
# be read. Raises InvalidZoneinfoFile if the number of bytes didn't match
# the number requested.
def check_read(file, bytes)
result = file.read(bytes)
unless result && result.length == bytes
raise InvalidZoneinfoFile, "Expected #{bytes} bytes reading '#{file.path}', but got #{result ? result.length : 0} bytes"
end
result
end
# Zoneinfo files don't include the offset from standard time (std_offset)
# for DST periods. Derive the base offset (utc_offset) where DST is
# observed from either the previous or next non-DST period.
#
# Returns the index of the offset to be used prior to the first
# transition.
def derive_offsets(transitions, offsets)
# The first non-DST offset (if there is one) is the offset observed
# before the first transition. Fallback to the first DST offset if there
# are no non-DST offsets.
first_non_dst_offset_index = offsets.index {|o| !o[:is_dst] }
first_offset_index = first_non_dst_offset_index || 0
return first_offset_index if transitions.empty?
# Determine the utc_offset of the next non-dst offset at each transition.
utc_offset_from_next = nil
transitions.reverse_each do |transition|
offset = offsets[transition[:offset]]
if offset[:is_dst]
transition[:utc_offset_from_next] = utc_offset_from_next if utc_offset_from_next
else
utc_offset_from_next = offset[:utc_total_offset]
end
end
utc_offset_from_previous = first_non_dst_offset_index ? offsets[first_non_dst_offset_index][:utc_total_offset] : nil
defined_offsets = {}
transitions.each do |transition|
offset_index = transition[:offset]
offset = offsets[offset_index]
utc_total_offset = offset[:utc_total_offset]
if offset[:is_dst]
utc_offset_from_next = transition[:utc_offset_from_next]
difference_to_previous = (utc_total_offset - (utc_offset_from_previous || utc_total_offset)).abs
difference_to_next = (utc_total_offset - (utc_offset_from_next || utc_total_offset)).abs
utc_offset = if difference_to_previous == 3600
utc_offset_from_previous
elsif difference_to_next == 3600
utc_offset_from_next
elsif difference_to_previous > 0 && difference_to_next > 0
difference_to_previous < difference_to_next ? utc_offset_from_previous : utc_offset_from_next
elsif difference_to_previous > 0
utc_offset_from_previous
elsif difference_to_next > 0
utc_offset_from_next
else
# No difference, assume a 1 hour offset from standard time.
utc_total_offset - 3600
end
if !offset[:utc_offset]
offset[:utc_offset] = utc_offset
defined_offsets[offset] = offset_index
elsif offset[:utc_offset] != utc_offset
# An earlier transition has already derived a different
# utc_offset. Define a new offset or reuse an existing identically
# defined offset.
new_offset = offset.dup
new_offset[:utc_offset] = utc_offset
offset_index = defined_offsets[new_offset]
unless offset_index
offsets << new_offset
offset_index = offsets.length - 1
defined_offsets[new_offset] = offset_index
end
transition[:offset] = offset_index
end
else
utc_offset_from_previous = utc_total_offset
end
end
first_offset_index
end
# Remove transitions before a minimum supported value. If there is not a
# transition exactly on the minimum supported value move the latest from
# before up to the minimum supported value.
def remove_unsupported_negative_transitions(transitions, min_supported)
result = transitions.drop_while {|t| t[:at] < min_supported }
if result.empty? || (result[0][:at] > min_supported && result.length < transitions.length)
last_before = transitions[-1 - result.length]
last_before[:at] = min_supported
[last_before] + result
else
result
end
end
# Determines if the offset from a transition matches the offset from a
# rule. This is a looser match than TimezoneOffset#==, not requiring that
# the utc_offset and std_offset both match (which have to be derived for
# transitions, but are known for rules.
def offset_matches_rule?(offset, rule_offset)
offset[:utc_total_offset] == rule_offset.utc_total_offset &&
offset[:is_dst] == rule_offset.dst? &&
offset[:abbr] == rule_offset.abbreviation.to_s
end
# Determins if the offset from a transition exactly matches the offset
# from a rule.
def offset_equals_rule?(offset, rule_offset)
offset_matches_rule?(offset, rule_offset) &&
(offset[:utc_offset] || (offset[:is_dst] ? offset[:utc_total_offset] - 3600 : offset[:utc_total_offset])) == rule_offset.utc_offset
end
# Finds an offset hash that is an exact match to the rule offset specified.
def find_existing_offset_index(offsets, rule_offset)
offsets.find_index {|o| offset_equals_rule?(o, rule_offset) }
end
# Gets an existing matching offset index or adds a new offset hash for a
# rule offset.
def get_rule_offset_index(offsets, offset)
index = find_existing_offset_index(offsets, offset)
unless index
index = offsets.length
offsets << {:utc_total_offset => offset.utc_total_offset, :utc_offset => offset.utc_offset, :is_dst => offset.dst?, :abbr => offset.abbreviation}
end
index
end
# Gets a hash mapping rule offsets to indexes in offsets, creating new
# offset hashes if required.
def get_rule_offset_indexes(offsets, annual_rules)
{
annual_rules.std_offset => get_rule_offset_index(offsets, annual_rules.std_offset),
annual_rules.dst_offset => get_rule_offset_index(offsets, annual_rules.dst_offset)
}
end
# Converts an array of rule transitions to hashes.
def convert_transitions_to_hashes(offset_indexes, transitions)
transitions.map {|t| {:at => t.at.to_i, :offset => offset_indexes[t.offset]} }
end
# Apply the rules from the TZ string when there were no defined
# transitions. Checks for a matching offset. Returns the rules-based
# constant offset or generates transitions from 1970 until 100 years into
# the future (at the time of loading zoneinfo_timezone_info.rb) or 2037 if
# limited to 32-bit Times.
def apply_rules_without_transitions(file, offsets, first_offset_index, rules)
first_offset = offsets[first_offset_index]
if rules.kind_of?(TimezoneOffset)
unless offset_matches_rule?(first_offset, rules)
raise InvalidZoneinfoFile, "Constant offset POSIX-style TZ string does not match constant offset in file '#{file.path}'."
end
first_offset[:utc_offset] = rules.utc_offset
[]
else
transitions = 1970.upto(GENERATE_UP_TO).map {|y| rules.transitions(y) }.flatten
first_transition = transitions[0]
if offset_matches_rule?(first_offset, first_transition.previous_offset)
# Correct the first offset if it isn't an exact match.
first_offset[:utc_offset] = first_transition.previous_offset.utc_offset
else
# Not transitioning from the designated first offset.
if offset_matches_rule?(first_offset, first_transition.offset)
# Correct the first offset if it isn't an exact match.
first_offset[:utc_offset] = first_transition.offset.utc_offset
# Skip an unnecessary transition to the first offset.
transitions.shift
end
# If the first offset doesn't match either the offset or previous
# offset, then it will be retained.
end
offset_indexes = get_rule_offset_indexes(offsets, rules)
convert_transitions_to_hashes(offset_indexes, transitions)
end
end
# Validates the rules offset against the offset of the last defined
# transition. Replaces the transition with an equivalent using the rules
# offset if the rules give a different definition for the base offset.
def replace_last_transition_offset_if_valid_and_needed(file, transitions, offsets)
last_transition = transitions.last
last_offset = offsets[last_transition[:offset]]
rule_offset = yield last_offset
unless offset_matches_rule?(last_offset, rule_offset)
raise InvalidZoneinfoFile, "Offset from POSIX-style TZ string does not match final transition in file '#{file.path}'."
end
# The total_utc_offset and abbreviation must always be the same. The
# base utc_offset and std_offset might differ. In which case the rule
# should be used as it will be more precise.
last_offset[:utc_offset] = rule_offset.utc_offset
last_transition
end
# todo: port over validate_and_fix_last_defined_transition_offset
# when fixing the previous offset will need to define a new one
# Validates the offset indicated to be observed by the rules before the
# first generated transition against the offset of the last defined
# transition.
#
# Fix the last defined transition if it differ on just base/std offsets
# (which are derived). Raise an error if the observed UTC offset or
# abbreviations differ.
def validate_and_fix_last_defined_transition_offset(file, offsets, last_defined, first_rule_offset)
offset_of_last_defined = offsets[last_defined[:offset]]
if offset_equals_rule?(offset_of_last_defined, first_rule_offset)
last_defined
else
if offset_matches_rule?(offset_of_last_defined, first_rule_offset)
# The same overall offset, but differing in the base or std
# offset (which are derived). Correct by using the rule.
offset_index = get_rule_offset_index(offsets, first_rule_offset)
{:at => last_defined[:at], :offset => offset_index}
else
raise InvalidZoneinfoFile, "The first offset indicated by the POSIX-style TZ string did not match the final defined offset in file '#{file.path}'."
end
end
end
# Apply the rules from the TZ string when there were defined transitions.
# Checks for a matching offset with the last transition. Redefines the
# last transition if required and if the rules don't specific a constant
# offset, generates transitions until 100 years into the future (at the
# time of loading zoneinfo_timezone_info.rb) or 2037 if limited to 32-bit
# Times.
def apply_rules_with_transitions(file, transitions, offsets, first_offset_index, rules)
last_defined = transitions[-1]
if rules.kind_of?(TimezoneOffset)
transitions[-1] = validate_and_fix_last_defined_transition_offset(file, offsets, last_defined, rules)
else
previous_offset_index = transitions.length > 1 ? transitions[-2][:offset] : first_offset_index
previous_offset = offsets[previous_offset_index]
last_year = (Time.at(last_defined[:at]).utc + previous_offset[:utc_total_offset]).year
if last_year <= GENERATE_UP_TO
last_defined_offset = offsets[last_defined[:offset]]
generated = rules.transitions(last_year).find_all do |t|
t.at > last_defined[:at] && !offset_matches_rule?(last_defined_offset, t.offset)
end
generated += (last_year + 1).upto(GENERATE_UP_TO).map {|y| rules.transitions(y) }.flatten
unless generated.empty?
transitions[-1] = validate_and_fix_last_defined_transition_offset(file, offsets, last_defined, generated[0].previous_offset)
rule_offset_indexes = get_rule_offset_indexes(offsets, rules)
transitions.concat(convert_transitions_to_hashes(rule_offset_indexes, generated))
end
end
end
end
# Defines an offset for the timezone based on the given index and offset
# Hash.
def define_offset(index, offset)
utc_total_offset = offset[:utc_total_offset]
utc_offset = offset[:utc_offset]
if utc_offset
# DST offset with base utc_offset derived by derive_offsets.
std_offset = utc_total_offset - utc_offset
elsif offset[:is_dst]
# DST offset unreferenced by a transition (offset in use before the
# first transition). No derived base UTC offset, so assume 1 hour
# DST.
utc_offset = utc_total_offset - 3600
std_offset = 3600
else
# Non-DST offset.
utc_offset = utc_total_offset
std_offset = 0
end
offset index, utc_offset, std_offset, RubyCoreSupport.untaint(offset[:abbr]).to_sym
end
# Parses a zoneinfo file and intializes the DataTimezoneInfo structures.
def parse(file, posix_tz_parser)
magic, version, ttisutccnt, ttisstdcnt, leapcnt, timecnt, typecnt, charcnt =
check_read(file, 44).unpack('a4 a x15 NNNNNN')
if magic != 'TZif'
raise InvalidZoneinfoFile, "The file '#{file.path}' does not start with the expected header."
end
if version == '2' || version == '3'
# Skip the first 32-bit section and read the header of the second
# 64-bit section. The 64-bit section is always used even if the
# runtime platform doesn't support 64-bit timestamps. In "slim" format
# zoneinfo files the 32-bit section will be empty.
file.seek(timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisutccnt, IO::SEEK_CUR)
prev_version = version
magic, version, ttisutccnt, ttisstdcnt, leapcnt, timecnt, typecnt, charcnt =
check_read(file, 44).unpack('a4 a x15 NNNNNN')
unless magic == 'TZif' && (version == prev_version)
raise InvalidZoneinfoFile, "The file '#{file.path}' contains an invalid 64-bit section header."
end
using_64bit = true
elsif version != '3' && version != '2' && version != "\0"
raise InvalidZoneinfoFile, "The file '#{file.path}' contains a version of the zoneinfo format that is not currently supported."
else
using_64bit = false
end
unless leapcnt == 0
raise InvalidZoneinfoFile, "The zoneinfo file '#{file.path}' contains leap second data. TZInfo requires zoneinfo files that omit leap seconds."
end
transitions = []
if using_64bit
timecnt.times do |i|
high, low = check_read(file, 8).unpack('NN'.freeze)
transition_time = make_signed_int64(high, low)
transitions << {:at => transition_time}
end
else
timecnt.times do |i|
transition_time = make_signed_int32(check_read(file, 4).unpack('N'.freeze)[0])
transitions << {:at => transition_time}
end
end
timecnt.times do |i|
localtime_type = check_read(file, 1).unpack('C'.freeze)[0]
transitions[i][:offset] = localtime_type
end
offsets = []
typecnt.times do |i|
gmtoff, isdst, abbrind = check_read(file, 6).unpack('NCC'.freeze)
gmtoff = make_signed_int32(gmtoff)
isdst = isdst == 1
offset = {:utc_total_offset => gmtoff, :is_dst => isdst, :abbr_index => abbrind}
unless isdst
offset[:utc_offset] = gmtoff
end
offsets << offset
end
abbrev = check_read(file, charcnt)
if using_64bit
# Skip to the POSIX-style TZ string.
file.seek(ttisstdcnt + ttisutccnt, IO::SEEK_CUR) # + leapcnt * 8, but leapcnt is checked above and guaranteed to be 0.
tz_string_start = check_read(file, 1)
raise InvalidZoneinfoFile, "Expected newline starting POSIX-style TZ string in file '#{file.path}'." unless tz_string_start == "\n"
tz_string = RubyCoreSupport.force_encoding(file.readline("\n"), 'UTF-8')
raise InvalidZoneinfoFile, "Expected newline ending POSIX-style TZ string in file '#{file.path}'." unless tz_string.chomp!("\n")
begin
rules = posix_tz_parser.parse(tz_string)
rescue InvalidPosixTimeZone => e
raise InvalidZoneinfoFile, "Failed to parse POSIX-style TZ string in file '#{file.path}': #{e}"
end
else
rules = nil
end
offsets.each do |o|
abbrev_start = o[:abbr_index]
raise InvalidZoneinfoFile, "Abbreviation index is out of range in file '#{file.path}'" unless abbrev_start < abbrev.length
abbrev_end = abbrev.index("\0", abbrev_start)
raise InvalidZoneinfoFile, "Missing abbreviation null terminator in file '#{file.path}'" unless abbrev_end
o[:abbr] = RubyCoreSupport.force_encoding(abbrev[abbrev_start...abbrev_end], 'UTF-8')
end
transitions.each do |t|
if t[:offset] < 0 || t[:offset] >= offsets.length
raise InvalidZoneinfoFile, "Invalid offset referenced by transition in file '#{file.path}'."
end
end
# Derive the offsets from standard time (std_offset).
first_offset_index = derive_offsets(transitions, offsets)
# Filter out transitions that are not supported by Time on this
# platform.
unless transitions.empty?
if !RubyCoreSupport.time_supports_negative
transitions = remove_unsupported_negative_transitions(transitions, 0)
elsif !RubyCoreSupport.time_supports_64bit
transitions = remove_unsupported_negative_transitions(transitions, -2**31)
else
# Ignore transitions that occur outside of a defined window. The
# transition index cannot handle a large range of transition times.
#
# This is primarily intended to ignore the far in the past
# transition added in zic 2014c (at timestamp -2**63 in zic 2014c
# and at the approximate time of the big bang from zic 2014d).
#
# Assumes MIN_TIMESTAMP is less than -2**31.
transitions = remove_unsupported_negative_transitions(transitions, MIN_TIMESTAMP)
end
if !RubyCoreSupport.time_supports_64bit
i = transitions.find_index {|t| t[:at] >= 2**31 }
had_later_transition = !!i
transitions = transitions.first(i) if i
else
had_later_transition = false
end
end
if rules && !had_later_transition
if transitions.empty?
transitions = apply_rules_without_transitions(file, offsets, first_offset_index, rules)
else
apply_rules_with_transitions(file, transitions, offsets, first_offset_index, rules)
end
end
define_offset(first_offset_index, offsets[first_offset_index])
used_offset_indexes = transitions.map {|t| t[:offset] }.to_set
offsets.each_with_index do |o, i|
define_offset(i, o) if i != first_offset_index && used_offset_indexes.include?(i)
end
# Ignore transitions that occur outside of a defined window. The
# transition index cannot handle a large range of transition times.
transitions.each do |t|
at = t[:at]
break if at >= MAX_TIMESTAMP
time = Time.at(at).utc
transition time.year, time.mon, t[:offset], at
end
end
end
end