Update timezone database information. [EN-17:09]

Approved by:	so

1 files changed, 156 insertions, 0 deletions

diff --git a/contrib/tzdata/zishrink.awk b/contrib/tzdata/zishrink.awk
new file mode 100644
index 0000000..02c883a
--- /dev/null
+++ b/contrib/tzdata/zishrink.awk
@@ -0,0 +1,156 @@
+# Convert tzdata source into a smaller version of itself.
+
+# Contributed by Paul Eggert.  This file is in the public domain.
+
+# This is not a general-purpose converter; it is designed for current tzdata.
+# 'zic' should treat this script's output as if it were identical to
+# this script's input.
+
+
+# Return a new rule name.
+# N_RULE_NAMES keeps track of how many rule names have been generated.
+
+function gen_rule_name(alphabet, base, rule_name, n, digit)
+{
+  alphabet = ""
+  alphabet = alphabet "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+  alphabet = alphabet "abcdefghijklmnopqrstuvwxyz"
+  alphabet = alphabet "!$%&'()*+,./:;<=>?@[\\]^_`{|}~"
+  base = length(alphabet)
+  rule_name = ""
+  n = n_rule_names++
+
+  do {
+    n -= rule_name && n <= base
+    digit = n % base
+    rule_name = substr(alphabet, digit + 1, 1) rule_name
+    n = (n - digit) / base
+  } while (n);
+
+  return rule_name
+}
+
+# Process an input line and save it for later output.
+
+function process_input_line(line, field, end, i, n, startdef)
+{
+  # Remove comments, normalize spaces, and append a space to each line.
+  sub(/#.*/, "", line)
+  line = line " "
+  gsub(/[[:space:]]+/, " ", line)
+
+  # Abbreviate keywords.  Do not abbreviate "Link" to just "L",
+  # as pre-2017c zic erroneously diagnoses "Li" as ambiguous.
+  sub(/^Link /, "Li ", line)
+  sub(/^Rule /, "R ", line)
+  sub(/^Zone /, "Z ", line)
+
+  # SystemV rules are not needed.
+  if (line ~ /^R SystemV /) return
+
+  # Replace FooAsia rules with the same rules without "Asia", as they
+  # are duplicates.
+  if (match(line, /[^ ]Asia /)) {
+    if (line ~ /^R /) return
+    line = substr(line, 1, RSTART) substr(line, RSTART + 5)
+  }
+
+  # Abbreviate times.
+  while (match(line, /[: ]0+[0-9]/))
+    line = substr(line, 1, RSTART) substr(line, RSTART + RLENGTH - 1)
+  while (match(line, /:0[^:]/))
+    line = substr(line, 1, RSTART - 1) substr(line, RSTART + 2)
+
+  # Abbreviate weekday names.  Do not abbreviate "Sun" and "Sat", as
+  # pre-2017c zic erroneously diagnoses "Su" and "Sa" as ambiguous.
+  while (match(line, / (last)?(Mon|Wed|Fri)[ <>]/)) {
+    end = RSTART + RLENGTH
+    line = substr(line, 1, end - 4) substr(line, end - 1)
+  }
+  while (match(line, / (last)?(Tue|Thu)[ <>]/)) {
+    end = RSTART + RLENGTH
+    line = substr(line, 1, end - 3) substr(line, end - 1)
+  }
+
+  # Abbreviate "max", "only" and month names.
+  # Do not abbreviate "min", as pre-2017c zic erroneously diagnoses "mi"
+  # as ambiguous.
+  gsub(/ max /, " ma ", line)
+  gsub(/ only /, " o ", line)
+  gsub(/ Jan /, " Ja ", line)
+  gsub(/ Feb /, " F ", line)
+  gsub(/ Apr /, " Ap ", line)
+  gsub(/ Aug /, " Au ", line)
+  gsub(/ Sep /, " S ", line)
+  gsub(/ Oct /, " O ", line)
+  gsub(/ Nov /, " N ", line)
+  gsub(/ Dec /, " D ", line)
+
+  # Strip leading and trailing space.
+  sub(/^ /, "", line)
+  sub(/ $/, "", line)
+
+  # Remove unnecessary trailing zero fields.
+  sub(/ 0+$/, "", line)
+
+  # Remove unnecessary trailing days-of-month "1".
+  if (match(line, /[[:alpha:]] 1$/))
+    line = substr(line, 1, RSTART)
+
+  # Remove unnecessary trailing " Ja" (for January).
+  sub(/ Ja$/, "", line)
+
+  n = split(line, field)
+
+  # Abbreviate rule names.
+  i = field[1] == "Z" ? 4 : field[1] == "Li" ? 0 : 2
+  if (i && field[i] ~ /^[^-+0-9]/) {
+    if (!rule[field[i]])
+      rule[field[i]] = gen_rule_name()
+    field[i] = rule[field[i]]
+  }
+
+  # If this zone supersedes an earlier one, delete the earlier one
+  # from the saved output lines.
+  startdef = ""
+  if (field[1] == "Z")
+    zonename = startdef = field[2]
+  else if (field[1] == "Li")
+    zonename = startdef = field[3]
+  else if (field[1] == "R")
+    zonename = ""
+  if (startdef) {
+    i = zonedef[startdef]
+    if (i) {
+      do
+	output_line[i - 1] = ""
+      while (output_line[i++] ~ /^[-+0-9]/);
+    }
+  }
+  zonedef[zonename] = nout + 1
+
+  # Save the line for later output.
+  line = field[1]
+  for (i = 2; i <= n; i++)
+    line = line " " field[i]
+  output_line[nout++] = line
+}
+
+function output_saved_lines(i)
+{
+  for (i = 0; i < nout; i++)
+    if (output_line[i])
+      print output_line[i]
+}
+
+BEGIN {
+  print "# This zic input file is in the public domain."
+}
+
+/^[[:space:]]*[^#[:space:]]/ {
+  process_input_line($0)
+}
+
+END {
+  output_saved_lines()
+}