scripts: no need for pytz to generate tz list

code/scripts/format_tzdata.py

@@ -0,0 +1,143 @@
+import argparse
+import mmap
+import os
+import pathlib
+import re
+import sys
+
+from importlib import resources
+
+import tzdata  # https://tzdata.readthedocs.io/en/latest/
+
+
+def tzdata_version():
+    return f"Generated with *{tzdata.IANA_VERSION=} {tzdata.__version__=}*"
+
+
+def maybe_fix_value(value):
+    return re.sub(r"<[^>]*>", "UNK", value)
+
+
+def maybe_skip_zone(zone):
+    return zone.startswith("Etc/") or zone in ("GB-Eire", "W-SU")
+
+
+def utc_alias(zone):
+    return zone in (
+        "Universal",
+        "UTC",
+        "UCT",
+        "Zulu",
+        "GMT",
+        "GMT+0",
+        "GMT-0",
+        "GMT0",
+        "Greenwich",
+    )
+
+
+def tzdata_resource_from_name(name):
+    pair = name.rsplit("/", 1)
+    if len(pair) == 1:
+        return resources.files("tzdata.zoneinfo") / pair[0]
+
+    return resources.files(f'tzdata.zoneinfo.{pair[0].replace("/", ".")}') / pair[1]
+
+
+def make_zones_list(zones):
+    with open(zones, "r") as f:
+        zones = [zone.strip() for zone in f.readlines()]
+
+    return zones
+
+
+def make_zones(args):
+    out = []
+
+    for zone in make_zones_list(args.zones):
+        target = tzdata_resource_from_name(zone)
+        with tzdata_resource_from_name(zone).open("rb") as f:
+            magic = f.read(4)
+            if magic != b"TZif":
+                continue
+
+            m = mmap.mmap(f.fileno(), 0, prot=mmap.PROT_READ)
+            newline = m.rfind(b"\n", 0, len(m) - 1)
+            if newline < 0:
+                continue
+
+            m.seek(newline + 1)
+            tz = m.readline().strip()
+
+            out.append([zone, tz.decode("ascii")])
+
+    out.sort(key=lambda x: x[0])
+    return out
+
+
+def markdown(zones):
+    utcs = []
+    rows = []
+
+    for name, value in zones:
+        if utc_alias(name):
+            utcs.append(name)
+            continue
+
+        if maybe_skip_zone(name):
+            continue
+
+        rows.append(f"|{name}|{maybe_fix_value(value)}|")
+
+    print("|Name|Value|")
+    print("|---|---|")
+    for name in utcs:
+        print(f"|{name}|UTC0|")
+
+    last = ""
+    for row in rows:
+        prefix, _, _ = row.partition("/")
+        if last != prefix:
+            last = prefix
+            print("|||")
+        print(row)
+    print()
+    print("---")
+    print()
+    print(tzdata_version())
+
+
+def header(zones):
+    print(f"// ! ! ! DO NOT EDIT, AUTOMATICALLY GENERATED ! ! !")
+    print(f"// {tzdata_version()}")
+    print()
+    print("#pragma once")
+    print()
+    for name, value in zones:
+        print(f'#define\tTZ_{name.replace("/", "_")}\tPSTR("{value}")')
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--format",
+        default="markdown",
+        choices=["markdown", "header"],
+    )
+    parser.add_argument(
+        "--zones",
+        help="Zone names, one per line",
+        default=os.path.join(os.path.dirname(tzdata.__file__), "zones"),
+    )
+    parser.add_argument(
+        "--root",
+        help="Where do we get raw zoneinfo files from",
+        default=os.path.join(os.path.dirname(tzdata.__file__), "zoneinfo"),
+    )
+    args = parser.parse_args()
+
+    zones = make_zones(args)
+    if args.format == "markdown":
+        markdown(zones)
+    elif args.format == "header":
+        header(zones)