| /* |
| ********************************************************************** |
| * Copyright (C) 1999, International Business Machines |
| * Corporation and others. All Rights Reserved. |
| ********************************************************************** |
| * Date Name Description |
| * 11/24/99 aliu Creation. |
| * 12/13/1999 srl Padded OffsetIndex to 4 byte values |
| ********************************************************************** |
| */ |
| |
| #ifndef TZDAT_H |
| #define TZDAT_H |
| |
| #include "unicode/utypes.h" |
| |
| /* This file defines the format of the memory-mapped data file |
| * containing system time zone data for icu. See also gentz |
| * and tz.pl. |
| * |
| * The format is designed specifically to allow certain operations: |
| * |
| * 1. Performing a fast binary search by name, and locating the |
| * corresponding zone data. This is the most important operation. |
| * It corresponds to the TimeZone::createTimeZone() method. |
| * |
| * 2. Performing a fast iteration over zones having a specific GMT |
| * offset. For this operation, the zone data need not be |
| * retrieved, just the IDs. This corresponds to the |
| * TimeZone::createAvailableIDs(int32_t) method. |
| * |
| * 3. Iterating over all zone IDs. This corresponds to the |
| * TimeZone::createAvailableIDs() method. |
| * |
| * The createAvailableIDs() methods return arrays of pointers to |
| * existing static UnicodeString IDs that it owns. Thus |
| * createAvailableIDs() needs a way to reference one of these IDs when |
| * iterating. Note that these IDs are _not_ stored in the |
| * memory-mapped data file, so we cannot store offsets. To solve this |
| * problem, we define a canonical index number for each zone. This |
| * index number runs from 0..n-1, where n is the total number of |
| * zones. The name table is stored in index number order, and we |
| * provide a table that is sorted by GMT offset with keys being GMT |
| * offset values and values being canonical index numbers. |
| * |
| * (Later, we might change createAvailableIDs() to return char* |
| * strings rather than UnicodeString pointers. In that case, this |
| * data structure could be modified to index into the name table |
| * directly.) |
| * |
| * In the following table, sizes are estimated sizes for a zone list |
| * of about 200 standard and 200 DST zones, which is typical in 1999. |
| * |
| * 0K TZHeader |
| * 2K Standard zone table (StandardZone[]) |
| * 4K DST zone table (Zone[]) |
| * 2K Index table, sorted by name, 4 bytes / zone |
| * This is a list of 'count' deltas sorted in ascending |
| * lexicographic order of name string. |
| * 1K Index table, sorted by gmtOffset then name. See |
| * OffsetIndex struct. |
| * 6K Name table - always last |
| * This is all the zone names, in lexicographic order, |
| * with zero bytes terminating each name. |
| * 14K TOTAL |
| * |
| * Any field with a name ending in "delta" is an offset value |
| * from the first byte of the TZHeader structure, unless otherwise |
| * specified. |
| * |
| * When using the name index table and the offset index table, |
| * code can determine whether an indexed zone is a standard |
| * zone or a DST zone by examining its delta. If the delta is |
| * less than dstDelta, it is a standard zone. Otherwise it |
| * is a DST zone. |
| */ |
| |
| struct TZHeader { |
| uint16_t versionYear; // e.g. "1999j" -> 1999 |
| uint16_t versionSuffix; // e.g. "1999j" -> 10 |
| |
| uint32_t count; // standardCount + dstCount |
| uint32_t standardCount; // # of standard zones |
| uint32_t dstCount; // # of dst zones |
| |
| uint32_t nameIndexDelta; // delta to name index table |
| uint32_t offsetIndexDelta; // delta to gmtOffset index table |
| uint32_t standardDelta; // delta to standard zones ALWAYS < dstDelta |
| uint32_t dstDelta; // delta to dst zones ALWAYS > standardDelta |
| uint32_t nameTableDelta; // delta to name (aka ID) table |
| |
| /* NOTE: Currently the standard and DST zone counts and deltas are |
| * unused (all zones are referenced via the name index table). |
| * However, they are retained for possible future use. |
| */ |
| }; |
| |
| struct StandardZone { |
| int32_t gmtOffset; // gmt offset in milliseconds |
| }; |
| |
| struct TZRule { |
| uint8_t month; // month |
| int8_t dowim; // dowim |
| int8_t dow; // dow |
| uint16_t time; // time in minutes |
| int8_t mode; // (w/s/u) == TimeZone::TimeMode enum as int |
| }; |
| |
| struct DSTZone { |
| int32_t gmtOffset; // gmtoffset in milliseconds |
| uint16_t dstSavings; // savings in minutes |
| TZRule onsetRule; // onset rule |
| TZRule ceaseRule; // cease rule |
| }; |
| |
| /** |
| * This variable-sized struct makes up the offset index table. To get |
| * from one table entry to the next, add the nextEntryDelta. If the |
| * nextEntryDelta is zero then this is the last entry. The offset |
| * index table is designed for sequential access, not random access. |
| * Given the small number of distinct offsets (39 in 1999j), this |
| * suffices. |
| * |
| * The value of default is the zone within this list that should be |
| * selected as the default zone in the absence of any other |
| * discriminating information. This information comes from the file |
| * tz.default. Note that this is itself a zone number, like |
| * those in the array starting at &zoneNumber. |
| * |
| * The gmtOffset field must be 4-aligned for some architectures. To |
| * ensure this, we do two things: 1. The entire struct is 4-aligned. |
| * 2. The gmtOffset is placed at a 4-aligned position within the |
| * struct. 3. The size of the whole structure is padded out to 4n |
| * bytes. We achieve this last condition by adding two bytes of |
| * padding after the last zoneNumber, if count is _even_. That is, |
| * the struct size is 10+2count+padding, where padding is (count%2==0 |
| * ? 2:0). See gentz for implementation. |
| */ |
| struct OffsetIndex { |
| int32_t gmtOffset; // in ms - 4-aligned |
| uint16_t nextEntryDelta; |
| uint16_t defaultZone; // a zone number from 0..TZHeader.count-1 |
| uint16_t count; |
| uint16_t zoneNumber; // There are actually 'count' uint16_t's here |
| // Following the 'count' uint16_t's starting with zoneNumber, |
| // there may be two bytes of padding to make the whole struct have |
| // a size of 4n. nextEntryDelta skips over any padding. |
| }; |
| |
| // Information used to identify and validate the data |
| |
| #define TZ_DATA_NAME "tz" |
| #define TZ_DATA_TYPE "dat" |
| |
| // Fields in UDataInfo: |
| static const char TZ_SIG[] = "zone"; // dataFormat |
| static const int8_t TZ_FORMAT_VERSION = 2; // formatVersion[0] |
| |
| #endif |