AuroraMiddleware/scuffed-code
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

ICU-1007 description of the unorm.dat file format

Browse Source 
X-SVN-Rev: 5634
This commit is contained in:
Markus Scherer 2001-08-30 20:37:59 +00:00
parent 91985fb45f
commit ae7730027b
1 changed files with 233 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

244
icu4c/source/common/unormimp.h
View File

@ -24,6 +24,12 @@
#endif #endif
#include "ustr_imp.h" #include "ustr_imp.h"
/*
* This new implementation of the normalization code loads its data from
* unorm.dat, which is generated with the gennorm tool.
* The format of that file is described at the end of this file.
*/
/* trie constants */ /* trie constants */
enum { enum {
/** /**
@ -63,17 +69,6 @@ enum {
_NORM_COMBINES_BACK=0x80, _NORM_COMBINES_BACK=0x80,
_NORM_COMBINES_ANY=0xc0, _NORM_COMBINES_ANY=0xc0,
#if 0
_NORM_CC_TYPE_MASK=0xc0,
_NORM_CC_TYPE_NONE=0, /* no cc - lead and trail cc are 0 */
_NORM_CC_TYPE_SAME=0x40, /* lead and trail cc are same, non-zero, and in value */
_NORM_CC_TYPE_TRAIL=0x80, /* lead cc=0, trail cc in value */
_NORM_CC_TYPE_TWO=0xc0, /* 0 != lead cc < trail cc, lead cc in value, trail cc in extra data */
_NORM_CC_HAS_LEAD=0x40, /* side effect of the above flags: if and only if bit 6 is 0, then lead cc is 0 */
_NORM_CC_HAS_LEAD_HAS_TRAIL=0x80, /* if(has lead) then one can check for (has trail) instead of (&cc mask==same/two) */
#endif
_NORM_CC_SHIFT=8, /* UnicodeData.txt combining class in bits 15..8 */ _NORM_CC_SHIFT=8, /* UnicodeData.txt combining class in bits 15..8 */
_NORM_CC_MASK=0xff00, _NORM_CC_MASK=0xff00,
@ -304,4 +299,231 @@ unorm_prevCompose(UChar *dest, int32_t destCapacity,
#endif #endif
/**
* Description of the format of unorm.dat.
*
* For more details of how to use the data structures see the code
* in unorm.cpp (runtime normalization code) and
* in gennorm.c and gennorm/store.c (build-time data generation).
*
*
* - Overall partition
*
* unorm.dat customarily begins with a UDataInfo structure, see udata.h and .c.
* After that there are the following arrays:
*
* uint16_t indexes[_NORM_INDEX_TOP]; -- _NORM_INDEX_TOP=indexes[0]=indexes[_NORM_INDEX_COUNT]
*
* uint16_t stage1[stage1Top]; -- stage1Top=indexes[_NORM_INDEX_TRIE_INDEX_COUNT]
* uint32_t norm32Table[norm32TableTop]; -- norm32TableTop=indexes[_NORM_INDEX_TRIE_DATA_COUNT]
*
* uint16_t extraData[extraDataTop]; -- extraDataTop=indexes[_NORM_INDEX_UCHAR_COUNT]
* uint16_t combiningTable[combiningTableTop]; -- combiningTableTop=indexes[_NORM_INDEX_COMBINE_DATA_COUNT]
*
* uint16_t fcdStage1[fcdStage1Top]; -- fcdStage1Top=indexes[_NORM_INDEX_FCD_TRIE_INDEX_COUNT]
* uint16_t fcdTable[fcdTableTop]; -- fcdTableTop=indexes[_NORM_INDEX_FCD_TRIE_DATA_COUNT]
*
*
* The indexes array contains lengths of the following arrays (and its own length)
* as well as the following values:
* indexes[_NORM_INDEX_COUNT]=_NORM_INDEX_TOP
* -- length of indexes[]
* indexes[_NORM_INDEX_TRIE_SHIFT]=_NORM_TRIE_SHIFT
* -- for trie indexes: shift UChars by this much
* indexes[_NORM_INDEX_COMBINE_FWD_COUNT]=combineFwdTop
* -- one more than the highest combining index computed for forward-only-combining characters
* indexes[_NORM_INDEX_COMBINE_BOTH_COUNT]=combineBothTop-combineFwdTop
* -- number of combining indexes computed for both-ways-combining characters
* indexes[_NORM_INDEX_COMBINE_BACK_COUNT]=combineBackTop-combineBothTop
* -- number of combining indexes computed for backward-only-combining characters
*
*
* - Tries
*
* The main structures are two trie tables ("compact arrays"),
* each with one index array and one data array.
* Generally, tries use the upper bits of an input value to access the index array,
* which results in an index to the data array where a block of values is stored.
* The lower bits of the same input value are then used to index inside that data
* block to get to the specific data element for the input value.
*
* In order to use each trie with a single base pointer, the index values in
* the index array are offset by the length of the index array.
* With this, a base pointer to the trie index array is also directly used
* with the index value to access the trie data array.
* For example, if trieIndex[n] refers to offset m in trieData[] then
* the actual value is q=trieIndex[n]=lengthof(trieIndex)+m
* and you access trieIndex[q] instead of trieData[m].
*
*
* - Folded tries
*
* The tries here are extended to work for lookups on UTF-16 strings with
* supplementary characters encoded with surrogate pairs.
* They are called "folded tries".
*
* Each 16-bit code unit (UChar, not code point UChar32) is looked up this way.
* If there is relevant data for any given code unit, then the data or the code unit
* must be checked for whether it is a leading surrogate.
* If so, then the data contains an offset that is used together with the following
* trailing surrogate code unit value for a second trie access.
* This uses a portion of the index array beyond what is accessible with 16-bit units,
* i.e., it uses the part of the trie index array starting at its index
* 0x10000>>_NORM_TRIE_SHIFT.
*
* Such folded tries are useful when processing UTF-16 strings, especially if
* many code points do not have relevant data, so that the check for
* surrogates and the second trie lookup are rarely performed.
* It avoids the overhead of a double-index trie that is necessary if the input
* is always with 21-bit code points.
*
*
* - Tries in unorm.dat
*
* The first trie consists of the stage1 and the norm32Table arrays.
* It provides data for the NF* quick checks and normalization.
* The second trie consists of the fcdStage1 and the fcdTable arrays
* and provides data just for FCD checks.
*
*
* - norm32 data words from the first trie
*
* The norm32Table contains one 32-bit word "norm32" per code point.
* It contains the following bit fields:
* 31..16 extra data index, _NORM_EXTRA_SHIFT is used to shift this field down
* if this index is <_NORM_EXTRA_INDEX_TOP then it is an index into
* extraData[] where variable-length normalization data for this
* code point is found
* if this index is <_NORM_EXTRA_INDEX_TOP+_NORM_EXTRA_SURROGATE_TOP
* then this is a norm32 for a leading surrogate, and the index
* value is used together with the following trailing surrogate
* code unit in the second trie access
* if this index is >=_NORM_EXTRA_INDEX_TOP+_NORM_EXTRA_SURROGATE_TOP
* then this is a norm32 for a "special" character,
* i.e., the character is a Hangul syllable or a Jamo
* see _NORM_EXTRA_HANGUL etc.
* generally, instead of extracting this index from the norm32 and
* comparing it with the above constants,
* the normalization code compares the entire norm32 value
* with _NORM_MIN_SPECIAL, _NORM_SURROGATES_TOP, _NORM_MIN_HANGUL etc.
*
* 15..8 combining class (cc) according to UnicodeData.txt
*
* 7..6 _NORM_COMBINES_ANY flags, used in composition to see if a character
* combines with any following or preceding character(s)
* at all
* 7 _NORM_COMBINES_BACK
* 6 _NORM_COMBINES_FWD
*
* 5..0 quick check flags, set for "no" or "maybe", with separate flags for
* each normalization form
* the higher bits are "maybe" flags; for NF*D there are no such flags
* the lower bits are "no" flags for all forms, in the same order
* as the "maybe" flags,
* which is (MSB to LSB): NFKD NFD NFKC NFC
* 5..4 _NORM_QC_ANY_MAYBE
* 3..0 _NORM_QC_ANY_NO
* see further related constants
*
*
* - Extra data per code point
*
* "Extra data" is referenced by the index in norm32.
* It is variable-length data. It is only present, and only those parts
* of it are, as needed for a given character.
* The norm32 extra data index is added to the beginning of extraData[]
* to get to a vector of 16-bit words with data at the following offsets:
*
* [-1] Combining index for composition.
* Stored only if norm32&_NORM_COMBINES_ANY .
* [0] Lengths of the canonical and compatibility decomposition strings.
* Stored only if there are decompositions, i.e.,
* if norm32&(_NORM_QC_NFD|_NORM_QC_NFKD)
* High byte: length of NFKD, or 0 if none
* Low byte: length of NFD, or 0 if none
* Each length byte also has another flag:
* Bit 7 of a length byte is set if there are non-zero
* combining classes (cc's) associated with the respective
* decomposition. If this flag is set, then the decomposition
* is preceded by a 16-bit word that contains the
* leading and trailing cc's.
* Bits 6..0 of a length byte are the length of the
* decomposition string, not counting the cc word.
* [1..n] NFD
* [n+1..] NFKD
*
* Each of the two decompositions consists of up to two parts:
* - The 16-bit words with the leading and trailing cc's.
* This is only stored if bit 7 of the corresponding length byte
* is set. In this case, at least one of the cc's is not zero.
* High byte: leading cc==cc of the first code point in the decomposition string
* Low byte: trailing cc==cc of the last code point in the decomposition string
* - The decomposition string in UTF-16, with length code units.
*
*
* - Combining indexes and combiningTable[]
*
* Combining indexes are stored at the [-1] offset of the extra data
* if the character combines forward or backward with any other characters.
* They are used for (re)composition in NF*C.
* Values of combining indexes are arranged according to whether a character
* combines forward, backward, or both ways:
* forward-only < both ways < backward-only
*
* The index values for forward-only and both-ways combining characters
* are indexes into the combiningTable[].
* The index values for backward-only combining characters are simply
* incremented from the preceding index values to be unique.
*
* In the combiningTable[], a variable-length list
* of variable-length (back-index, code point) pair entries is stored
* for each forward-combining character.
*
* These back-indexes are the combining indexes of both-ways or backward-only
* combining characters that the forward-combining character combines with.
*
* Each list is sorted in ascending order of back-indexes.
* Each list is terminated with the last back-index having bit 15 set.
*
* Each pair (back-index, code point) takes up either 2 or 3
* 16-bit words.
* The first word of a list entry is the back-index, with its bit 15 set if
* this is the last pair in the list.
*
* The second word contains flags in bits 15..13 that determine
* if there is a third word and how the combined character is encoded:
* 15 set if there is a third word in this list entry
* 14 set if the result is a supplementary character
* 13 set if the result itself combines forward
*
* According to these bits 15..14 of the second word,
* the result character is encoded as follows:
* 00 or 01 The result is <=0x1fff and stored in bits 12..0 of
* the second word.
* 10 The result is 0x2000..0xffff and stored in the third word.
* Bits 12..0 of the second word are not used.
* 11 The result is a supplementary character.
* Bits 9..0 of the leading surrogate are in bits 9..0 of
* the second word.
* Add 0xd800 to these bits to get the complete surrogate.
* Bits 12..10 of the second word are not used.
* The trailing surrogate is stored in the third word.
*
*
* - FCD trie
*
* The FCD trie is very simple.
* It is a folded trie with 16-bit data words.
* In each word, the high byte contains the leading cc of the character,
* and the low byte contains the trailing cc of the character.
* These cc's are the cc's of the first and last code points in the
* canonical decomposition of the character.
*
* Since all 16 bits are used for cc's, lead surrogates must be tested
* by checking the code unit instead of the trie data.
* This is done only if the 16-bit data word is not zero.
* If the code unit is a leading surrogate and the data word is not zero,
* then instead of cc's it contains the offset for the second trie lookup.
*/
#endif #endif