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// Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
package cases
// This file contains definitions for interpreting the trie value of the case
// trie generated by "go run gen*.go". It is shared by both the generator
// program and the resultant package. Sharing is achieved by the generator
// copying gen_trieval.go to trieval.go and changing what's above this comment.
// info holds case information for a single rune. It is the value returned
// by a trie lookup. Most mapping information can be stored in a single 16-bit
// value. If not, for example when a rune is mapped to multiple runes, the value
// stores some basic case data and an index into an array with additional data.
//
// The per-rune values have the following format:
//
// if (exception) {
// 15..4 unsigned exception index
// } else {
// 15..8 XOR pattern or index to XOR pattern for case mapping
// Only 13..8 are used for XOR patterns.
// 7 inverseFold (fold to upper, not to lower)
// 6 index: interpret the XOR pattern as an index
// or isMid if case mode is cIgnorableUncased.
// 5..4 CCC: zero (normal or break), above or other
// }
// 3 exception: interpret this value as an exception index
// (TODO: is this bit necessary? Probably implied from case mode.)
// 2..0 case mode
//
// For the non-exceptional cases, a rune must be either uncased, lowercase or
// uppercase. If the rune is cased, the XOR pattern maps either a lowercase
// rune to uppercase or an uppercase rune to lowercase (applied to the 10
// least-significant bits of the rune).
//
// See the definitions below for a more detailed description of the various
// bits.
type info uint16
const (
casedMask = 0x0003
fullCasedMask = 0x0007
ignorableMask = 0x0006
ignorableValue = 0x0004
inverseFoldBit = 1 << 7
isMidBit = 1 << 6
exceptionBit = 1 << 3
exceptionShift = 4
numExceptionBits = 12
xorIndexBit = 1 << 6
xorShift = 8
// There is no mapping if all xor bits and the exception bit are zero.
hasMappingMask = 0xff80 | exceptionBit
)
// The case mode bits encodes the case type of a rune. This includes uncased,
// title, upper and lower case and case ignorable. (For a definition of these
// terms see Chapter 3 of The Unicode Standard Core Specification.) In some rare
// cases, a rune can be both cased and case-ignorable. This is encoded by
// cIgnorableCased. A rune of this type is always lower case. Some runes are
// cased while not having a mapping.
//
// A common pattern for scripts in the Unicode standard is for upper and lower
// case runes to alternate for increasing rune values (e.g. the accented Latin
// ranges starting from U+0100 and U+1E00 among others and some Cyrillic
// characters). We use this property by defining a cXORCase mode, where the case
// mode (always upper or lower case) is derived from the rune value. As the XOR
// pattern for case mappings is often identical for successive runes, using
// cXORCase can result in large series of identical trie values. This, in turn,
// allows us to better compress the trie blocks.
const (
cUncased info = iota // 000
cTitle // 001
cLower // 010
cUpper // 011
cIgnorableUncased // 100
cIgnorableCased // 101 // lower case if mappings exist
cXORCase // 11x // case is cLower | ((rune&1) ^ x)
maxCaseMode = cUpper
)
func (c info) isCased() bool {
return c&casedMask != 0
}
func (c info) isCaseIgnorable() bool {
return c&ignorableMask == ignorableValue
}
func (c info) isNotCasedAndNotCaseIgnorable() bool {
return c&fullCasedMask == 0
}
func (c info) isCaseIgnorableAndNotCased() bool {
return c&fullCasedMask == cIgnorableUncased
}
func (c info) isMid() bool {
return c&(fullCasedMask|isMidBit) == isMidBit|cIgnorableUncased
}
// The case mapping implementation will need to know about various Canonical
// Combining Class (CCC) values. We encode two of these in the trie value:
// cccZero (0) and cccAbove (230). If the value is cccOther, it means that
// CCC(r) > 0, but not 230. A value of cccBreak means that CCC(r) == 0 and that
// the rune also has the break category Break (see below).
const (
cccBreak info = iota << 4
cccZero
cccAbove
cccOther
cccMask = cccBreak | cccZero | cccAbove | cccOther
)
const (
starter = 0
above = 230
iotaSubscript = 240
)
// The exceptions slice holds data that does not fit in a normal info entry.
// The entry is pointed to by the exception index in an entry. It has the
// following format:
//
// Header:
//
// byte 0:
// 7..6 unused
// 5..4 CCC type (same bits as entry)
// 3 unused
// 2..0 length of fold
//
// byte 1:
// 7..6 unused
// 5..3 length of 1st mapping of case type
// 2..0 length of 2nd mapping of case type
//
// case 1st 2nd
// lower -> upper, title
// upper -> lower, title
// title -> lower, upper
//
// Lengths with the value 0x7 indicate no value and implies no change.
// A length of 0 indicates a mapping to zero-length string.
//
// Body bytes:
//
// case folding bytes
// lowercase mapping bytes
// uppercase mapping bytes
// titlecase mapping bytes
// closure mapping bytes (for NFKC_Casefold). (TODO)
//
// Fallbacks:
//
// missing fold -> lower
// missing title -> upper
// all missing -> original rune
//
// exceptions starts with a dummy byte to enforce that there is no zero index
// value.
const (
lengthMask = 0x07
lengthBits = 3
noChange = 0
)
// References to generated trie.
var trie = newCaseTrie(0)
var sparse = sparseBlocks{
values: sparseValues[:],
offsets: sparseOffsets[:],
}
// Sparse block lookup code.
// valueRange is an entry in a sparse block.
type valueRange struct {
value uint16
lo, hi byte
}
type sparseBlocks struct {
values []valueRange
offsets []uint16
}
// lookup returns the value from values block n for byte b using binary search.
func (s *sparseBlocks) lookup(n uint32, b byte) uint16 {
lo := s.offsets[n]
hi := s.offsets[n+1]
for lo < hi {
m := lo + (hi-lo)/2
r := s.values[m]
if r.lo <= b && b <= r.hi {
return r.value
}
if b < r.lo {
hi = m
} else {
lo = m + 1
}
}
return 0
}
// lastRuneForTesting is the last rune used for testing. Everything after this
// is boring.
const lastRuneForTesting = rune(0x1FFFF)
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