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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [exp/] [norm/] [trie.go] - Rev 861
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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package norm
type valueRange struct {
value uint16 // header: value:stride
lo, hi byte // header: lo:n
}
type trie struct {
index []uint8
values []uint16
sparse []valueRange
sparseOffset []uint16
cutoff uint8 // indices >= cutoff are sparse
}
// lookupValue determines the type of block n and looks up the value for b.
// For n < t.cutoff, the block is a simple lookup table. Otherwise, the block
// is a list of ranges with an accompanying value. Given a matching range r,
// the value for b is by r.value + (b - r.lo) * stride.
func (t *trie) lookupValue(n uint8, b byte) uint16 {
if n < t.cutoff {
return t.values[uint16(n)<<6+uint16(b&maskx)]
}
offset := t.sparseOffset[n-t.cutoff]
header := t.sparse[offset]
lo := offset + 1
hi := lo + uint16(header.lo)
for lo < hi {
m := lo + (hi-lo)/2
r := t.sparse[m]
if r.lo <= b && b <= r.hi {
return r.value + uint16(b-r.lo)*header.value
}
if b < r.lo {
hi = m
} else {
lo = m + 1
}
}
return 0
}
const (
t1 = 0x00 // 0000 0000
tx = 0x80 // 1000 0000
t2 = 0xC0 // 1100 0000
t3 = 0xE0 // 1110 0000
t4 = 0xF0 // 1111 0000
t5 = 0xF8 // 1111 1000
t6 = 0xFC // 1111 1100
te = 0xFE // 1111 1110
maskx = 0x3F // 0011 1111
mask2 = 0x1F // 0001 1111
mask3 = 0x0F // 0000 1111
mask4 = 0x07 // 0000 0111
)
// lookup returns the trie value for the first UTF-8 encoding in s and
// the width in bytes of this encoding. The size will be 0 if s does not
// hold enough bytes to complete the encoding. len(s) must be greater than 0.
func (t *trie) lookup(s []byte) (v uint16, sz int) {
c0 := s[0]
switch {
case c0 < tx:
return t.values[c0], 1
case c0 < t2:
return 0, 1
case c0 < t3:
if len(s) < 2 {
return 0, 0
}
i := t.index[c0]
c1 := s[1]
if c1 < tx || t2 <= c1 {
return 0, 1
}
return t.lookupValue(i, c1), 2
case c0 < t4:
if len(s) < 3 {
return 0, 0
}
i := t.index[c0]
c1 := s[1]
if c1 < tx || t2 <= c1 {
return 0, 1
}
o := uint16(i)<<6 + uint16(c1)&maskx
i = t.index[o]
c2 := s[2]
if c2 < tx || t2 <= c2 {
return 0, 2
}
return t.lookupValue(i, c2), 3
case c0 < t5:
if len(s) < 4 {
return 0, 0
}
i := t.index[c0]
c1 := s[1]
if c1 < tx || t2 <= c1 {
return 0, 1
}
o := uint16(i)<<6 + uint16(c1)&maskx
i = t.index[o]
c2 := s[2]
if c2 < tx || t2 <= c2 {
return 0, 2
}
o = uint16(i)<<6 + uint16(c2)&maskx
i = t.index[o]
c3 := s[3]
if c3 < tx || t2 <= c3 {
return 0, 3
}
return t.lookupValue(i, c3), 4
}
// Illegal rune
return 0, 1
}
// lookupString returns the trie value for the first UTF-8 encoding in s and
// the width in bytes of this encoding. The size will be 0 if s does not
// hold enough bytes to complete the encoding. len(s) must be greater than 0.
func (t *trie) lookupString(s string) (v uint16, sz int) {
c0 := s[0]
switch {
case c0 < tx:
return t.values[c0], 1
case c0 < t2:
return 0, 1
case c0 < t3:
if len(s) < 2 {
return 0, 0
}
i := t.index[c0]
c1 := s[1]
if c1 < tx || t2 <= c1 {
return 0, 1
}
return t.lookupValue(i, c1), 2
case c0 < t4:
if len(s) < 3 {
return 0, 0
}
i := t.index[c0]
c1 := s[1]
if c1 < tx || t2 <= c1 {
return 0, 1
}
o := uint16(i)<<6 + uint16(c1)&maskx
i = t.index[o]
c2 := s[2]
if c2 < tx || t2 <= c2 {
return 0, 2
}
return t.lookupValue(i, c2), 3
case c0 < t5:
if len(s) < 4 {
return 0, 0
}
i := t.index[c0]
c1 := s[1]
if c1 < tx || t2 <= c1 {
return 0, 1
}
o := uint16(i)<<6 + uint16(c1)&maskx
i = t.index[o]
c2 := s[2]
if c2 < tx || t2 <= c2 {
return 0, 2
}
o = uint16(i)<<6 + uint16(c2)&maskx
i = t.index[o]
c3 := s[3]
if c3 < tx || t2 <= c3 {
return 0, 3
}
return t.lookupValue(i, c3), 4
}
// Illegal rune
return 0, 1
}
// lookupUnsafe returns the trie value for the first UTF-8 encoding in s.
// s must hold a full encoding.
func (t *trie) lookupUnsafe(s []byte) uint16 {
c0 := s[0]
if c0 < tx {
return t.values[c0]
}
if c0 < t2 {
return 0
}
i := t.index[c0]
if c0 < t3 {
return t.lookupValue(i, s[1])
}
i = t.index[uint16(i)<<6+uint16(s[1])&maskx]
if c0 < t4 {
return t.lookupValue(i, s[2])
}
i = t.index[uint16(i)<<6+uint16(s[2])&maskx]
if c0 < t5 {
return t.lookupValue(i, s[3])
}
return 0
}
// lookupStringUnsafe returns the trie value for the first UTF-8 encoding in s.
// s must hold a full encoding.
func (t *trie) lookupStringUnsafe(s string) uint16 {
c0 := s[0]
if c0 < tx {
return t.values[c0]
}
if c0 < t2 {
return 0
}
i := t.index[c0]
if c0 < t3 {
return t.lookupValue(i, s[1])
}
i = t.index[uint16(i)<<6+uint16(s[1])&maskx]
if c0 < t4 {
return t.lookupValue(i, s[2])
}
i = t.index[uint16(i)<<6+uint16(s[2])&maskx]
if c0 < t5 {
return t.lookupValue(i, s[3])
}
return 0
}
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