blob: 2035008e7713ecf0a7aada001542fde5353a94c7 [file] [log] [blame]
// Copyright 2014 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 seq
import (
"errors"
"fmt"
"unicode/utf16"
"unsafe"
)
// Based heavily on package unicode/utf16 from the Go standard library.
const (
replacementChar = '\uFFFD' // Unicode replacement character
maxRune = '\U0010FFFF' // Maximum valid Unicode code point.
)
const (
// 0xd800-0xdc00 encodes the high 10 bits of a pair.
// 0xdc00-0xe000 encodes the low 10 bits of a pair.
// the value is those 20 bits plus 0x10000.
surr1 = 0xd800
surr2 = 0xdc00
surr3 = 0xe000
surrSelf = 0x10000
)
func writeUint16(b []byte, v rune) {
*(*uint16)(unsafe.Pointer(&b[0])) = uint16(v)
}
func (b *Buffer) WriteUTF16(s string) {
// The first 4 bytes is the length, as int32 (4-byte aligned).
// written last.
// The next n bytes is utf-16 string (1-byte aligned).
offset0 := align(b.Offset, 4) // length.
offset1 := align(offset0+4, 1) // contents.
if len(b.Data)-offset1 < 4*len(s) {
// worst case estimate, everything is surrogate pair
b.grow(offset1 + 4*len(s) - len(b.Data))
}
data := b.Data[offset1:]
n := 0
for _, v := range s {
switch {
case v < 0, surr1 <= v && v < surr3, v > maxRune:
v = replacementChar
fallthrough
case v < surrSelf:
writeUint16(data[n:], v)
n += 2
default:
// surrogate pair, two uint16 values
r1, r2 := utf16.EncodeRune(v)
writeUint16(data[n:], r1)
writeUint16(data[n+2:], r2)
n += 4
}
}
// write length at b.Data[b.Offset:], before contents.
// length is number of uint16 values, not number of bytes.
b.WriteInt32(int32(n / 2))
b.Offset = offset1 + n
}
func (b *Buffer) WriteUTF8(s string) {
n := len(s)
b.WriteInt32(int32(n))
if len(s) == 0 {
return
}
offset := align(b.Offset, 1)
if len(b.Data)-offset < n {
b.grow(offset + n - len(b.Data))
}
copy(b.Data[offset:], s)
b.Offset = offset + n
}
const maxSliceLen = (1<<31 - 1) / 2
func (b *Buffer) ReadError() error {
if s := b.ReadString(); s != "" {
return errors.New(s)
}
return nil
}
func (b *Buffer) ReadUTF16() string {
size := int(b.ReadInt32())
if size == 0 {
return ""
}
if size < 0 {
panic(fmt.Sprintf("string size negative: %d", size))
}
offset := align(b.Offset, 1)
u := (*[maxSliceLen]uint16)(unsafe.Pointer(&b.Data[offset]))[:size]
s := string(utf16.Decode(u)) // TODO: save the []rune alloc
b.Offset = offset + 2*size
return s
}
func (b *Buffer) ReadUTF8() string {
size := int(b.ReadInt32())
if size == 0 {
return ""
}
if size < 0 {
panic(fmt.Sprintf("string size negative: %d", size))
}
offset := align(b.Offset, 1)
b.Offset = offset + size
return string(b.Data[offset : offset+size])
}