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pool.go
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pool.go
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// Copyright 2015 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 binres
import (
"fmt"
"unicode/utf16"
)
const (
SortedFlag uint32 = 1 << 0
UTF8Flag = 1 << 8
)
// PoolRef is the i'th string in a pool.
type PoolRef uint32
// Resolve returns the string entry of PoolRef in pl.
func (ref PoolRef) Resolve(pl *Pool) string {
return pl.strings[ref]
}
// Pool is a container for string and style span collections.
//
// Pool has the following structure marshalled:
// chunkHeader
// uint32 number of strings in this pool
// uint32 number of style spans in pool
// uint32 SortedFlag, UTF8Flag
// uint32 index of string data from header
// uint32 index of style data from header
// []uint32 string indices starting at zero
// []uint16 or []uint8 concatenation of string entries
//
// UTF-16 entries are as follows:
// uint16 string length, exclusive
// uint16 [optional] low word if high bit of length set
// [n]byte data
// uint16 0x0000 terminator
//
// UTF-8 entries are as follows:
// uint8 character length, exclusive
// uint8 [optional] low word if high bit of character length set
// uint8 byte length, exclusive
// uint8 [optional] low word if high bit of byte length set
// [n]byte data
// uint8 0x00 terminator
type Pool struct {
chunkHeader
strings []string
styles []*Span
flags uint32 // SortedFlag, UTF8Flag
}
// ref returns the PoolRef of s, inserting s if it doesn't exist.
func (pl *Pool) ref(s string) PoolRef {
for i, x := range pl.strings {
if s == x {
return PoolRef(i)
}
}
pl.strings = append(pl.strings, s)
return PoolRef(len(pl.strings) - 1)
}
// RefByName returns the PoolRef of s, or error if not exists.
func (pl *Pool) RefByName(s string) (PoolRef, error) {
for i, x := range pl.strings {
if s == x {
return PoolRef(i), nil
}
}
return 0, fmt.Errorf("PoolRef by name %q does not exist", s)
}
func (pl *Pool) IsSorted() bool { return pl.flags&SortedFlag == SortedFlag }
func (pl *Pool) IsUTF8() bool { return pl.flags&UTF8Flag == UTF8Flag }
func (pl *Pool) UnmarshalBinary(bin []byte) error {
if err := (&pl.chunkHeader).UnmarshalBinary(bin); err != nil {
return err
}
if pl.typ != ResStringPool {
return fmt.Errorf("have type %s, want %s", pl.typ, ResStringPool)
}
pl.strings = make([]string, btou32(bin[8:]))
pl.styles = make([]*Span, btou32(bin[12:]))
pl.flags = btou32(bin[16:])
offstrings := btou32(bin[20:])
offstyle := btou32(bin[24:])
hdrlen := 28
if pl.IsUTF8() {
for i := range pl.strings {
offset := int(offstrings + btou32(bin[hdrlen+i*4:]))
// if leading bit set for nchars and nbytes,
// treat first byte as 7-bit high word and next as low word.
nchars := int(bin[offset])
offset++
if nchars&(1<<7) != 0 {
n0 := nchars ^ (1 << 7) // high word
n1 := int(bin[offset]) // low word
nchars = n0*(1<<8) + n1
offset++
}
// TODO(d) At least one case in android.jar (api-10) resource table has only
// highbit set, making 7-bit highword zero. The reason for this is currently
// unknown but would make tests that unmarshal-marshal to match bytes impossible.
// The values noted were high-word: 0 (after highbit unset), low-word: 141
// The size may be treated as an int8 triggering the use of two bytes to store size
// even though the implementation uses uint8.
nbytes := int(bin[offset])
offset++
if nbytes&(1<<7) != 0 {
n0 := nbytes ^ (1 << 7) // high word
n1 := int(bin[offset]) // low word
nbytes = n0*(1<<8) + n1
offset++
}
data := bin[offset : offset+nbytes]
if x := uint8(bin[offset+nbytes]); x != 0 {
return fmt.Errorf("expected zero terminator, got 0x%02X for nchars=%v nbytes=%v data=%q", x, nchars, nbytes, data)
}
pl.strings[i] = string(data)
}
} else {
for i := range pl.strings {
offset := int(offstrings + btou32(bin[hdrlen+i*4:])) // read index of string
// if leading bit set for nchars, treat first byte as 7-bit high word and next as low word.
nchars := int(btou16(bin[offset:]))
offset += 2
if nchars&(1<<15) != 0 { // TODO(d) this is untested
n0 := nchars ^ (1 << 15) // high word
n1 := int(btou16(bin[offset:])) // low word
nchars = n0*(1<<16) + n1
offset += 2
}
data := make([]uint16, nchars)
for i := range data {
data[i] = btou16(bin[offset+2*i:])
}
if x := btou16(bin[offset+nchars*2:]); x != 0 {
return fmt.Errorf("expected zero terminator, got 0x%04X for nchars=%v data=%q", x, nchars, data)
}
pl.strings[i] = string(utf16.Decode(data))
}
}
// TODO decode styles
_ = offstyle
return nil
}
func (pl *Pool) MarshalBinary() ([]byte, error) {
if pl.IsUTF8() {
return nil, fmt.Errorf("encode utf8 not supported")
}
var (
hdrlen = 28
// indices of string indices
iis = make([]uint32, len(pl.strings))
iislen = len(iis) * 4
// utf16 encoded strings concatenated together
strs []uint16
)
for i, x := range pl.strings {
if len(x)>>16 > 0 {
panic(fmt.Errorf("string lengths over 1<<15 not yet supported, got len %d", len(x)))
}
p := utf16.Encode([]rune(x))
if len(p) == 0 {
strs = append(strs, 0x0000, 0x0000)
} else {
strs = append(strs, uint16(len(p))) // string length (implicitly includes zero terminator to follow)
strs = append(strs, p...)
strs = append(strs, 0) // zero terminated
}
// indices start at zero
if i+1 != len(iis) {
iis[i+1] = uint32(len(strs) * 2) // utf16 byte index
}
}
// check strings is 4-byte aligned, pad with zeros if not.
for x := (len(strs) * 2) % 4; x != 0; x -= 2 {
strs = append(strs, 0x0000)
}
strslen := len(strs) * 2
hdr := chunkHeader{
typ: ResStringPool,
headerByteSize: 28,
byteSize: uint32(28 + iislen + strslen),
}
bin := make([]byte, hdr.byteSize)
hdrbin, err := hdr.MarshalBinary()
if err != nil {
return nil, err
}
copy(bin, hdrbin)
putu32(bin[8:], uint32(len(pl.strings)))
putu32(bin[12:], uint32(len(pl.styles)))
putu32(bin[16:], pl.flags)
putu32(bin[20:], uint32(hdrlen+iislen))
putu32(bin[24:], 0) // index of styles start, is 0 when styles length is 0
buf := bin[28:]
for _, x := range iis {
putu32(buf, x)
buf = buf[4:]
}
for _, x := range strs {
putu16(buf, x)
buf = buf[2:]
}
if len(buf) != 0 {
panic(fmt.Errorf("failed to fill allocated buffer, %v bytes left over", len(buf)))
}
return bin, nil
}
type Span struct {
name PoolRef
firstChar, lastChar uint32
}
func (spn *Span) UnmarshalBinary(bin []byte) error {
const end = 0xFFFFFFFF
spn.name = PoolRef(btou32(bin))
if spn.name == end {
return nil
}
spn.firstChar = btou32(bin[4:])
spn.lastChar = btou32(bin[8:])
return nil
}
// Map contains a uint32 slice mapping strings in the string
// pool back to resource identifiers. The i'th element of the slice
// is also the same i'th element of the string pool.
type Map struct {
chunkHeader
rs []TableRef
}
func (m *Map) UnmarshalBinary(bin []byte) error {
(&m.chunkHeader).UnmarshalBinary(bin)
buf := bin[m.headerByteSize:m.byteSize]
m.rs = make([]TableRef, len(buf)/4)
for i := range m.rs {
m.rs[i] = TableRef(btou32(buf[i*4:]))
}
return nil
}
func (m *Map) MarshalBinary() ([]byte, error) {
m.typ = ResXMLResourceMap
m.headerByteSize = 8
m.byteSize = uint32(m.headerByteSize) + uint32(len(m.rs)*4)
bin := make([]byte, m.byteSize)
b, err := m.chunkHeader.MarshalBinary()
if err != nil {
return nil, err
}
copy(bin, b)
for i, r := range m.rs {
putu32(bin[8+i*4:], uint32(r))
}
return bin, nil
}