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improve readability of Pool.UnmarshalBinary

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Change-Id: If0a0ac668f910a8dd5a05b87e841403b8d390de1
Reviewed-on: https://go-review.googlesource.com/18121
Reviewed-by: David Crawshaw <crawshaw@golang.org>
This commit is contained in:
Daniel Skinner 2015-12-22 14:37:17 -06:00 committed by David Crawshaw
parent 54b4a066d7
commit d6f00813f9
1 changed files with 42 additions and 65 deletions
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107
internal/binres/pool.go
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@ -53,101 +53,78 @@ func (pl *Pool) UnmarshalBinary(bin []byte) error {
return fmt.Errorf("have type %s, want %s", pl.typ, ResStringPool)
}
nstrings := btou32(bin[8:])
pl.strings = make([]string, nstrings)
nstyles := btou32(bin[12:])
pl.styles = make([]*Span, nstyles)
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
hdrlen := 28 // header size is always 28
if pl.IsUTF8() {
for i := range pl.strings {
ii := btou32(bin[hdrlen+i*4:]) // index of string index
r := int(offstrings + ii) // read index of string
offset := int(offstrings + btou32(bin[hdrlen+i*4:]))
// for char and byte sizes below, if leading bit set,
// treat first as 7-bit high word and the next byte as low word.
// get char size of string
cn := uint8(bin[r])
rcn := int(cn)
r++
if cn&(1<<7) != 0 {
cn0 := int(cn ^ (1 << 7)) // high word
cn1 := int(bin[r]) // low word
rcn = cn0*256 + cn1
r++
// 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++
}
// get byte size of string
// TODO(d) i've seen at least one case in android.jar resource table that has only
// highbit set, effectively making 7-bit highword zero. The reason for this is currently
// unknown but would make tests that unmarshal-marshal to match bytes impossible to pass.
// 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
// I don't recall character count but was around ?78?
// The case here may very well be that the size is treated like int8 triggering the use of
// two bytes to store size even though the implementation uses uint8.
n := uint8(bin[r])
r++
rn := int(n)
if n&(1<<7) != 0 {
n0 := int(n ^ (1 << 7)) // high word
n1 := int(bin[r]) // low word
rn = n0*(1<<8) + n1
r++
// 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[r : r+rn]
if x := uint8(bin[r+rn]); x != 0 {
return fmt.Errorf("expected zero terminator, got %v for byte size %v char len %v", x, rn, rcn)
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 {
ii := btou32(bin[hdrlen+i*4:]) // index of string index
r := int(offstrings + ii) // read index of string
n := btou16(bin[r:]) // string length
rn := int(n)
r += 2
offset := int(offstrings + btou32(bin[hdrlen+i*4:])) // read index of string
if n&(1<<15) != 0 { // TODO this is untested
n0 := int(n ^ (1 << 15)) // high word
n1 := int(btou16(bin[r:]))
rn = n0*(1<<16) + n1
r += 2
// 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, int(rn))
data := make([]uint16, nchars)
for i := range data {
data[i] = btou16(bin[r+(2*i):])
data[i] = btou16(bin[offset+2*i:])
}
r += int(n * 2)
if x := btou16(bin[r:]); x != 0 {
return fmt.Errorf("expected zero terminator, got 0x%04X\n%s", x)
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
// TODO decode styles
_ = offstyle
// styii := hdrlen + int(nstrings*4)
// for i := range pl.styles {
// ii := btou32(bin[styii+i*4:])
// r := int(offstyle + ii)
// spn := new(binSpan)
// spn.UnmarshalBinary(bin[r:])
// pl.styles[i] = spn
// }
return nil
}