116 lines
1.9 KiB
Go
116 lines
1.9 KiB
Go
package atom
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import (
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"io"
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"io/ioutil"
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"log"
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)
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func ReadBytes(r io.Reader, n int) (res []byte, err error) {
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res = make([]byte, n)
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if n, err = r.Read(res); err != nil {
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return
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}
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return
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}
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func ReadUInt(r io.Reader, n int) (res uint, err error) {
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var b []byte
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if b, err = ReadBytes(r, n); err != nil {
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return
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}
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for i := 0; i < n; i++ {
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res <<= 8
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res += uint(b[i])
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}
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return
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}
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func ReadInt(r io.Reader, n int) (res int, err error) {
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var uval uint
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if uval, err = ReadUInt(r, n); err != nil {
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return
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}
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if uval&(1<<uint(n*8-1)) != 0 {
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res = -int((1 << uint(n*8)) - uval)
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} else {
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res = int(uval)
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}
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return
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}
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func ReadFixed(r io.Reader, n int) (res Fixed, err error) {
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var ui uint
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if ui, err = ReadUInt(r, n); err != nil {
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return
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}
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if n == 2 {
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res = Fixed(ui << 8)
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} else if n == 4 {
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res = Fixed(ui)
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} else {
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panic("only fixed32 and fixed16 is supported")
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}
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return
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}
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func ReadTimeStamp(r io.Reader, n int) (res TimeStamp, err error) {
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var ui uint
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if ui, err = ReadUInt(r, n); err != nil {
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return
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}
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res = TimeStamp(ui)
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return
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}
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func ReadString(r io.Reader, n int) (res string, err error) {
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var b []byte
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if b, err = ReadBytes(r, n); err != nil {
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return
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}
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res = string(b)
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return
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}
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func ReadDummy(r io.Reader, n int) (res int, err error) {
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_, err = io.CopyN(ioutil.Discard, r, int64(n))
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return
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}
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func ReadAtomHeader(r io.Reader, targetCC4 string) (res *io.LimitedReader, cc4 string, err error) {
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for {
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var size int
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if size, err = ReadInt(r, 4); err != nil {
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return
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}
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if size == 0 {
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continue
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}
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if cc4, err = ReadString(r, 4); err != nil {
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return
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}
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size = size - 8
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if false {
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log.Println(cc4, targetCC4, size, cc4 == targetCC4)
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}
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if targetCC4 != "" && cc4 != targetCC4 {
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log.Println("ReadAtomHeader skip:", cc4)
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if _, err = ReadDummy(r, size); err != nil {
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return
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}
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continue
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}
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res = &io.LimitedReader{
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R: r,
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N: int64(size),
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}
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return
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}
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}
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