mirror of https://github.com/beego/bee.git
127 lines
2.0 KiB
Go
127 lines
2.0 KiB
Go
package util
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import (
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"bytes"
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"io"
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)
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// The Little Endian Base 128 format is defined in the DWARF v4 standard,
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// section 7.6, page 161 and following.
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// DecodeULEB128 decodes an unsigned Little Endian Base 128
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// represented number.
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func DecodeULEB128(buf *bytes.Buffer) (uint64, uint32) {
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var (
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result uint64
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shift uint64
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length uint32
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)
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if buf.Len() == 0 {
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return 0, 0
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}
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for {
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b, err := buf.ReadByte()
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if err != nil {
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panic("Could not parse ULEB128 value")
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}
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length++
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result |= uint64((uint(b) & 0x7f) << shift)
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// If high order bit is 1.
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if b&0x80 == 0 {
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break
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}
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shift += 7
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}
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return result, length
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}
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// DecodeSLEB128 decodes a signed Little Endian Base 128
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// represented number.
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func DecodeSLEB128(buf *bytes.Buffer) (int64, uint32) {
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var (
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b byte
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err error
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result int64
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shift uint64
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length uint32
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)
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if buf.Len() == 0 {
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return 0, 0
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}
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for {
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b, err = buf.ReadByte()
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if err != nil {
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panic("Could not parse SLEB128 value")
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}
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length++
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result |= int64((int64(b) & 0x7f) << shift)
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shift += 7
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if b&0x80 == 0 {
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break
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}
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}
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if (shift < 8*uint64(length)) && (b&0x40 > 0) {
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result |= -(1 << shift)
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}
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return result, length
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}
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// EncodeULEB128 encodes x to the unsigned Little Endian Base 128 format
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// into out.
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func EncodeULEB128(out io.ByteWriter, x uint64) {
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for {
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b := byte(x & 0x7f)
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x = x >> 7
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if x != 0 {
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b = b | 0x80
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}
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out.WriteByte(b)
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if x == 0 {
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break
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}
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}
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}
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// EncodeSLEB128 encodes x to the signed Little Endian Base 128 format
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// into out.
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func EncodeSLEB128(out io.ByteWriter, x int64) {
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for {
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b := byte(x & 0x7f)
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x >>= 7
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signb := b & 0x40
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last := false
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if (x == 0 && signb == 0) || (x == -1 && signb != 0) {
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last = true
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} else {
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b = b | 0x80
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}
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out.WriteByte(b)
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if last {
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break
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}
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}
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}
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func ParseString(data *bytes.Buffer) (string, uint32) {
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str, err := data.ReadString(0x0)
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if err != nil {
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panic("Could not parse string")
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}
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return str[:len(str)-1], uint32(len(str))
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}
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