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parser.go
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/
parser.go
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package main
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"github.com/golang-collections/collections/stack"
"io"
"os"
)
var unicodeString byte = 'X'
var shortBinaryString byte = 'U'
var binaryInteger byte = 'J'
var binaryLong byte = 0x8A
var binaryInput byte = 'q'
var longBinaryInput byte = 'r'
var endIndexPrefix byte = 0x87
var endIndex byte = 0x86
func Unpickle(data []byte) ([]ArchiveIndex, error) {
// Prepare an empty slice of archive indices.
var indices []ArchiveIndex
// Validate pickle identifier and pickle version.
reader := bytes.NewReader(data)
protocolIdentifier, err := reader.ReadByte()
if err != nil {
return nil, err
}
protocolVersion, err := reader.ReadByte()
if err != nil {
return nil, err
}
if protocolIdentifier != 0x80 || protocolVersion != 2 {
return nil, errors.New("specified pickle is invalid or not supported")
}
// Skip the next four bytes as their not relevant for parsing the pickle.
reader.Seek(4, 1)
// Prepare a new stack to store values.
elementStack := stack.New()
var skipElement bool
for {
// Read next marker byte and check for end of file.
b, err := reader.ReadByte()
if err == io.EOF {
break
} else if err != nil {
return nil, err
}
if skipElement {
if b != endIndexPrefix && b != endIndex && b != ']' {
continue
} else if b == ']' {
skipElement = false
reader.Seek(2, 1)
continue
}
}
skipElement = false
switch b {
case unicodeString:
// Read length prefix to determine string length.
length, err := readInteger(reader)
if err != nil {
return nil, err
}
// Create buffer to fit the string into.
buffer := make([]byte, length)
bytesRead, err := reader.Read(buffer)
if err != nil {
return nil, err
} else if bytesRead != int(length) {
return nil, errors.New("insufficient bytes left in stream")
}
// Push element to stack.
elementStack.Push(buffer)
skipElement = true
case binaryLong:
// Read length of integer.
length, err := reader.ReadByte()
if err != nil {
return nil, err
}
// Create buffer to fit in integer.
buffer := make([]byte, length)
_, err = reader.Read(buffer)
var number int
switch length {
case 4:
number = int(binary.LittleEndian.Uint32(buffer))
case 8:
number = int(binary.LittleEndian.Uint64(buffer))
default:
return nil, errors.New(fmt.Sprintf("%d is not a valid binary input length", length))
}
// Push element to stack.
elementStack.Push(number)
case binaryInteger:
number, err := readInteger(reader)
if err != nil {
return nil, err
}
// Push element to stack.
elementStack.Push(number)
case shortBinaryString:
length, err := reader.ReadByte()
if err != nil {
return nil, err
}
buffer := make([]byte, length)
readBytes, err := reader.Read(buffer)
if err != nil {
return nil, err
} else if readBytes != int(length) {
return nil, errors.New("insufficient bytes left in stream")
}
elementStack.Push(buffer)
case longBinaryInput:
reader.Seek(4, 1)
case binaryInput:
reader.Seek(1, 1)
case endIndex, endIndexPrefix:
var prefixObject interface{}
if b == endIndexPrefix {
prefixObject = elementStack.Pop()
}
lengthObject := elementStack.Pop()
offsetObject := elementStack.Pop()
pathObject := elementStack.Pop()
if lengthObject == nil || offsetObject == nil || pathObject == nil || (b == endIndexPrefix && prefixObject == nil) {
// Push valid popped values back to stack.
if offsetObject != nil {
elementStack.Push(offsetObject)
}
if lengthObject != nil {
elementStack.Push(lengthObject)
}
if prefixObject != nil {
elementStack.Push(prefixObject)
}
position, _ := reader.Seek(0, 1)
fmt.Fprintf(os.Stdout, "(Warning) Failed to pop sufficient values from stack. (at mem-pos: %d)\n", position)
continue
}
offset, err := castInteger(offsetObject)
if err != nil {
return nil, err
}
length, err := castInteger(lengthObject)
if err != nil {
return nil, err
}
indices = append(indices, ArchiveIndex{string(pathObject.([]byte)), int64(offset), int(length), prefixObject.([]byte)})
reader.Seek(3, 1)
}
}
return indices, nil
}