133 lines
2.9 KiB
Go
133 lines
2.9 KiB
Go
// Copyright 2014 The Cayley Authors. All rights reserved.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
//go:generate ragel -Z -G2 parse.rl
|
|
|
|
// Package nquads implements parsing the RDF 1.1 N-Quads line-based syntax
|
|
// for RDF datasets.
|
|
//
|
|
// N-Quad parsing is performed as defined by http://www.w3.org/TR/n-quads/
|
|
// with the exception that the nquads package will allow relative IRI values,
|
|
// which are prohibited by the N-Quads quad-Quads specifications.
|
|
package nquads
|
|
|
|
import (
|
|
"bufio"
|
|
"bytes"
|
|
"fmt"
|
|
"io"
|
|
"strconv"
|
|
|
|
"github.com/google/cayley/quad"
|
|
)
|
|
|
|
// Decoder implements N-Quad document parsing according to the RDF
|
|
// 1.1 N-Quads specification.
|
|
type Decoder struct {
|
|
r *bufio.Reader
|
|
line []byte
|
|
}
|
|
|
|
// NewDecoder returns an N-Quad decoder that takes its input from the
|
|
// provided io.Reader.
|
|
func NewDecoder(r io.Reader) *Decoder {
|
|
return &Decoder{r: bufio.NewReader(r)}
|
|
}
|
|
|
|
// Unmarshal returns the next valid N-Quad as a quad.Quad, or an error.
|
|
func (dec *Decoder) Unmarshal() (quad.Quad, error) {
|
|
dec.line = dec.line[:0]
|
|
var line []byte
|
|
for {
|
|
for {
|
|
l, pre, err := dec.r.ReadLine()
|
|
if err != nil {
|
|
return quad.Quad{}, err
|
|
}
|
|
dec.line = append(dec.line, l...)
|
|
if !pre {
|
|
break
|
|
}
|
|
}
|
|
if line = bytes.TrimSpace(dec.line); len(line) != 0 && line[0] != '#' {
|
|
break
|
|
}
|
|
dec.line = dec.line[:0]
|
|
}
|
|
q, err := Parse(string(line))
|
|
if err != nil {
|
|
return quad.Quad{}, fmt.Errorf("failed to parse %q: %v", dec.line, err)
|
|
}
|
|
if !q.IsValid() {
|
|
return dec.Unmarshal()
|
|
}
|
|
return q, nil
|
|
}
|
|
|
|
func unEscape(r []rune, isEscaped bool) string {
|
|
if !isEscaped {
|
|
return string(r)
|
|
}
|
|
|
|
buf := bytes.NewBuffer(make([]byte, 0, len(r)))
|
|
|
|
for i := 0; i < len(r); {
|
|
switch r[i] {
|
|
case '\\':
|
|
i++
|
|
var c byte
|
|
switch r[i] {
|
|
case 't':
|
|
c = '\t'
|
|
case 'b':
|
|
c = '\b'
|
|
case 'n':
|
|
c = '\n'
|
|
case 'r':
|
|
c = '\r'
|
|
case 'f':
|
|
c = '\f'
|
|
case '"':
|
|
c = '"'
|
|
case '\'':
|
|
c = '\''
|
|
case '\\':
|
|
c = '\\'
|
|
case 'u':
|
|
rc, err := strconv.ParseInt(string(r[i+1:i+5]), 16, 32)
|
|
if err != nil {
|
|
panic(fmt.Errorf("internal parser error: %v", err))
|
|
}
|
|
buf.WriteRune(rune(rc))
|
|
i += 5
|
|
continue
|
|
case 'U':
|
|
rc, err := strconv.ParseInt(string(r[i+1:i+9]), 16, 32)
|
|
if err != nil {
|
|
panic(fmt.Errorf("internal parser error: %v", err))
|
|
}
|
|
buf.WriteRune(rune(rc))
|
|
i += 9
|
|
continue
|
|
}
|
|
buf.WriteByte(c)
|
|
default:
|
|
buf.WriteRune(r[i])
|
|
}
|
|
i++
|
|
}
|
|
|
|
return buf.String()
|
|
}
|