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