5aba71f2e7
At this stage this is just a comment for users. The directive will have
effect at go tip when go CL125580044 is submitted. When that happens, at
tip parser code generation can be acheived in the default case with:
go generate
in the relevant package directory.
132 lines
3 KiB
Go
132 lines
3 KiB
Go
// 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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triple, 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 !triple.IsValid() {
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return dec.Unmarshal()
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}
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return triple, 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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