add changeset parser

parser/changeset/doc.go

@@ -0,0 +1,4 @@
+/*
+Package changeset provides a parser for OSM changeset files.
+*/
+package changeset

parser/changeset/parser.go

@@ -0,0 +1,78 @@
+package changeset
+
+import (
+	"compress/gzip"
+	"encoding/xml"
+	"os"
+	"time"
+)
+
+type changeFile struct {
+	XMLName   string      `xml:"osm"`
+	Generator string      `xml:"generator,attr"`
+	Changes   []Changeset `xml:"changeset"`
+}
+
+type Changeset struct {
+	Id         int       `xml:"id,attr"`
+	CreatedAt  IsoTime   `xml:"created_at,attr"`
+	ClosedAt   IsoTime   `xml:"closed_at,attr"`
+	Open       bool      `xml:"open,attr"`
+	User       string    `xml:"user,attr"`
+	UserId     int       `xml:"uid,attr"`
+	NumChanges int       `xml:"num_changes,attr"`
+	MinLon     float64   `xml:"min_lon,attr"`
+	MinLat     float64   `xml:"min_lat,attr"`
+	MaxLon     float64   `xml:"max_lon,attr"`
+	MaxLat     float64   `xml:"max_lat,attr"`
+	Comments   []Comment `xml:"discussion>comment"`
+	Tags       []Tag     `xml:"tag"`
+}
+
+type Comment struct {
+	UserId int     `xml:"uid,attr"`
+	User   string  `xml:"user,attr"`
+	Date   IsoTime `xml:"date,attr"`
+	Text   string  `xml:"text"`
+}
+
+type IsoTime struct {
+	time.Time
+}
+
+type Tag struct {
+	Key   string `xml:"k,attr"`
+	Value string `xml:"v,attr"`
+}
+
+func (t *IsoTime) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+	var v string
+	d.DecodeElement(&v, &start)
+	parse, err := time.Parse(time.RFC3339, v)
+	if err != nil {
+		return err
+	}
+	*t = IsoTime{parse}
+	return nil
+}
+
+// ParseAllOsmGz parses all changesets from a .osm.gz file.
+func ParseAllOsmGz(change string) ([]Changeset, error) {
+	file, err := os.Open(change)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	reader, err := gzip.NewReader(file)
+	if err != nil {
+		return nil, err
+	}
+	cf := changeFile{}
+	err = xml.NewDecoder(reader).Decode(&cf)
+	if err != nil {
+		return nil, err
+	}
+
+	return cf.Changes, nil
+}

parser/changeset/parser_test.go

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+package changeset
+
+import "testing"
+
+func TestParse(t *testing.T) {
+	changes, err := ParseAllOsmGz("999.osm.gz")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n := len(changes); n != 27 {
+		t.Error("expected 27 changes, got", n)
+	}
+	c := changes[0]
+	if c.Id != 43406602 || c.NumChanges != 314 {
+		t.Error("unexpected changeset", c)
+	}
+	if n := len(c.Comments); n != 3 {
+		t.Error("expected 3 comments in changeset", c)
+	}
+
+}