112 lines
2.3 KiB
Go
112 lines
2.3 KiB
Go
package binary
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import (
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"encoding/binary"
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"errors"
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"github.com/omniscale/imposm3/element"
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)
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func MarshalDeltaNodes(nodes []element.Node, buf []byte) []byte {
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estimatedLength := len(nodes)*4*3 + binary.MaxVarintLen64
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if cap(buf) < estimatedLength {
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buf = make([]byte, estimatedLength)
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} else {
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// resize slice to full capacity
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buf = buf[:cap(buf)-1]
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}
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lastId := int64(0)
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nextPos := binary.PutUvarint(buf, uint64(len(nodes)))
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for i := range nodes {
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if len(buf)-nextPos < binary.MaxVarintLen64 {
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tmp := make([]byte, len(buf)*3/2)
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copy(tmp, buf)
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buf = tmp
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}
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nextPos += binary.PutVarint(buf[nextPos:], nodes[i].Id-lastId)
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lastId = nodes[i].Id
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}
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lastLong := int64(0)
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for i := range nodes {
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if len(buf)-nextPos < binary.MaxVarintLen64 {
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tmp := make([]byte, len(buf)*3/2)
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copy(tmp, buf)
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buf = tmp
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}
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long := int64(CoordToInt(nodes[i].Long))
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nextPos += binary.PutVarint(buf[nextPos:], long-lastLong)
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lastLong = long
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}
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lastLat := int64(0)
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for i := range nodes {
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if len(buf)-nextPos < binary.MaxVarintLen64 {
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tmp := make([]byte, len(buf)*3/2)
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copy(tmp, buf)
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buf = tmp
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}
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lat := int64(CoordToInt(nodes[i].Lat))
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nextPos += binary.PutVarint(buf[nextPos:], lat-lastLat)
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lastLat = lat
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}
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return buf[:nextPos]
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}
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var varintErr = errors.New("unmarshal delta coords: missing data for varint or overflow")
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func UnmarshalDeltaNodes(buf []byte, nodes []element.Node) ([]element.Node, error) {
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length, n := binary.Uvarint(buf)
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if n <= 0 {
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return nil, varintErr
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}
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var offset = n
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if uint64(cap(nodes)) < length {
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nodes = make([]element.Node, length)
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} else {
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nodes = nodes[:length]
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}
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lastId := int64(0)
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for i := 0; uint64(i) < length; i++ {
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id, n := binary.Varint(buf[offset:])
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if n <= 0 {
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return nil, varintErr
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}
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offset += n
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id = lastId + id
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nodes[i].Id = id
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lastId = id
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}
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lastLong := int64(0)
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for i := 0; uint64(i) < length; i++ {
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long, n := binary.Varint(buf[offset:])
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if n <= 0 {
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return nil, varintErr
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}
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offset += n
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long = lastLong + long
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nodes[i].Long = IntToCoord(uint32(long))
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lastLong = long
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}
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lastLat := int64(0)
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for i := 0; uint64(i) < length; i++ {
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lat, n := binary.Varint(buf[offset:])
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if n <= 0 {
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return nil, varintErr
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}
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offset += n
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lat = lastLat + lat
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nodes[i].Lat = IntToCoord(uint32(lat))
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lastLat = lat
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}
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return nodes, nil
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}
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