magic number check/enforcement and spec version in show command [#27]

protomaps · Oct 27, 2022 · 6a77030 · 6a77030
1 parent 79c9f52
commit 6a77030
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Showing 4 changed files with 28 additions and 5 deletions.
diff --git a/pmtiles/directory.go b/pmtiles/directory.go
@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"compress/gzip"
 	"encoding/binary"
+	"fmt"
 )
 
 type Compression uint8
@@ -30,6 +31,7 @@ const (
 const HEADERV3_LEN_BYTES = 127
 
 type HeaderV3 struct {
+	SpecVersion         uint8
 	RootOffset          uint64
 	RootLength          uint64
 	MetadataOffset      uint64
@@ -228,8 +230,19 @@ func serialize_header(header HeaderV3) []byte {
 	return b
 }
 
-func deserialize_header(d []byte) HeaderV3 {
+func deserialize_header(d []byte) (HeaderV3, error) {
 	h := HeaderV3{}
+	magic_number := d[0:7]
+	if string(magic_number) != "PMTiles" {
+		return h, fmt.Errorf("Magic number not detected. Are you sure this is a PMTiles archive?")
+	}
+
+	spec_version := d[7]
+	if spec_version > uint8(3) {
+		return h, fmt.Errorf("Archive is spec version %d, but this program only supports version 3: upgrade your pmtiles program.", spec_version)
+	}
+
+	h.SpecVersion = spec_version
 	h.RootOffset = binary.LittleEndian.Uint64(d[8 : 8+8])
 	h.RootLength = binary.LittleEndian.Uint64(d[16 : 16+8])
 	h.MetadataOffset = binary.LittleEndian.Uint64(d[24 : 24+8])
@@ -255,7 +268,7 @@ func deserialize_header(d []byte) HeaderV3 {
 	h.CenterLonE7 = int32(binary.LittleEndian.Uint32(d[119 : 119+4]))
 	h.CenterLatE7 = int32(binary.LittleEndian.Uint32(d[123 : 123+4]))
 
-	return h
+	return h, nil
 }
 
 func build_roots_leaves(entries []EntryV3, leaf_size int) ([]byte, []byte, int) {

diff --git a/pmtiles/directory_test.go b/pmtiles/directory_test.go
@@ -83,7 +83,7 @@ func TestHeaderRoundtrip(t *testing.T) {
 	header.CenterLonE7 = 3.1 * 10000000
 	header.CenterLatE7 = 3.2 * 10000000
 	b := serialize_header(header)
-	result := deserialize_header(b)
+	result, _ := deserialize_header(b)
 	if result.RootOffset != 1 {
 		t.Fatalf(`expected to be 1`)
 	}

diff --git a/pmtiles/loop.go b/pmtiles/loop.go
@@ -138,7 +138,11 @@ func (loop *Loop) Start() {
 						}
 
 						if is_root {
-							header := deserialize_header(b[0:HEADERV3_LEN_BYTES])
+							header, err := deserialize_header(b[0:HEADERV3_LEN_BYTES])
+							if err != nil {
+								loop.logger.Printf("parsing header failed: %v", err)
+								return
+							}
 
 							// populate the root first before header
 							root_entries := deserialize_entries(bytes.NewBuffer(b[header.RootOffset : header.RootOffset+header.RootLength]))

diff --git a/pmtiles/show.go b/pmtiles/show.go
@@ -46,7 +46,12 @@ func Show(logger *log.Logger, args []string) error {
 	}
 	r.Close()
 
-	header := deserialize_header(b[0:HEADERV3_LEN_BYTES])
+	header, err := deserialize_header(b[0:HEADERV3_LEN_BYTES])
+	if err != nil {
+		// check to see if it's a V2 file
+
+		return fmt.Errorf("Failed to read %s, %w", file, err)
+	}
 
 	if arg_z == "" {
 		var tile_type string
@@ -62,6 +67,7 @@ func Show(logger *log.Logger, args []string) error {
 		default:
 			tile_type = "Unknown"
 		}
+		fmt.Printf("pmtiles spec version: %d\n", header.SpecVersion)
 		fmt.Printf("total size: %s\n", humanize.Bytes(uint64(r.Size())))
 		fmt.Printf("tile type: %s\n", tile_type)
 		fmt.Printf("bounds: %f,%f %f,%f\n", float64(header.MinLonE7)/10000000, float64(header.MinLatE7)/10000000, float64(header.MaxLonE7)/10000000, float64(header.MaxLatE7)/10000000)