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mirror of https://github.com/wader/fq.git synced 2024-11-23 18:56:52 +03:00
fq/format/ape/apev2.go
Mattias Wadman 2fc0a71a47 decode: Refactor scalar usage
Move scalar into own package.
Split scalar code into decode related scalar code (that reads etc) and
scalar code that just transform the scalar value.
Use a scalar.Mapper interface instead of just a function.
Make mappers, assert and validat impement the interface.
2021-12-02 17:39:26 +01:00

80 lines
1.9 KiB
Go

package ape
// http://wiki.hydrogenaud.io/index.php?title=APE_Tags_Header
import (
"github.com/wader/fq/format"
"github.com/wader/fq/format/registry"
"github.com/wader/fq/pkg/decode"
)
var imageFormat decode.Group
func init() {
registry.MustRegister(decode.Format{
Name: format.APEV2,
Description: "APEv2 metadata tag",
DecodeFn: apev2Decode,
Dependencies: []decode.Dependency{
{Names: []string{format.IMAGE}, Group: &imageFormat},
},
})
}
func apev2Decode(d *decode.D, in interface{}) interface{} {
d.Endian = decode.LittleEndian
headerFooterFn := func(d *decode.D, name string) uint64 {
var tagCount uint64
d.FieldStruct(name, func(d *decode.D) {
d.FieldUTF8("preamble", 8, d.AssertStr("APETAGEX"))
d.FieldU32("version")
d.FieldU32("tag_size")
tagCount = d.FieldU32("item_count")
d.FieldU32("flags")
d.FieldRawLen("reserved", 64, d.BitBufIsZero())
})
return tagCount
}
tagCount := headerFooterFn(d, "header")
if tagCount > 1000 {
d.Fatalf("too many tags %d", tagCount)
}
d.FieldArray("tags", func(d *decode.D) {
for i := uint64(0); i < tagCount; i++ {
d.FieldStruct("tag", func(d *decode.D) {
itemSize := d.FieldU32("item_size")
var binaryItem bool
d.FieldStruct("item_flags", func(d *decode.D) {
d.FieldU6("unused0")
binaryItem = d.FieldBool("binary")
d.FieldU25("unused1")
})
keyLen := d.PeekFindByte(0, -1)
d.FieldUTF8("key", int(keyLen))
d.FieldU8("key_terminator")
if binaryItem {
d.LenFn(int64(itemSize)*8, func(d *decode.D) {
d.FieldUTF8Null("filename")
// assume image if binary
dv, _, _ := d.TryFieldFormat("value", imageFormat, nil)
if dv == nil {
// TODO: framed and unknown instead?
d.FieldRawLen("value", d.BitsLeft())
}
})
} else {
d.FieldUTF8("value", int(itemSize))
}
})
}
})
// TODO: check footer flag
headerFooterFn(d, "footer")
return nil
}