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package v2
import "bytes"
const (
chunkSigLen = 4 // Length of a chunk signature
chunkSigOffset = 4 // Offset of each chunk signature in chunkSignatures
)
// chunkSignatures contains the coalesced byte signatures for each chunk type.
// The order of the signatures must match the order of the ChunkType constants.
// (When adding new chunk types you must avoid introducing ambiguity, and you may need to add padding separators to this list or reorder these signatures.)
// (i.e. it would not be possible to add a new chunk type with the signature "IDFO" without some reordering or the addition of separators.)
var chunkSignatures = []byte("OIDFOIDLCDATGDA2GDO2EDGEBIDXBDATBASE\000\000\000\000")
// ChunkType represents the type of a chunk in the commit graph file.
type ChunkType int
const (
OIDFanoutChunk ChunkType = iota // "OIDF"
OIDLookupChunk // "OIDL"
CommitDataChunk // "CDAT"
GenerationDataChunk // "GDA2"
GenerationDataOverflowChunk // "GDO2"
ExtraEdgeListChunk // "EDGE"
BloomFilterIndexChunk // "BIDX"
BloomFilterDataChunk // "BDAT"
BaseGraphsListChunk // "BASE"
ZeroChunk // "\000\000\000\000"
)
// Signature returns the byte signature for the chunk type.
func (ct ChunkType) Signature() []byte {
if ct >= BaseGraphsListChunk || ct < 0 { // not a valid chunk type just return ZeroChunk
return chunkSignatures[ZeroChunk*chunkSigOffset : ZeroChunk*chunkSigOffset+chunkSigLen]
}
return chunkSignatures[ct*chunkSigOffset : ct*chunkSigOffset+chunkSigLen]
}
// ChunkTypeFromBytes returns the chunk type for the given byte signature.
func ChunkTypeFromBytes(b []byte) (ChunkType, bool) {
idx := bytes.Index(chunkSignatures, b)
if idx == -1 || idx%chunkSigOffset != 0 { // not found, or not aligned at chunkSigOffset
return -1, false
}
return ChunkType(idx / chunkSigOffset), true
}
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