commitgraph: Move out of format/

1 files changed, 114 insertions, 0 deletions

diff --git a/commitgraph/read/bloom.go b/commitgraph/read/bloom.go
new file mode 100644
index 00000000..c7e3e426
--- /dev/null
+++ b/commitgraph/read/bloom.go
@@ -0,0 +1,114 @@
+package read
+
+import (
+	"encoding/binary"
+
+	"codeberg.org/lindenii/furgit/commitgraph/bloom"
+	"codeberg.org/lindenii/furgit/internal/intconv"
+)
+
+// HasBloom reports whether any layer has changed-path Bloom data.
+func (reader *Reader) HasBloom() bool {
+	for i := range reader.layers {
+		layer := &reader.layers[i]
+		if layer.chunkBloomIndex != nil && layer.chunkBloomData != nil && layer.bloomSettings != nil {
+			return true
+		}
+	}
+
+	return false
+}
+
+// BloomVersion returns the changed-path Bloom hash version, or 0 if absent.
+func (reader *Reader) BloomVersion() uint8 {
+	for i := len(reader.layers) - 1; i >= 0; i-- {
+		layer := &reader.layers[i]
+		if layer.bloomSettings != nil {
+			version, err := intconv.Uint32ToUint8(layer.bloomSettings.HashVersion)
+			if err != nil {
+				return 0
+			}
+
+			return version
+		}
+	}
+
+	return 0
+}
+
+// BloomFilterAt returns one commit's changed-path Bloom filter.
+//
+// Returns BloomUnavailableError when this commit graph has no Bloom data.
+func (reader *Reader) BloomFilterAt(pos Position) (*bloom.Filter, error) {
+	layer, err := reader.layerByPosition(pos)
+	if err != nil {
+		return nil, err
+	}
+
+	if layer.chunkBloomIndex == nil || layer.chunkBloomData == nil || layer.bloomSettings == nil {
+		return nil, &BloomUnavailableError{Pos: pos}
+	}
+
+	start, end, err := bloomRange(layer, pos.Index)
+	if err != nil {
+		return nil, err
+	}
+
+	filter := bloom.NewFilter(
+		layer.chunkBloomData[bloom.DataHeaderSize+start:bloom.DataHeaderSize+end],
+		*layer.bloomSettings,
+	)
+
+	return filter, nil
+}
+
+func bloomRange(layer *layer, commitIndex uint32) (int, int, error) {
+	off64 := uint64(commitIndex) * 4
+
+	off, err := intconv.Uint64ToInt(off64)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	end := binary.BigEndian.Uint32(layer.chunkBloomIndex[off : off+4])
+
+	var start uint32
+
+	if commitIndex > 0 {
+		prevOff64 := uint64(commitIndex-1) * 4
+
+		prevOff, err := intconv.Uint64ToInt(prevOff64)
+		if err != nil {
+			return 0, 0, err
+		}
+
+		start = binary.BigEndian.Uint32(layer.chunkBloomIndex[prevOff : prevOff+4])
+	}
+
+	if end < start {
+		return 0, 0, &MalformedError{Path: layer.path, Reason: "invalid BIDX range"}
+	}
+
+	bdatLen := len(layer.chunkBloomData) - bloom.DataHeaderSize
+
+	bdatLenU32, err := intconv.IntToUint32(bdatLen)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	if end > bdatLenU32 {
+		return 0, 0, &MalformedError{Path: layer.path, Reason: "BIDX range out of BDAT bounds"}
+	}
+
+	startInt, err := intconv.Uint64ToInt(uint64(start))
+	if err != nil {
+		return 0, 0, err
+	}
+
+	endInt, err := intconv.Uint64ToInt(uint64(end))
+	if err != nil {
+		return 0, 0, err
+	}
+
+	return startInt, endInt, nil
+}