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package read
import (
"bufio"
"errors"
"fmt"
"os"
"strings"
"codeberg.org/lindenii/furgit/internal/intconv"
"codeberg.org/lindenii/furgit/objectid"
)
func openChain(root *os.Root, algo objectid.Algorithm) (*Reader, error) {
chainPath := "info/commit-graphs/commit-graph-chain"
file, err := root.Open(chainPath)
if err != nil {
if errors.Is(err, os.ErrNotExist) {
return nil, &MalformedError{Path: chainPath, Reason: "missing commit-graph-chain"}
}
return nil, err
}
scanner := bufio.NewScanner(file)
hashes := make([]string, 0)
for scanner.Scan() {
line := strings.TrimSpace(scanner.Text())
if line == "" {
continue
}
hashes = append(hashes, line)
}
scanErr := scanner.Err()
closeErr := file.Close()
if scanErr != nil {
return nil, scanErr
}
if closeErr != nil {
return nil, closeErr
}
if len(hashes) == 0 {
return nil, &MalformedError{Path: chainPath, Reason: "empty chain"}
}
layers := make([]layer, 0, len(hashes))
var total uint32
hashVersion, err := intconv.Uint32ToUint8(algo.PackHashID())
if err != nil {
return nil, err
}
for i, hashHex := range hashes {
expectedBaseCount, err := intconv.IntToUint32(i)
if err != nil {
closeLayers(layers)
return nil, err
}
if len(hashHex) != algo.HexLen() {
closeLayers(layers)
return nil, &MalformedError{
Path: chainPath,
Reason: fmt.Sprintf("invalid graph hash length at line %d", i+1),
}
}
relPath := fmt.Sprintf("info/commit-graphs/graph-%s.graph", hashHex)
loaded, loadErr := openLayer(root, relPath, algo)
if loadErr != nil {
closeLayers(layers)
return nil, loadErr
}
if loaded.baseCount != expectedBaseCount {
_ = loaded.close()
closeLayers(layers)
return nil, &MalformedError{
Path: relPath,
Reason: fmt.Sprintf("BASE count %d does not match chain depth %d", loaded.baseCount, i),
}
}
validateErr := validateChainBaseHashes(algo, hashes, i, loaded)
if validateErr != nil {
_ = loaded.close()
closeLayers(layers)
return nil, validateErr
}
loaded.globalFrom = total
loaded.baseCount = expectedBaseCount
totalNext := total + loaded.numCommits
if totalNext < total {
_ = loaded.close()
closeLayers(layers)
return nil, &MalformedError{Path: relPath, Reason: "total commit count overflow"}
}
total = totalNext
layers = append(layers, *loaded)
}
out := &Reader{
algo: algo,
hashVersion: hashVersion,
layers: layers,
total: total,
}
return out, nil
}
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