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package apply
import (
"fmt"
"io"
)
// ReadHeaderSizes reads the first two varints in one inflated delta stream.
func ReadHeaderSizes(reader io.Reader) (int, int, error) {
// Two Git varints are read here. Each can take up to 10 bytes.
var buf [20]byte
n := 0
for {
if n >= len(buf) {
return 0, 0, fmt.Errorf("format/delta/apply: malformed delta varint")
}
if _, err := io.ReadFull(reader, buf[n:n+1]); err != nil {
return 0, 0, fmt.Errorf("format/delta/apply: malformed delta varint: %w", err)
}
n++
if buf[n-1]&0x80 == 0 {
break
}
}
pos := 0
srcSize, err := readVarint(buf[:n], &pos)
if err != nil {
return 0, 0, err
}
for {
if n >= len(buf) {
return 0, 0, fmt.Errorf("format/delta/apply: malformed delta varint")
}
if _, err := io.ReadFull(reader, buf[n:n+1]); err != nil {
return 0, 0, fmt.Errorf("format/delta/apply: malformed delta varint: %w", err)
}
n++
if buf[n-1]&0x80 == 0 {
break
}
}
dstSize, err := readVarint(buf[:n], &pos)
if err != nil {
return 0, 0, err
}
return srcSize, dstSize, nil
}
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