vaultik/internal/blobgen/compress.go

// Package blobgen implements the blob data pipeline: streaming zstd
// compression, age encryption, and SHA256 content hashing for blob
// creation, plus the matching decrypt/decompress/verify reader.
package blobgen

import (
	"bytes"
	"encoding/hex"
	"fmt"
	"io"
)

// CompressResult contains the results of compression
type CompressResult struct {
	Data             []byte
	UncompressedSize int64
	CompressedSize   int64
	SHA256           string
}

// CompressData compresses and encrypts data, returning the result with hash
func CompressData(
	data []byte, compressionLevel int, recipients []string,
) (*CompressResult, error) {
	var buf bytes.Buffer

	// Create writer
	w, err := NewWriter(&buf, compressionLevel, recipients)
	if err != nil {
		return nil, fmt.Errorf("creating writer: %w", err)
	}

	// Write data
	_, err = w.Write(data)
	if err != nil {
		_ = w.Close()

		return nil, fmt.Errorf("writing data: %w", err)
	}

	// Close to flush
	err = w.Close()
	if err != nil {
		return nil, fmt.Errorf("closing writer: %w", err)
	}

	return &CompressResult{
		Data:             buf.Bytes(),
		UncompressedSize: int64(len(data)),
		CompressedSize:   int64(buf.Len()),
		SHA256:           hex.EncodeToString(w.Sum256()),
	}, nil
}

// CompressStream compresses and encrypts from reader to writer, returning
// the number of uncompressed bytes written and the content hash.
func CompressStream(
	dst io.Writer, src io.Reader, compressionLevel int, recipients []string,
) (int64, string, error) {
	// Create writer
	w, err := NewWriter(dst, compressionLevel, recipients)
	if err != nil {
		return 0, "", fmt.Errorf("creating writer: %w", err)
	}

	closed := false
	defer func() {
		if !closed {
			_ = w.Close()
		}
	}()

	// Copy data
	_, err = io.Copy(w, src)
	if err != nil {
		return 0, "", fmt.Errorf("copying data: %w", err)
	}

	// Close to flush
	err = w.Close()
	if err != nil {
		return 0, "", fmt.Errorf("closing writer: %w", err)
	}

	closed = true

	return w.BytesWritten(), hex.EncodeToString(w.Sum256()), nil
}