press: Added experimental compression remote - implements #2098, #1356, #675

backend/press/alg_exec.go

@@ -0,0 +1,98 @@
+package press
+
+// This file implements shell exec algorithms that require binaries.
+import (
+	"bytes"
+	"io"
+	"os/exec"
+)
+
+// XZ command
+const xzcommand = "xz" // Name of xz binary (if available)
+
+// ExecHeader - Header we add to an exec file. We don't need this.
+var ExecHeader = []byte{}
+
+// Function that checks whether XZ is present in the system
+func checkXZ() bool {
+	_, err := exec.LookPath("xz")
+	if err != nil {
+		return false
+	}
+	return true
+}
+
+// Function that gets binary paths if needed
+func getBinPaths(c *Compression, mode int) (err error) {
+	err = nil
+	if mode == XZMin || mode == XZDefault {
+		c.BinPath, err = exec.LookPath(xzcommand)
+	}
+	return err
+}
+
+// Function that compresses a block using a shell command without wrapping in gzip. Requires an binary corresponding with the command.
+func (c *Compression) compressBlockExec(in []byte, out io.Writer, binaryPath string, args []string) (compressedSize uint32, uncompressedSize int64, err error) {
+	// Initialize compression subprocess
+	subprocess := exec.Command(binaryPath, args...)
+	stdin, err := subprocess.StdinPipe()
+	if err != nil {
+		return 0, 0, err
+	}
+
+	// Run subprocess that creates compressed file
+	stdinError := make(chan error)
+	go func() {
+		_, err := stdin.Write(in)
+		_ = stdin.Close()
+		stdinError <- err
+	}()
+
+	// Get output
+	output, err := subprocess.Output()
+	if err != nil {
+		return 0, 0, err
+	}
+
+	// Copy over
+	n, err := io.Copy(out, bytes.NewReader(output))
+	if err != nil {
+		return uint32(n), int64(len(in)), err
+	}
+
+	// Check if there was an error and return
+	err = <-stdinError
+
+	return uint32(n), int64(len(in)), err
+}
+
+// Utility function to decompress a block range using a shell command which wasn't wrapped in gzip
+func decompressBlockRangeExec(in io.Reader, out io.Writer, binaryPath string, args []string) (n int, err error) {
+	// Decompress actual compression
+	// Initialize decompression subprocess
+	subprocess := exec.Command(binaryPath, args...)
+	stdin, err := subprocess.StdinPipe()
+	if err != nil {
+		return 0, err
+	}
+
+	// Run subprocess that copies over compressed block
+	stdinError := make(chan error)
+	go func() {
+		_, err := io.Copy(stdin, in)
+		_ = stdin.Close()
+		stdinError <- err
+	}()
+
+	// Get output, copy, and return
+	output, err := subprocess.Output()
+	if err != nil {
+		return 0, err
+	}
+	n64, err := io.Copy(out, bytes.NewReader(output))
+	if err != nil {
+		return int(n64), err
+	}
+	err = <-stdinError
+	return int(n64), err
+}