Finishing touches

Added FastOptions as an alternative to DefaultOptions
A few performance improvements
A few bug fixes

extraction_options.go

@@ -3,28 +3,47 @@ package squashfs
 import (
 	"io"
 	"io/fs"
-	"os"
+	"runtime"
 
 	"github.com/CalebQ42/squashfs/internal/routinemanager"
 )
 
 type ExtractionOptions struct {
 	manager            *routinemanager.Manager
-	LogOutput          io.Writer   //Where the verbose log should write. Defaults to os.Stdout.
+	LogOutput          io.Writer   //Where the verbose log should write.
 	DereferenceSymlink bool        //Replace symlinks with the target file.
 	UnbreakSymlink     bool        //Try to make sure symlinks remain unbroken when extracted, without changing the symlink.
 	Verbose            bool        //Prints extra info to log on an error.
 	IgnorePerm         bool        //Ignore file's permissions and instead use Perm.
 	Perm               fs.FileMode //Permission to use when IgnorePerm. Defaults to 0777.
-	SimultaneousFiles  uint16      //Number of files to process in parallel. Defaults to 10.
-	ExtractionRoutines uint16      //Number of goroutines to use for each file's extraction. Only applies to regular files. Defaults to 10.
+	SimultaneousFiles  uint16      //Number of files to process in parallel. Default set based on runtime.NumCPU().
+	ExtractionRoutines uint16      //Number of goroutines to use for each file's extraction. Only applies to regular files. Default set based on runtime.NumCPU().
 }
 
+// The default extraction options.
 func DefaultOptions() *ExtractionOptions {
+	cores := uint16(runtime.NumCPU() / 2)
+	var files, routines uint16
+	if cores <= 4 {
+		files = 1
+		routines = cores
+	} else {
+		files = cores - 4
+		routines = 4
+	}
 	return &ExtractionOptions{
-		LogOutput:          os.Stdout,
 		Perm:               0777,
-		SimultaneousFiles:  10,
-		ExtractionRoutines: 10,
+		SimultaneousFiles:  files,
+		ExtractionRoutines: routines,
+	}
+}
+
+// Less limited default options. Can run up 2x faster than DefaultOptions.
+// Tends to use all available CPU resources.
+func FastOptions() *ExtractionOptions {
+	return &ExtractionOptions{
+		Perm:               0777,
+		SimultaneousFiles:  uint16(runtime.NumCPU()),
+		ExtractionRoutines: uint16(runtime.NumCPU()),
 	}
 }