Change default scan buffer size to 256kb

...and make it configurable

README.md

@@ -251,6 +251,18 @@ Default value for StickySelection is false.
 
 OnCancel is equivalent to `--on-cancel` command line option.
 
+### MaxScanBufferSize
+
+```json
+{
+    "MaxScanBufferSize": 256
+}
+```
+
+Controls the buffer sized used by `bufio.Scanner`, which is responsible for
+reading the input lines. If you believe that your input has very long lines
+that prohibit peco from reading them, try increasing this number
+
 ## Keymaps
 
 Example:

interface.go

@@ -78,6 +78,7 @@ type Peco struct {
 	keymap                  Keymap
 	layoutType              string
 	location                Location
+	maxScanBufferSize       int
 	mutex                   sync.Mutex
 	onCancel                string
 	prompt                  string
@@ -167,9 +168,9 @@ type Screen interface {
 
 // Termbox just hands out the processing to the termbox library
 type Termbox struct {
-	mutex sync.Mutex
-	resumeCh chan(struct{})
-	suspendCh chan(struct{})
+	mutex     sync.Mutex
+	resumeCh  chan (struct{})
+	suspendCh chan (struct{})
 }
 
 // View handles the drawing/updating the screen
@@ -299,6 +300,7 @@ type Config struct {
 	Command             []CommandConfig
 	QueryExecutionDelay int
 	StickySelection     bool
+	MaxScanBufferSize   int
 
 	// If this is true, then the prefix for single key jump mode
 	// is displayed by default.

peco.go

@@ -503,6 +503,11 @@ func (p *Peco) ApplyConfig(opts CLIOptions) error {
 		}
 	}
 
+	p.maxScanBufferSize = 256
+	if v := p.config.MaxScanBufferSize; v > 0 {
+		p.maxScanBufferSize = v
+	}
+
 	p.enableSep = opts.OptEnableNullSep
 
 	if i := opts.OptInitialIndex; i >= 0 {

source.go

@@ -77,7 +77,12 @@ func (s *Source) Setup(ctx context.Context, state *Peco) {
 		// Note: this will be a no-op if notify.Do has been called before
 		defer notify.Do(notifycb)
 
+		if pdebug.Enabled {
+			pdebug.Printf("Source: using buffer size of %dkb", state.maxScanBufferSize)
+		}
+		scanbuf := make([]byte, state.maxScanBufferSize*1024)
 		scanner := bufio.NewScanner(s.in)
+		scanner.Buffer(scanbuf, 0)
 		defer func() {
 			if util.IsTty(s.in) {
 				return
@@ -95,7 +100,18 @@ func (s *Source) Setup(ctx context.Context, state *Peco) {
 			}
 
 			defer close(lines)
-			for scanner.Scan() {
+			for loop := true; loop; {
+				if !scanner.Scan() {
+					switch err := scanner.Err(); err {
+					case nil: // if error was io.EOF, returns nil
+						loop = false
+					default:
+						if pdebug.Enabled {
+							pdebug.Printf("err: %s", err)
+						}
+					}
+					continue
+				}
 				lines <- scanner.Text()
 				scanned++
 			}