Reuse bufio.Reader, fix examples, and fix lint issues

Store a single *bufio.Reader on Controller instead of allocating one per
Query/QueryController call, avoiding repeated allocations and potential
buffered data loss. Fix examples to use updated query.Bool API and
non-constant format strings. Fix misspelling and unchecked error return
flagged by linter. Reformat long lines with golines.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: matthewrankin

.golangci.yaml

@@ -0,0 +1,28 @@
+version: "2"
+
+linters:
+  default: standard
+  enable:
+    - staticcheck
+    - govet
+    - errcheck
+    - ineffassign
+    - unused
+    - gosec
+    - misspell
+    - bodyclose
+    - contextcheck
+
+formatters:
+  enable:
+    - gofmt
+    - goimports
+    - golines
+
+run:
+  timeout: 5m
+  tests: true
+
+issues:
+  max-issues-per-linter: 0
+  max-same-issues: 0

CLAUDE.md

@@ -4,7 +4,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 ## Project Overview
 
-Go package for communicating with Prologix GPIB-USB and GPIB-ETHERNET controllers, which bridge a computer to GPIB (IEEE 488) test instruments. Part of the [gotmc](https://github.com/gotmc) ecosystem and designed to work with the [ivi](https://github.com/gotmc/ivi) package for standardized instrument control.
+Go package for communicating with Prologix GPIB-USB and GPIB-ETHERNET controllers, which bridge a computer to GPIB (IEEE 488) test instruments. Part of the [gotmc](https://github.com/gotmc) ecosystem and designed to work with the [ivi](https://github.com/gotmc/ivi) package for standardized instrument control. Requires Go 1.25+.
 
 ## Build & Test Commands
 
@@ -23,6 +23,8 @@ go test -run TestIsPrimaryAddressValid ./...
 
 # HTML coverage report
 just cover
+
+# Run example (requires hardware): just key3631 /dev/ttyUSB0 5
 ```
 
 `just` (Justfile) is the task runner; there is no Makefile.
@@ -34,13 +36,14 @@ The package uses a layered design separating transport from GPIB protocol logic:
 - **Transport layer** (`driver/`): Provides `io.ReadWriter` implementations for different connection types. Currently only `driver/vcp/` (Virtual COM Port via serial) is implemented. The `driver/usb/` and `driver/net/` directories are placeholders for future D2XX and Ethernet support.
 - **Controller** (`controller.go`): Core type wrapping any `io.ReadWriter`. Constructed via `NewController()` with functional options (`WithSecondaryAddress`, `WithDebug`, `WithAR488`). Handles GPIB address setup, controller initialization commands, and the `++` command prefix for Prologix-specific commands.
 - **Commands** (`commands.go`): Methods on `Controller` for Prologix `++` commands (e.g., `ClearDevice`, `SetReadTimeout`, `Version`, `InstrumentAddress`).
+- **Examples** (`examples/vcp/`): Working examples for real instruments (E3631A, DS345, Fluke 45, 33220A). All follow the same pattern: open VCP → create Controller → query version → run device commands → restore front panel → close.
 
 Key design points:
 - `Controller` distinguishes between instrument communication (`Command`, `Query`, `Write`) and Prologix controller commands (`CommandController`, `QueryController`) which prepend `++`.
 - Context-aware I/O: `Controller` checks if the underlying `io.ReadWriter` implements optional `ContextReader`/`ContextWriter` interfaces. If so, it delegates directly; otherwise it falls back to goroutine-based context handling.
 - The `WithAR488()` option skips `verbose` and `savecfg` commands for Arduino AR488 compatibility.
 - `Query` automatically sends `++read eoi` when auto read-after-write is disabled.
-- Binary data methods (`Write`/`Read`) vs string methods (`WriteString`, `Command`, `Query`) handle GPIB character escaping differently.
+- Binary data methods (`Write`/`Read`) vs string methods (`WriteString`, `Command`, `Query`) handle GPIB character escaping differently. Prologix strips unescaped LF, CR, ESC, and `+` characters, so `Write` escapes them automatically.
 - VCP serial config is hardcoded to Prologix defaults: 115200 baud, 7 data bits, even parity, 1 stop bit.
 
 ## Dependencies

commands.go

@@ -101,8 +101,14 @@ func (c *Controller) InstrumentAddress() (int, int, error) {
 	var errs []error
 
 	if int(pri) != c.primaryAddr {
-		errs = append(errs,
-			fmt.Errorf("internal state mismatch, primary address was %d now %d", c.primaryAddr, pri))
+		errs = append(
+			errs,
+			fmt.Errorf(
+				"internal state mismatch, primary address was %d now %d",
+				c.primaryAddr,
+				pri,
+			),
+		)
 	}
 	c.primaryAddr = int(pri)
 
@@ -117,8 +123,14 @@ func (c *Controller) InstrumentAddress() (int, int, error) {
 		}
 	}
 	if c.secondaryAddr != int(sec) {
-		errs = append(errs,
-			fmt.Errorf("internal state mismatch, secondary address was %d now %d", c.secondaryAddr, sec))
+		errs = append(
+			errs,
+			fmt.Errorf(
+				"internal state mismatch, secondary address was %d now %d",
+				c.secondaryAddr,
+				sec,
+			),
+		)
 	}
 	c.secondaryAddr = int(sec)
 

controller.go

@@ -30,6 +30,7 @@ type ContextWriter interface {
 // Controller models a GPIB controller-in-charge.
 type Controller struct {
 	rw               io.ReadWriter
+	reader           *bufio.Reader
 	primaryAddr      int
 	hasSecondaryAddr bool
 	secondaryAddr    int
@@ -57,6 +58,7 @@ func NewController(
 ) (*Controller, error) {
 	c := Controller{
 		rw:               rw,
+		reader:           bufio.NewReader(rw),
 		primaryAddr:      addr,
 		hasSecondaryAddr: false,
 		auto:             false,
@@ -130,7 +132,7 @@ func WithSecondaryAddress(addr int) ControllerOption {
 // WithDebug causes commands and responses to be logged.
 func WithDebug() ControllerOption { return func(c *Controller) { c.debug = true } }
 
-// WithAR488 slightly alters the init commands, for compatiblity with the
+// WithAR488 slightly alters the init commands, for compatibility with the
 // Arduino-based AR488. Specifically, we do not emit 'verbose 0', nor do
 // we toggle savecfg.
 func WithAR488() ControllerOption { return func(c *Controller) { c.ar488 = true } }
@@ -258,7 +260,7 @@ func (c *Controller) Query(cmd string) (string, error) {
 			return "", fmt.Errorf("error sending %q command: %w", readCmd, err)
 		}
 	}
-	s, err := bufio.NewReader(c.rw).ReadString(c.eotChar)
+	s, err := c.reader.ReadString(c.eotChar)
 	if errors.Is(err, io.EOF) {
 		log.Printf("found EOF")
 		return s, nil
@@ -276,7 +278,7 @@ func (c *Controller) QueryController(cmd string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	s, err := bufio.NewReader(c.rw).ReadString(c.eotChar)
+	s, err := c.reader.ReadString(c.eotChar)
 	if c.debug {
 		log.Printf("read data: %q", s)
 	}

driver/vcp/vcp.go

@@ -65,7 +65,7 @@ func (vcp *VCP) ReadContext(ctx context.Context, p []byte) (n int, err error) {
 		if err := vcp.port.SetReadTimeout(timeout); err != nil {
 			return 0, err
 		}
-		defer vcp.port.SetReadTimeout(serial.NoTimeout)
+		defer func() { _ = vcp.port.SetReadTimeout(serial.NoTimeout) }()
 	}
 	n, err = vcp.port.Read(p)
 	if err != nil {

examples/vcp/ds345/main.go

@@ -116,7 +116,7 @@ func main() {
 	}
 	for _, cmd := range cmds {
 		log.Printf("Sending command: %s", cmd)
-		err = gpib.Command(cmd)
+		err = gpib.Command("%s", cmd)
 		if err != nil {
 			log.Fatal(err)
 		}

examples/vcp/e3631a/main.go

@@ -9,10 +9,10 @@ import (
 	"flag"
 	"io"
 	"log"
+	"strings"
 
 	"github.com/gotmc/prologix"
 	"github.com/gotmc/prologix/driver/vcp"
-	"github.com/gotmc/query"
 )
 
 var (
@@ -112,17 +112,18 @@ func main() {
 	}
 
 	for _, cmd := range cmds {
-		err = gpib.Command(cmd)
+		err = gpib.Command("%s", cmd)
 		if err != nil {
 			log.Fatal(err)
 		}
 	}
 
 	// Query the output state
-	state, err := query.Bool(gpib, "OUTP:STAT?")
+	stateStr, err := gpib.Query("OUTP:STAT?")
 	if err != nil && err != io.EOF {
 		log.Fatalf("error querying serial port: %s", err)
 	}
+	state := strings.TrimSpace(stateStr) == "1"
 	if state {
 		log.Println("output is enabled")
 	} else {
@@ -135,7 +136,7 @@ func main() {
 	}
 
 	for _, cmd := range cmds {
-		err = gpib.Command(cmd)
+		err = gpib.Command("%s", cmd)
 		if err != nil {
 			log.Fatal(err)
 		}
@@ -156,10 +157,11 @@ func main() {
 	log.Printf("voltage = %s", volt)
 
 	// Query the output state
-	state, err = query.Bool(gpib, "OUTP:STAT?")
+	stateStr, err = gpib.Query("OUTP:STAT?")
 	if err != nil && err != io.EOF {
 		log.Fatalf("error querying serial port: %s", err)
 	}
+	state = strings.TrimSpace(stateStr) == "1"
 	if state {
 		log.Println("output is enabled")
 	} else {

examples/vcp/key33220a/main.go

@@ -125,7 +125,7 @@ func main() {
 	}
 	for _, cmd := range cmds {
 		log.Printf("Sending command: %s", cmd)
-		err = gpib.Command(cmd)
+		err = gpib.Command("%s", cmd)
 		if err != nil {
 			log.Fatal(err)
 		}