golang.org/x/sys v0.22.0: unix.Read

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify golang.org/x/sys/unix.Read in pkg:golang/golang.org/x/sys@v0.22.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/sys@v0.22.0
Demonstrate these symbols/APIs:
  - golang.org/x/sys/unix.Read

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:bf8d3b7aa93c3bbee1bde790692159ced8481698146803977a52f893f9ecbe70","contract":["unix.Read reads bytes from a valid file descriptor into a buffer","unix.Read returns n=0 and nil error when reading into an empty slice","unix.Read returns n=0 and nil error at end of file","unix.Read returns unix.EBADF for an invalid file descriptor","unix.Read returns unix.EBADF after a file descriptor is closed"],"goal":"verify golang.org/x/sys/unix.Read in pkg:golang/golang.org/x/sys@v0.22.0","kind":"HOW","packages":["pkg:golang/golang.org/x/sys@v0.22.0"],"schemaVersion":1,"symbols":["golang.org/x/sys/unix.Read"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/sys@v0.22.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/sys@v0.22.0","symbols":["golang.org/x/sys/unix.Read"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require golang.org/x/sys v0.22.0

golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

package main

import (
	"fmt"
	"os"

	"golang.org/x/sys/unix"
)

func main() {
	var fds [2]int
	if err := unix.Pipe(fds[:]); err != nil {
		fmt.Fprintf(os.Stderr, "failed to create pipe: %v\n", err)
		os.Exit(1)
	}
	defer unix.Close(fds[0])
	defer unix.Close(fds[1])

	message := []byte("hello unix.Read")
	if _, err := unix.Write(fds[1], message); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write to pipe: %v\n", err)
		os.Exit(1)
	}

	buf := make([]byte, len(message))
	n, err := unix.Read(fds[0], buf)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unix.Read failed: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Read %d bytes: %s\n", n, string(buf[:n]))
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.Read in pkg:golang/golang.org/x/sys@v0.22.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/sys@v0.22.0"
  ],
  "symbols": [
    "golang.org/x/sys/unix.Read"
  ]
}

package main

import (
	"bytes"
	"errors"
	"fmt"
	"os"

	"golang.org/x/sys/unix"
)

func main() {
	if err := runTests(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract test failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All contract assertions passed.")
}

func runTests() error {
	// 1. unix.Read reads bytes from a valid file descriptor into a buffer
	var p1 [2]int
	if err := unix.Pipe(p1[:]); err != nil {
		return fmt.Errorf("pipe creation failed: %w", err)
	}
	defer unix.Close(p1[0])
	defer unix.Close(p1[1])

	data := []byte("contract-read-data")
	if _, err := unix.Write(p1[1], data); err != nil {
		return fmt.Errorf("unix.Write failed: %w", err)
	}

	buf := make([]byte, len(data))
	n, err := unix.Read(p1[0], buf)
	if err != nil {
		return fmt.Errorf("unix.Read failed on valid fd: %w", err)
	}
	if n != len(data) || !bytes.Equal(buf[:n], data) {
		return fmt.Errorf("read mismatch: expected %q, got %q", string(data), string(buf[:n]))
	}

	// 2. unix.Read returns n=0 and nil error when reading into an empty slice
	var p2 [2]int
	if err := unix.Pipe(p2[:]); err != nil {
		return fmt.Errorf("pipe creation failed: %w", err)
	}
	defer unix.Close(p2[0])
	defer unix.Close(p2[1])

	nEmpty, err := unix.Read(p2[0], []byte{})
	if err != nil {
		return fmt.Errorf("unix.Read with empty slice returned error: %w", err)
	}
	if nEmpty != 0 {
		return fmt.Errorf("expected 0 bytes read for empty slice, got %d", nEmpty)
	}

	// 3. unix.Read returns n=0 and nil error at end of file
	var p3 [2]int
	if err := unix.Pipe(p3[:]); err != nil {
		return fmt.Errorf("pipe creation failed: %w", err)
	}
	defer unix.Close(p3[0])

	msg := []byte("eof-check")
	if _, err := unix.Write(p3[1], msg); err != nil {
		unix.Close(p3[1])
		return fmt.Errorf("unix.Write failed: %w", err)
	}
	if err := unix.Close(p3[1]); err != nil {
		return fmt.Errorf("closing write end failed: %w", err)
	}

	drainBuf := make([]byte, len(msg))
	nDrain, err := unix.Read(p3[0], drainBuf)
	if err != nil {
		return fmt.Errorf("unix.Read drain failed: %w", err)
	}
	if nDrain != len(msg) {
		return fmt.Errorf("expected %d bytes drained, got %d", len(msg), nDrain)
	}

	eofBuf := make([]byte, 10)
	nEOF, err := unix.Read(p3[0], eofBuf)
	if err != nil {
		return fmt.Errorf("expected nil error on EOF, got: %w", err)
	}
	if nEOF != 0 {
		return fmt.Errorf("expected 0 bytes read on EOF, got %d", nEOF)
	}

	// 4. unix.Read returns unix.EBADF for an invalid file descriptor
	invalidBuf := make([]byte, 10)
	_, err = unix.Read(-1, invalidBuf)
	if err == nil {
		return fmt.Errorf("expected unix.Read(-1) to fail, but succeeded")
	}
	if !errors.Is(err, unix.EBADF) {
		return fmt.Errorf("expected unix.EBADF for fd=-1, got: %w", err)
	}

	// 5. unix.Read returns unix.EBADF after a file descriptor is closed
	var p5 [2]int
	if err := unix.Pipe(p5[:]); err != nil {
		return fmt.Errorf("pipe creation failed: %w", err)
	}
	if err := unix.Close(p5[0]); err != nil {
		unix.Close(p5[1])
		return fmt.Errorf("failed to close read end: %w", err)
	}
	unix.Close(p5[1])

	closedBuf := make([]byte, 10)
	_, err = unix.Read(p5[0], closedBuf)
	if err == nil {
		return fmt.Errorf("expected unix.Read on closed fd to fail, but succeeded")
	}
	if !errors.Is(err, unix.EBADF) {
		return fmt.Errorf("expected unix.EBADF for closed fd, got: %w", err)
	}

	return nil
}