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main.go
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main.go
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// This code comes from https://github.com/golang/exp/blob/master/shiny/driver/x11driver/shm_linux_amd64.go
package main
import (
"fmt"
"io"
"os"
"strconv"
"github.com/ghetzel/cli"
"github.com/ghetzel/go-stockutil/log"
"github.com/ghetzel/shmtool/shm"
)
const DefaultLogLevel = `info`
func main() {
app := cli.NewApp()
app.Name = `shmtool`
app.Usage = `a command line utility for interacting with SysV-style shared memory segments`
app.Version = shm.Version
app.EnableBashCompletion = false
app.Flags = []cli.Flag{
cli.StringFlag{
Name: `log-level, L`,
Usage: `Level of logging verbosity`,
Value: DefaultLogLevel,
EnvVar: `LOGLEVEL`,
},
}
app.Before = func(c *cli.Context) error {
log.SetLevelString(c.String(`log-level`))
return nil
}
app.Commands = []cli.Command{
{
Name: `open`,
Usage: `Create or open a shared memory buffer and write the contents of standard input to it`,
ArgsUsage: `[ID]`,
Flags: []cli.Flag{
cli.IntFlag{
Name: `offset, o`,
Usage: `The number of bytes to skip before beginning the write operation`,
},
cli.IntFlag{
Name: `size, s`,
Usage: `The size (in bytes) of the shared memory segment (if creating)`,
},
},
Action: func(c *cli.Context) {
var size int
if c.NArg() == 0 {
size = c.Int(`size`)
if size == 0 {
log.Fatalf("Must specify a segment size")
}
}
var segment *shm.Segment
var err error
if size > 0 {
segment, err = shm.Create(size)
} else {
if segmentId, err := strconv.ParseUint(c.Args().First(), 10, 64); err == nil {
if segment, err = shm.Open(int(segmentId)); err != nil {
log.Fatalf("Failed to open segment %d: %v", segmentId, err)
}
} else {
log.Fatalf("Failed to parse segment ID: %v", err)
return
}
}
if err == nil {
if offset := int64(c.Int(`offset`)); offset > 0 {
segment.Seek(offset, 0)
}
log.Debugf("Opened shared memory segment %d: size is %d, offset is %d", segment.Id, segment.Size, segment.Position())
fmt.Printf("%d\n", segment.Id)
if n, err := io.Copy(segment, os.Stdin); err == nil || err == io.EOF {
log.Infof("Wrote %d bytes to shared memory", n)
} else {
log.Errorf("Failed to copy input: %v", err)
}
} else {
log.Fatalf("Failed to open shared memory segment: %v", err)
}
},
}, {
Name: `read`,
Usage: `Read the contents of a shared memory buffer to standard output`,
ArgsUsage: `ID`,
Flags: []cli.Flag{
cli.IntFlag{
Name: `offset, o`,
Usage: `The number of bytes to skip before beginning the read operation`,
},
cli.IntFlag{
Name: `size, s`,
Usage: `The number of bytes to read from the shared memory segment`,
},
},
Action: func(c *cli.Context) {
if id, err := strconv.ParseUint(c.Args().First(), 10, 64); err == nil {
segmentId := int(id)
if segment, err := shm.Open(segmentId); err == nil {
readSize := int64(c.Int(`size`))
if readSize > segment.Size || readSize == 0 {
readSize = segment.Size
}
if offset := int64(c.Int(`offset`)); offset > 0 {
segment.Seek(offset, 0)
}
log.Debugf("Opened shared memory segment %d: size is %d, offset is %d", segment.Id, segment.Size, segment.Position())
log.Debugf("Reading %d bytes...", readSize)
if n, err := io.CopyN(os.Stdout, segment, int64(readSize)); err == nil {
log.Infof("Read %d bytes from shared memory", n)
} else {
log.Fatalf("Failed to read from shared memory segment: %v", err)
}
} else {
log.Fatalf("Failed to open shared memory segment %d: %v", segmentId, err)
}
} else {
log.Fatalf("Must specify a valid segment ID: %v", err)
}
},
}, {
Name: `rm`,
Usage: `Remove a shared memory segment`,
ArgsUsage: `ID`,
Action: func(c *cli.Context) {
if id, err := strconv.ParseUint(c.Args().First(), 10, 64); err == nil {
if err := shm.DestroySegment(int(id)); err == nil {
log.Infof("Destroyed segment %d", id)
} else {
log.Fatalf("Failed to destroy segment %d: %v", id, err)
}
} else {
log.Fatalf("Must specify a segment ID: %v", err)
}
},
},
}
app.Run(os.Args)
}