package martini
import (
"bytes"
"fmt"
"io/ioutil"
"log"
"net/http"
"runtime"
"github.com/codegangsta/inject"
)
const (
panicHtml = `
PANIC: %s
PANIC
%s
%s
`
)
var (
dunno = []byte("???")
centerDot = []byte("·")
dot = []byte(".")
slash = []byte("/")
)
// stack returns a nicely formated stack frame, skipping skip frames
func stack(skip int) []byte {
buf := new(bytes.Buffer) // the returned data
// As we loop, we open files and read them. These variables record the currently
// loaded file.
var lines [][]byte
var lastFile string
for i := skip; ; i++ { // Skip the expected number of frames
pc, file, line, ok := runtime.Caller(i)
if !ok {
break
}
// Print this much at least. If we can't find the source, it won't show.
fmt.Fprintf(buf, "%s:%d (0x%x)\n", file, line, pc)
if file != lastFile {
data, err := ioutil.ReadFile(file)
if err != nil {
continue
}
lines = bytes.Split(data, []byte{'\n'})
lastFile = file
}
fmt.Fprintf(buf, "\t%s: %s\n", function(pc), source(lines, line))
}
return buf.Bytes()
}
// source returns a space-trimmed slice of the n'th line.
func source(lines [][]byte, n int) []byte {
n-- // in stack trace, lines are 1-indexed but our array is 0-indexed
if n < 0 || n >= len(lines) {
return dunno
}
return bytes.TrimSpace(lines[n])
}
// function returns, if possible, the name of the function containing the PC.
func function(pc uintptr) []byte {
fn := runtime.FuncForPC(pc)
if fn == nil {
return dunno
}
name := []byte(fn.Name())
// The name includes the path name to the package, which is unnecessary
// since the file name is already included. Plus, it has center dots.
// That is, we see
// runtime/debug.*T·ptrmethod
// and want
// *T.ptrmethod
// Also the package path might contains dot (e.g. code.google.com/...),
// so first eliminate the path prefix
if lastslash := bytes.LastIndex(name, slash); lastslash >= 0 {
name = name[lastslash+1:]
}
if period := bytes.Index(name, dot); period >= 0 {
name = name[period+1:]
}
name = bytes.Replace(name, centerDot, dot, -1)
return name
}
// Recovery returns a middleware that recovers from any panics and writes a 500 if there was one.
// While Martini is in development mode, Recovery will also output the panic as HTML.
func Recovery() Handler {
return func(c Context, log *log.Logger) {
defer func() {
if err := recover(); err != nil {
stack := stack(3)
log.Printf("PANIC: %s\n%s", err, stack)
// Lookup the current responsewriter
val := c.Get(inject.InterfaceOf((*http.ResponseWriter)(nil)))
res := val.Interface().(http.ResponseWriter)
// respond with panic message while in development mode
var body []byte
if Env == Dev {
res.Header().Set("Content-Type", "text/html")
body = []byte(fmt.Sprintf(panicHtml, err, err, stack))
} else {
body = []byte("500 Internal Server Error")
}
res.WriteHeader(http.StatusInternalServerError)
if nil != body {
res.Write(body)
}
}
}()
c.Next()
}
}