read safari homepage in go

homepage.go

package main

/*
#cgo LDFLAGS: -framework IOKit -framework ApplicationServices
#include <CoreFoundation/CoreFoundation.h>
#include <stdlib.h>

// cfstring_utf8_length returns the number of characters successfully converted to UTF-8 and
// the bytes required to store them.
static inline CFIndex cfstring_utf8_length(CFStringRef str, CFIndex *need) {
  CFIndex n, usedBufLen;
  CFRange rng = CFRangeMake(0, CFStringGetLength(str));
  return CFStringGetBytes(str, rng, kCFStringEncodingUTF8, 0, 0, NULL, 0, need);
}
*/
import "C"

import (
	"fmt"
	"reflect"
	"unsafe"
)

// cfstringGo creates a Go string for a CoreFoundation string using the CoreFoundation UTF-8 converter.
// For short strings this is an efficiency nightmare! In this package this function is not currently used
// in any critical path.
func cfstringGo(cfs C.CFStringRef) string {
	var usedBufLen C.CFIndex
	n := C.cfstring_utf8_length(cfs, &usedBufLen)
	if n <= 0 {
		return ""
	}
	rng := C.CFRange{location: C.CFIndex(0), length: n}
	buf := make([]byte, int(usedBufLen))

	bufp := unsafe.Pointer(&buf[0])
	C.CFStringGetBytes(cfs, rng, C.kCFStringEncodingUTF8, 0, 0, (*C.UInt8)(bufp), C.CFIndex(len(buf)), &usedBufLen)

	sh := &reflect.StringHeader{
		Data: uintptr(bufp),
		Len:  int(usedBufLen),
	}
	return *(*string)(unsafe.Pointer(sh))
}

// cfstring efficiently creates a CFString from a Go String.
func cfstring(s string) C.CFStringRef {
	n := C.CFIndex(len(s))
	return C.CFStringCreateWithBytes(nil, *(**C.UInt8)(unsafe.Pointer(&s)), n, C.kCFStringEncodingUTF8, 0)
}

func main() {
	hp := cfstring("HomePage")
	saf := cfstring("com.Apple.Safari")
	cs := C.CFPreferencesCopyAppValue(hp, saf)
	if cs == nil {
		return
	}
	fmt.Printf("%#v\n", cfstringGo(C.CFStringRef(cs)))
}

I'm looking for something like this but can't get it to work. Getting an error:

package main: /Users/myuser/go/src/github.com/myuser/go_CFPreferencesCopyAppValue/main.go: invalid #cgo verb: #cgo LDFLGS: -framework IOKit -framework ApplicationServices

Any ideas?

Maybe https://github.com/golang/go/wiki/InvalidFlag ? I don't know that com.Apple.Safari is a valid key to check anymore, but other keys should work.

@noelmom, this is pretty old. I believe some examples in
https://github.com/kolide/launcher/blob/0936d6f8cd865432fb78264ca9bef8e352fd4228/pkg/osquery/table/sus_darwin.go
https://github.com/kolide/launcher/blob/0936d6f8cd865432fb78264ca9bef8e352fd4228/pkg/osquery/table/corefoundation_helpers_darwin.go#L18

Thanks! I'll check it out.