github.com/code-reading/golang@v0.0.0-20220303082512-ba5bc0e589a3/go/src/os/user/listgroups_unix.go (about)

     1  // Copyright 2016 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build (dragonfly || darwin || freebsd || (!android && linux) || netbsd || openbsd || (solaris && !illumos)) && cgo && !osusergo
     6  // +build dragonfly darwin freebsd !android,linux netbsd openbsd solaris,!illumos
     7  // +build cgo
     8  // +build !osusergo
     9  
    10  package user
    11  
    12  import (
    13  	"fmt"
    14  	"strconv"
    15  	"unsafe"
    16  )
    17  
    18  /*
    19  #include <unistd.h>
    20  #include <sys/types.h>
    21  */
    22  import "C"
    23  
    24  const maxGroups = 2048
    25  
    26  func listGroups(u *User) ([]string, error) {
    27  	ug, err := strconv.Atoi(u.Gid)
    28  	if err != nil {
    29  		return nil, fmt.Errorf("user: list groups for %s: invalid gid %q", u.Username, u.Gid)
    30  	}
    31  	userGID := C.gid_t(ug)
    32  	nameC := make([]byte, len(u.Username)+1)
    33  	copy(nameC, u.Username)
    34  
    35  	n := C.int(256)
    36  	gidsC := make([]C.gid_t, n)
    37  	rv := getGroupList((*C.char)(unsafe.Pointer(&nameC[0])), userGID, &gidsC[0], &n)
    38  	if rv == -1 {
    39  		// Mac is the only Unix that does not set n properly when rv == -1, so
    40  		// we need to use different logic for Mac vs. the other OS's.
    41  		if err := groupRetry(u.Username, nameC, userGID, &gidsC, &n); err != nil {
    42  			return nil, err
    43  		}
    44  	}
    45  	gidsC = gidsC[:n]
    46  	gids := make([]string, 0, n)
    47  	for _, g := range gidsC[:n] {
    48  		gids = append(gids, strconv.Itoa(int(g)))
    49  	}
    50  	return gids, nil
    51  }