From 7330cf70eac2e320bef27e86b82ffcf713fe388a Mon Sep 17 00:00:00 2001
From: Manfred Touron <94029+moul@users.noreply.github.com>
Date: Fri, 3 Jul 2020 23:05:46 +0200
Subject: [PATCH] feat: add IsTooManyError helper

Signed-off-by: Manfred Touron <94029+moul@users.noreply.github.com>
---
 Makefile           | 33 +++++++++++++++++++++++++++++++++
 openfiles.go       | 27 ++++++++++++++++++++++++---
 openfiles_linux.go | 22 +++++++++++++++++++---
 openfiles_test.go  | 23 +++++++++++++++++++++++
 4 files changed, 99 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index edb0a8f..078aa6f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,36 @@
 GOPKG ?=	moul.io/openfiles
 
+.PHONY: test-archs
+test-archs:
+	GOOS=darwin    GOARCH=386      go test -v -c -o /dev/null
+	GOOS=darwin    GOARCH=amd64    go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=386      go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=amd64    go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=arm      go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=arm64    go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=ppc64    go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=ppc64le  go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=mips     go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=mipsle   go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=mips64   go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=mips64le go test -v -c -o /dev/null
+	GOOS=linux     GOARCH=s390x    go test -v -c -o /dev/null
+	GOOS=js        GOARCH=wasm     go test -v -c -o /dev/null
+	GOOS=dragonfly GOARCH=amd64    go test -v -c -o /dev/null
+	GOOS=freebsd   GOARCH=386      go test -v -c -o /dev/null
+	GOOS=freebsd   GOARCH=amd64    go test -v -c -o /dev/null
+	GOOS=freebsd   GOARCH=arm      go test -v -c -o /dev/null
+	GOOS=netbsd    GOARCH=386      go test -v -c -o /dev/null
+	GOOS=netbsd    GOARCH=amd64    go test -v -c -o /dev/null
+	GOOS=netbsd    GOARCH=arm      go test -v -c -o /dev/null
+	GOOS=openbsd   GOARCH=386      go test -v -c -o /dev/null
+	GOOS=openbsd   GOARCH=amd64    go test -v -c -o /dev/null
+	GOOS=openbsd   GOARCH=arm      go test -v -c -o /dev/null
+	GOOS=plan9     GOARCH=386      go test -v -c -o /dev/null
+	GOOS=plan9     GOARCH=amd64    go test -v -c -o /dev/null
+	GOOS=plan9     GOARCH=arm      go test -v -c -o /dev/null
+	GOOS=solaris   GOARCH=amd64    go test -v -c -o /dev/null
+	GOOS=windows   GOARCH=386      go test -v -c -o /dev/null
+	GOOS=windows   GOARCH=amd64    go test -v -c -o /dev/null
+
 include rules.mk
diff --git a/openfiles.go b/openfiles.go
index 7283369..1109809 100644
--- a/openfiles.go
+++ b/openfiles.go
@@ -1,6 +1,27 @@
 package openfiles
 
-import "errors"
+import (
+	"errors"
+	"os"
+	"syscall"
+)
 
-// ErrNotSupported indicates an unsupported GOOS or GOARCH
-var ErrNotSupported = errors.New("not supported environment")
+var (
+	// ErrNotSupported is raised on an unsupported GOOS or GOARCH
+	ErrNotSupported = errors.New("moul.io/openfiles: not supported environment")
+
+	// ErrInternal represents an internal error
+	ErrInternal = errors.New("moul.io/openfiles: internal error")
+)
+
+func IsTooManyError(err error) bool {
+	if err == syscall.EMFILE {
+		return true
+	}
+
+	if err, isPathError := err.(*os.PathError); isPathError {
+		return err.Err == syscall.EMFILE
+	}
+
+	return false
+}
diff --git a/openfiles_linux.go b/openfiles_linux.go
index 4d94406..2467bf9 100644
--- a/openfiles_linux.go
+++ b/openfiles_linux.go
@@ -5,14 +5,30 @@ package openfiles
 import (
 	"fmt"
 	"os"
-	"path/filepath"
 )
 
 func Count() (int64, error) {
 	pid := os.Getpid()
-	m, err := filepath.Glob(fmt.Sprintf("/proc/%d/fd/*", pid))
+	dir := fmt.Sprintf("/proc/%d/fd", pid)
+	fi, err := os.Stat(dir)
 	if err != nil {
 		return -1, err
 	}
-	return int64(len(m)), nil
+
+	if !fi.IsDir() {
+		return -1, ErrInternal
+	}
+
+	d, err := os.Open(dir) // guardrails-disable-line
+	if err != nil {
+		return -1, err
+	}
+	defer d.Close()
+
+	fds, err := d.Readdirnames(-1)
+	if err != nil {
+		return -1, err
+	}
+
+	return int64(len(fds)), nil
 }
diff --git a/openfiles_test.go b/openfiles_test.go
index 498b4ec..7f3a597 100644
--- a/openfiles_test.go
+++ b/openfiles_test.go
@@ -1,6 +1,10 @@
 package openfiles_test
 
 import (
+	"errors"
+	"fmt"
+	"os"
+	"syscall"
 	"testing"
 
 	"moul.io/openfiles"
@@ -19,3 +23,22 @@ func TestCount(t *testing.T) {
 	}
 	t.Logf("nofile: %d", nofile)
 }
+
+func TestIsTooManyError(t *testing.T) {
+	cases := []struct {
+		input     error
+		isTooMany bool
+	}{
+		{errors.New("blah"), false},
+		{errors.New("too many open files"), false},
+		{syscall.EMFILE, true},
+		{&os.PathError{Err: syscall.EMFILE}, true},
+	}
+
+	for _, tt := range cases {
+		k := fmt.Sprintf("%v", tt.input)
+		t.Run(k, func(t *testing.T) {
+
+		})
+	}
+}