Fix various style-related linters (#170)

* style: apply gofmt (darwin)

* style: add copyright in each go file

* style: add comments for packages, exported functions, exported types (mostly darwin)

* style: fix receiver naming lint warning

* style: fix unused argument lint warning (darwin)

* style: fix unnecessary conversion lint warning

* style: fix miscellaneous linter warnings, eg. error format specifier, invalid argument for function, typo

* style: fix capitalized error message lint warning

* style: fix typo warn lint

* style: add missing comments on exported fields, const and packages (windows)

* style: fix naming lint warnings (windows)

* style: fix unused types / functions / fields and unnecessary cast lint warnings (windows)

* style: add missing comments on exported fields, const and packages (windows continued)

* style: fix naming lint warnings (windows, continued)

* style: fix unused types / functions / fields and unnecessary cast lint warnings (windows continued)

* style: fix naming lint warnings (windows, continued)

* style: fix unnecessary cast lint warnings (windows continued)

* style: fix naming lint warnings (windows, continued)

* Update filesystem/filesystem.go

Co-authored-by: Srdjan Grubor <[email protected]>

* style: fix var-naming lint warning about Ip,Cpu,Json,Id capitalization

* style: fix indent

---------

Co-authored-by: Srdjan Grubor <[email protected]>

cpu/cpu.go

@@ -1,3 +1,9 @@
+// This file is licensed under the MIT License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright © 2015 Kentaro Kuribayashi <[email protected]>
+// Copyright 2014-present Datadog, Inc.
+
+// Package cpu regroups collecting information about the CPU
 package cpu
 
 import (
@@ -9,6 +15,8 @@ import (
 )
 
 // Cpu holds metadata about the host CPU
+//
+//nolint:revive
 type Cpu struct {
 	// VendorId the CPU vendor ID
 	VendorId string
@@ -43,20 +51,24 @@ type Cpu struct {
 
 const name = "cpu"
 
-func (self *Cpu) Name() string {
+// Name returns the name of the package
+func (cpu *Cpu) Name() string {
 	return name
 }
 
-func (self *Cpu) Collect() (result interface{}, err error) {
-	result, err = getCpuInfo()
+// Collect collects the CPU information.
+// Returns an object which can be converted to a JSON or an error if nothing could be collected.
+// Tries to collect as much information as possible.
+func (cpu *Cpu) Collect() (result interface{}, err error) {
+	result, err = getCPUInfo()
 	return
 }
 
-// Get returns a Cpu struct already initialized, a list of warnings and an error. The method will try to collect as much
+// Get returns a CPU struct already initialized, a list of warnings and an error. The method will try to collect as much
 // metadata as possible, an error is returned if nothing could be collected. The list of warnings contains errors if
 // some metadata could not be collected.
 func Get() (*Cpu, []string, error) {
-	cpuInfo, err := getCpuInfo()
+	cpuInfo, err := getCPUInfo()
 	if err != nil {
 		return nil, nil, err
 	}

cpu/cpu_darwin.go

@@ -1,3 +1,8 @@
+// This file is licensed under the MIT License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright © 2015 Kentaro Kuribayashi <[email protected]>
+// Copyright 2014-present Datadog, Inc.
+
 package cpu
 
 import (
@@ -17,8 +22,7 @@ var cpuMap = map[string]string{
 	"machdep.cpu.stepping":     "stepping",
 }
 
-func getCpuInfo() (cpuInfo map[string]string, err error) {
-
+func getCPUInfo() (cpuInfo map[string]string, err error) {
 	cpuInfo = make(map[string]string)
 
 	for option, key := range cpuMap {

cpu/cpu_linux_arm64.go

@@ -1,5 +1,10 @@
-// +build linux
-// +build arm64
+// This file is licensed under the MIT License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright © 2015 Kentaro Kuribayashi <[email protected]>
+// Copyright 2014-present Datadog, Inc.
+
+//go:build linux && arm64
+// +build linux,arm64
 
 package cpu
 
@@ -18,7 +23,7 @@ import (
 // nodeNRegex recognizes directories named `nodeNN`
 var nodeNRegex = regexp.MustCompile("^node[0-9]+$")
 
-func getCpuInfo() (cpuInfo map[string]string, err error) {
+func getCPUInfo() (cpuInfo map[string]string, err error) {
 	cpuInfo = make(map[string]string)
 
 	procCpu, err := readProcCpuInfo()

cpu/cpu_linux_default.go

@@ -1,5 +1,10 @@
-// +build linux
-// +build !arm64
+// This file is licensed under the MIT License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright © 2015 Kentaro Kuribayashi <[email protected]>
+// Copyright 2014-present Datadog, Inc.
+
+//go:build linux && !arm64
+// +build linux,!arm64
 
 package cpu
 
@@ -28,7 +33,7 @@ var perPhysicalProcValues = []string{
 	"cpu_logical_processors",
 }
 
-func getCpuInfo() (cpuInfo map[string]string, err error) {
+func getCPUInfo() (cpuInfo map[string]string, err error) {
 	lines, err := readProcFile()
 	if err != nil {
 		return

cpu/cpu_windows.go

@@ -1,3 +1,8 @@
+// This file is licensed under the MIT License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright © 2015 Kentaro Kuribayashi <[email protected]>
+// Copyright 2014-present Datadog, Inc.
+
 package cpu
 
 import (
@@ -11,24 +16,33 @@ import (
 	"golang.org/x/sys/windows/registry"
 )
 
-var getCpuInfo = GetCpuInfo
-
-// Values that need to be multiplied by the number of physical processors
-var perPhysicalProcValues = []string{
-	"cpu_cores",
-	"cpu_logical_processors",
-}
+var getCPUInfo = GetCpuInfo
 
+// ERROR_INSUFFICIENT_BUFFER is the error number associated with the
+// "insufficient buffer size" error
+//
+//nolint:revive
 const ERROR_INSUFFICIENT_BUFFER syscall.Errno = 122
+
 const registryHive = "HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0"
 
+// CACHE_DESCRIPTOR contains cache related information
+// see https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-cache_descriptor
+//
+//nolint:unused,revive
 type CACHE_DESCRIPTOR struct {
 	Level         uint8
 	Associativity uint8
 	LineSize      uint16
 	Size          uint32
 	cacheType     uint32
 }
+
+// SYSTEM_LOGICAL_PROCESSOR_INFORMATION describes the relationship
+// between the specified processor set.
+// see https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-system_logical_processor_information
+//
+//nolint:unused,revive
 type SYSTEM_LOGICAL_PROCESSOR_INFORMATION struct {
 	ProcessorMask uintptr
 	Relationship  int // enum (int)
@@ -39,16 +53,32 @@ type SYSTEM_LOGICAL_PROCESSOR_INFORMATION struct {
 
 //.const SYSTEM_LOGICAL_PROCESSOR_INFORMATION_SIZE = 32
 
+// GROUP_AFFINITY represents a processor group-specific affinity,
+// such as the affinity of a thread.
+// see https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-group_affinity
+//
+//nolint:revive
 type GROUP_AFFINITY struct {
 	Mask     uintptr
 	Group    uint16
 	Reserved [3]uint16
 }
+
+// NUMA_NODE_RELATIONSHIP represents information about a NUMA node
+// in a processor group.
+// see https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-numa_node_relationship
+//
+//nolint:revive
 type NUMA_NODE_RELATIONSHIP struct {
 	NodeNumber uint32
 	Reserved   [20]uint8
 	GroupMask  GROUP_AFFINITY
 }
+
+// CACHE_RELATIONSHIP describes cache attributes.
+// see https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-cache_relationship
+//
+//nolint:revive
 type CACHE_RELATIONSHIP struct {
 	Level         uint8
 	Associativity uint8
@@ -59,18 +89,34 @@ type CACHE_RELATIONSHIP struct {
 	GroupMask     GROUP_AFFINITY
 }
 
+// PROCESSOR_GROUP_INFO represents the number and affinity of processors
+// in a processor group.
+// see https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-processor_group_info
+//
+//nolint:revive
 type PROCESSOR_GROUP_INFO struct {
 	MaximumProcessorCount uint8
 	ActiveProcessorCount  uint8
 	Reserved              [38]uint8
 	ActiveProcessorMask   uintptr
 }
+
+// GROUP_RELATIONSHIP represents information about processor groups.
+// see https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-group_relationship
+//
+//nolint:revive
 type GROUP_RELATIONSHIP struct {
 	MaximumGroupCount uint16
 	ActiveGroupCount  uint16
 	Reserved          [20]uint8
 	// variable size array of PROCESSOR_GROUP_INFO
 }
+
+// PROCESSOR_RELATIONSHIP represents information about affinity
+// within a processor group.
+// see https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-processor_relationship
+//
+//nolint:unused,revive
 type PROCESSOR_RELATIONSHIP struct {
 	Flags           uint8
 	EfficiencyClass uint8
@@ -79,6 +125,11 @@ type PROCESSOR_RELATIONSHIP struct {
 	// what follows is an array of zero or more GROUP_AFFINITY structures
 }
 
+// SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX contains information about
+// the relationships of logical processors and related hardware.
+// https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-system_logical_processor_information_ex
+//
+//nolint:revive
 type SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX struct {
 	Relationship int
 	Size         uint32
@@ -89,12 +140,31 @@ type SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX struct {
 	// GROUP_RELATIONSHIP
 }
 
-const RelationProcessorCore = 0
-const RelationNumaNode = 1
-const RelationCache = 2
-const RelationProcessorPackage = 3
-const RelationGroup = 4
+// see https://learn.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getlogicalprocessorinformationex
+const (
+	// RelationProcessorCore retrieves information about logical processors
+	// that share a single processor core.
+	RelationProcessorCore = 0
+	// RelationNumaNode retrieves information about logical processors
+	// that are part of the same NUMA node.
+	RelationNumaNode = 1
+	// RelationCache retrieves information about logical processors
+	// that share a cache.
+	RelationCache = 2
+	// RelationProcessorPackage retrieves information about logical processors
+	// that share a physical package.
+	RelationProcessorPackage = 3
+	// RelationGroup retrieves information about logical processors
+	// that share a processor group.
+	RelationGroup = 4
+)
 
+// SYSTEM_INFO contains information about the current computer system.
+// This includes the architecture and type of the processor, the number
+// of processors in the system, the page size, and other such information.
+// see https://learn.microsoft.com/en-us/windows/win32/api/sysinfoapi/ns-sysinfoapi-system_info
+//
+//nolint:revive
 type SYSTEM_INFO struct {
 	wProcessorArchitecture  uint16
 	wReserved               uint16
@@ -109,6 +179,9 @@ type SYSTEM_INFO struct {
 	wProcessorRevision      uint16
 }
 
+// CPU_INFO contains information about cpu, eg. number of cores, cache size
+//
+//nolint:revive
 type CPU_INFO struct {
 	numaNodeCount       int    // number of NUMA nodes
 	pkgcount            int    // number of packages (physical CPUS)

cpu/cpu_windows_386.go

@@ -1,3 +1,8 @@
+// This file is licensed under the MIT License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright © 2015 Kentaro Kuribayashi <[email protected]>
+// Copyright 2014-present Datadog, Inc.
+
 package cpu
 
 import (
@@ -6,11 +11,16 @@ import (
 	"unsafe"
 )
 
+// SYSTEM_LOGICAL_PROCESSOR_INFORMATION_SIZE is the size of
+// SYSTEM_LOGICAL_PROCESSOR_INFORMATION struct
+//
+//nolint:revive
 const SYSTEM_LOGICAL_PROCESSOR_INFORMATION_SIZE = 24
 
 func getSystemLogicalProcessorInformationSize() int {
 	return SYSTEM_LOGICAL_PROCESSOR_INFORMATION_SIZE
 }
+
 func byteArrayToProcessorStruct(data []byte) (info SYSTEM_LOGICAL_PROCESSOR_INFORMATION) {
 	info.ProcessorMask = uintptr(binary.LittleEndian.Uint32(data))
 	info.Relationship = int(binary.LittleEndian.Uint32(data[4:]))