From 6e5568b54d1aaee5899c0083c5776f88b8c5b907 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Tue, 20 Oct 2020 00:58:12 +0200 Subject: [PATCH] unix,windows,plan9: add Byte{Slice,Ptr}ToString functions We already provide ByteSliceFromString and BytePtrFromString, and on Windows we provide UTF16FromString, UTF16PtrFromString, UTF16ToString, and UTF16PtrToString. So this commit fills in the remaining two Byte-oriented functions: ByteSliceToString and BytePtrToString. Since the existing two are available on windows, unix, and plan9, we add the remaining two to the same places. This helps eliminate unsafe pointer options in addition to triggering checkptr in Go 1.15, by eliminating the use of prior idioms for these types of casts. Change-Id: I85ae49f2756e142c2462fe8b2428216b6992e089 Reviewed-on: https://go-review.googlesource.com/c/sys/+/263757 Run-TryBot: Jason A. Donenfeld TryBot-Result: Go Bot Reviewed-by: Ian Lance Taylor Trust: Brad Fitzpatrick Trust: Jason A. Donenfeld --- plan9/syscall.go | 49 ++++++++++++++++++++++++++++++++++---- unix/syscall.go | 43 ++++++++++++++++++++++++++++++++- windows/syscall.go | 46 +++++++++++++++++++++++++++++++---- windows/syscall_windows.go | 6 ++--- 4 files changed, 131 insertions(+), 13 deletions(-) diff --git a/plan9/syscall.go b/plan9/syscall.go index 163254ce..e7363a2f 100644 --- a/plan9/syscall.go +++ b/plan9/syscall.go @@ -24,16 +24,20 @@ // holds a value of type syscall.ErrorString. package plan9 // import "golang.org/x/sys/plan9" -import "unsafe" +import ( + "bytes" + "strings" + "unsafe" + + "golang.org/x/sys/internal/unsafeheader" +) // ByteSliceFromString returns a NUL-terminated slice of bytes // containing the text of s. If s contains a NUL byte at any // location, it returns (nil, EINVAL). func ByteSliceFromString(s string) ([]byte, error) { - for i := 0; i < len(s); i++ { - if s[i] == 0 { - return nil, EINVAL - } + if strings.IndexByte(s, 0) != -1 { + return nil, EINVAL } a := make([]byte, len(s)+1) copy(a, s) @@ -51,6 +55,41 @@ func BytePtrFromString(s string) (*byte, error) { return &a[0], nil } +// ByteSliceToString returns a string form of the text represented by the slice s, with a terminating NUL and any +// bytes after the NUL removed. +func ByteSliceToString(s []byte) string { + if i := bytes.IndexByte(s, 0); i != -1 { + s = s[:i] + } + return string(s) +} + +// BytePtrToString takes a pointer to a sequence of text and returns the corresponding string. +// If the pointer is nil, it returns the empty string. It assumes that the text sequence is terminated +// at a zero byte; if the zero byte is not present, the program may crash. +func BytePtrToString(p *byte) string { + if p == nil { + return "" + } + if *p == 0 { + return "" + } + + // Find NUL terminator. + n := 0 + for ptr := unsafe.Pointer(p); *(*byte)(ptr) != 0; n++ { + ptr = unsafe.Pointer(uintptr(ptr) + 1) + } + + var s []byte + h := (*unsafeheader.Slice)(unsafe.Pointer(&s)) + h.Data = unsafe.Pointer(p) + h.Len = n + h.Cap = n + + return string(s) +} + // Single-word zero for use when we need a valid pointer to 0 bytes. // See mksyscall.pl. var _zero uintptr diff --git a/unix/syscall.go b/unix/syscall.go index fd4ee8eb..ab75ef9c 100644 --- a/unix/syscall.go +++ b/unix/syscall.go @@ -24,7 +24,13 @@ // holds a value of type syscall.Errno. package unix // import "golang.org/x/sys/unix" -import "strings" +import ( + "bytes" + "strings" + "unsafe" + + "golang.org/x/sys/internal/unsafeheader" +) // ByteSliceFromString returns a NUL-terminated slice of bytes // containing the text of s. If s contains a NUL byte at any @@ -49,5 +55,40 @@ func BytePtrFromString(s string) (*byte, error) { return &a[0], nil } +// ByteSliceToString returns a string form of the text represented by the slice s, with a terminating NUL and any +// bytes after the NUL removed. +func ByteSliceToString(s []byte) string { + if i := bytes.IndexByte(s, 0); i != -1 { + s = s[:i] + } + return string(s) +} + +// BytePtrToString takes a pointer to a sequence of text and returns the corresponding string. +// If the pointer is nil, it returns the empty string. It assumes that the text sequence is terminated +// at a zero byte; if the zero byte is not present, the program may crash. +func BytePtrToString(p *byte) string { + if p == nil { + return "" + } + if *p == 0 { + return "" + } + + // Find NUL terminator. + n := 0 + for ptr := unsafe.Pointer(p); *(*byte)(ptr) != 0; n++ { + ptr = unsafe.Pointer(uintptr(ptr) + 1) + } + + var s []byte + h := (*unsafeheader.Slice)(unsafe.Pointer(&s)) + h.Data = unsafe.Pointer(p) + h.Len = n + h.Cap = n + + return string(s) +} + // Single-word zero for use when we need a valid pointer to 0 bytes. var _zero uintptr diff --git a/windows/syscall.go b/windows/syscall.go index af828a91..6122f557 100644 --- a/windows/syscall.go +++ b/windows/syscall.go @@ -25,17 +25,20 @@ package windows // import "golang.org/x/sys/windows" import ( + "bytes" + "strings" "syscall" + "unsafe" + + "golang.org/x/sys/internal/unsafeheader" ) // ByteSliceFromString returns a NUL-terminated slice of bytes // containing the text of s. If s contains a NUL byte at any // location, it returns (nil, syscall.EINVAL). func ByteSliceFromString(s string) ([]byte, error) { - for i := 0; i < len(s); i++ { - if s[i] == 0 { - return nil, syscall.EINVAL - } + if strings.IndexByte(s, 0) != -1 { + return nil, syscall.EINVAL } a := make([]byte, len(s)+1) copy(a, s) @@ -53,6 +56,41 @@ func BytePtrFromString(s string) (*byte, error) { return &a[0], nil } +// ByteSliceToString returns a string form of the text represented by the slice s, with a terminating NUL and any +// bytes after the NUL removed. +func ByteSliceToString(s []byte) string { + if i := bytes.IndexByte(s, 0); i != -1 { + s = s[:i] + } + return string(s) +} + +// BytePtrToString takes a pointer to a sequence of text and returns the corresponding string. +// If the pointer is nil, it returns the empty string. It assumes that the text sequence is terminated +// at a zero byte; if the zero byte is not present, the program may crash. +func BytePtrToString(p *byte) string { + if p == nil { + return "" + } + if *p == 0 { + return "" + } + + // Find NUL terminator. + n := 0 + for ptr := unsafe.Pointer(p); *(*byte)(ptr) != 0; n++ { + ptr = unsafe.Pointer(uintptr(ptr) + 1) + } + + var s []byte + h := (*unsafeheader.Slice)(unsafe.Pointer(&s)) + h.Data = unsafe.Pointer(p) + h.Len = n + h.Cap = n + + return string(s) +} + // Single-word zero for use when we need a valid pointer to 0 bytes. // See mksyscall.pl. var _zero uintptr diff --git a/windows/syscall_windows.go b/windows/syscall_windows.go index bbd075df..cd71f570 100644 --- a/windows/syscall_windows.go +++ b/windows/syscall_windows.go @@ -92,11 +92,11 @@ func UTF16FromString(s string) ([]uint16, error) { } // UTF16ToString returns the UTF-8 encoding of the UTF-16 sequence s, -// with a terminating NUL removed. +// with a terminating NUL and any bytes after the NUL removed. func UTF16ToString(s []uint16) string { for i, v := range s { if v == 0 { - s = s[0:i] + s = s[:i] break } } @@ -120,7 +120,7 @@ func UTF16PtrFromString(s string) (*uint16, error) { } // UTF16PtrToString takes a pointer to a UTF-16 sequence and returns the corresponding UTF-8 encoded string. -// If the pointer is nil, this returns the empty string. This assumes that the UTF-16 sequence is terminated +// If the pointer is nil, it returns the empty string. It assumes that the UTF-16 sequence is terminated // at a zero word; if the zero word is not present, the program may crash. func UTF16PtrToString(p *uint16) string { if p == nil {