mirror of https://github.com/cheat/cheat.git
133 lines
3.4 KiB
Go
133 lines
3.4 KiB
Go
package stringbuffer
|
|
|
|
import (
|
|
"sync"
|
|
"unicode/utf16"
|
|
)
|
|
|
|
// TODO: worth exporting and using in mkwinsyscall?
|
|
|
|
// Uint16BufferSize is the buffer size in the pool, chosen somewhat arbitrarily to accommodate
|
|
// large path strings:
|
|
// MAX_PATH (260) + size of volume GUID prefix (49) + null terminator = 310.
|
|
const MinWStringCap = 310
|
|
|
|
// use *[]uint16 since []uint16 creates an extra allocation where the slice header
|
|
// is copied to heap and then referenced via pointer in the interface header that sync.Pool
|
|
// stores.
|
|
var pathPool = sync.Pool{ // if go1.18+ adds Pool[T], use that to store []uint16 directly
|
|
New: func() interface{} {
|
|
b := make([]uint16, MinWStringCap)
|
|
return &b
|
|
},
|
|
}
|
|
|
|
func newBuffer() []uint16 { return *(pathPool.Get().(*[]uint16)) }
|
|
|
|
// freeBuffer copies the slice header data, and puts a pointer to that in the pool.
|
|
// This avoids taking a pointer to the slice header in WString, which can be set to nil.
|
|
func freeBuffer(b []uint16) { pathPool.Put(&b) }
|
|
|
|
// WString is a wide string buffer ([]uint16) meant for storing UTF-16 encoded strings
|
|
// for interacting with Win32 APIs.
|
|
// Sizes are specified as uint32 and not int.
|
|
//
|
|
// It is not thread safe.
|
|
type WString struct {
|
|
// type-def allows casting to []uint16 directly, use struct to prevent that and allow adding fields in the future.
|
|
|
|
// raw buffer
|
|
b []uint16
|
|
}
|
|
|
|
// NewWString returns a [WString] allocated from a shared pool with an
|
|
// initial capacity of at least [MinWStringCap].
|
|
// Since the buffer may have been previously used, its contents are not guaranteed to be empty.
|
|
//
|
|
// The buffer should be freed via [WString.Free]
|
|
func NewWString() *WString {
|
|
return &WString{
|
|
b: newBuffer(),
|
|
}
|
|
}
|
|
|
|
func (b *WString) Free() {
|
|
if b.empty() {
|
|
return
|
|
}
|
|
freeBuffer(b.b)
|
|
b.b = nil
|
|
}
|
|
|
|
// ResizeTo grows the buffer to at least c and returns the new capacity, freeing the
|
|
// previous buffer back into pool.
|
|
func (b *WString) ResizeTo(c uint32) uint32 {
|
|
// allready sufficient (or n is 0)
|
|
if c <= b.Cap() {
|
|
return b.Cap()
|
|
}
|
|
|
|
if c <= MinWStringCap {
|
|
c = MinWStringCap
|
|
}
|
|
// allocate at-least double buffer size, as is done in [bytes.Buffer] and other places
|
|
if c <= 2*b.Cap() {
|
|
c = 2 * b.Cap()
|
|
}
|
|
|
|
b2 := make([]uint16, c)
|
|
if !b.empty() {
|
|
copy(b2, b.b)
|
|
freeBuffer(b.b)
|
|
}
|
|
b.b = b2
|
|
return c
|
|
}
|
|
|
|
// Buffer returns the underlying []uint16 buffer.
|
|
func (b *WString) Buffer() []uint16 {
|
|
if b.empty() {
|
|
return nil
|
|
}
|
|
return b.b
|
|
}
|
|
|
|
// Pointer returns a pointer to the first uint16 in the buffer.
|
|
// If the [WString.Free] has already been called, the pointer will be nil.
|
|
func (b *WString) Pointer() *uint16 {
|
|
if b.empty() {
|
|
return nil
|
|
}
|
|
return &b.b[0]
|
|
}
|
|
|
|
// String returns the returns the UTF-8 encoding of the UTF-16 string in the buffer.
|
|
//
|
|
// It assumes that the data is null-terminated.
|
|
func (b *WString) String() string {
|
|
// Using [windows.UTF16ToString] would require importing "golang.org/x/sys/windows"
|
|
// and would make this code Windows-only, which makes no sense.
|
|
// So copy UTF16ToString code into here.
|
|
// If other windows-specific code is added, switch to [windows.UTF16ToString]
|
|
|
|
s := b.b
|
|
for i, v := range s {
|
|
if v == 0 {
|
|
s = s[:i]
|
|
break
|
|
}
|
|
}
|
|
return string(utf16.Decode(s))
|
|
}
|
|
|
|
// Cap returns the underlying buffer capacity.
|
|
func (b *WString) Cap() uint32 {
|
|
if b.empty() {
|
|
return 0
|
|
}
|
|
return b.cap()
|
|
}
|
|
|
|
func (b *WString) cap() uint32 { return uint32(cap(b.b)) }
|
|
func (b *WString) empty() bool { return b == nil || b.cap() == 0 }
|