github.com/selefra/selefra-utils@v0.0.4/pkg/string_builder/string_builder.go

package string_builder

import (
	"strconv"
	"unicode/utf8"
	"unsafe"
)

// StringBuilder A Builder is used to efficiently build a string using Write methods.
// It minimizes memory copying. The zero value is ready to use.
// Do not copy a non-zero Builder.
type StringBuilder struct {
	addr *StringBuilder // of receiver, to detect copies by value
	buf  []byte
}

func New(initCap ...int) *StringBuilder {
	b := &StringBuilder{}
	if len(initCap) > 0 {
		b = b.Grow(initCap[0])
	}
	return b
}

// noescape hides a pointer from escape analysis.  noescape is
// the identity function but escape analysis doesn't think the
// output depends on the input. noescape is inlined and currently
// compiles down to zero instructions.
// USE CAREFULLY!
// This was copied from the runtime; see issues 23382 and 7921.
//go:nosplit
//go:nocheckptr
func noescape(p unsafe.Pointer) unsafe.Pointer {
	x := uintptr(p)
	return unsafe.Pointer(x ^ 0)
}

func (b *StringBuilder) copyCheck() {
	if b.addr == nil {
		// This hack works around a failing of Go's escape analysis
		// that was causing b to escape and be heap allocated.
		// See issue 23382.
		// TODO: once issue 7921 is fixed, this should be reverted to
		// just "b.addr = b".
		b.addr = (*StringBuilder)(noescape(unsafe.Pointer(b)))
	} else if b.addr != b {
		panic("strings: illegal use of non-zero Builder copied by value")
	}
}

// String returns the accumulated string.
func (b *StringBuilder) String() string {
	return *(*string)(unsafe.Pointer(&b.buf))
}

// Len returns the number of accumulated bytes; b.Len() == len(b.String()).
func (b *StringBuilder) Len() int { return len(b.buf) }

// Cap returns the capacity of the builder's underlying byte slice. It is the
// total space allocated for the string being built and includes any bytes
// already written.
func (b *StringBuilder) Cap() int { return cap(b.buf) }

// Reset resets the Builder to be empty.
func (b *StringBuilder) Reset() *StringBuilder {
	b.addr = nil
	b.buf = nil
	return b
}

// grow copies the buffer to a new, larger buffer so that there are at least n
// bytes of capacity beyond len(b.buf).
func (b *StringBuilder) grow(n int) {
	buf := make([]byte, len(b.buf), 2*cap(b.buf)+n)
	copy(buf, b.buf)
	b.buf = buf
}

// Grow grows b's capacity, if necessary, to guarantee space for
// another n bytes. After Grow(n), at least n bytes can be written to b
// without another allocation. If n is negative, Grow panics.
func (b *StringBuilder) Grow(n int) *StringBuilder {
	b.copyCheck()
	if n < 0 {
		panic("strings.Builder.Grow: negative count")
	}
	if cap(b.buf)-len(b.buf) < n {
		b.grow(n)
	}
	return b
}

// Write appends the contents of p to b's buffer.
// Write always returns len(p), nil.
func (b *StringBuilder) Write(p []byte) (int, error) {
	b.copyCheck()
	b.buf = append(b.buf, p...)
	return len(p), nil
}

func (b *StringBuilder) Append(p []byte) *StringBuilder {
	_, _ = b.Write(p)
	return b
}

// WriteByte appends the byte c to b's buffer.
// The returned error is always nil.
func (b *StringBuilder) WriteByte(c byte) error {
	b.copyCheck()
	b.buf = append(b.buf, c)
	return nil
}

func (b *StringBuilder) AppendByte(c byte) *StringBuilder {
	_ = b.WriteByte(c)
	return b
}

// WriteRune appends the UTF-8 encoding of Unicode code point r to b's buffer.
// It returns the length of r and a nil error.
func (b *StringBuilder) WriteRune(r rune) (int, error) {
	b.copyCheck()
	// Compare as uint32 to correctly handle negative runes.
	if uint32(r) < utf8.RuneSelf {
		b.buf = append(b.buf, byte(r))
		return 1, nil
	}
	l := len(b.buf)
	if cap(b.buf)-l < utf8.UTFMax {
		b.grow(utf8.UTFMax)
	}
	n := utf8.EncodeRune(b.buf[l:l+utf8.UTFMax], r)
	b.buf = b.buf[:l+n]
	return n, nil
}

func (b *StringBuilder) AppendRune(r rune) *StringBuilder {
	_, _ = b.WriteRune(r)
	return b
}

// WriteString appends the contents of s to b's buffer.
// It returns the length of s and a nil error.
func (b *StringBuilder) WriteString(s string) (int, error) {
	b.copyCheck()
	b.buf = append(b.buf, s...)
	return len(s), nil
}

func (b *StringBuilder) AppendString(s string) *StringBuilder {
	_, _ = b.WriteString(s)
	return b
}

func (b *StringBuilder) AppendInt(n int) *StringBuilder {
	b.AppendString(strconv.Itoa(n))
	return b
}