135 lines
3.4 KiB
Go
135 lines
3.4 KiB
Go
package byteutil
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import (
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"errors"
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"io"
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"unicode/utf8"
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)
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var (
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// ensure we conform to interfaces.
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_ interface {
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io.Writer
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io.ByteWriter
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WriteRune(rune) (int, error)
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io.StringWriter
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io.WriterAt
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WriteStringAt(string, int64) (int, error)
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} = (*Buffer)(nil)
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// ErrBeyondBufferLen is returned if .WriteAt() is attempted beyond buffer length.
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ErrBeyondBufferLen = errors.New("start beyond buffer length")
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)
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// Buffer is a simple wrapper around a byte slice.
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type Buffer struct{ B []byte }
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// WriteByte will append given byte to buffer, fulfilling io.ByteWriter.
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func (buf *Buffer) WriteByte(c byte) error {
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buf.B = append(buf.B, c)
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return nil
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}
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// WriteRune will append given rune to buffer.
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func (buf *Buffer) WriteRune(r rune) (int, error) {
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// Check for single-byte rune
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if r < utf8.RuneSelf {
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buf.B = append(buf.B, byte(r))
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return 1, nil
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}
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// Before-len
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l := len(buf.B)
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// Grow to max size rune
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buf.Grow(utf8.UTFMax)
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// Write encoded rune to buffer
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n := utf8.EncodeRune(buf.B[l:len(buf.B)], r)
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buf.B = buf.B[:l+n]
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return n, nil
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}
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// Write will append given byte slice to buffer, fulfilling io.Writer.
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func (buf *Buffer) Write(b []byte) (int, error) {
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buf.B = append(buf.B, b...)
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return len(b), nil
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}
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// WriteString will append given string to buffer, fulfilling io.StringWriter.
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func (buf *Buffer) WriteString(s string) (int, error) {
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buf.B = append(buf.B, s...)
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return len(s), nil
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}
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// WriteAt will append given byte slice to buffer at index 'start', fulfilling io.WriterAt.
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func (buf *Buffer) WriteAt(b []byte, start int64) (int, error) {
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if start > int64(len(buf.B)) {
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return 0, ErrBeyondBufferLen
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}
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buf.Grow(len(b) - int(int64(len(buf.B))-start))
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return copy(buf.B[start:], b), nil
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}
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// WriteStringAt will append given string to buffer at index 'start'.
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func (buf *Buffer) WriteStringAt(s string, start int64) (int, error) {
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if start > int64(len(buf.B)) {
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return 0, ErrBeyondBufferLen
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}
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buf.Grow(len(s) - int(int64(len(buf.B))-start))
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return copy(buf.B[start:], s), nil
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}
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// Len returns the length of the buffer's underlying byte slice.
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func (buf *Buffer) Len() int {
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return len(buf.B)
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}
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// Cap returns the capacity of the buffer's underlying byte slice.
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func (buf *Buffer) Cap() int {
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return cap(buf.B)
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}
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// Grow will increase the buffers length by 'sz', and the capacity by at least this.
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func (buf *Buffer) Grow(sz int) {
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buf.Guarantee(sz)
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buf.B = buf.B[:len(buf.B)+sz]
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}
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// Guarantee will guarantee buffer containers at least 'sz' remaining capacity.
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func (buf *Buffer) Guarantee(sz int) {
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if sz > cap(buf.B)-len(buf.B) {
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nb := make([]byte, 2*cap(buf.B)+sz)
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copy(nb, buf.B)
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buf.B = nb[:len(buf.B)]
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}
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}
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// Truncate will reduce the length of the buffer by 'n'.
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func (buf *Buffer) Truncate(n int) {
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if n > len(buf.B) {
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n = len(buf.B)
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}
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buf.B = buf.B[:len(buf.B)-n]
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}
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// Reset will reset the buffer length to 0 (retains capacity).
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func (buf *Buffer) Reset() {
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buf.B = buf.B[:0]
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}
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// String returns the underlying byte slice as a string. Please note
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// this value is tied directly to the underlying byte slice, if you
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// write to the buffer then returned string values will also change.
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//
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// To get an immutable string from buffered data, use string(buf.B).
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func (buf *Buffer) String() string {
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return B2S(buf.B)
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}
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// Full returns the full capacity byteslice allocated for this buffer.
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func (buf *Buffer) Full() []byte {
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return buf.B[0:cap(buf.B)]
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}
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