83 lines
1.8 KiB
Go
83 lines
1.8 KiB
Go
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package hodu
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import "bytes"
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import "golang.org/x/text/transform"
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type Transformer struct {
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replacement []byte
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needle []byte
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needle_len int
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}
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func NewBytesTransformer(needle []byte, replacement []byte) *Transformer {
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return &Transformer{needle: needle, replacement: replacement, needle_len: len(needle)}
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}
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func NewStringTransformer(needle string, replacement string) *Transformer {
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return NewBytesTransformer([]byte(needle), []byte(replacement))
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}
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func (t *Transformer) Reset() {
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// do nothing
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}
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func (t *Transformer) Transform(dst []byte, src []byte, at_eof bool) (int, int, error) {
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var n int
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var i int
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var ndst int
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var nsrc int
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var rem int
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var err error
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if t.needle_len <= 0 {
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n, err = t.copy_all(dst, src)
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return n, n, err
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}
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nsrc = 0; ndst = 0
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for {
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i = bytes.Index(src[nsrc:], t.needle)
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if i == -1 { break }
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// copy the part before the match
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n, err = t.copy_all(dst[ndst:], src[nsrc:nsrc+i])
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nsrc += n; ndst += n
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if err != nil { goto done }
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// copy the new value in place of the match
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n, err = t.copy_all(dst[ndst:], t.replacement)
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if err != nil { goto done }
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ndst += n; nsrc += t.needle_len
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}
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if at_eof {
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n, err = t.copy_all(dst[ndst:], src[nsrc:])
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ndst += n; nsrc += n
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goto done
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}
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rem = len(src[nsrc:])
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if rem >= t.needle_len {
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n, err = t.copy_all(dst[ndst:], src[nsrc: nsrc + (rem - t.needle_len) + 1])
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nsrc += n; ndst += n
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if err != nil { goto done }
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}
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// ErrShortSrc means that the source buffer has insufficient data to
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// complete the transformation.
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err = transform.ErrShortSrc
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done:
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return ndst, nsrc, err
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}
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func (t *Transformer) copy_all(dst []byte, src []byte) (int, error) {
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var n int
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var err error
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n = copy(dst, src)
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// ErrShortDst means that the destination buffer was too short to
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// receive all of the transformed bytes.
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if n < len(src) { err = transform.ErrShortDst }
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return n, err
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}
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