go transform 源码
golang transform 代码
文件路径：/src/vendor/golang.org/x/text/unicode/norm/transform.go
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package norm
import (
"unicode/utf8"
"golang.org/x/text/transform"
)
// Reset implements the Reset method of the transform.Transformer interface.
func (Form) Reset() {}
// Transform implements the Transform method of the transform.Transformer
// interface. It may need to write segments of up to MaxSegmentSize at once.
// Users should either catch ErrShortDst and allow dst to grow or have dst be at
// least of size MaxTransformChunkSize to be guaranteed of progress.
func (f Form) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
// Cap the maximum number of src bytes to check.
b := src
eof := atEOF
if ns := len(dst); ns < len(b) {
err = transform.ErrShortDst
eof = false
b = b[:ns]
}
i, ok := formTable[f].quickSpan(inputBytes(b), 0, len(b), eof)
n := copy(dst, b[:i])
if !ok {
nDst, nSrc, err = f.transform(dst[n:], src[n:], atEOF)
return nDst + n, nSrc + n, err
}
if err == nil && n < len(src) && !atEOF {
err = transform.ErrShortSrc
}
return n, n, err
}
func flushTransform(rb *reorderBuffer) bool {
// Write out (must fully fit in dst, or else it is an ErrShortDst).
if len(rb.out) < rb.nrune*utf8.UTFMax {
return false
}
rb.out = rb.out[rb.flushCopy(rb.out):]
return true
}
var errs = []error{nil, transform.ErrShortDst, transform.ErrShortSrc}
// transform implements the transform.Transformer interface. It is only called
// when quickSpan does not pass for a given string.
func (f Form) transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
// TODO: get rid of reorderBuffer. See CL 23460044.
rb := reorderBuffer{}
rb.init(f, src)
for {
// Load segment into reorder buffer.
rb.setFlusher(dst[nDst:], flushTransform)
end := decomposeSegment(&rb, nSrc, atEOF)
if end < 0 {
return nDst, nSrc, errs[-end]
}
nDst = len(dst) - len(rb.out)
nSrc = end
// Next quickSpan.
end = rb.nsrc
eof := atEOF
if n := nSrc + len(dst) - nDst; n < end {
err = transform.ErrShortDst
end = n
eof = false
}
end, ok := rb.f.quickSpan(rb.src, nSrc, end, eof)
n := copy(dst[nDst:], rb.src.bytes[nSrc:end])
nSrc += n
nDst += n
if ok {
if err == nil && n < rb.nsrc && !atEOF {
err = transform.ErrShortSrc
}
return nDst, nSrc, err
}
}
}
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