filter.go

     1  // Copyright 2025 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package scan
     6  
     7  import "unsafe"
     8  
     9  // FilterNil packs non-nil (non-zero) values in bufp together
    10  // at the beginning of bufp, returning the length of the
    11  // packed buffer. It treats bufp as an array of size n.
    12  //
    13  // TODO(mknyszek): Add a faster SIMD-based implementation.
    14  func FilterNil(bufp *uintptr, n int32) int32 {
    15  	buf := unsafe.Slice(bufp, int(n))
    16  	lo := 0
    17  	hi := len(buf) - 1
    18  	for lo < hi {
    19  		for lo < hi && buf[hi] == 0 {
    20  			hi--
    21  		}
    22  		for lo < hi && buf[lo] != 0 {
    23  			lo++
    24  		}
    25  		if lo >= hi {
    26  			break
    27  		}
    28  		buf[lo] = buf[hi]
    29  		hi--
    30  	}
    31  	if hi >= 0 && buf[hi] == 0 {
    32  		hi--
    33  	}
    34  	return int32(hi) + 1
    35  }
    36
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