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internal/span: fix another off-by-one in ToUTF16Column 

The current tests contain a bug in the priming of funnyString; the
subslicing leaves the resulting content slice with a capacity greater
than its length. This allowed a bug ToUTF16Column to sneak through where
we were not using 0-based column as the offset within the line.

Fix the priming of funnyString, and fix the implementation of
ToUTF16Column.

Change-Id: I2618878d85bba26f52f99a3fc136ad21fe198dfc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/174357
Reviewed-by: Ian Cottrell <iancottrell@google.com>
Run-TryBot: Ian Cottrell <iancottrell@google.com>
This commit is contained in:
Paul Jolly 2019-04-29 18:36:30 +01:00 committed by Paul Jolly
parent c6e1543aba
commit 7af746645d
2 changed files with 8 additions and 10 deletions
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14
internal/span/utf16.go
View File

@ -24,14 +24,14 @@ func ToUTF16Column(p Point, content []byte) (int, error) {
if !p.HasOffset() { if !p.HasOffset() {
return -1, fmt.Errorf("ToUTF16Column: point is missing offset") return -1, fmt.Errorf("ToUTF16Column: point is missing offset")
} }
offset := p.Offset() offset := p.Offset() // 0-based
col := p.Column() colZero := p.Column() - 1 // 0-based
if col == 1 { if colZero == 0 {
// column 1, so it must be chr 1 // 0-based column 0, so it must be chr 1
return 1, nil return 1, nil
} }
// work out the offset at the start of the line using the column // work out the offset at the start of the line using the column
lineOffset := offset - (col - 1) lineOffset := offset - colZero
if lineOffset < 0 || offset > len(content) { if lineOffset < 0 || offset > len(content) {
return -1, fmt.Errorf("ToUTF16Column: offsets %v-%v outside file contents (%v)", lineOffset, offset, len(content)) return -1, fmt.Errorf("ToUTF16Column: offsets %v-%v outside file contents (%v)", lineOffset, offset, len(content))
} }
@ -40,10 +40,10 @@ func ToUTF16Column(p Point, content []byte) (int, error) {
start := content[lineOffset:] start := content[lineOffset:]
// Now, truncate down to the supplied column. // Now, truncate down to the supplied column.
start = start[:col] start = start[:colZero]
// and count the number of utf16 characters // and count the number of utf16 characters
// in theory we could do this by hand more efficiently... // in theory we could do this by hand more efficiently...
return len(utf16.Encode([]rune(string(start)))), nil return len(utf16.Encode([]rune(string(start)))) + 1, nil
} }
// FromUTF16Column advances the point by the utf16 character offset given the // FromUTF16Column advances the point by the utf16 character offset given the

4
internal/span/utf16_test.go
View File

@ -12,9 +12,7 @@ import (
) )
// The funny character below is 4 bytes long in UTF-8; two UTF-16 code points // The funny character below is 4 bytes long in UTF-8; two UTF-16 code points
var funnyString = []byte(` var funnyString = []byte("𐐀23\n𐐀45")
𐐀23
𐐀45`[1:])
var toUTF16Tests = []struct { var toUTF16Tests = []struct {
scenario string scenario string