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fixes #21273; fixes an io.readLine off by one bug [backport 1.0] (#21276)

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fixes #21273; io.readLine off by one
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ringabout 2023-01-26 03:56:19 +08:00 • committed by GitHub
commit c4d3d650ba
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2 changed files with 22 additions and 3 deletions
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7
lib/std/syncio.nim
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@ -484,11 +484,12 @@ proc readLine*(f: File, line: var string): bool {.tags: [ReadIOEffect],
if last > 0 and line[last-1] == '\c': if last > 0 and line[last-1] == '\c':
line.setLen(last-1) line.setLen(last-1)
return last > 1 or fgetsSuccess return last > 1 or fgetsSuccess
# We have to distinguish between two possible cases: elif last > 0 and line[last-1] == '\0':
# We have to distinguish among three possible cases:
# \0\l\0 => line ending in a null character. # \0\l\0 => line ending in a null character.
# \0\l\l => last line without newline, null was put there by fgets. # \0\l\l => last line without newline, null was put there by fgets.
elif last > 0 and line[last-1] == '\0': # \0\l => last line without newline, null was put there by fgets.
if last < pos + sp - 1 and line[last+1] != '\0': if last >= pos + sp - 1 or line[last+1] != '\0': # bug #21273
dec last dec last
line.setLen(last) line.setLen(last)
return last > 0 or fgetsSuccess return last > 0 or fgetsSuccess

18
tests/stdlib/tio.nim
View file

@ -36,3 +36,21 @@ block: # readChars
break break
doAssert n2s == @[2,2,2,1,0] doAssert n2s == @[2,2,2,1,0]
doAssert s2 == s doAssert s2 == s
import std/strutils
block: # bug #21273
let FILE = buildDir / "D20220119T134305.txt"
let hex = "313632313920313632343720313632353920313632363020313632393020323035363520323037323120323131353020323239393820323331303520323332313020323332343820323332363820"
writeFile FILE, parseHexStr(hex)
doAssert readFile(FILE).toHex == hex
let f = open(FILE)
var s = newString(80)
while f.readLine(s):
doAssert s.toHex == hex