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Reject out-of-range integers instead of silently truncating #112

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Reject out-of-range integers instead of silently truncating #112

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21 changes: 16 additions & 5 deletions src/jsony.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,12 @@ proc parseHook*(s: string, i: var int, v: var SomeUnsignedInt) =
v2: uint64 = 0
startI = i
while i < s.len and s[i] in {'0'..'9'}:
v2 = v2 * 10 + (s[i].ord - '0'.ord).uint64
let digit = (s[i].ord - '0'.ord).uint64
# Reject numbers that do not fit the target type instead of silently
# wrapping modulo (unsigned conversions are unchecked). See issue #109.
if v2 > (uint64(high(type(v))) - digit) div 10:
error("Number type to small to contain the number.", i)
v2 = v2 * 10 + digit
inc i
if startI == i:
error("Number expected.", i)
Expand All @@ -123,14 +128,20 @@ proc parseHook*(s: string, i: var int, v: var SomeSignedInt) =
var v2: uint64
inc i
parseHook(s, i, v2)
v = -type(v)(v2)
# The negative range extends one past high(T) (e.g. int8 reaches -128).
# Range-check explicitly; release builds do not raise. See issue #109.
if v2 > uint64(high(type(v))) + 1:
error("Number type to small to contain the number.", i)
elif v2 == uint64(high(type(v))) + 1:
v = low(type(v))
else:
v = -type(v)(v2)
else:
var v2: uint64
parseHook(s, i, v2)
try:
v = type(v)(v2)
except:
if v2 > uint64(high(type(v))):
error("Number type to small to contain the number.", i)
v = type(v)(v2)

proc parseHook*(s: string, i: var int, v: var SomeFloat) =
## Will parse float32 and float64.
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15 changes: 15 additions & 0 deletions tests/test_numbers.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -51,3 +51,18 @@ block:
@["hi", "bye", "maybe"]
doAssert """[["hi", "bye"], ["maybe"], []]""".fromJson(seq[seq[string]]) ==
@[@["hi", "bye"], @["maybe"], @[]]

block:
# Out-of-range integers must raise instead of silently wrapping/truncating.
# See https://github.com/treeform/jsony/issues/109
doAssertRaises(JsonError): discard "256".fromJson(uint8)
doAssertRaises(JsonError): discard "99999999999999999999999999".fromJson(uint64)
doAssertRaises(JsonError): discard "128".fromJson(int8)
doAssertRaises(JsonError): discard "-129".fromJson(int8)
doAssertRaises(JsonError): discard "300".fromJson(uint8)
# Boundary values still parse correctly.
doAssert "255".fromJson(uint8) == 255'u8
doAssert "127".fromJson(int8) == 127'i8
doAssert "-128".fromJson(int8) == -128'i8
doAssert "65535".fromJson(uint16) == 65535'u16
doAssert "18446744073709551615".fromJson(uint64) == 18446744073709551615'u64