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update comment on bounds checks

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KodrAus 2021-11-16 07:40:59 +10:00
parent beac70a80a
commit 708315e597
1 changed files with 13 additions and 9 deletions
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22
shared/parser.rs
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@ -38,7 +38,8 @@ pub const fn try_parse(input: &str) -> Result<[u8; 16], InvalidUuid> {
#[inline] #[inline]
const fn parse_simple(s: &[u8]) -> Result<[u8; 16], ()> { const fn parse_simple(s: &[u8]) -> Result<[u8; 16], ()> {
// Should be optimized away as redundant // This length check here removes all other bounds
// checks in this function
if s.len() != 32 { if s.len() != 32 {
return Err(()); return Err(());
} }
@ -69,24 +70,27 @@ const fn parse_simple(s: &[u8]) -> Result<[u8; 16], ()> {
#[inline] #[inline]
const fn parse_hyphenated(s: &[u8]) -> Result<[u8; 16], ()> { const fn parse_hyphenated(s: &[u8]) -> Result<[u8; 16], ()> {
// Should be optimized away as redundant // This length check here removes all other bounds
// checks in this function
if s.len() != 36 { if s.len() != 36 {
return Err(()); return Err(());
} }
// We look at two hex-encoded values (4 chars) at a time because
// that's the size of the smallest group in a hyphenated UUID.
// The indexes we're interested in are:
//
// uuid : 936da01f-9abd-4d9d-80c7-02af85c822a8
// | | || || || || | |
// hyphens : | | 8| 13| 18| 23| | |
// positions: 0 4 9 14 19 24 28 32
// First, ensure the hyphens appear in the right places // First, ensure the hyphens appear in the right places
match [s[8], s[13], s[18], s[23]] { match [s[8], s[13], s[18], s[23]] {
[b'-', b'-', b'-', b'-'] => {} [b'-', b'-', b'-', b'-'] => {}
_ => return Err(()), _ => return Err(()),
} }
// We look at two hex-encoded values (4 chars) at a time because
// that's the size of the smallest group in a hyphenated UUID:
//
// uuid : 936da01f-9abd-4d9d-80c7-02af85c822a8
// | | || || || || | |
// hyphens : | | 8| 13| 18| 23| | |
// positions: 0 4 9 14 19 24 28 32
let positions: [u8; 8] = [0, 4, 9, 14, 19, 24, 28, 32]; let positions: [u8; 8] = [0, 4, 9, 14, 19, 24, 28, 32];
let mut buf: [u8; 16] = [0; 16]; let mut buf: [u8; 16] = [0; 16];
let mut j = 0; let mut j = 0;