1 // Copyright (c) 2017 Gilad Naaman 2 // 3 // Permission is hereby granted, free of charge, to any person obtaining a copy 4 // of this software and associated documentation files (the "Software"), to deal 5 // in the Software without restriction, including without limitation the rights 6 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 7 // copies of the Software, and to permit persons to whom the Software is 8 // furnished to do so, subject to the following conditions: 9 // 10 // The above copyright notice and this permission notice shall be included in all 11 // copies or substantial portions of the Software. 12 // 13 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 14 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 15 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 16 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 17 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 18 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 19 // SOFTWARE. 20 21 /// Reexport for `local_inner_macros`; see 22 /// <https://doc.rust-lang.org/edition-guide/rust-2018/macros/macro-changes.html#macros-using-local_inner_macros>. 23 #[doc(hidden)] 24 #[macro_export] 25 macro_rules! _memoffset__compile_error { 26 ($($inner:tt)*) => { 27 compile_error! { $($inner)* } 28 } 29 } 30 31 /// Produces a range instance representing the sub-slice containing the specified member. 32 /// 33 /// This macro provides 2 forms of differing functionalities. 34 /// 35 /// The first form is identical to the appearance of the `offset_of!` macro. 36 /// 37 /// ```ignore 38 /// span_of!(Struct, member) 39 /// ``` 40 /// 41 /// The second form of `span_of!` returns a sub-slice which starts at one field, and ends at another. 42 /// The general pattern of this form is: 43 /// 44 /// ```ignore 45 /// // Exclusive 46 /// span_of!(Struct, member_a .. member_b) 47 /// // Inclusive 48 /// span_of!(Struct, member_a ..= member_b) 49 /// 50 /// // Open-ended ranges 51 /// span_of!(Struct, .. end) 52 /// span_of!(Struct, start ..) 53 /// ``` 54 /// 55 /// *Note*: 56 /// This macro uses recursion in order to resolve the range expressions, so there is a limit to 57 /// the complexity of the expression. 58 /// In order to raise the limit, the compiler's recursion limit should be lifted. 59 /// 60 /// ## Examples 61 /// ``` 62 /// #[macro_use] 63 /// extern crate memoffset; 64 /// 65 /// #[repr(C)] 66 /// struct Florp { 67 /// a: u32 68 /// } 69 /// 70 /// #[repr(C)] 71 /// struct Blarg { 72 /// x: [u32; 2], 73 /// y: [u8; 56], 74 /// z: Florp, 75 /// egg: [[u8; 4]; 4] 76 /// } 77 /// 78 /// fn main() { 79 /// assert_eq!(0..84, span_of!(Blarg, ..)); 80 /// assert_eq!(0..8, span_of!(Blarg, .. y)); 81 /// assert_eq!(0..64, span_of!(Blarg, ..= y)); 82 /// assert_eq!(0..8, span_of!(Blarg, x)); 83 /// assert_eq!(8..84, span_of!(Blarg, y ..)); 84 /// assert_eq!(0..8, span_of!(Blarg, x .. y)); 85 /// assert_eq!(0..64, span_of!(Blarg, x ..= y)); 86 /// } 87 /// ``` 88 #[macro_export(local_inner_macros)] 89 macro_rules! span_of { 90 (@helper $root:ident, [] ..=) => { 91 _memoffset__compile_error!("Expected a range, found '..='") 92 }; 93 (@helper $root:ident, [] ..) => { 94 _memoffset__compile_error!("Expected a range, found '..'") 95 }; 96 // No explicit begin for range. 97 (@helper $root:ident, $parent:path, [] ..) => {{ 98 ($root as usize, 99 $root as usize + $crate::__priv::size_of_pointee($root)) 100 }}; 101 (@helper $root:ident, $parent:path, [] ..= $end:tt) => {{ 102 let end = raw_field!($root, $parent, $end); 103 ($root as usize, end as usize + $crate::__priv::size_of_pointee(end)) 104 }}; 105 (@helper $root:ident, $parent:path, [] .. $end:tt) => {{ 106 ($root as usize, raw_field!($root, $parent, $end) as usize) 107 }}; 108 // Explicit begin and end for range. 109 (@helper $root:ident, $parent:path, # $begin:tt [] ..= $end:tt) => {{ 110 let begin = raw_field!($root, $parent, $begin); 111 let end = raw_field!($root, $parent, $end); 112 (begin as usize, end as usize + $crate::__priv::size_of_pointee(end)) 113 }}; 114 (@helper $root:ident, $parent:path, # $begin:tt [] .. $end:tt) => {{ 115 (raw_field!($root, $parent, $begin) as usize, 116 raw_field!($root, $parent, $end) as usize) 117 }}; 118 // No explicit end for range. 119 (@helper $root:ident, $parent:path, # $begin:tt [] ..) => {{ 120 (raw_field!($root, $parent, $begin) as usize, 121 $root as usize + $crate::__priv::size_of_pointee($root)) 122 }}; 123 (@helper $root:ident, $parent:path, # $begin:tt [] ..=) => {{ 124 _memoffset__compile_error!( 125 "Found inclusive range to the end of a struct. Did you mean '..' instead of '..='?") 126 }}; 127 // Just one field. 128 (@helper $root:ident, $parent:path, # $field:tt []) => {{ 129 let field = raw_field!($root, $parent, $field); 130 (field as usize, field as usize + $crate::__priv::size_of_pointee(field)) 131 }}; 132 // Parsing. 133 (@helper $root:ident, $parent:path, $(# $begin:tt)+ [] $tt:tt $($rest:tt)*) => {{ 134 span_of!(@helper $root, $parent, $(#$begin)* #$tt [] $($rest)*) 135 }}; 136 (@helper $root:ident, $parent:path, [] $tt:tt $($rest:tt)*) => {{ 137 span_of!(@helper $root, $parent, #$tt [] $($rest)*) 138 }}; 139 140 // Entry point. 141 ($sty:path, $($exp:tt)+) => ({ 142 // Get a base pointer. 143 _memoffset__let_base_ptr!(root, $sty); 144 let base = root as usize; 145 let (begin, end) = span_of!(@helper root, $sty, [] $($exp)*); 146 begin-base..end-base 147 }); 148 } 149 150 #[cfg(test)] 151 mod tests { 152 use core::mem; 153 154 #[test] 155 fn span_simple() { 156 #[repr(C)] 157 struct Foo { 158 a: u32, 159 b: [u8; 2], 160 c: i64, 161 } 162 163 assert_eq!(span_of!(Foo, a), 0..4); 164 assert_eq!(span_of!(Foo, b), 4..6); 165 assert_eq!(span_of!(Foo, c), 8..8 + 8); 166 } 167 168 #[test] 169 #[cfg_attr(miri, ignore)] // this creates unaligned references 170 fn span_simple_packed() { 171 #[repr(C, packed)] 172 struct Foo { 173 a: u32, 174 b: [u8; 2], 175 c: i64, 176 } 177 178 assert_eq!(span_of!(Foo, a), 0..4); 179 assert_eq!(span_of!(Foo, b), 4..6); 180 assert_eq!(span_of!(Foo, c), 6..6 + 8); 181 } 182 183 #[test] 184 fn span_forms() { 185 #[repr(C)] 186 struct Florp { 187 a: u32, 188 } 189 190 #[repr(C)] 191 struct Blarg { 192 x: u64, 193 y: [u8; 56], 194 z: Florp, 195 egg: [[u8; 4]; 5], 196 } 197 198 // Love me some brute force 199 assert_eq!(0..8, span_of!(Blarg, x)); 200 assert_eq!(64..68, span_of!(Blarg, z)); 201 assert_eq!(68..mem::size_of::<Blarg>(), span_of!(Blarg, egg)); 202 203 assert_eq!(8..64, span_of!(Blarg, y..z)); 204 assert_eq!(0..64, span_of!(Blarg, x..=y)); 205 } 206 207 #[test] 208 fn ig_test() { 209 #[repr(C)] 210 struct Member { 211 foo: u32, 212 } 213 214 #[repr(C)] 215 struct Test { 216 x: u64, 217 y: [u8; 56], 218 z: Member, 219 egg: [[u8; 4]; 4], 220 } 221 222 assert_eq!(span_of!(Test, ..x), 0..0); 223 assert_eq!(span_of!(Test, ..=x), 0..8); 224 assert_eq!(span_of!(Test, ..y), 0..8); 225 assert_eq!(span_of!(Test, ..=y), 0..64); 226 assert_eq!(span_of!(Test, ..z), 0..64); 227 assert_eq!(span_of!(Test, ..=z), 0..68); 228 assert_eq!(span_of!(Test, ..egg), 0..68); 229 assert_eq!(span_of!(Test, ..=egg), 0..84); 230 assert_eq!(span_of!(Test, ..), 0..mem::size_of::<Test>()); 231 assert_eq!( 232 span_of!(Test, x..), 233 offset_of!(Test, x)..mem::size_of::<Test>() 234 ); 235 assert_eq!( 236 span_of!(Test, y..), 237 offset_of!(Test, y)..mem::size_of::<Test>() 238 ); 239 240 assert_eq!( 241 span_of!(Test, z..), 242 offset_of!(Test, z)..mem::size_of::<Test>() 243 ); 244 assert_eq!( 245 span_of!(Test, egg..), 246 offset_of!(Test, egg)..mem::size_of::<Test>() 247 ); 248 assert_eq!( 249 span_of!(Test, x..y), 250 offset_of!(Test, x)..offset_of!(Test, y) 251 ); 252 assert_eq!( 253 span_of!(Test, x..=y), 254 offset_of!(Test, x)..offset_of!(Test, y) + mem::size_of::<[u8; 56]>() 255 ); 256 } 257 } 258