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 // ANDROID: use std instead of core, since we're not building wiht no-std. 153 use std::mem; 154 155 #[test] span_simple()156 fn span_simple() { 157 #[repr(C)] 158 struct Foo { 159 a: u32, 160 b: [u8; 2], 161 c: i64, 162 } 163 164 assert_eq!(span_of!(Foo, a), 0..4); 165 assert_eq!(span_of!(Foo, b), 4..6); 166 assert_eq!(span_of!(Foo, c), 8..8 + 8); 167 } 168 169 #[test] 170 #[cfg_attr(miri, ignore)] // this creates unaligned references span_simple_packed()171 fn span_simple_packed() { 172 #[repr(C, packed)] 173 struct Foo { 174 a: u32, 175 b: [u8; 2], 176 c: i64, 177 } 178 179 assert_eq!(span_of!(Foo, a), 0..4); 180 assert_eq!(span_of!(Foo, b), 4..6); 181 assert_eq!(span_of!(Foo, c), 6..6 + 8); 182 } 183 184 #[test] span_forms()185 fn span_forms() { 186 #[repr(C)] 187 struct Florp { 188 a: u32, 189 } 190 191 #[repr(C)] 192 struct Blarg { 193 x: u64, 194 y: [u8; 56], 195 z: Florp, 196 egg: [[u8; 4]; 5], 197 } 198 199 // Love me some brute force 200 assert_eq!(0..8, span_of!(Blarg, x)); 201 assert_eq!(64..68, span_of!(Blarg, z)); 202 assert_eq!(68..mem::size_of::<Blarg>(), span_of!(Blarg, egg)); 203 204 assert_eq!(8..64, span_of!(Blarg, y..z)); 205 assert_eq!(0..64, span_of!(Blarg, x..=y)); 206 } 207 208 #[test] ig_test()209 fn ig_test() { 210 #[repr(C)] 211 struct Member { 212 foo: u32, 213 } 214 215 #[repr(C)] 216 struct Test { 217 x: u64, 218 y: [u8; 56], 219 z: Member, 220 egg: [[u8; 4]; 4], 221 } 222 223 assert_eq!(span_of!(Test, ..x), 0..0); 224 assert_eq!(span_of!(Test, ..=x), 0..8); 225 assert_eq!(span_of!(Test, ..y), 0..8); 226 assert_eq!(span_of!(Test, ..=y), 0..64); 227 assert_eq!(span_of!(Test, ..z), 0..64); 228 assert_eq!(span_of!(Test, ..=z), 0..68); 229 assert_eq!(span_of!(Test, ..egg), 0..68); 230 assert_eq!(span_of!(Test, ..=egg), 0..84); 231 assert_eq!(span_of!(Test, ..), 0..mem::size_of::<Test>()); 232 assert_eq!( 233 span_of!(Test, x..), 234 offset_of!(Test, x)..mem::size_of::<Test>() 235 ); 236 assert_eq!( 237 span_of!(Test, y..), 238 offset_of!(Test, y)..mem::size_of::<Test>() 239 ); 240 241 assert_eq!( 242 span_of!(Test, z..), 243 offset_of!(Test, z)..mem::size_of::<Test>() 244 ); 245 assert_eq!( 246 span_of!(Test, egg..), 247 offset_of!(Test, egg)..mem::size_of::<Test>() 248 ); 249 assert_eq!( 250 span_of!(Test, x..y), 251 offset_of!(Test, x)..offset_of!(Test, y) 252 ); 253 assert_eq!( 254 span_of!(Test, x..=y), 255 offset_of!(Test, x)..offset_of!(Test, y) + mem::size_of::<[u8; 56]>() 256 ); 257 } 258 } 259