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Diffstat (limited to 'doc/tutorial/ffi.md')
| -rw-r--r-- | doc/tutorial/ffi.md | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/doc/tutorial/ffi.md b/doc/tutorial/ffi.md index cca3669f10d..7b90f64a6ba 100644 --- a/doc/tutorial/ffi.md +++ b/doc/tutorial/ffi.md @@ -67,6 +67,7 @@ most notably the Windows API, use other calling conventions, so Rust provides a way to to hint to the compiler which is expected by using the `"abi"` attribute: + #[cfg(target_os = "win32")] #[abi = "stdcall"] native mod kernel32 { fn SetEnvironmentVariableA(n: *u8, v: *u8) -> int; @@ -81,7 +82,9 @@ or `"stdcall"`. Other conventions may be defined in the future. The native `SHA1` function is declared to take three arguments, and return a pointer. + # native mod crypto { fn SHA1(src: *u8, sz: uint, out: *u8) -> *u8; + # } When declaring the argument types to a foreign function, the Rust compiler has no way to check whether your declaration is correct, so @@ -106,6 +109,9 @@ null pointers. The `sha1` function is the most obscure part of the program. + # import std::{str, vec}; + # mod crypto { fn SHA1(src: *u8, sz: uint, out: *u8) -> *u8 { out } } + # fn as_hex(data: [u8]) -> str { "hi" } fn sha1(data: str) -> str unsafe { let bytes = str::bytes(data); let hash = crypto::SHA1(vec::unsafe::to_ptr(bytes), @@ -141,10 +147,15 @@ Rust's safety mechanisms. Let's look at our `sha1` function again. + # import std::{str, vec}; + # mod crypto { fn SHA1(src: *u8, sz: uint, out: *u8) -> *u8 { out } } + # fn as_hex(data: [u8]) -> str { "hi" } + # fn x(data: str) -> str unsafe { let bytes = str::bytes(data); let hash = crypto::SHA1(vec::unsafe::to_ptr(bytes), vec::len(bytes), std::ptr::null()); ret as_hex(vec::unsafe::from_buf(hash, 20u)); + # } The `str::bytes` function is perfectly safe, it converts a string to an `[u8]`. This byte array is then fed to `vec::unsafe::to_ptr`, which |