1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Android ABI-compatibility module
13 //! The ABI of Android has changed quite a bit over time, and libstd attempts to
14 //! be both forwards and backwards compatible as much as possible. We want to
15 //! always work with the most recent version of Android, but we also want to
16 //! work with older versions of Android for whenever projects need to.
18 //! Our current minimum supported Android version is `android-9`, e.g. Android
19 //! with API level 9. We then in theory want to work on that and all future
20 //! versions of Android!
22 //! Some of the detection here is done at runtime via `dlopen` and
23 //! introspection. Other times no detection is performed at all and we just
24 //! provide a fallback implementation as some versions of Android we support
25 //! don't have the function.
27 //! You'll find more details below about why each compatibility shim is needed.
29 #![cfg(target_os = "android")]
31 use libc
::{c_int, c_void, sighandler_t, size_t, ssize_t}
;
32 use libc
::{ftruncate, pread, pwrite}
;
35 use super::{cvt, cvt_r}
;
37 // The `log2` and `log2f` functions apparently appeared in android-18, or at
38 // least you can see they're not present in the android-17 header [1] and they
39 // are present in android-18 [2].
41 // [1]: https://chromium.googlesource.com/android_tools/+/20ee6d20/ndk/platforms
42 // /android-17/arch-arm/usr/include/math.h
43 // [2]: https://chromium.googlesource.com/android_tools/+/20ee6d20/ndk/platforms
44 // /android-18/arch-arm/usr/include/math.h
46 // Note that these shims are likely less precise than directly calling `log2`,
47 // but hopefully that should be enough for now...
49 // Note that mathematically, for any arbitrary `y`:
51 // log_2(x) = log_y(x) / log_y(2)
52 // = log_y(x) / (1 / log_2(y))
53 // = log_y(x) * log_2(y)
55 // Hence because `ln` (log_e) is available on all Android we just choose `y = e`
58 // log_2(x) = ln(x) * log_2(e)
61 pub fn log2f32(f
: f32) -> f32 {
62 f
.ln() * ::f32::consts
::LOG2_E
66 pub fn log2f64(f
: f64) -> f64 {
67 f
.ln() * ::f64::consts
::LOG2_E
70 // Back in the day [1] the `signal` function was just an inline wrapper
71 // around `bsd_signal`, but starting in API level android-20 the `signal`
72 // symbols was introduced [2]. Finally, in android-21 the API `bsd_signal` was
75 // Basically this means that if we want to be binary compatible with multiple
76 // Android releases (oldest being 9 and newest being 21) then we need to check
77 // for both symbols and not actually link against either.
79 // [1]: https://chromium.googlesource.com/android_tools/+/20ee6d20/ndk/platforms
80 // /android-18/arch-arm/usr/include/signal.h
81 // [2]: https://chromium.googlesource.com/android_tools/+/fbd420/ndk_experimental
82 // /platforms/android-20/arch-arm
83 // /usr/include/signal.h
84 // [3]: https://chromium.googlesource.com/android_tools/+/20ee6d/ndk/platforms
85 // /android-21/arch-arm/usr/include/signal.h
86 pub unsafe fn signal(signum
: c_int
, handler
: sighandler_t
) -> sighandler_t
{
87 weak
!(fn signal(c_int
, sighandler_t
) -> sighandler_t
);
88 weak
!(fn bsd_signal(c_int
, sighandler_t
) -> sighandler_t
);
90 let f
= signal
.get().or_else(|| bsd_signal
.get());
91 let f
= f
.expect("neither `signal` nor `bsd_signal` symbols found");
95 // The `ftruncate64` symbol apparently appeared in android-12, so we do some
96 // dynamic detection to see if we can figure out whether `ftruncate64` exists.
98 // If it doesn't we just fall back to `ftruncate`, generating an error for
100 #[cfg(target_pointer_width = "32")]
101 pub fn ftruncate64(fd
: c_int
, size
: u64) -> io
::Result
<()> {
102 weak
!(fn ftruncate64(c_int
, i64) -> c_int
);
105 match ftruncate64
.get() {
106 Some(f
) => cvt_r(|| f(fd
, size
as i64)).map(|_
| ()),
108 if size
> i32::max_value() as u64 {
109 Err(io
::Error
::new(io
::ErrorKind
::InvalidInput
,
110 "cannot truncate >2GB"))
112 cvt_r(|| ftruncate(fd
, size
as i32)).map(|_
| ())
119 #[cfg(target_pointer_width = "64")]
120 pub fn ftruncate64(fd
: c_int
, size
: u64) -> io
::Result
<()> {
122 cvt_r(|| ftruncate(fd
, size
as i64)).map(|_
| ())
126 #[cfg(target_pointer_width = "32")]
127 pub unsafe fn cvt_pread64(fd
: c_int
, buf
: *mut c_void
, count
: size_t
, offset
: i64)
128 -> io
::Result
<ssize_t
>
130 use convert
::TryInto
;
131 weak
!(fn pread64(c_int
, *mut c_void
, size_t
, i64) -> ssize_t
);
132 pread64
.get().map(|f
| cvt(f(fd
, buf
, count
, offset
))).unwrap_or_else(|| {
133 if let Ok(o
) = offset
.try_into() {
134 cvt(pread(fd
, buf
, count
, o
))
136 Err(io
::Error
::new(io
::ErrorKind
::InvalidInput
,
137 "cannot pread >2GB"))
142 #[cfg(target_pointer_width = "32")]
143 pub unsafe fn cvt_pwrite64(fd
: c_int
, buf
: *const c_void
, count
: size_t
, offset
: i64)
144 -> io
::Result
<ssize_t
>
146 use convert
::TryInto
;
147 weak
!(fn pwrite64(c_int
, *const c_void
, size_t
, i64) -> ssize_t
);
148 pwrite64
.get().map(|f
| cvt(f(fd
, buf
, count
, offset
))).unwrap_or_else(|| {
149 if let Ok(o
) = offset
.try_into() {
150 cvt(pwrite(fd
, buf
, count
, o
))
152 Err(io
::Error
::new(io
::ErrorKind
::InvalidInput
,
153 "cannot pwrite >2GB"))
158 #[cfg(target_pointer_width = "64")]
159 pub unsafe fn cvt_pread64(fd
: c_int
, buf
: *mut c_void
, count
: size_t
, offset
: i64)
160 -> io
::Result
<ssize_t
>
162 cvt(pread(fd
, buf
, count
, offset
))
165 #[cfg(target_pointer_width = "64")]
166 pub unsafe fn cvt_pwrite64(fd
: c_int
, buf
: *const c_void
, count
: size_t
, offset
: i64)
167 -> io
::Result
<ssize_t
>
169 cvt(pwrite(fd
, buf
, count
, offset
))