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};
36 use super::{cvt, cvt_r};
38 // The `log2` and `log2f` functions apparently appeared in android-18, or at
39 // least you can see they're not present in the android-17 header [1] and they
40 // are present in android-18 [2].
42 // [1]: https://chromium.googlesource.com/android_tools/+/20ee6d20/ndk/platforms
43 // /android-17/arch-arm/usr/include/math.h
44 // [2]: https://chromium.googlesource.com/android_tools/+/20ee6d20/ndk/platforms
45 // /android-18/arch-arm/usr/include/math.h
47 // Note that these shims are likely less precise than directly calling `log2`,
48 // but hopefully that should be enough for now...
50 // Note that mathematically, for any arbitrary `y`:
52 // log_2(x) = log_y(x) / log_y(2)
53 // = log_y(x) / (1 / log_2(y))
54 // = log_y(x) * log_2(y)
56 // Hence because `ln` (log_e) is available on all Android we just choose `y = e`
59 // log_2(x) = ln(x) * log_2(e)
62 pub fn log2f32(f: f32) -> f32 {
63 f.ln() * ::f32::consts::LOG2_E
67 pub fn log2f64(f: f64) -> f64 {
68 f.ln() * ::f64::consts::LOG2_E
71 // Back in the day [1] the `signal` function was just an inline wrapper
72 // around `bsd_signal`, but starting in API level android-20 the `signal`
73 // symbols was introduced [2]. Finally, in android-21 the API `bsd_signal` was
76 // Basically this means that if we want to be binary compatible with multiple
77 // Android releases (oldest being 9 and newest being 21) then we need to check
78 // for both symbols and not actually link against either.
80 // [1]: https://chromium.googlesource.com/android_tools/+/20ee6d20/ndk/platforms
81 // /android-18/arch-arm/usr/include/signal.h
82 // [2]: https://chromium.googlesource.com/android_tools/+/fbd420/ndk_experimental
83 // /platforms/android-20/arch-arm
84 // /usr/include/signal.h
85 // [3]: https://chromium.googlesource.com/android_tools/+/20ee6d/ndk/platforms
86 // /android-21/arch-arm/usr/include/signal.h
87 pub unsafe fn signal(signum: c_int, handler: sighandler_t) -> sighandler_t {
88 weak!(fn signal(c_int, sighandler_t) -> sighandler_t);
89 weak!(fn bsd_signal(c_int, sighandler_t) -> sighandler_t);
91 let f = signal.get().or_else(|| bsd_signal.get());
92 let f = f.expect("neither `signal` nor `bsd_signal` symbols found");
96 // The `ftruncate64` symbol apparently appeared in android-12, so we do some
97 // dynamic detection to see if we can figure out whether `ftruncate64` exists.
99 // If it doesn't we just fall back to `ftruncate`, generating an error for
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 pub unsafe fn cvt_pread64(fd: c_int, buf: *mut c_void, count: size_t, offset: i64)
120 -> io::Result<ssize_t>
122 weak!(fn pread64(c_int, *mut c_void, size_t, i64) -> ssize_t);
123 pread64.get().map(|f| cvt(f(fd, buf, count, offset))).unwrap_or_else(|| {
124 if let Ok(o) = offset.try_into() {
125 cvt(pread(fd, buf, count, o))
127 Err(io::Error::new(io::ErrorKind::InvalidInput,
128 "cannot pread >2GB"))
133 pub unsafe fn cvt_pwrite64(fd: c_int, buf: *const c_void, count: size_t, offset: i64)
134 -> io::Result<ssize_t>
136 weak!(fn pwrite64(c_int, *const c_void, size_t, i64) -> ssize_t);
137 pwrite64.get().map(|f| cvt(f(fd, buf, count, offset))).unwrap_or_else(|| {
138 if let Ok(o) = offset.try_into() {
139 cvt(pwrite(fd, buf, count, o))
141 Err(io::Error::new(io::ErrorKind::InvalidInput,
142 "cannot pwrite >2GB"))