cmds: Add evemu-record command

This is a Rust implementation of the command of the same name in the
FreeDesktop evemu suite [0].

The first version of this CL caused a build breakage on x86 due to
different sizes of the fields in libc::timeval. This version uses the
nix crate's wrapper to handle changes in timeval size by platform.

[0]: https://gitlab.freedesktop.org/libevdev/evemu

Bug: 302297266
Test: record events from an input peripheral (such as a mouse) and
      replay them using the FreeDesktop implementation of evemu-play
Ignore-AOSP-First: the directory does not yet exist in AOSP, so OWNERS
                   can safely be added here
Change-Id: I7851f6770e08babc2caa8c58c18612ee8543b401

4 files changed, 506 insertions, 0 deletions

diff --git a/cmds/evemu-record/Android.bp b/cmds/evemu-record/Android.bp
new file mode 100644
index 0000000000..1edacec384
--- /dev/null
+++ b/cmds/evemu-record/Android.bp
@@ -0,0 +1,13 @@
+package {
+    default_applicable_licenses: ["frameworks_native_license"],
+}
+
+rust_binary {
+    name: "evemu-record",
+    srcs: ["main.rs"],
+    rustlibs: [
+        "libclap",
+        "liblibc",
+        "libnix",
+    ],
+}
diff --git a/cmds/evemu-record/OWNERS b/cmds/evemu-record/OWNERS
new file mode 100644
index 0000000000..c88bfe97ca
--- /dev/null
+++ b/cmds/evemu-record/OWNERS
@@ -0,0 +1 @@
+include platform/frameworks/base:/INPUT_OWNERS
diff --git a/cmds/evemu-record/evdev.rs b/cmds/evemu-record/evdev.rs
new file mode 100644
index 0000000000..35feea1930
--- /dev/null
+++ b/cmds/evemu-record/evdev.rs
@@ -0,0 +1,299 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//! Wrappers for the Linux evdev APIs.
+
+use std::fs::File;
+use std::io;
+use std::mem;
+use std::os::fd::{AsRawFd, OwnedFd};
+use std::path::Path;
+
+use libc::c_int;
+use nix::sys::time::TimeVal;
+
+pub const SYN_CNT: usize = 0x10;
+pub const KEY_CNT: usize = 0x300;
+pub const REL_CNT: usize = 0x10;
+pub const ABS_CNT: usize = 0x40;
+pub const MSC_CNT: usize = 0x08;
+pub const SW_CNT: usize = 0x11;
+pub const LED_CNT: usize = 0x10;
+pub const SND_CNT: usize = 0x08;
+pub const REP_CNT: usize = 0x02;
+
+// Disable naming warnings, as these are supposed to match the EV_ constants in input-event-codes.h.
+#[allow(non_camel_case_types)]
+// Some of these types aren't referenced for evemu purposes, but are included for completeness.
+#[allow(dead_code)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[repr(u16)]
+pub enum EventType {
+    SYN = 0x00,
+    KEY = 0x01,
+    REL = 0x02,
+    ABS = 0x03,
+    MSC = 0x04,
+    SW = 0x05,
+    LED = 0x11,
+    SND = 0x12,
+    REP = 0x14,
+    FF = 0x15,
+    PWR = 0x16,
+    FF_STATUS = 0x17,
+}
+
+impl EventType {
+    fn code_count(&self) -> usize {
+        match self {
+            EventType::SYN => SYN_CNT,
+            EventType::KEY => KEY_CNT,
+            EventType::REL => REL_CNT,
+            EventType::ABS => ABS_CNT,
+            EventType::MSC => MSC_CNT,
+            EventType::SW => SW_CNT,
+            EventType::LED => LED_CNT,
+            EventType::SND => SND_CNT,
+            EventType::REP => REP_CNT,
+            _ => {
+                panic!("Event type {self:?} does not have a defined code count.");
+            }
+        }
+    }
+}
+
+pub const EVENT_TYPES_WITH_BITMAPS: [EventType; 7] = [
+    EventType::KEY,
+    EventType::REL,
+    EventType::ABS,
+    EventType::MSC,
+    EventType::SW,
+    EventType::LED,
+    EventType::SND,
+];
+
+const INPUT_PROP_CNT: usize = 32;
+
+/// The `ioctl_*!` macros create public functions by default, so this module makes them private.
+mod ioctl {
+    use nix::{ioctl_read, ioctl_read_buf};
+
+    ioctl_read!(eviocgid, b'E', 0x02, super::DeviceId);
+    ioctl_read_buf!(eviocgname, b'E', 0x06, u8);
+    ioctl_read_buf!(eviocgprop, b'E', 0x09, u8);
+}
+
+#[derive(Default)]
+#[repr(C)]
+pub struct DeviceId {
+    pub bus_type: u16,
+    pub vendor: u16,
+    pub product: u16,
+    pub version: u16,
+}
+
+#[derive(Default)]
+#[repr(C)]
+pub struct AbsoluteAxisInfo {
+    pub value: i32,
+    pub minimum: i32,
+    pub maximum: i32,
+    pub fuzz: i32,
+    pub flat: i32,
+    pub resolution: i32,
+}
+
+#[repr(C)]
+pub struct InputEvent {
+    pub time: TimeVal,
+    pub type_: u16,
+    pub code: u16,
+    pub value: i32,
+}
+
+impl InputEvent {
+    pub fn offset_time_by(&self, offset: TimeVal) -> InputEvent {
+        InputEvent { time: self.time - offset, ..*self }
+    }
+}
+
+impl Default for InputEvent {
+    fn default() -> Self {
+        InputEvent { time: TimeVal::new(0, 0), type_: 0, code: 0, value: 0 }
+    }
+}
+
+/// An object representing an input device using Linux's evdev protocol.
+pub struct Device {
+    fd: OwnedFd,
+}
+
+/// # Safety
+///
+/// `ioctl` must be safe to call with the given file descriptor and a pointer to a buffer of
+/// `initial_buf_size` `u8`s.
+unsafe fn buf_from_ioctl(
+    ioctl: unsafe fn(c_int, &mut [u8]) -> nix::Result<c_int>,
+    fd: &OwnedFd,
+    initial_buf_size: usize,
+) -> Result<Vec<u8>, nix::errno::Errno> {
+    let mut buf = vec![0; initial_buf_size];
+    // SAFETY:
+    // Here we're relying on the safety guarantees for `ioctl` made by the caller.
+    match unsafe { ioctl(fd.as_raw_fd(), buf.as_mut_slice()) } {
+        Ok(len) if len < 0 => {
+            panic!("ioctl returned invalid length {len}");
+        }
+        Ok(len) => {
+            buf.truncate(len as usize);
+            Ok(buf)
+        }
+        Err(err) => Err(err),
+    }
+}
+
+impl Device {
+    /// Opens a device from the evdev node at the given path.
+    pub fn open(path: &Path) -> io::Result<Device> {
+        Ok(Device { fd: OwnedFd::from(File::open(path)?) })
+    }
+
+    /// Returns the name of the device, as set by the relevant kernel driver.
+    pub fn name(&self) -> Result<String, nix::errno::Errno> {
+        // There's no official maximum length for evdev device names. The Linux HID driver
+        // currently supports names of at most 151 bytes (128 from the device plus a suffix of up
+        // to 23 bytes). 256 seems to be the buffer size most commonly used in evdev bindings, so
+        // we use it here.
+        //
+        // SAFETY:
+        // We know that fd is a valid file descriptor as it comes from a File that we have open.
+        //
+        // The ioctl_read_buf macro prevents the retrieved data from overflowing the buffer created
+        // by buf_from_ioctl by passing in the size to the ioctl, meaning that the kernel's
+        // str_to_user function will truncate the string to that length.
+        let mut buf = unsafe { buf_from_ioctl(ioctl::eviocgname, &self.fd, 256)? };
+        assert!(!buf.is_empty(), "buf is too short for an empty null-terminated string");
+        assert_eq!(buf.pop().unwrap(), 0, "buf is not a null-terminated string");
+        Ok(String::from_utf8_lossy(buf.as_slice()).into_owned())
+    }
+
+    pub fn ids(&self) -> Result<DeviceId, nix::errno::Errno> {
+        let mut ids = DeviceId::default();
+        // SAFETY:
+        // We know that fd is a valid file descriptor as it comes from a File that we have open.
+        //
+        // We know that the pointer to ids is valid because we just allocated it.
+        unsafe { ioctl::eviocgid(self.fd.as_raw_fd(), &mut ids) }.map(|_| ids)
+    }
+
+    pub fn properties_bitmap(&self) -> Result<Vec<u8>, nix::errno::Errno> {
+        let buf_size = (INPUT_PROP_CNT + 7) / 8;
+        // SAFETY:
+        // We know that fd is a valid file descriptor as it comes from a File that we have open.
+        //
+        // The ioctl_read_buf macro prevents the retrieved data from overflowing the buffer created
+        // by buf_from_ioctl by passing in the size to the ioctl, meaning that the kernel's
+        // str_to_user function will truncate the string to that length.
+        unsafe { buf_from_ioctl(ioctl::eviocgprop, &self.fd, buf_size) }
+    }
+
+    pub fn bitmap_for_event_type(&self, event_type: EventType) -> nix::Result<Vec<u8>> {
+        let buf_size = (event_type.code_count() + 7) / 8;
+        let mut buf = vec![0; buf_size];
+
+        // The EVIOCGBIT ioctl can't be bound using ioctl_read_buf! like the others, since it uses
+        // part of its ioctl code as an additional parameter, for the event type. Hence this unsafe
+        // block is a manual expansion of ioctl_read_buf!.
+        //
+        // SAFETY:
+        // We know that fd is a valid file descriptor as it comes from a File that we have open.
+        //
+        // We prevent the retrieved data from overflowing buf by passing in the size of buf to the
+        // ioctl, meaning that the kernel's str_to_user function will truncate the string to that
+        // length. We also panic if the ioctl returns a length longer than buf, hopefully before the
+        // overflow can do any damage.
+        match nix::errno::Errno::result(unsafe {
+            libc::ioctl(
+                self.fd.as_raw_fd(),
+                nix::request_code_read!(b'E', 0x20 + event_type as u16, buf.len())
+                    as nix::sys::ioctl::ioctl_num_type,
+                buf.as_mut_ptr(),
+            )
+        }) {
+            Ok(len) if len < 0 => {
+                panic!("EVIOCGBIT returned invalid length {len} for event type {event_type:?}");
+            }
+            Ok(len) => {
+                buf.truncate(len as usize);
+                Ok(buf)
+            }
+            Err(err) => Err(err),
+        }
+    }
+
+    pub fn supported_axes_of_type(&self, event_type: EventType) -> nix::Result<Vec<u16>> {
+        let mut axes = Vec::new();
+        for (i, byte_ref) in self.bitmap_for_event_type(event_type)?.iter().enumerate() {
+            let mut byte = *byte_ref;
+            for j in 0..8 {
+                if byte & 1 == 1 {
+                    axes.push((i * 8 + j) as u16);
+                }
+                byte >>= 1;
+            }
+        }
+        Ok(axes)
+    }
+
+    pub fn absolute_axis_info(&self, axis: u16) -> nix::Result<AbsoluteAxisInfo> {
+        let mut info = AbsoluteAxisInfo::default();
+        // The EVIOCGABS ioctl can't be bound using ioctl_read! since it uses part of its ioctl code
+        // as an additional parameter, for the axis code. Hence this unsafe block is a manual
+        // expansion of ioctl_read!.
+        //
+        // SAFETY:
+        // We know that fd is a valid file descriptor as it comes from a File that we have open.
+        //
+        // We know that the pointer to info is valid because we just allocated it.
+        nix::errno::Errno::result(unsafe {
+            nix::libc::ioctl(
+                self.fd.as_raw_fd(),
+                nix::request_code_read!(b'E', 0x40 + axis, mem::size_of::<AbsoluteAxisInfo>()),
+                &mut info,
+            )
+        })
+        .map(|_| info)
+    }
+
+    pub fn read_event(&self) -> nix::Result<InputEvent> {
+        let mut event = InputEvent::default();
+
+        // SAFETY:
+        // We know that fd is a valid file descriptor as it comes from a File that we have open.
+        //
+        // We know that the pointer to event is valid because we just allocated it, and that the
+        // data structures match up because InputEvent is repr(C) and all its members are repr(C)
+        // or primitives that support all representations without niches.
+        nix::errno::Errno::result(unsafe {
+            libc::read(
+                self.fd.as_raw_fd(),
+                &mut event as *mut _ as *mut std::ffi::c_void,
+                mem::size_of::<InputEvent>(),
+            )
+        })
+        .map(|_| event)
+    }
+}
diff --git a/cmds/evemu-record/main.rs b/cmds/evemu-record/main.rs
new file mode 100644
index 0000000000..6f5deb96b2
--- /dev/null
+++ b/cmds/evemu-record/main.rs
@@ -0,0 +1,193 @@
+/*
+ * Copyright 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//! A Rust implementation of the evemu-record command from the [FreeDesktop evemu suite][evemu] of
+//! tools.
+//!
+//! [evemu]: https://gitlab.freedesktop.org/libevdev/evemu
+
+use std::cmp;
+use std::error::Error;
+use std::fs;
+use std::io;
+use std::io::{BufRead, Write};
+use std::path::PathBuf;
+
+use clap::Parser;
+use nix::sys::time::TimeVal;
+
+mod evdev;
+
+/// Records evdev events from an input device in a format compatible with the FreeDesktop evemu
+/// library.
+#[derive(Parser, Debug)]
+struct Args {
+    /// The path to the input device to record. If omitted, offers a list of devices to choose from.
+    device: Option<PathBuf>,
+    /// The file to save the recording to. Defaults to standard output.
+    output_file: Option<PathBuf>,
+}
+
+fn get_choice(max: u32) -> u32 {
+    fn read_u32() -> Result<u32, std::num::ParseIntError> {
+        io::stdin().lock().lines().next().unwrap().unwrap().parse::<u32>()
+    }
+    let mut choice = read_u32();
+    while choice.is_err() || choice.clone().unwrap() > max {
+        eprint!("Enter a number between 0 and {max} inclusive: ");
+        choice = read_u32();
+    }
+    choice.unwrap()
+}
+
+fn pick_input_device() -> Result<PathBuf, io::Error> {
+    eprintln!("Available devices:");
+    let mut entries =
+        fs::read_dir("/dev/input")?.filter_map(|entry| entry.ok()).collect::<Vec<_>>();
+    entries.sort_by_key(|entry| entry.path());
+    let mut highest_number = 0;
+    for entry in entries {
+        let path = entry.path();
+        let file_name = path.file_name().unwrap().to_str().unwrap();
+        if path.is_dir() || !file_name.starts_with("event") {
+            continue;
+        }
+        let number = file_name.strip_prefix("event").unwrap().parse::<u32>();
+        if number.is_err() {
+            continue;
+        }
+        let number = number.unwrap();
+        match evdev::Device::open(path.as_path()) {
+            Ok(dev) => {
+                highest_number = cmp::max(highest_number, number);
+                eprintln!(
+                    "{}:\t{}",
+                    path.display(),
+                    dev.name().unwrap_or("[could not read name]".to_string()),
+                );
+            }
+            Err(_) => {
+                eprintln!("Couldn't open {}", path.display());
+            }
+        }
+    }
+    eprint!("Select the device event number [0-{highest_number}]: ");
+    let choice = get_choice(highest_number);
+    Ok(PathBuf::from(format!("/dev/input/event{choice}")))
+}
+
+fn print_device_description(
+    device: &evdev::Device,
+    output: &mut impl Write,
+) -> Result<(), Box<dyn Error>> {
+    // TODO(b/302297266): report LED and SW states, then bump the version to EVEMU 1.3.
+    writeln!(output, "# EVEMU 1.2")?;
+    writeln!(output, "N: {}", device.name()?)?;
+
+    let ids = device.ids()?;
+    writeln!(
+        output,
+        "I: {:04x} {:04x} {:04x} {:04x}",
+        ids.bus_type, ids.vendor, ids.product, ids.version,
+    )?;
+
+    fn print_in_8_byte_chunks(
+        output: &mut impl Write,
+        prefix: &str,
+        data: &Vec<u8>,
+    ) -> Result<(), io::Error> {
+        for (i, byte) in data.iter().enumerate() {
+            if i % 8 == 0 {
+                write!(output, "{prefix}")?;
+            }
+            write!(output, " {:02x}", byte)?;
+            if (i + 1) % 8 == 0 {
+                writeln!(output)?;
+            }
+        }
+        if data.len() % 8 != 0 {
+            for _ in (data.len() % 8)..8 {
+                write!(output, " 00")?;
+            }
+            writeln!(output)?;
+        }
+        Ok(())
+    }
+
+    let props = device.properties_bitmap()?;
+    print_in_8_byte_chunks(output, "P:", &props)?;
+
+    // The SYN event type can't be queried through the EVIOCGBIT ioctl, so just hard-code it to
+    // SYN_REPORT, SYN_CONFIG, and SYN_DROPPED.
+    writeln!(output, "B: 00 0b 00 00 00 00 00 00 00")?;
+    for event_type in evdev::EVENT_TYPES_WITH_BITMAPS {
+        let bits = device.bitmap_for_event_type(event_type)?;
+        print_in_8_byte_chunks(output, format!("B: {:02x}", event_type as u16).as_str(), &bits)?;
+    }
+
+    for axis in device.supported_axes_of_type(evdev::EventType::ABS)? {
+        let info = device.absolute_axis_info(axis)?;
+        writeln!(
+            output,
+            "A: {axis:02x} {} {} {} {} {}",
+            info.minimum, info.maximum, info.fuzz, info.flat, info.resolution
+        )?;
+    }
+    Ok(())
+}
+
+fn print_events(device: &evdev::Device, output: &mut impl Write) -> Result<(), Box<dyn Error>> {
+    fn print_event(output: &mut impl Write, event: &evdev::InputEvent) -> Result<(), io::Error> {
+        // TODO(b/302297266): Translate events into human-readable names and add those as comments.
+        writeln!(
+            output,
+            "E: {}.{:06} {:04x} {:04x} {:04}",
+            event.time.tv_sec(),
+            event.time.tv_usec(),
+            event.type_,
+            event.code,
+            event.value,
+        )?;
+        Ok(())
+    }
+    let event = device.read_event()?;
+    // Due to a bug in the C implementation of evemu-play [0] that has since become part of the API,
+    // the timestamp of the first event in a recording shouldn't be exactly 0.0 seconds, so offset
+    // it by 1µs.
+    //
+    // [0]: https://gitlab.freedesktop.org/libevdev/evemu/-/commit/eba96a4d2be7260b5843e65c4b99c8b06a1f4c9d
+    let start_time = event.time - TimeVal::new(0, 1);
+    print_event(output, &event.offset_time_by(start_time))?;
+    loop {
+        let event = device.read_event()?;
+        print_event(output, &event.offset_time_by(start_time))?;
+    }
+}
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let args = Args::parse();
+
+    let device_path = args.device.unwrap_or_else(|| pick_input_device().unwrap());
+
+    let device = evdev::Device::open(device_path.as_path())?;
+    let mut output = match args.output_file {
+        Some(path) => Box::new(fs::File::create(path)?) as Box<dyn Write>,
+        None => Box::new(io::stdout().lock()),
+    };
+    print_device_description(&device, &mut output)?;
+    print_events(&device, &mut output)?;
+    Ok(())
+}