1 files changed, 88 insertions, 0 deletions
diff --git a/cortex-m-semihosting/src/hio.rs b/cortex-m-semihosting/src/hio.rs
new file mode 100644
index 0000000..61ac749
--- /dev/null
+++ b/cortex-m-semihosting/src/hio.rs
@@ -0,0 +1,88 @@
+//! Host I/O
+
+use core::{fmt, slice};
+use crate::nr;
+
+/// Host's standard error
+#[derive(Clone, Copy)]
+pub struct HStderr {
+    fd: usize,
+}
+
+impl HStderr {
+    /// Attempts to write an entire `buffer` into this sink
+    pub fn write_all(&mut self, buffer: &[u8]) -> Result<(), ()> {
+        write_all(self.fd, buffer)
+    }
+}
+
+impl fmt::Write for HStderr {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.write_all(s.as_bytes()).map_err(|_| fmt::Error)
+    }
+}
+
+/// Host's standard output
+#[derive(Clone, Copy)]
+pub struct HStdout {
+    fd: usize,
+}
+
+impl HStdout {
+    /// Attempts to write an entire `buffer` into this sink
+    pub fn write_all(&mut self, buffer: &[u8]) -> Result<(), ()> {
+        write_all(self.fd, buffer)
+    }
+}
+
+impl fmt::Write for HStdout {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.write_all(s.as_bytes()).map_err(|_| fmt::Error)
+    }
+}
+
+/// Construct a new handle to the host's standard error.
+pub fn hstderr() -> Result<HStderr, ()> {
+    // There is actually no stderr access in ARM Semihosting documentation. Use
+    // convention used in libgloss.
+    // See: libgloss/arm/syscalls.c, line 139.
+    // https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=blob;f=libgloss/arm/syscalls.c#l139
+    open(":tt\0", nr::open::W_APPEND).map(|fd| HStderr { fd })
+}
+
+/// Construct a new handle to the host's standard output.
+pub fn hstdout() -> Result<HStdout, ()> {
+    open(":tt\0", nr::open::W_TRUNC).map(|fd| HStdout { fd })
+}
+
+fn open(name: &str, mode: usize) -> Result<usize, ()> {
+    let name = name.as_bytes();
+    match unsafe { syscall!(OPEN, name.as_ptr(), mode, name.len() - 1) } as
+        isize {
+        -1 => Err(()),
+        fd => Ok(fd as usize),
+    }
+}
+
+fn write_all(fd: usize, mut buffer: &[u8]) -> Result<(), ()> {
+    while !buffer.is_empty() {
+        match unsafe { syscall!(WRITE, fd, buffer.as_ptr(), buffer.len()) } {
+            // Done
+            0 => return Ok(()),
+            // `n` bytes were not written
+            n if n <= buffer.len() => {
+                let offset = (buffer.len() - n) as isize;
+                buffer = unsafe {
+                    slice::from_raw_parts(buffer.as_ptr().offset(offset), n)
+                }
+            }
+            #[cfg(feature = "jlink-quirks")]
+            // Error (-1) - should be an error but JLink can return -1, -2, -3,...
+            // For good measure, we allow up to negative 15.
+            n if n > 0xfffffff0 => return Ok(()),
+            // Error
+            _ => return Err(()),
+        }
+    }
+    Ok(())
+}