Fix semihosting writer

core/src/core/experimental/semihosting.zig

@@ -58,29 +58,40 @@ pub const Debug = struct {
         len: usize,
     };
 
-    fn drain(_: *std.Io.Writer, data: []const []const u8, splat: usize) std.Io.Writer.Error!usize {
-        _ = splat;
-        // TODO: implement splat
+    fn drain(io_w: *std.Io.Writer, data: []const []const u8, splat: usize) std.Io.Writer.Error!usize {
+        const buf = io_w.buffered();
+
         var ret: usize = 0;
-        for (data) |d| {
+        if (buf.len > 0) {
+            ret += try writerfn({}, buf);
+            _ = io_w.consumeAll();
+        }
+        for (data[0 .. data.len - 1]) |d| {
             ret += try writerfn({}, d);
         }
+        for (0..splat) |_| {
+            const to_splat = data[data.len - 1];
+            ret += try writerfn({}, to_splat);
+        }
 
         return ret;
     }
 
     //this is ssssssslow but WriteC is even more slow and Write0 requires '\0' sentinel
     fn writerfn(_: void, data: []const u8) std.Io.Writer.Error!usize {
-        var len = data.len;
+        const len = data.len;
+        if (len == 0) return 0;
 
         if (len != 1) {
             const tmp_c = data[len - 1]; //check if last char is a sentinel
             if (tmp_c != 0) {
-                len -= 1; //last char is gonna be change to '\0'
+                // Temporarily change last char to null byte
                 var tmp_data: []u8 = @constCast(data);
-                tmp_data[len] = 0;
+                tmp_data[len - 1] = 0;
                 write0(@ptrCast(tmp_data.ptr));
-                tmp_data[len] = tmp_c;
+                tmp_data[len - 1] = tmp_c;
+                // Write the last character separately
+                write_byte(tmp_c);
                 return len;
             }
             write0(@ptrCast(data.ptr));
@@ -121,18 +132,18 @@ pub const Debug = struct {
         const MAGIC: [4]u8 = .{ 0x53, 0x48, 0x46, 0x42 };
         var magic_buffer: [4]u8 = undefined;
 
-        //try open extension file
+        // Try opening the extension file
         const ext_file = fs.open(":semihosting-features", .R) catch return false;
 
-        //check the size
+        // Check the size
         const byte_size = ext_file.size() catch return false;
         if (byte_size < (MAGIC.len + feature_byte + 1)) return false;
 
         var read_buf: [256]u8 = undefined;
         var file_reader = ext_file.reader(&read_buf);
         _ = file_reader.interface.readSliceShort(&magic_buffer) catch return false;
 
-        //check the magic number
+        // Check the magic number
         for (magic_buffer, MAGIC) |number, magic| {
             if (number != magic) return false;
         }
@@ -459,7 +470,7 @@ fn call(number: Syscalls, param: *const anyopaque) isize {
     return asm volatile (
         \\mov r0, %[num]
         \\mov r1, %[p]
-        \\BKPT #0xAB
+        \\bkpt #0xAB
         \\mov %[ret], r0
         : [ret] "=r" (-> isize),
         : [num] "r" (number),

examples/nordic/nrf5x/build.zig

@@ -30,6 +30,7 @@ pub fn build(b: *std.Build) void {
         .{ .target = nrf52840_mdk, .name = "nrf52840_mdk_i2c_hall_effect", .file = "src/i2c_hall_effect.zig" },
         .{ .target = nrf52840_mdk, .name = "nrf52840_mdk_i2c_temp", .file = "src/i2c_temp.zig" },
         .{ .target = nrf52840_mdk, .name = "nrf52840_mdk_rtt_log", .file = "src/rtt_log.zig" },
+        .{ .target = nrf52840_mdk, .name = "nrf52840_mdk_semihosting", .file = "src/semihosting.zig" },
         .{ .target = nrf52840_mdk, .name = "nrf52840_mdk_spi_master", .file = "src/spi_master.zig" },
 
         .{ .target = pca10040, .name = "pca10040_blinky", .file = "src/blinky.zig" },

examples/nordic/nrf5x/src/semihosting.zig

@@ -0,0 +1,61 @@
+const std = @import("std");
+const microzig = @import("microzig");
+const board = microzig.board;
+const nrf = microzig.hal;
+
+const semihosting = microzig.core.experimental.ARM_semihosting;
+
+pub fn main() void {
+    board.init();
+    const path = "";
+    const file_name = path ++ "foo.txt";
+    const new_name = path ++ "bar.txt";
+    var some_buf: [80]u8 = undefined;
+
+    // Debug features
+    semihosting.Debug.print("Hello World\n", .{});
+
+    const args = semihosting.Debug.get_cmd_args(&some_buf) catch return;
+    semihosting.Debug.print("receive args: {s}\n", .{args});
+
+    semihosting.Debug.print("feature support: STDOUT FILE: {any}, EXIT CODE {any}\n", .{
+        semihosting.Debug.check_extensions(0, 1),
+        semihosting.Debug.check_extensions(0, 0),
+    });
+
+    const stdout = semihosting.Debug.stdout() catch return;
+    stdout.print("hello STDOUT!!!!\n", .{});
+
+    // Time features
+    const clock = semihosting.Time.absolute();
+    const host_time = semihosting.Time.system_time();
+
+    // fs features
+    const file = semihosting.fs.open(file_name, .@"W+") catch {
+        semihosting.Debug.print("fail to open {s}!", .{file_name});
+        return;
+    };
+
+    file.print("[{any}:{d}] | Hello File {s} id {d}", .{
+        clock,
+        host_time,
+        file_name,
+        @intFromEnum(file),
+    });
+
+    const f_size = file.size() catch return;
+
+    semihosting.Debug.print("now file has size {d}\n", .{f_size});
+    file.close() catch {
+        semihosting.Debug.print("fail to close {s}!", .{file_name});
+        return;
+    };
+
+    semihosting.fs.rename(file_name, new_name) catch {
+        semihosting.Debug.print("fail to rename {s} to {s}", .{ file_name, new_name });
+    };
+
+    semihosting.Debug.exit(0);
+
+    while (true) {}
+}

examples/stmicro/stm32/src/semihosting.zig

@@ -8,7 +8,7 @@ pub fn main() void {
     const new_name = path ++ "bar.txt";
     var some_buf: [80]u8 = undefined;
 
-    //debug features
+    // Debug features
     semihosting.Debug.print("Hello World\n", .{});
 
     const args = semihosting.Debug.get_cmd_args(&some_buf) catch return;
@@ -22,11 +22,11 @@ pub fn main() void {
     const stdout = semihosting.Debug.stdout() catch return;
     stdout.print("hello STDOUT!!!!\n", .{});
 
-    //time features
+    // Time features
     const clock = semihosting.Time.absolute();
     const host_time = semihosting.Time.system_time();
 
-    //fs features
+    // fs features
     const file = semihosting.fs.open(file_name, .@"W+") catch {
         semihosting.Debug.print("fail to open {s}!", .{file_name});
         return;