Use string instead of float as clock device output format (#696)

* Use string instead of float as clock device output format

* Update lisp library

* Simplify read command

* Update comments

dsk/lib/lisp/file.lsp

@@ -77,11 +77,11 @@
 
 (def (clock/boot)
   "Returns the number of seconds since boot"
-  (binary->number (read-binary "/dev/clk/boot") "float"))
+  (str->num (read "/dev/clk/boot")))
 
 (def (clock/epoch)
   "Returns the number of seconds since epoch"
-  (binary->number (read-binary "/dev/clk/epoch") "float"))
+  (str->num (read "/dev/clk/epoch")))
 
 # Path
 

src/sys/clk/boot.rs

@@ -2,6 +2,8 @@ use super::timer;
 
 use crate::api::fs::{FileIO, IO};
 
+use alloc::format;
+
 #[derive(Debug, Clone)]
 pub struct BootTime;
 
@@ -11,16 +13,17 @@ impl BootTime {
     }
 
     pub fn size() -> usize {
-        core::mem::size_of::<f64>()
+        // Must be at least 20 + 1 + 6 bytes: "<seconds>.<nanoseconds>"
+        32
     }
 }
 
 impl FileIO for BootTime {
     fn read(&mut self, buf: &mut [u8]) -> Result<usize, ()> {
-        let time = boot_time().to_be_bytes();
+        let time = format!("{:.6}", boot_time());
         let n = time.len();
         if buf.len() >= n {
-            buf[0..n].clone_from_slice(&time);
+            buf[0..n].clone_from_slice(time.as_bytes());
             Ok(n)
         } else {
             Err(())

src/sys/clk/epoch.rs

@@ -3,6 +3,8 @@ use super::timer;
 
 use crate::api::fs::{FileIO, IO};
 
+use alloc::format;
+
 const DAYS_BEFORE_MONTH: [u64; 13] = [
     0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365
 ];
@@ -16,16 +18,17 @@ impl EpochTime {
     }
 
     pub fn size() -> usize {
-        core::mem::size_of::<f64>()
+        // Must be at least 20 + 1 + 6 bytes: "<seconds>.<nanoseconds>"
+        32
     }
 }
 
 impl FileIO for EpochTime {
     fn read(&mut self, buf: &mut [u8]) -> Result<usize, ()> {
-        let time = epoch_time().to_be_bytes();
+        let time = format!("{:.6}", epoch_time());
         let n = time.len();
         if buf.len() >= n {
-            buf[0..n].clone_from_slice(&time);
+            buf[0..n].clone_from_slice(time.as_bytes());
             Ok(n)
         } else {
             Err(())

src/sys/vga/screen.rs

@@ -197,7 +197,8 @@ impl VgaMode {
     }
 
     pub fn size() -> usize {
-        16 // Must be larger than 8 bytes to be readable as a block device
+        // Must be at least 4 + 1 + 4 bytes: "<width>x<height>"
+        16
     }
 }
 

src/usr/read.rs

@@ -8,7 +8,6 @@ use crate::{api, usr};
 use alloc::borrow::ToOwned;
 use alloc::format;
 use alloc::vec::Vec;
-use core::convert::TryInto;
 
 pub fn main(args: &[&str]) -> Result<(), ExitCode> {
     if args.len() != 2 {
@@ -94,7 +93,6 @@ pub fn main(args: &[&str]) -> Result<(), ExitCode> {
             // file.
             let n = info.size();
             let is_char_device = n == 4;
-            let is_float_device = n == 8;
             let is_block_device = n > 8;
             loop {
                 if console::end_of_text() || console::end_of_transmission() {
@@ -115,12 +113,6 @@ pub fn main(args: &[&str]) -> Result<(), ExitCode> {
                             _ => {}
                         }
                     }
-                    if is_float_device && bytes.len() == 8 {
-                        let f = f64::from_be_bytes(bytes[0..8].try_into().
-                            unwrap());
-                        println!("{:.6}", f);
-                        return Ok(());
-                    }
                     for b in bytes {
                         print!("{}", b as char);
                     }