Finish truncate applet (untested)

corebox/commands/truncate/mod.rs

@@ -1,7 +1,9 @@
+use std::fs::File;
+
 use {
     super::Cmd,
     clap::{Arg, ArgAction, ArgGroup, Command, ValueHint},
-    std::{error::Error, fmt, fs, num::ParseIntError},
+    std::{error::Error, fmt, fs, num::ParseIntError, path::PathBuf},
 };
 
 #[derive(Debug, Default)]
@@ -65,12 +67,49 @@ impl Cmd for Truncate {
     fn run(&self, matches: &clap::ArgMatches) -> Result<(), Box<dyn std::error::Error>> {
         let size = if let Some(file) = matches.get_one::<String>("reference") {
             let num: i64 = fs::metadata(file)?.len().try_into()?;
-            Size { operator: Operator::Equal, num }
+            Size {
+                operator: Operator::Equal,
+                num,
+            }
         } else if let Some(s) = matches.get_one::<String>("size") {
             parse_size(s)?
         } else {
             unreachable!();
         };
+        matches
+            .get_many::<String>("file")
+            .unwrap()
+            .try_for_each(|file| {
+                let path = PathBuf::from(file);
+                if !matches.get_flag("create") && !path.exists() {
+                    return Ok(());
+                }
+                let fd = File::options().write(true).create(true).open(&path)?;
+                let current: i64 = fd.metadata()?.len().try_into()?;
+                let len = match size.operator {
+                    Operator::Equal => size.num,
+                    Operator::Add => size.num + current,
+                    Operator::Remove => current - size.num,
+                    Operator::ModUp => {
+                        if current % size.num == 0 {
+                            current
+                        } else {
+                            let fraction = current / size.num;
+                            (fraction + 1) * size.num
+                        }
+                    }
+                    Operator::ModDown => {
+                        if current % size.num == 0 {
+                            current
+                        } else {
+                            let fraction = current / size.num;
+                            fraction * size.num
+                        }
+                    }
+                };
+                unistd::ftruncate(&fd, len)?;
+                Ok::<(), Box<dyn Error>>(())
+            })?;
         Ok(())
     }
 
@@ -79,6 +118,7 @@ impl Cmd for Truncate {
     }
 }
 
+#[derive(PartialEq)]
 enum Operator {
     Equal,
     Add,
@@ -201,13 +241,16 @@ fn parse_size(size: &str) -> Result<Size, ParseSizeError> {
     if let Some(m) = multiplier {
         match m {
             Multiplier::Kilo => num *= 1024,
-            Multiplier::Mega => num *= (1024 * 1024),
+            Multiplier::Mega => num *= 1024 * 1024,
-            Multiplier::Giga => num *= (1024 * 1024 * 1024),
+            Multiplier::Giga => num *= 1024 * 1024 * 1024,
-            Multiplier::Tera => num *= (1024 * 1024 * 1024 * 1024),
+            Multiplier::Tera => num *= 1024 * 1024 * 1024 * 1024,
         }
     }
     match operator {
         Some(operator) => Ok(Size { operator, num }),
-        None => Ok(Size { operator: Operator::Equal, num }),
+        None => Ok(Size {
+            operator: Operator::Equal,
+            num,
+        }),
     }
 }