Simplify read_file

src/error.rs

@@ -2,7 +2,7 @@ use std::{error::Error, fmt};
 
 use crate::colors::{BitDepth, ColorType};
 
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 #[non_exhaustive]
 pub enum PngError {
     APNGOutOfOrder,
@@ -15,7 +15,9 @@ pub enum PngError {
     InvalidData,
     InvalidDepthForType(BitDepth, ColorType),
     NotPNG,
+    ReadFailed(String, std::io::Error),
     TruncatedData,
+    WriteFailed(String, std::io::Error),
     Other(Box<str>),
 }
 
@@ -47,9 +49,11 @@ impl fmt::Display for PngError {
                 write!(f, "Invalid bit depth {d} for color type {c}")
             }
             PngError::NotPNG => f.write_str("Invalid header detected; Not a PNG file"),
+            PngError::ReadFailed(ref s, ref e) => write!(f, "Failed to read from {s}: {e}"),
             PngError::TruncatedData => {
                 f.write_str("Missing data in the file; the file is truncated")
             }
+            PngError::WriteFailed(ref s, ref e) => write!(f, "Failed to write to {s}: {e}"),
             PngError::Other(ref s) => f.write_str(s),
         }
     }

src/lib.rs

@@ -221,7 +221,7 @@ pub fn optimize(input: &InFile, output: &OutFile, opts: &Options) -> PngResult<(
             let mut data = Vec::new();
             stdin()
                 .read_to_end(&mut data)
-                .map_err(|e| PngError::new(&format!("Error reading stdin: {e}")))?;
+                .map_err(|e| PngError::ReadFailed("stdin".into(), e))?;
             data
         }
     };
@@ -270,20 +270,15 @@ pub fn optimize(input: &InFile, output: &OutFile, opts: &Options) -> PngResult<(
             let mut buffer = BufWriter::new(stdout());
             buffer
                 .write_all(&optimized_output)
-                .map_err(|e| PngError::new(&format!("Unable to write to stdout: {e}")))?;
+                .map_err(|e| PngError::WriteFailed("stdout".into(), e))?;
         }
         (OutFile::Path { path, .. }, _) => {
             let output_path = path
                 .as_ref()
                 .map(|p| p.as_path())
                 .unwrap_or_else(|| input.path().unwrap());
-            let out_file = File::create(output_path).map_err(|err| {
+            let out_file = File::create(output_path)
-                PngError::new(&format!(
+                .map_err(|err| PngError::WriteFailed(output_path.display().to_string(), err))?;
-                    "Unable to write to file {}: {}",
-                    output_path.display(),
-                    err
-                ))
-            })?;
             if let Some(metadata_input) = &opt_metadata_preserved {
                 copy_permissions(metadata_input, &out_file)?;
             }
@@ -293,13 +288,7 @@ pub fn optimize(input: &InFile, output: &OutFile, opts: &Options) -> PngResult<(
                 .write_all(&optimized_output)
                 // flush BufWriter so IO errors don't get swallowed silently on close() by drop!
                 .and_then(|()| buffer.flush())
-                .map_err(|e| {
+                .map_err(|e| PngError::WriteFailed(output_path.display().to_string(), e))?;
-                    PngError::new(&format!(
-                        "Unable to write to {}: {}",
-                        output_path.display(),
-                        e
-                    ))
-                })?;
             // force drop and thereby closing of file handle before modifying any timestamp
             std::mem::drop(buffer);
             if let Some(metadata_input) = &opt_metadata_preserved {

src/png/mod.rs

@@ -1,9 +1,4 @@
-use std::{
+use std::{fs, io::Write, path::Path, sync::Arc};
-    fs::File,
-    io::{BufReader, Read, Write},
-    path::Path,
-    sync::Arc,
-};
 
 use bitvec::bitarr;
 use libdeflater::{CompressionLvl, Compressor};
@@ -62,28 +57,7 @@ impl PngData {
     }
 
     pub fn read_file(filepath: &Path) -> Result<Vec<u8>, PngError> {
-        let file = match File::open(filepath) {
+        fs::read(filepath).map_err(|e| PngError::ReadFailed(filepath.display().to_string(), e))
-            Ok(f) => f,
-            Err(_) => return Err(PngError::new("Failed to open file for reading")),
-        };
-        let file_len = file.metadata().map(|m| m.len() as usize).unwrap_or(0);
-        let mut reader = BufReader::new(file);
-        // Check file for PNG header
-        let mut header = [0; 8];
-        if reader.read_exact(&mut header).is_err() {
-            return Err(PngError::new("Not a PNG file: too small"));
-        }
-        if !file_header_is_valid(&header) {
-            return Err(PngError::new("Invalid PNG header detected"));
-        }
-        // Read raw png data into memory
-        let mut byte_data: Vec<u8> = Vec::with_capacity(file_len);
-        byte_data.extend_from_slice(&header);
-        match reader.read_to_end(&mut byte_data) {
-            Ok(_) => (),
-            Err(_) => return Err(PngError::new("Failed to read from file")),
-        }
-        Ok(byte_data)
     }
 
     /// Create a new `PngData` struct by reading a slice