Migrate from String to properly typed TiffFormatError

src/decoder/ifd.rs

@@ -4,7 +4,7 @@ use std::io::{self, Read, Seek};
 use std::collections::{HashMap};
 
 use super::stream::{ByteOrder, SmartReader, EndianReader};
-use ::{TiffError, TiffResult};
+use ::{TiffError, TiffFormatError, TiffResult};
 
 use self::Value::{Unsigned, List, Rational};
 
@@ -86,7 +86,7 @@ pub enum Type {
 
 
 #[allow(unused_qualifications)]
-#[derive(Debug)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub enum Value {
     //Signed(i32),
     Unsigned(u32),
@@ -98,9 +98,7 @@ impl Value {
     pub fn into_u32(self) -> TiffResult<u32> {
         match self {
             Unsigned(val) => Ok(val),
-            val => Err(TiffError::FormatError(format!(
+            val => Err(TiffError::FormatError(TiffFormatError::UnsignedIntegerExpected(val))),
-                "Expected unsigned integer, {:?} found.", val
-            )))
         }
     }
     pub fn into_u32_vec(self) -> TiffResult<Vec<u32>> {

src/decoder/mod.rs

@@ -3,7 +3,7 @@ use std::mem;
 use num_traits::{FromPrimitive, Num};
 use std::collections::HashMap;
 
-use ::{ColorType, TiffError, TiffResult};
+use ::{ColorType, TiffError, TiffFormatError, TiffResult};
 
 use self::ifd::Directory;
 
@@ -187,12 +187,10 @@ impl<R: Read + Seek> Decoder<R> {
             b"MM" => {
                 self.byte_order = ByteOrder::BigEndian;
                 self.reader.byte_order = ByteOrder::BigEndian;  },
-            _ => return Err(TiffError::FormatError(
+            _ => return Err(TiffError::FormatError(TiffFormatError::TiffSignatureNotFound))
-                "TIFF signature not found.".to_string()
-            ))
         }
         if try!(self.read_short()) != 42 {
-            return Err(TiffError::FormatError("TIFF signature invalid.".to_string()))
+            return Err(TiffError::FormatError(TiffFormatError::TiffSignatureInvalid))
         }
         self.next_ifd = match try!(self.read_long()) {
             0 => None,
@@ -323,9 +321,7 @@ impl<R: Read + Seek> Decoder<R> {
     fn read_ifd(&mut self) -> TiffResult<Directory> {
         let mut dir: Directory = HashMap::new();
         match self.next_ifd {
-            None => return Err(TiffError::FormatError(
+            None => return Err(TiffError::FormatError(TiffFormatError::ImageFileDirectoryNotFound)),
-                "Image file directory not found.".to_string())
-            ),
             Some(offset) => try!(self.goto_offset(offset))
         }
         for _ in 0..try!(self.read_short()) {
@@ -379,9 +375,7 @@ impl<R: Read + Seek> Decoder<R> {
     pub fn get_tag(&mut self, tag: ifd::Tag) -> TiffResult<ifd::Value> {
         match try!(self.find_tag(tag)) {
             Some(val) => Ok(val),
-            None => Err(TiffError::FormatError(format!(
+            None => Err(TiffError::FormatError(TiffFormatError::RequiredTagNotFound(tag))),
-                "Required tag `{:?}` not found.", tag
-            )))
         }
     }
 
@@ -420,7 +414,7 @@ impl<R: Read + Seek> Decoder<R> {
         };
         Ok(match (color_type, buffer) {
             (ColorType:: RGB(8), DecodingBuffer::U8(ref mut buffer)) |
-            (ColorType::RGBA(8), DecodingBuffer::U8(ref mut buffer)) | 
+            (ColorType::RGBA(8), DecodingBuffer::U8(ref mut buffer)) |
             (ColorType::CMYK(8), DecodingBuffer::U8(ref mut buffer)) => {
                 try!(reader.read(&mut buffer[..bytes]))
             }
@@ -533,9 +527,7 @@ impl<R: Read + Seek> Decoder<R> {
                         try!(self.colortype())
                     ))
                 },
-                None => return Err(TiffError::FormatError(
+                None => return Err(TiffError::FormatError(TiffFormatError::UnknownPredictor(predictor))),
-                    format!("Unknown predictor “{}” encountered", predictor)
-                ))
             }
         }
         Ok(result)

src/error.rs

@@ -2,11 +2,13 @@ use std::error::Error;
 use std::fmt;
 use std::io;
 
+use decoder::ifd::{Tag, Value};
+
 /// Tiff error kinds.
 #[derive(Debug)]
 pub enum TiffError {
     /// The Image is not formatted properly
-    FormatError(String),
+    FormatError(TiffFormatError),
 
     /// The Decoder does not support this image format
     UnsupportedError(String),
@@ -15,6 +17,30 @@ pub enum TiffError {
     IoError(io::Error),
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum TiffFormatError {
+    TiffSignatureNotFound,
+    TiffSignatureInvalid,
+    ImageFileDirectoryNotFound,
+    RequiredTagNotFound(Tag),
+    UnknownPredictor(u32),
+    UnsignedIntegerExpected(Value),
+}
+
+impl fmt::Display for TiffFormatError {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        use self::TiffFormatError::*;
+        match *self {
+            TiffSignatureNotFound => write!(fmt, "TIFF signature not found."),
+            TiffSignatureInvalid => write!(fmt, "TIFF signature invalid."),
+            ImageFileDirectoryNotFound => write!(fmt, "Image file directory not found."),
+            RequiredTagNotFound(ref tag) => write!(fmt, "Required tag `{:?}` not found.", tag),
+            UnknownPredictor(ref predictor) => write!(fmt, "Unknown predictor “{}” encountered", predictor),
+            UnsignedIntegerExpected(ref val) => write!(fmt,  "Expected unsigned integer, {:?} found.", val),
+        }
+    }
+}
+
 impl fmt::Display for TiffError {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
         match *self {

src/lib.rs

@@ -14,7 +14,7 @@ extern crate num_traits;
 pub mod decoder;
 mod error;
 
-pub use self::error::{TiffError, TiffResult};
+pub use self::error::{TiffError, TiffFormatError, TiffResult};
 
 /// An enumeration over supported color types and their bit depths
 #[derive(Copy, PartialEq, Eq, Debug, Clone, Hash)]