1 files changed, 76 insertions, 19 deletions

diff --git a/src/id3v2.rs b/src/id3v2.rs
index a8dccb9..934bdf3 100644
--- a/src/id3v2.rs
+++ b/src/id3v2.rs
@@ -1,9 +1,11 @@
 // http://id3.org/id3v2.3.0
 
+use std::convert::TryFrom;
 use std::io::{self, Read};
+use std::iter;
+use std::num::TryFromIntError;
 use crate::encoding::{from_latin_1, from_ucs_2_bom};
 use crate::error::IntoIOError;
-use crate::options::EncodingOptions;
 use crate::util::read_big_endian;
 
 fn parse_id3v2_header(bytes: &[u8]) -> Option<(u16, u8, usize)> {
@@ -46,6 +48,30 @@ pub enum Frame {
     TRCK(String),
 }
 
+struct ArrayIter2<T> {
+    arr: [T; 2],
+    cursor: u8,
+}
+
+impl<T> ArrayIter2<T> {
+    fn new(arr: [T; 2]) -> Self {
+        Self { arr, cursor: 0 }
+    }
+}
+
+impl<T: Clone> Iterator for ArrayIter2<T> {
+    type Item = T;
+    fn next(&mut self) -> Option<T> {
+        if (self.cursor as usize) < self.arr.len() {
+            let i = self.cursor;
+            self.cursor += 1;
+            Some(self.arr[i as usize].clone())
+        } else {
+            None
+        }
+    }
+}
+
 impl RawFrame {
     fn parse(data: &[u8]) -> Result<Option<(Self, usize)>, String> {
         if data.len() < 10 {
@@ -69,16 +95,12 @@ impl RawFrame {
         Ok(Some((RawFrame { id, flags, body }, 10 + size)))
     }
 
-    fn interpret_encoded_string(&self, encopts: &EncodingOptions) -> io::Result<String> {
+    fn interpret_encoded_string(&self) -> io::Result<String> {
         match self.body.get(0).ok_or("String field too small".ioerr())? {
             0 => {  // Latin-1
                 let mut i = self.body.len();
                 while i > 0 && self.body[i-1] == 0 { i -= 1; }
-                if encopts.latin1_as_utf8 {
-                    String::from_utf8(self.body[1..i].to_vec()).map_err(|e| e.ioerr())
-                } else {
-                    from_latin_1(&self.body[1..i]).ok_or("Invalid Latin-1 string field".ioerr())
-                }
+                from_latin_1(&self.body[1..i]).ok_or("Invalid Latin-1 string field".ioerr())
             }
 
             1 => {  // UCS-2
@@ -93,21 +115,56 @@ impl RawFrame {
         }
     }
 
-    pub fn interpret(&self, encopts: &EncodingOptions) -> io::Result<Option<Frame>> {
-        if self.id == "TIT2" {
-            self.interpret_encoded_string(encopts).map(Frame::TIT2).map(Some)
-        } else if self.id == "TYER" {
-            self.interpret_encoded_string(encopts).map(Frame::TYER).map(Some)
-        } else if self.id == "TPE1" {
-            self.interpret_encoded_string(encopts).map(Frame::TPE1).map(Some)
-        } else if self.id == "TALB" {
-            self.interpret_encoded_string(encopts).map(Frame::TALB).map(Some)
-        } else if self.id == "TRCK" {
-            self.interpret_encoded_string(encopts).map(Frame::TRCK).map(Some)
-        } else {
+    fn encode_string(s: &str) -> io::Result<Vec<u8>> {
+        let as_latin1 = || iter::once(Ok(0))
+                                .chain(s.chars().map(|c| u8::try_from(u32::from(c))))
+                                .collect::<Result<Vec<u8>, _>>();
+
+        let as_ucs2 = || {
+            let nibbles = s.chars()
+                                .map(|c| u16::try_from(u32::from(c)))
+                                .collect::<Result<Vec<u16>, _>>()?;
+            Ok(iter::once(1)
+                    .chain(nibbles.iter().flat_map(|&n| ArrayIter2::new([(n >> 8) as u8, n as u8])))
+                    .collect::<Vec<u8>>())
+        };
+
+        as_latin1()
+            .or_else(|_| as_ucs2())
+            .map_err(|e: TryFromIntError| e.ioerr())
+    }
+
+    pub fn interpret(&self) -> io::Result<Option<Frame>> {
+        let type_t = |typ: fn(String) -> Frame| self.interpret_encoded_string().map(typ).map(Some);
+
+        if      self.id == "TIT2" { type_t(Frame::TIT2) }
+        else if self.id == "TYER" { type_t(Frame::TYER) }
+        else if self.id == "TPE1" { type_t(Frame::TPE1) }
+        else if self.id == "TALB" { type_t(Frame::TALB) }
+        else if self.id == "TRCK" { type_t(Frame::TRCK) }
+        else {
             Ok(None)
         }
     }
+
+    pub fn map_string<F: Fn(String) -> String>(self, f: F) -> io::Result<Option<Self>> {
+        let type_t = |id: &str, body: String| -> io::Result<Self> {
+            Ok(Self {
+                id: id.to_string(),
+                flags: 0,
+                body: Self::encode_string(&body)?,
+            })
+        };
+
+        match self.interpret()? {
+            Some(Frame::TIT2(s)) => Ok(Some(type_t("TIT2", f(s))?)),
+            Some(Frame::TYER(s)) => Ok(Some(type_t("TYER", f(s))?)),
+            Some(Frame::TPE1(s)) => Ok(Some(type_t("TPE1", f(s))?)),
+            Some(Frame::TALB(s)) => Ok(Some(type_t("TALB", f(s))?)),
+            Some(Frame::TRCK(s)) => Ok(Some(type_t("TRCK", f(s))?)),
+            None => Ok(Some(self)),
+        }
+    }
 }
 
 impl ID3v2 {