Implement async `postproc_pagebreaks`

src/adapters/postproc.rs

@@ -119,14 +119,12 @@ pub fn postproc_encoding(
     ))*/
 }
 
-/**
- * adds the given prefix to each line in a AsyncRead
- */
+/// Adds the given prefix to each line in an `AsyncRead`.
 pub fn postproc_prefix(line_prefix: &str, inp: impl AsyncRead + Send) -> impl AsyncRead + Send {
     let line_prefix_n = format!("\n{}", line_prefix); // clone since we need it later
     let line_prefix_o = Bytes::copy_from_slice(line_prefix.as_bytes());
     let regex = regex::bytes::Regex::new("\n").unwrap();
-    let mut inp_stream = ReaderStream::new(inp);
+    let inp_stream = ReaderStream::new(inp);
     let oup_stream = stream! {
         yield Ok(line_prefix_o);
         for await chunk in inp_stream {
@@ -145,30 +143,35 @@ pub fn postproc_prefix(line_prefix: &str, inp: impl AsyncRead + Send) -> impl As
     StreamReader::new(oup_stream)
 }
 
-/**
- * adds the prefix `Page N:` to each line,
- * where N starts at one and is incremented for each ASCII Form Feed character in the input stream.
- * (That's the format output by pdftotext)
- */
+/// Adds the prefix "Page N:" to each line,
+/// where N starts at one and is incremented for each ASCII Form Feed character in the input stream.
+/// ASCII form feeds are the page delimiters output by `pdftotext`.
 pub fn postproc_pagebreaks(line_prefix: &str, inp: impl AsyncRead) -> impl AsyncRead {
-    let line_prefix = line_prefix.to_string(); // clone since
-    let mut page_count = 1;
+    let form_feed = b'\x0c';
+    let regex = regex::bytes::Regex::new("\n").unwrap();
+    let mut page_count = 0;
+    let mut line_prefix = format!("\n{}Page {}:", line_prefix, page_count + 1);
 
-    panic!("todo!");
-    tokio::io::empty()
-    /*ByteReplacer {
-        inner: inp,
-        next_read: format!("{}Page {}:", line_prefix, page_count).into_bytes(),
-        haystacker: Box::new(|buf| memchr::memchr2(b'\n', b'\x0c', buf)),
-        replacer: Box::new(move |b| match b {
-            b'\n' => format!("\n{}Page {}:", line_prefix, page_count).into_bytes(),
-            b'\x0c' => {
-                page_count += 1;
-                format!("\n{}Page {}:", line_prefix, page_count).into_bytes()
+    let inp_stream = ReaderStream::new(inp);
+    let oup_stream = stream! {
+        yield Ok(Bytes::copy_from_slice(line_prefix.as_bytes()));
+        for await chunk in inp_stream {
+            match chunk {
+                Err(e) => yield Err(e),
+                Ok(chunk) => {
+                    let chunk_iter = chunk.split(|byte| byte == &form_feed);
+                    for sub_chunk in chunk_iter {
+                        if sub_chunk.contains(&b'\n') {
+                            yield Ok(Bytes::copy_from_slice(&regex.replace_all(&sub_chunk, line_prefix.as_bytes())));
+                            page_count += 1;
+                            line_prefix = format!("\n{}Page {}:", line_prefix, page_count);
+                        }
+                    }
+                }
             }
-            _ => b"[[imposs]]".to_vec(),
-        }),
-    }*/
+        }
+    };
+    StreamReader::new(oup_stream)
 }
 
 #[cfg(test)]