Add function to BDFWriter to set the entries per chunk

src/chunks.rs

@@ -27,7 +27,7 @@ pub struct GenericChunk {
 #[derive(Debug, Clone)]
 pub struct MetaChunk {
     pub chunk_count: u32,
-    entries_per_chunk: u32,
+    pub entries_per_chunk: u32,
     pub entry_count: u64,
     pub compression_method: Option<String>,
 }

src/io.rs

@@ -62,7 +62,7 @@ impl BDFWriter {
     /// the data will be written to the file
     pub fn add_data_entry(&mut self, data_entry: DataEntry) -> Result<(), Error> {
         self.data_entries.push(data_entry);
-        if self.data_entries.len() >= ENTRIES_PER_CHUNK as usize {
+        if self.data_entries.len() >= self.metadata.entries_per_chunk as usize {
             self.flush()?;
         }
 
@@ -102,6 +102,17 @@ impl BDFWriter {
     pub fn set_compression_level(&mut self, level: u32) {
         self.compression_level = level;
     }
+
+    /// Changes the entries per chunk value.
+    /// Returns an error if the metadata has already been written.
+    pub fn set_entries_per_chunk(&mut self, number: u32) -> Result<(), Error>{
+        if self.head_written {
+            return Err(Error::new(ErrorKind::Other, "the head has already been written"))
+        }
+        self.metadata.entries_per_chunk = number;
+        
+        Ok(())
+    }
 }
 
 impl BDFReader {

src/lib.rs

@@ -13,6 +13,7 @@ mod tests {
     #[test]
     fn it_writes_uncompressed() -> Result<(), Error> {
         let mut writer = new_writer("tmp1.bdf", 2, false)?;
+        writer.set_entries_per_chunk(24)?;
 
         writer.add_lookup_entry(HashEntry::new(BAR.to_string(), 5))?;
         writer.add_lookup_entry(HashEntry::new(FOO.to_string(), 4))?;