Fix off by one error in dbase::File

dbase::File calculated the position of the record/field
assuming the record size by using the header's info
which includes the implicit deletion flag size, and dbase::File
added the deletion flag size again resulting of bad readings.

src/datafusion.rs

@@ -436,6 +436,9 @@ mod test {
         // +-----------------------+
         // | Franconia-Springfield |
         // | Federal Center SW     |
+        // | "Foggy Bottom GWU"    |
+        // | "Farragut West"       |
+        // | "Federal Triangle"    |
         // +-----------------------+
 
         // extract first (and only) RecordBatch from dataframe
@@ -448,7 +451,13 @@ mod test {
         // ensure values match
         assert_eq!(
             result[0].column(0).as_ref(),
-            &StringArray::from(vec!["Franconia-Springfield", "Federal Center SW"])
+            &StringArray::from(vec![
+                "Franconia-Springfield",
+                "Federal Center SW",
+                "Foggy Bottom GWU",
+                "Farragut West",
+                "Federal Triangle"
+            ])
         );
         Ok(())
     }

src/file.rs

@@ -53,7 +53,7 @@ impl<'a, T> FieldRef<'a, T> {
             .map(|i| i.field_length as u64)
             .sum::<u64>();
 
-        record_position + position_in_record
+        record_position + position_in_record + DELETION_FLAG_SIZE as u64
     }
 }
 
@@ -206,14 +206,16 @@ where
     pub fn seek_to_beginning(&mut self) -> Result<u64, FieldIOError> {
         self.file
             .inner
-            .seek(SeekFrom::Start(self.position_in_source()))
+            .seek(SeekFrom::Start(
+                self.position_in_source() + DELETION_FLAG_SIZE as u64,
+            ))
             .map_err(|e| FieldIOError::new(ErrorKind::IoError(e), None))
     }
 
     pub fn seek_before_deletion_flag(&mut self) -> Result<u64, FieldIOError> {
         self.file
             .inner
-            .seek(SeekFrom::Start(self.position_in_source() - 1))
+            .seek(SeekFrom::Start(self.position_in_source()))
             .map_err(|e| FieldIOError::new(ErrorKind::IoError(e), None))
     }
 }
@@ -227,7 +229,7 @@ where
     /// - true -> the record is marked as deleted
     /// - false -> the record is **not** marked as deleted
     pub fn is_deleted(&mut self) -> Result<bool, Error> {
-        let deletion_flag_pos = self.position_in_source() - DELETION_FLAG_SIZE as u64;
+        let deletion_flag_pos = self.position_in_source();
         self.file
             .inner
             .seek(SeekFrom::Start(deletion_flag_pos))
@@ -329,7 +331,7 @@ impl<'a, T> FileRecordIterator<'a, T> {
 /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
 /// let mut file = dbase::File::open_read_only("tests/data/stations.dbf")?;
 ///
-/// assert_eq!(file.num_records(), 6);
+/// assert_eq!(file.num_records(), 86);
 ///
 /// let name_idx = file.field_index("name").unwrap();
 /// let marker_color_idx = file.field_index("marker-col").unwrap();
@@ -501,8 +503,8 @@ impl<T: Write + Seek> File<T> {
         );
 
         let end_of_last_record = self.header.offset_to_first_record as u64
-            + self.num_records() as u64
-                * (DELETION_FLAG_SIZE as u64 + self.header.size_of_record as u64);
+            + (self.num_records() as u64 * self.header.size_of_record as u64);
+
         self.inner
             .seek(SeekFrom::Start(end_of_last_record))
             .map_err(|error| Error::io_error(error, self.num_records()))?;

src/header.rs

@@ -4,7 +4,6 @@ use crate::encoding::DynEncoding;
 use std::io::{Read, Write};
 
 use crate::field::types::Date;
-use crate::field::DELETION_FLAG_SIZE;
 use crate::memo::MemoFileType;
 
 // Used this as source: https://blog.codetitans.pl/post/dbf-and-language-code-page/
@@ -412,9 +411,8 @@ impl Header {
         if index >= self.num_records as usize {
             None
         } else {
-            let offset = self.offset_to_first_record as usize
-                + (index * (self.size_of_record as usize + DELETION_FLAG_SIZE))
-                + DELETION_FLAG_SIZE;
+            let offset =
+                self.offset_to_first_record as usize + (index * self.size_of_record as usize);
             Some(offset)
         }
     }

tests/test_file.rs

@@ -30,7 +30,7 @@ fn copy_to_named_tmp_file(origin: &str) -> std::io::Result<tempfile::NamedTempFi
 fn test_file_read_only() -> Result<(), Box<dyn std::error::Error>> {
     let mut file = dbase::File::open_read_only("tests/data/stations.dbf")?;
 
-    assert_eq!(file.num_records(), 6);
+    assert_eq!(file.num_records(), STATIONS_DBG_NUM_RECORDS);
 
     let name_idx = file.field_index("name").unwrap();
     let marker_color_idx = file.field_index("marker-col").unwrap();
@@ -89,12 +89,14 @@ fn test_file_read_only() -> Result<(), Box<dyn std::error::Error>> {
     Ok(())
 }
 
+const STATIONS_DBG_NUM_RECORDS: usize = 86;
+
 #[test]
 fn test_file_read_write() -> Result<(), Box<dyn std::error::Error>> {
     let tmp_file = copy_to_tmp_file("tests/data/stations.dbf")?;
     let mut file = dbase::File::open(tmp_file)?;
 
-    assert_eq!(file.num_records(), 6);
+    assert_eq!(file.num_records(), STATIONS_DBG_NUM_RECORDS);
 
     let name_idx = file.field_index("name").unwrap();
     let marker_color_idx = file.field_index("marker-col").unwrap();
@@ -222,20 +224,20 @@ fn test_file_append_record() -> Result<(), Box<dyn std::error::Error>> {
 
     {
         let mut file = dbase::File::open_read_write(tmp_file.path())?;
-        assert_eq!(file.num_records(), 6);
+        assert_eq!(file.num_records(), STATIONS_DBG_NUM_RECORDS);
         file.append_record(&new_record)?;
 
-        assert_eq!(file.num_records(), 7);
-        let record = file.record(6).unwrap().read()?;
+        assert_eq!(file.num_records(), STATIONS_DBG_NUM_RECORDS + 1);
+        let record = file.record(STATIONS_DBG_NUM_RECORDS).unwrap().read()?;
         assert_eq!(record, new_record);
     }
 
     {
         // Check that after closing the file, if we re-open it,
         // our appended record is still here
         let mut file = dbase::File::open_read_write(tmp_file.path())?;
-        assert_eq!(file.num_records(), 7);
-        let record = file.record(6).unwrap().read()?;
+        assert_eq!(file.num_records(), STATIONS_DBG_NUM_RECORDS + 1);
+        let record = file.record(STATIONS_DBG_NUM_RECORDS).unwrap().read()?;
         assert_eq!(record, new_record);
     }
 
@@ -299,11 +301,25 @@ fn test_file_char_trimming() -> Result<(), Box<dyn std::error::Error>> {
         }
     );
 
+    let mut file = dbase::File::open_read_only("tests/data/stations.dbf")?;
+    let reading = dbase::ReadingOptions::default().character_trim(dbase::TrimOption::End);
+    file.set_options(reading);
+
+    let expected_trim_end = StationRecord {
+        name: format!("{}", "Franconia-Springfield",),
+        marker_col: format!("{}", "#0000ff",),
+        marker_sym: format!("{}", "rail-metro",),
+        line: format!("{}", "blue",),
+    };
+
+    let record = file.record(1).unwrap().read_as::<StationRecord>()?;
+    assert_eq!(record, expected_trim_end);
+
     let mut file = dbase::File::open_read_only("tests/data/stations.dbf")?;
     let reading = dbase::ReadingOptions::default().character_trim(dbase::TrimOption::Begin);
     file.set_options(reading);
 
-    let expected = StationRecord {
+    let expected_trim_begin = StationRecord {
         name: format!(
             "{:width$}",
             "Franconia-Springfield",
@@ -325,11 +341,8 @@ fn test_file_char_trimming() -> Result<(), Box<dyn std::error::Error>> {
             width = file.fields()[0].length() as usize
         ),
     };
-
     let record = file.record(1).unwrap().read_as::<StationRecord>()?;
-
-    assert_eq!(record, expected);
-
+    assert_eq!(record, expected_trim_begin);
     Ok(())
 }