use std::io::Write trait when export to matrix market

nalgebra-sparse/src/io/matrix_market.rs

@@ -508,9 +508,9 @@ mod internal {
         /// When matrix is a Hermitian matrix, it will convert itself to its conjugate.
         fn conjugate(self) -> Result<Self, MatrixMarketError>;
         /// Returns the name of SupportedMatrixMarketScalar, used when write the matrix
-        fn typename() -> &'static str;
+        fn typename() -> &'static [u8];
-        /// Convert the data to string
+        /// Convert the data to bytes
-        fn to_matrixmarket_string(&self) -> String;
+        fn to_matrixmarket_bytes(&self) -> Vec<u8>;
     }
 
     pub trait SupportedMatrixMarketExport<T: SupportedMatrixMarketScalar> {
@@ -574,12 +574,12 @@ macro_rules! mm_int_impl {
                 Ok(-self)
             }
             #[inline]
-            fn typename() -> &'static str {
+            fn typename() -> &'static [u8] {
-                "integer"
+                b"integer"
             }
             #[inline]
-            fn to_matrixmarket_string(&self) -> String {
+            fn to_matrixmarket_bytes(&self) -> Vec<u8> {
-                self.to_string()
+                self.to_string().into_bytes()
             }
         }
     };
@@ -627,12 +627,12 @@ macro_rules! mm_real_impl {
                 Ok(-self)
             }
             #[inline]
-            fn typename() -> &'static str {
+            fn typename() -> &'static [u8] {
-                "real"
+                b"real"
             }
             #[inline]
-            fn to_matrixmarket_string(&self) -> String {
+            fn to_matrixmarket_bytes(&self) -> Vec<u8> {
-                self.to_string()
+                self.to_string().into_bytes()
             }
         }
     };
@@ -681,12 +681,12 @@ macro_rules! mm_complex_impl {
                 Ok(-self)
             }
             #[inline]
-            fn typename() -> &'static str {
+            fn typename() -> &'static [u8] {
-                "complex"
+                b"complex"
             }
             #[inline]
-            fn to_matrixmarket_string(&self) -> String {
+            fn to_matrixmarket_bytes(&self) -> Vec<u8> {
-                self.re.to_string() + " " + &self.im.to_string()
+                (self.re.to_string() + " " + &self.im.to_string()).into_bytes()
             }
         }
     };
@@ -738,13 +738,12 @@ macro_rules! mm_pattern_impl {
                 ))
             }
             #[inline]
-            fn typename() -> &'static str {
+            fn typename() -> &'static [u8] {
-                "pattern"
+                b"pattern"
             }
             #[inline]
-            fn to_matrixmarket_string(&self) -> String {
+            fn to_matrixmarket_bytes(&self) -> Vec<u8> {
-                // pattern type will return an empty string
+                Vec::<u8>::new()
-                String::new()
             }
         }
     };
@@ -1444,34 +1443,14 @@ fn next_dense_coordinate(
 pub fn write_to_matrix_market_str<T: MatrixMarketScalar, S: MatrixMarketExport<T>>(
     sparse_matrix: &S,
 ) -> String {
-    let mut matrixmarket_string = String::new();
+    let mut bytes = Vec::<u8>::new();
-
+    // This will call impl<A: Allocator> Write for Vec<u8, A>
-    // write header
+    // The vector will grow as needed.
-    matrixmarket_string.push_str("%%matrixmarket matrix coordinate ");
+    // So, unwrap here won't cause any issue.
-    matrixmarket_string.push_str(T::typename());
+    write_to_matrix_market(&mut bytes, sparse_matrix).unwrap();
-    matrixmarket_string.push_str(" general\n");
+    // safety issue is because 'from_utf8_unchecked' does not check that the bytes passed to it are valid UTF-8.
-
+    // Since 'bytes' created here is valid UTF-8 data, so it will not cause any problem.
-    //write comment
+    unsafe { String::from_utf8_unchecked(bytes) }
-    matrixmarket_string.push_str("% matrixmarket file generated by nalgebra-sparse.\n");
-
-    // write shape information
-    matrixmarket_string.push_str(&sparse_matrix.nrows().to_string());
-    matrixmarket_string.push(' ');
-    matrixmarket_string.push_str(&sparse_matrix.ncols().to_string());
-    matrixmarket_string.push(' ');
-    matrixmarket_string.push_str(&sparse_matrix.nnz().to_string());
-    matrixmarket_string.push('\n');
-
-    //write triplets
-    for (r, c, d) in sparse_matrix.triplet_iter() {
-        matrixmarket_string.push_str(&(r + 1).to_string());
-        matrixmarket_string.push_str("  ");
-        matrixmarket_string.push_str(&(c + 1).to_string());
-        matrixmarket_string.push_str("  ");
-        matrixmarket_string.push_str(&d.to_matrixmarket_string());
-        matrixmarket_string.push_str("\n");
-    }
-    matrixmarket_string
 }
 
 /// Write a sparse matrix into Matrix Market format file.
@@ -1508,38 +1487,40 @@ pub fn write_to_matrix_market_file<
     sparse_matrix: &S,
     path: P,
 ) -> Result<(), MatrixMarketError> {
-    // The code is basically the same as write_to_matrix_market_str, but write the matrix into file instead.
     let mut file = File::create(path)?;
-
+    write_to_matrix_market(&mut file, sparse_matrix)?;
-    // write header
+    Ok(())
-    write!(
+}
-        file,
+
-        "%%matrixmarket matrix coordinate  {} general\n",
+/// low level implementation of writing sparse matrix into any [std::io::Write] object
-        T::typename()
+fn write_to_matrix_market<T: MatrixMarketScalar, S: MatrixMarketExport<T>, W: Write>(
-    )?;
+    w: &mut W,
-
+    sparse_matrix: &S,
-    // write comments
+) -> Result<(), MatrixMarketError> {
-    write!(file, "% matrixmarket file generated by nalgebra-sparse.\n",)?;
+    // write header
-
+    w.write_all(b"%%matrixmarket matrix coordinate ")?;
-    // write shape information
+    w.write_all(T::typename())?;
-    write!(
+    w.write_all(b" general\n")?;
-        file,
+
-        "{} {} {}\n",
+    //write comment
-        sparse_matrix.nrows(),
+    w.write_all(b"% matrixmarket file generated by nalgebra-sparse.\n")?;
-        sparse_matrix.ncols(),
+
-        sparse_matrix.nnz()
+    // write shape information
-    )?;
+    w.write_all(sparse_matrix.nrows().to_string().as_bytes())?;
-
+    w.write_all(b" ")?;
-    // write triplets
+    w.write_all(sparse_matrix.ncols().to_string().as_bytes())?;
-    for (r, c, d) in sparse_matrix.triplet_iter() {
+    w.write_all(b" ")?;
-        write!(
+    w.write_all(sparse_matrix.nnz().to_string().as_bytes())?;
-            file,
+    w.write_all(b"\n")?;
-            "{}  {}  {}\n",
+
-            r + 1,
+    //write triplets
-            c + 1,
+    for (r, c, d) in sparse_matrix.triplet_iter() {
-            d.to_matrixmarket_string()
+        w.write_all((r + 1).to_string().as_bytes())?;
-        )?;
+        w.write_all(b"  ")?;
-    }
+        w.write_all((c + 1).to_string().as_bytes())?;
-
+        w.write_all(b"  ")?;
+        w.write_all(&d.to_matrixmarket_bytes())?;
+        w.write_all(b"\n")?;
+    }
     Ok(())
 }