Expose the tensor write-bytes function. (#412)

candle-core/src/convert.rs

@@ -1,6 +1,6 @@
 //! Implement conversion traits for tensors
-use crate::{Device, Error, Tensor, WithDType};
-use half::{bf16, f16};
+use crate::{DType, Device, Error, Tensor, WithDType};
+use half::{bf16, f16, slice::HalfFloatSliceExt};
 use std::convert::TryFrom;
 
 impl<T: WithDType> TryFrom<&Tensor> for Vec<T> {
@@ -94,3 +94,46 @@ from_tensor!(f16);
 from_tensor!(bf16);
 from_tensor!(u32);
 from_tensor!(u8);
+
+impl Tensor {
+    pub fn write_bytes<W: std::io::Write>(&self, f: &mut W) -> crate::Result<()> {
+        use byteorder::{LittleEndian, WriteBytesExt};
+
+        let vs = self.flatten_all()?;
+        match self.dtype() {
+            DType::BF16 => {
+                let vs = vs.to_vec1::<bf16>()?;
+                for &v in vs.reinterpret_cast() {
+                    f.write_u16::<LittleEndian>(v)?
+                }
+            }
+            DType::F16 => {
+                let vs = vs.to_vec1::<f16>()?;
+                for &v in vs.reinterpret_cast() {
+                    f.write_u16::<LittleEndian>(v)?
+                }
+            }
+            DType::F32 => {
+                // TODO: Avoid using a buffer when data is already on the CPU.
+                for v in vs.to_vec1::<f32>()? {
+                    f.write_f32::<LittleEndian>(v)?
+                }
+            }
+            DType::F64 => {
+                for v in vs.to_vec1::<f64>()? {
+                    f.write_f64::<LittleEndian>(v)?
+                }
+            }
+            DType::U32 => {
+                for v in vs.to_vec1::<u32>()? {
+                    f.write_u32::<LittleEndian>(v)?
+                }
+            }
+            DType::U8 => {
+                let vs = vs.to_vec1::<u8>()?;
+                f.write_all(&vs)?;
+            }
+        }
+        Ok(())
+    }
+}