Allow usage of a provided buffer

fitsio/src/hdu.rs

@@ -4,7 +4,7 @@ use crate::errors::{check_status, Result};
 use crate::fitsfile::CaseSensitivity;
 use crate::fitsfile::FitsFile;
 use crate::headers::{ReadsKey, WritesKey};
-use crate::images::{ImageType, ReadImage, WriteImage};
+use crate::images::{ImageType, ReadImage, ReadImageInto, WriteImage};
 use crate::longnam::*;
 use crate::tables::{
     ColumnIterator, ConcreteColumnDescription, DescribesColumnLocation, FitsRow, ReadsCol,
@@ -124,6 +124,17 @@ impl FitsHdu {
         T::read_section(fits_file, self, start..end)
     }
 
+    /// Read a section of an image into a pre-existing buffer
+    pub fn read_section_into<T: ReadImageInto>(
+        &self,
+        fits_file: &mut FitsFile,
+        start: usize,
+        buf: &mut [T],
+    ) -> Result<()> {
+        fits_file.make_current(self)?;
+        T::read_section_into(fits_file, self, start, buf)
+    }
+
     /**
     # Example
 

fitsio/src/images.rs

@@ -46,6 +46,17 @@ pub trait ReadImage: Sized {
     }
 }
 
+/// Reading image data into buffers
+pub trait ReadImageInto: Sized {
+    #[doc(hidden)]
+    fn read_section_into(
+        fits_file: &mut FitsFile,
+        hdu: &FitsHdu,
+        start: usize,
+        buf: &mut [Self],
+    ) -> Result<()>;
+}
+
 /// Reading fits images
 pub trait WriteImage: Sized {
     #[doc(hidden)]
@@ -287,6 +298,43 @@ macro_rules! write_image_impl {
     };
 }
 
+macro_rules! read_image_into_impl {
+    ($t:ty, $data_type:expr) => {
+        impl ReadImageInto for $t {
+            fn read_section_into(
+                fits_file: &mut FitsFile,
+                hdu: &FitsHdu,
+                start: usize,
+                buf: &mut [Self],
+            ) -> Result<()> {
+                match hdu.info {
+                    HduInfo::ImageInfo { .. } => {
+                        let nelements = buf.len();
+                        let mut status = 0;
+                        unsafe {
+                            fits_read_img(
+                                fits_file.fptr.as_mut() as *mut _,
+                                $data_type.into(),
+                                (start + 1) as _,
+                                nelements as i64,
+                                ptr::null_mut(),
+                                buf.as_mut_ptr() as *mut _,
+                                ptr::null_mut(),
+                                &mut status,
+                            );
+                        }
+                        check_status(status).map(|_| ())
+                    }
+                    HduInfo::TableInfo { .. } => {
+                        Err("cannot read image data from a table hdu".into())
+                    }
+                    HduInfo::AnyInfo => unreachable!(),
+                }
+            }
+        }
+    };
+}
+
 read_image_impl_vec!(i8, i8::default(), DataType::TSBYTE);
 read_image_impl_vec!(i16, i16::default(), DataType::TSHORT);
 read_image_impl_vec!(i32, i32::default(), DataType::TINT);
@@ -321,6 +369,8 @@ write_image_impl!(u64, u64::default(), DataType::TLONGLONG);
 write_image_impl!(f32, f32::default(), DataType::TFLOAT);
 write_image_impl!(f64, f64::default(), DataType::TDOUBLE);
 
+read_image_into_impl!(u32, DataType::TUINT);
+
 /// Description of a new image
 #[derive(Clone)]
 pub struct ImageDescription<'a> {

fitsio/tests/test_images.rs

@@ -0,0 +1,13 @@
+use fitsio::FitsFile;
+
+#[test]
+fn test_read_into_buffer() {
+    let filename = "../testdata/full_example.fits";
+    let mut f = FitsFile::open(filename).unwrap();
+    let phdu = f.primary_hdu().unwrap();
+
+    let mut buf = vec![0u32; 10];
+    phdu.read_section_into(&mut f, 0, &mut buf).unwrap();
+
+    assert_eq!(buf, vec![108, 176, 166, 177, 104, 110, 100, 193, 150, 197]);
+}

flake.nix

@@ -12,8 +12,34 @@
   outputs = { nixpkgs, flake-utils, rust-overlay, ... }:
     flake-utils.lib.eachDefaultSystem (system:
       let
+        python-overlay = self: super: {
+          python310 = super.python310.override {
+            packageOverrides = pyself: pysuper: {
+              fitsio = pysuper.buildPythonPackage rec {
+                pname = "fitsio";
+                version = "1.1.8";
+                src = pysuper.fetchPypi {
+                  inherit pname version;
+                  hash = "sha256-YfVpsmgqDK3OUsllPwybgflR0ABSLO9kXOHLSfeDAPk=";
+                };
+                propagatedBuildInputs = [
+                  pyself.setuptools
+                  pyself.ipython
+                ];
+                buildInputs = [
+                  pyself.numpy
+                  self.pkg-config
+                  self.bzip2
+                ];
+                MAKEFLAGS = "-j";
+              };
+            };
+          };
+        };
+
         overlays = [
           rust-overlay.overlays.default
+          python-overlay
         ];
         pkgs = import nixpkgs {
           inherit overlays system;
@@ -32,7 +58,11 @@
             pkgs.cargo-release
             pkgs.rust-analyzer
             # for bin/test
-            pkgs.python3
+            (pkgs.python310.withPackages
+              (ps: with ps; [
+                numpy
+                fitsio
+              ]))
           ] ++ pkgs.lib.optionals pkgs.stdenv.isLinux [
             pkgs.cargo-tarpaulin
           ];