add interface to build npy_array_list objects from C (#30)

* add interface to build npy_array_list objects from C

* rename to deepcopy

---------

Co-authored-by: Lennart Klebl (alcubierre-drive)

Author: alcubierre-drive

.gitignore

@@ -3,3 +3,7 @@
 *~
 *.npy
 *.npz
+Makefile
+*.so
+*.pc
+*.d

README.md

@@ -119,11 +119,12 @@ And the linked list structure for `.npz` files:
     } npy_array_list_t;
 
 ## API
-The API is really simple. There is only ~~ten~~eleven public functions:
+The API is really simple. There is only ~~eleven~~twelve public functions:
 
     /* These are the four functions for loading and saving .npy files */
     npy_array_t*      npy_array_load        ( const char *filename);
     npy_array_t*      npy_array_mmap        ( const char *filename);
+    npy_array_t*      npy_array_alloc       ( const npy_array_t *m );
     void              npy_array_dump        ( const npy_array_t *m );
     void              npy_array_save        ( const char *filename, const npy_array_t *m );
     void              npy_array_free        ( npy_array_t *m );
@@ -156,6 +157,27 @@ You can then run example with a _NumPy_ file as argument.
         return 0;
     }
 
+## Saving lists of numpy arrays (and building them)
+Here is an example of saving multiple arrays into a single .npz file. You can
+compile this with:
+
+    gcc -O3 -Wall -Wextra -pedantic -std=c11 -c example_list.c
+    gcc -o example_list example_list.o npy_array.o npy_array_list.o -lzip
+
+You can the run example_list with a filename (_NumPy_ compressed) as argument.
+
+    #include "npy_array_list.h"
+    int main(int argc, char *argv[])
+    {
+        if( argc != 2 ) return -1;
+        double data[] = {0,1,2,3,4,5};
+        npy_array_list_t* list = NULL;
+        list = npy_array_list_append( list, NPY_ARRAY_ALLOCATOR(data, SHAPE(3,2), NPY_DTYPE_FLOAT64), "matrix" );
+        list = npy_array_list_append( list, NPY_ARRAY_ALLOCATOR(data, SHAPE(2,1,2), NPY_DTYPE_FLOAT64), "tensor" );
+        npy_array_list_save_compressed( argv[1], list, ZIP_CM_DEFAULT, 0 );
+        npy_array_list_free( list );
+    }
+
 ## Saving other arraylike data as _NumPy_ format.
 You may have a pointer to an N-dimensional array, which you want to store as NumPy format, such
 that you can load it in Python/Jupiter and plot in matplotlib or whatever you find more

npy_array.c

@@ -45,7 +45,7 @@ IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <ctype.h>
 #include <assert.h>
 
-#define NPY_ARRAY_MAGIC_STRING {0x93,'N','U','M','P','Y'}
+#define NPY_ARRAY_MAGIC_STRING {-109,'N','U','M','P','Y'}
 #define NPY_ARRAY_MAJOR_VERSION_IDX 6
 #define NPY_ARRAY_MINOR_VERSION_IDX 7
 
@@ -397,3 +397,24 @@ void npy_array_free( npy_array_t *m )
 
     free( m );
 }
+
+#define MIN( x, y ) ((x) < (y) ? (x) : (y))
+npy_array_t* npy_array_deepcopy( const npy_array_t* m ) {
+    npy_array_t* ary = calloc( 1, sizeof(*ary) );
+    if (!ary) {
+        fprintf(stderr, "Cannot allocate data structure!\n");
+        return NULL;
+    }
+    ary->ndim = MIN( m->ndim, NPY_ARRAY_MAX_DIMENSIONS );
+    memcpy( ary->shape, m->shape, sizeof(ary->shape) );
+    ary->typechar = m->typechar;
+    ary->elem_size = m->elem_size;
+    ary->data = malloc( npy_array_calculate_datasize(ary) );
+    if (!ary->data) {
+        fprintf(stderr, "Cannot allocate memory!\n");
+        free(ary);
+        return NULL;
+    }
+    memcpy( ary->data, m->data, npy_array_calculate_datasize(ary) );
+    return ary;
+}

npy_array.h

@@ -60,6 +60,7 @@ typedef struct _npy_array_t {
 
 npy_array_t*      npy_array_load       ( const char *filename );
 npy_array_t*      npy_array_mmap       ( const char *filename );
+npy_array_t*      npy_array_deepcopy   ( const npy_array_t *m );
 void              npy_array_dump       ( const npy_array_t *m );
 void              npy_array_save       ( const char *filename, const npy_array_t *m );
 void              npy_array_free       ( npy_array_t *m );
@@ -86,6 +87,8 @@ npy_array_t *     _read_matrix( void *fp, reader_func read_func );
 #define SHAPE(...) .shape = {__VA_ARGS__}, .ndim = _NARG(__VA_ARGS__)
 #define NPY_ARRAY_BUILDER(_data,_shape,...) \
     &(npy_array_t){ .data=(char*)_data, _shape, __VA_ARGS__ } 
+#define NPY_ARRAY_ALLOCATOR(...) \
+    npy_array_deepcopy(NPY_ARRAY_BUILDER(__VA_ARGS__))
 
 #define NPY_DTYPE_FLOAT16    .typechar='f', .elem_size=2
 #define NPY_DTYPE_FLOAT32    .typechar='f', .elem_size=4