diff --git a/Examples/python/index.html b/Examples/python/index.html index f80417bd2..802db9b75 100644 --- a/Examples/python/index.html +++ b/Examples/python/index.html @@ -17,6 +17,7 @@ be used to wrap a C function, a global variable, and a constant.
  • constants. This shows how preprocessor macros and certain C declarations are turned into constants.
  • variables. An example showing how to access C global variables from Python. +
  • value. How to pass and return structures by value.

    Compilation Issues

    diff --git a/Examples/python/value/Makefile b/Examples/python/value/Makefile new file mode 100644 index 000000000..ecfeef983 --- /dev/null +++ b/Examples/python/value/Makefile @@ -0,0 +1,18 @@ +TOP = ../.. +SWIG = $(TOP)/../swig +SRCS = example.c +TARGET = example +INTERFACE = example.i + +all:: + $(MAKE) -f $(TOP)/Makefile SRCS='$(SRCS)' SWIG='$(SWIG)' \ + TARGET='$(TARGET)' INTERFACE='$(INTERFACE)' python + +static:: + $(MAKE) -f $(TOP)/Makefile SRCS='$(SRCS)' SWIG='$(SWIG)' \ + TARGET='mypython' INTERFACE='$(INTERFACE)' python_static + +clean:: + rm -f *_wrap* *.o *~ *.so mypython *.pyc .~* core + + diff --git a/Examples/python/value/example.c b/Examples/python/value/example.c new file mode 100644 index 000000000..4ed2fe10a --- /dev/null +++ b/Examples/python/value/example.c @@ -0,0 +1,15 @@ +/* File : example.c */ + +#include "example.h" + +double dot_product(Vector a, Vector b) { + return (a.x*b.x + a.y*b.y + a.z*b.z); +} + +Vector vector_add(Vector a, Vector b) { + Vector r; + r.x = a.x + b.x; + r.y = a.y + b.y; + r.z = a.z + b.z; + return r; +} diff --git a/Examples/python/value/example.h b/Examples/python/value/example.h new file mode 100644 index 000000000..212cf4bdb --- /dev/null +++ b/Examples/python/value/example.h @@ -0,0 +1,5 @@ +/* File : example.h */ + +typedef struct { + double x, y, z; +} Vector; diff --git a/Examples/python/value/example.i b/Examples/python/value/example.i new file mode 100644 index 000000000..83c1f9cd6 --- /dev/null +++ b/Examples/python/value/example.i @@ -0,0 +1,30 @@ +// Tests SWIG's handling of pass-by-value for complex datatypes +%module example + +%{ +#include "example.h" +%} + +/* Some functions that manipulate Vectors by value */ +extern double dot_product(Vector a, Vector b); +extern Vector vector_add(Vector a, Vector b); + +/* Include this because the vector_add() function will leak memory */ +void free(void *); + +/* Some helper functions for our interface */ +%inline %{ + +Vector *new_Vector(double x, double y, double z) { + Vector *v = (Vector *) malloc(sizeof(Vector)); + v->x = x; + v->y = y; + v->z = z; + return v; +} + +void vector_print(Vector *v) { + printf("Vector %x = (%g, %g, %g)\n", v, v->x, v->y, v->z); +} +%} + diff --git a/Examples/python/value/index.html b/Examples/python/value/index.html new file mode 100644 index 000000000..67870b562 --- /dev/null +++ b/Examples/python/value/index.html @@ -0,0 +1,128 @@ + + +SWIG:Examples:python:value + + + + + +SWIG/Examples/python/value/ +
    + +

    Passing and Returning Structures by Value

    + +$Header$
    + +

    +Occasionally, a C program will manipulate structures by value such as shown in the +following code: + +

    +
    +/* File : example.c */
+
+typedef struct Vector {
+   double x, y, z;
+} Vector;
+
+double dot_product(Vector a, Vector b) {
+  return (a.x*b.x + a.y*b.y + a.z*b.z);
+}
+
+Vector vector_add(Vector a, Vector b) {
+  Vector r;
+  r.x = a.x + b.x;
+  r.y = a.y + b.y;
+  r.z = a.z + b.z;
+  return r;
+}
+
    +
    + +Since SWIG only knows how to manage pointers to structures (not their internal +representation), the following translations are made when wrappers are +created: + +
    +
    +double wrap_dot_product(Vector *a, Vector *b) {
+    return dot_product(*a,*b);
+}
+
+Vector *wrap_vector_add(Vector *a, Vector *b) {
+    Vector *r = (Vector *) malloc(sizeof(Vector));
+    *r = vector_add(*a,*b);
+    return r;
+}
+
    +
    + +The functions are then called using pointers from the scripting language interface. +It should also be noted that any function that returns a structure by value results +in an implicit memory allocation. This will be a memory leak unless you take steps +to free the result (see below). + +

    The SWIG interface

    + +Click here to see a SWIG interface file that +wraps these two functions. In this file, there are a few essential features: + + + +

    A Python Script

    + +Click here to see a script that uses these functions from Python. + +

    Notes

    + + + +
    + +