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redesigned format_descriptor<> and npy_format_descriptor<>

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This somewhat heavyweight solution will avoid size_t/long long/long/int
mismatches on various platforms once and for all. The previous template
overloads could e.g. not handle size_t on Darwin.

One gotcha: the 'format_descriptor<T>::value()' syntax changed to just
'format_descriptor<T>::value'
This commit is contained in:
Wenzel Jakob 2016-05-04 22:22:48 +02:00
parent c62360d994
commit 876eeab4ca
4 changed files with 43 additions and 36 deletions
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16
docs/advanced.rst
View File

@ -825,12 +825,12 @@ completely avoid copy operations with Python expressions like
py::class_<Matrix>(m, "Matrix")
.def_buffer([](Matrix &m) -> py::buffer_info {
return py::buffer_info(
m.data(), /* Pointer to buffer */
sizeof(float), /* Size of one scalar */
py::format_descriptor<float>::value(), /* Python struct-style format descriptor */
2, /* Number of dimensions */
{ m.rows(), m.cols() }, /* Buffer dimensions */
{ sizeof(float) * m.rows(), /* Strides (in bytes) for each index */
m.data(), /* Pointer to buffer */
sizeof(float), /* Size of one scalar */
py::format_descriptor<float>::value, /* Python struct-style format descriptor */
2, /* Number of dimensions */
{ m.rows(), m.cols() }, /* Buffer dimensions */
{ sizeof(float) * m.rows(), /* Strides (in bytes) for each index */
sizeof(float) }
);
});
@ -867,7 +867,7 @@ objects (e.g. a NumPy matrix).
py::buffer_info info = b.request();
/* Some sanity checks ... */
if (info.format != py::format_descriptor<double>::value())
if (info.format != py::format_descriptor<double>::value)
throw std::runtime_error("Incompatible format: expected a double array!");
if (info.ndim != 2)
@ -994,7 +994,7 @@ simply using ``vectorize``).
auto result = py::array(py::buffer_info(
nullptr, /* Pointer to data (nullptr -> ask NumPy to allocate!) */
sizeof(double), /* Size of one item */
py::format_descriptor<double>::value(), /* Buffer format */
py::format_descriptor<double>::value, /* Buffer format */
buf1.ndim, /* How many dimensions? */
{ buf1.shape[0] }, /* Number of elements for each dimension */
{ sizeof(double) } /* Strides for each dimension */

14
example/example7.cpp
View File

@ -80,7 +80,7 @@ void init_ex7(py::module &m) {
/// Construct from a buffer
.def("__init__", [](Matrix &v, py::buffer b) {
py::buffer_info info = b.request();
if (info.format != py::format_descriptor<float>::value() || info.ndim != 2)
if (info.format != py::format_descriptor<float>::value || info.ndim != 2)
throw std::runtime_error("Incompatible buffer format!");
new (&v) Matrix(info.shape[0], info.shape[1]);
memcpy(v.data(), info.ptr, sizeof(float) * v.rows() * v.cols());
@ -103,12 +103,12 @@ void init_ex7(py::module &m) {
/// Provide buffer access
.def_buffer([](Matrix &m) -> py::buffer_info {
return py::buffer_info(
m.data(), /* Pointer to buffer */
sizeof(float), /* Size of one scalar */
py::format_descriptor<float>::value(), /* Python struct-style format descriptor */
2, /* Number of dimensions */
{ m.rows(), m.cols() }, /* Buffer dimensions */
{ sizeof(float) * m.rows(), /* Strides (in bytes) for each index */
m.data(), /* Pointer to buffer */
sizeof(float), /* Size of one scalar */
py::format_descriptor<float>::value, /* Python struct-style format descriptor */
2, /* Number of dimensions */
{ m.rows(), m.cols() }, /* Buffer dimensions */
{ sizeof(float) * m.rows(), /* Strides (in bytes) for each index */
sizeof(float) }
);
});

27
include/pybind11/common.h
View File

@ -191,13 +191,6 @@ enum class return_value_policy : int {
reference_internal
};
/// Format strings for basic number types
template <typename type> struct format_descriptor { };
#define PYBIND11_DECL_FMT(t, n) template<> struct format_descriptor<t> { static std::string value() { return n; }; }
PYBIND11_DECL_FMT(int8_t, "b"); PYBIND11_DECL_FMT(uint8_t, "B"); PYBIND11_DECL_FMT(int16_t, "h"); PYBIND11_DECL_FMT(uint16_t, "H");
PYBIND11_DECL_FMT(int32_t, "i"); PYBIND11_DECL_FMT(uint32_t, "I"); PYBIND11_DECL_FMT(int64_t, "q"); PYBIND11_DECL_FMT(uint64_t, "Q");
PYBIND11_DECL_FMT(float, "f"); PYBIND11_DECL_FMT(double, "d"); PYBIND11_DECL_FMT(bool, "?");
/// Information record describing a Python buffer object
struct buffer_info {
void *ptr; // Pointer to the underlying storage
@ -234,6 +227,8 @@ private:
NAMESPACE_BEGIN(detail)
static constexpr int log2(size_t n, int k = 0) { return (n <= 1) ? k : log2(n >> 1, k + 1); }
inline std::string error_string();
/// Core part of the 'instance' type which POD (needed to be able to use 'offsetof')
@ -296,13 +291,6 @@ template <typename T, size_t N> struct intrinsic_type<T[N]> { typedef type
/// Helper type to replace 'void' in some expressions
struct void_type { };
/// to_string variant which also accepts strings
template <typename T> inline typename std::enable_if<!std::is_enum<T>::value, std::string>::type
to_string(const T &value) { return std::to_string(value); }
template <> inline std::string to_string(const std::string &value) { return value; }
template <typename T> inline typename std::enable_if<std::is_enum<T>::value, std::string>::type
to_string(T value) { return std::to_string((int) value); }
NAMESPACE_END(detail)
#define PYBIND11_RUNTIME_EXCEPTION(name) \
@ -321,4 +309,15 @@ PYBIND11_RUNTIME_EXCEPTION(cast_error) /// Thrown when pybind11::cast or handle:
[[noreturn]] PYBIND11_NOINLINE inline void pybind11_fail(const char *reason) { throw std::runtime_error(reason); }
[[noreturn]] PYBIND11_NOINLINE inline void pybind11_fail(const std::string &reason) { throw std::runtime_error(reason); }
/// Format strings for basic number types
#define PYBIND11_DECL_FMT(t, v) template<> struct format_descriptor<t> { static constexpr const char *value = v; }
template <typename T, typename SFINAE = void> struct format_descriptor { };
template <typename T> struct format_descriptor<T, typename std::enable_if<std::is_integral<T>::value>::type> {
static constexpr const char value[2] =
{ "bBhHiIqQ"[detail::log2(sizeof(T))*2 + (std::is_unsigned<T>::value ? 1 : 0)], '\0' };
};
template <typename T> constexpr const char format_descriptor<
T, typename std::enable_if<std::is_integral<T>::value>::type>::value[2];
PYBIND11_DECL_FMT(float, "f"); PYBIND11_DECL_FMT(double, "d"); PYBIND11_DECL_FMT(bool, "?");
NAMESPACE_END(pybind11)

22
include/pybind11/numpy.h
View File

@ -21,7 +21,7 @@
NAMESPACE_BEGIN(pybind11)
template <typename type> struct npy_format_descriptor { };
template <typename type, typename SFINAE = void> struct npy_format_descriptor { };
class array : public buffer {
public:
@ -138,12 +138,20 @@ public:
}
};
template <typename T> struct npy_format_descriptor<T, typename std::enable_if<std::is_integral<T>::value>::type> {
private:
constexpr static const int values[] = {
array::API::NPY_BYTE_, array::API::NPY_UBYTE_, array::API::NPY_SHORT_, array::API::NPY_USHORT_,
array::API::NPY_INT_, array::API::NPY_UINT_, array::API::NPY_LONGLONG_, array::API::NPY_ULONGLONG_ };
public:
enum { value = values[detail::log2(sizeof(T)) * 2 + (std::is_unsigned<T>::value ? 1 : 0)] };
};
template <typename T> constexpr const int npy_format_descriptor<
T, typename std::enable_if<std::is_integral<T>::value>::type>::values[8];
#define DECL_FMT(t, n) template<> struct npy_format_descriptor<t> { enum { value = array::API::n }; }
DECL_FMT(int8_t, NPY_BYTE_); DECL_FMT(uint8_t, NPY_UBYTE_); DECL_FMT(int16_t, NPY_SHORT_);
DECL_FMT(uint16_t, NPY_USHORT_); DECL_FMT(int32_t, NPY_INT_); DECL_FMT(uint32_t, NPY_UINT_);
DECL_FMT(int64_t, NPY_LONGLONG_); DECL_FMT(uint64_t, NPY_ULONGLONG_); DECL_FMT(float, NPY_FLOAT_);
DECL_FMT(double, NPY_DOUBLE_); DECL_FMT(bool, NPY_BOOL_); DECL_FMT(std::complex<float>, NPY_CFLOAT_);
DECL_FMT(std::complex<double>, NPY_CDOUBLE_);
DECL_FMT(float, NPY_FLOAT_); DECL_FMT(double, NPY_DOUBLE_); DECL_FMT(bool, NPY_BOOL_);
DECL_FMT(std::complex<float>, NPY_CFLOAT_); DECL_FMT(std::complex<double>, NPY_CDOUBLE_);
#undef DECL_FMT
NAMESPACE_BEGIN(detail)
@ -328,7 +336,7 @@ struct vectorize_helper {
return cast(f(*((Args *) buffers[Index].ptr)...));
array result(buffer_info(nullptr, sizeof(Return),
format_descriptor<Return>::value(),
format_descriptor<Return>::value,
ndim, shape, strides));
buffer_info buf = result.request();