py: Add float-to-int classification function

2 files changed, 56 insertions, 0 deletions

diff --git a/py/objint.c b/py/objint.c
index e8d86ad7ec..370c6a5df3 100644
--- a/py/objint.c
+++ b/py/objint.c
@@ -78,6 +78,52 @@ STATIC mp_obj_t mp_obj_int_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_uint_
     }
 }
 
+#if MICROPY_PY_BUILTINS_FLOAT
+mp_fp_as_int_class_t mp_classify_fp_as_int(mp_float_t val) {
+    union {
+        mp_float_t f;
+#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
+        uint32_t i;
+#elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
+        uint32_t i[2];
+#endif
+    } u = {val};
+
+    uint32_t e;
+#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
+    e = u.i;
+#elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
+    e = u.i[MP_ENDIANNESS_LITTLE];
+#endif
+#define MP_FLOAT_SIGN_SHIFT_I32 ((MP_FLOAT_FRAC_BITS + MP_FLOAT_EXP_BITS) % 32)
+#define MP_FLOAT_EXP_SHIFT_I32 (MP_FLOAT_FRAC_BITS % 32)
+
+    if (e & (1 << MP_FLOAT_SIGN_SHIFT_I32)) {
+#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
+        e |= u.i[MP_ENDIANNESS_BIG] != 0;
+#endif
+        e += ((1 << MP_FLOAT_EXP_BITS) - 1) << MP_FLOAT_EXP_SHIFT_I32;
+    } else {
+        e &= ~((1 << MP_FLOAT_EXP_SHIFT_I32) - 1);
+    }
+    if (e <= ((BITS_PER_WORD + MP_FLOAT_EXP_BIAS - 3) << MP_FLOAT_EXP_SHIFT_I32)) {
+        return MP_FP_CLASS_FIT_SMALLINT;
+    }
+#if MICROPY_LONGINT_IMPL == MICROPY_LONGINT_IMPL_LONGLONG
+    if (e <= (((sizeof(long long) * BITS_PER_BYTE) + MP_FLOAT_EXP_BIAS - 2) << MP_FLOAT_EXP_SHIFT_I32)) {
+        return MP_FP_CLASS_FIT_LONGINT;
+    }
+#endif
+#if MICROPY_LONGINT_IMPL == MICROPY_LONGINT_IMPL_MPZ
+    return MP_FP_CLASS_FIT_LONGINT;
+#else
+    return MP_FP_CLASS_OVERFLOW;
+#endif
+}
+#undef MP_FLOAT_SIGN_SHIFT_I32
+#undef MP_FLOAT_EXP_SHIFT_I32
+#endif
+
 void mp_obj_int_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
     (void)kind;
     // The size of this buffer is rather arbitrary. If it's not large
diff --git a/py/objint.h b/py/objint.h
index fff325df84..c995f2632a 100644
--- a/py/objint.h
+++ b/py/objint.h
@@ -40,6 +40,16 @@ typedef struct _mp_obj_int_t {
 
 extern const mp_obj_int_t mp_maxsize_obj;
 
+#if MICROPY_PY_BUILTINS_FLOAT
+typedef enum {
+    MP_FP_CLASS_FIT_SMALLINT,
+    MP_FP_CLASS_FIT_LONGINT,
+    MP_FP_CLASS_OVERFLOW
+} mp_fp_as_int_class_t;
+
+mp_fp_as_int_class_t mp_classify_fp_as_int(mp_float_t val);
+#endif // MICROPY_PY_BUILTINS_FLOAT
+
 void mp_obj_int_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind);
 char *mp_obj_int_formatted(char **buf, mp_uint_t *buf_size, mp_uint_t *fmt_size, mp_const_obj_t self_in,
                            int base, const char *prefix, char base_char, char comma);