micropython · pfalcon · Jan 5, 2017 · Jan 15, 2017 · Jan 15, 2017 · Jan 19, 2017
diff --git a/py/mpz.c b/py/mpz.c
@@ -909,6 +909,37 @@ mp_uint_t mpz_set_from_str(mpz_t *z, const char *str, mp_uint_t len, bool neg, m
     return cur - str;
 }
 
+void mpz_set_from_bytes(mpz_t *z, bool big_endian, mp_uint_t len, const byte *buf) {
+    int delta = 1;
+    if (big_endian) {
+        buf += len - 1;
+        delta = -1;
+    }
+
+    mpz_need_dig(z, (len * 8 + DIG_SIZE - 1) / DIG_SIZE);
+
+    mpz_dig_t d = 0;
+    int num_bits = 0;
+    z->neg = 0;
+    z->len = 0;
+    while (len) {
+        while (len && num_bits < DIG_SIZE) {
+            d |= *buf << num_bits;
+            num_bits += 8;
+            buf += delta;
+            len--;
+        }
+        z->dig[z->len++] = d & DIG_MASK;
+        // Need this #if because it's C undefined behavior to do: uint32_t >> 32
+        #if DIG_SIZE != 8 && DIG_SIZE != 16 && DIG_SIZE != 32
+        d >>= DIG_SIZE;
+        #else
+        d = 0;
+        #endif
+        num_bits -= DIG_SIZE;
+    }
+}
+
 bool mpz_is_zero(const mpz_t *z) {
     return z->len == 0;
 }

diff --git a/py/mpz.h b/py/mpz.h
@@ -109,6 +109,7 @@ void mpz_set_from_ll(mpz_t *z, long long i, bool is_signed);
 void mpz_set_from_float(mpz_t *z, mp_float_t src);
 #endif
 mp_uint_t mpz_set_from_str(mpz_t *z, const char *str, mp_uint_t len, bool neg, mp_uint_t base);
+void mpz_set_from_bytes(mpz_t *z, bool big_endian, mp_uint_t len, const byte *buf);
 
 bool mpz_is_zero(const mpz_t *z);
 int mpz_cmp(const mpz_t *lhs, const mpz_t *rhs);

diff --git a/py/objint.c b/py/objint.c
@@ -374,26 +374,33 @@ mp_obj_t mp_obj_int_binary_op_extra_cases(mp_uint_t op, mp_obj_t lhs_in, mp_obj_
 
 // this is a classmethod
 STATIC mp_obj_t int_from_bytes(size_t n_args, const mp_obj_t *args) {
-    // TODO: Support long ints
-    // TODO: Support byteorder param
     // TODO: Support signed param (assumes signed=False at the moment)
     (void)n_args;
 
-    if (args[2] != MP_OBJ_NEW_QSTR(MP_QSTR_little)) {
-        mp_not_implemented("");
-    }
-
     // get the buffer info
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_READ);
 
-    // convert the bytes to an integer
-    mp_uint_t value = 0;
-    for (const byte* buf = (const byte*)bufinfo.buf + bufinfo.len - 1; buf >= (byte*)bufinfo.buf; buf--) {
-        value = (value << 8) | *buf;
-    }
+    #if MICROPY_LONGINT_IMPL != MICROPY_LONGINT_IMPL_NONE
+    // If result guaranteedly fits in small int, use that
+    if (!MP_SMALL_INT_FITS(1 << (bufinfo.len * 8 - 1))) {
+        return mp_obj_int_from_bytes_impl(args[2] != MP_OBJ_NEW_QSTR(MP_QSTR_little), bufinfo.len, bufinfo.buf);
+    } else
+    #endif
+    {
+        const byte* buf = (const byte*)bufinfo.buf;
+        int delta = 1;
+        if (args[2] == MP_OBJ_NEW_QSTR(MP_QSTR_little)) {
+            buf += bufinfo.len - 1;
+            delta = -1;
+        }
 
-    return mp_obj_new_int_from_uint(value);
+        mp_uint_t value = 0;
+        for (; bufinfo.len--; buf += delta) {
+            value = (value << 8) | *buf;
+        }
+        return mp_obj_new_int_from_uint(value);
+    }
 }
 
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(int_from_bytes_fun_obj, 3, 4, int_from_bytes);

diff --git a/py/objint.h b/py/objint.h
@@ -59,6 +59,7 @@ char *mp_obj_int_formatted(char **buf, size_t *buf_size, size_t *fmt_size, mp_co
 char *mp_obj_int_formatted_impl(char **buf, size_t *buf_size, size_t *fmt_size, mp_const_obj_t self_in,
                                 int base, const char *prefix, char base_char, char comma);
 mp_int_t mp_obj_int_hash(mp_obj_t self_in);
+mp_obj_t mp_obj_int_from_bytes_impl(bool big_endian, size_t len, const byte *buf);
 void mp_obj_int_to_bytes_impl(mp_obj_t self_in, bool big_endian, size_t len, byte *buf);
 int mp_obj_int_sign(mp_obj_t self_in);
 mp_obj_t mp_obj_int_abs(mp_obj_t self_in);

diff --git a/py/objint_longlong.c b/py/objint_longlong.c
@@ -53,6 +53,10 @@
 const mp_obj_int_t mp_maxsize_obj = {{&mp_type_int}, MP_SSIZE_MAX};
 #endif
 
+mp_obj_t mp_obj_int_from_bytes_impl(bool big_endian, size_t len, const byte *buf) {
+    mp_not_implemented("");
+}
+
 void mp_obj_int_to_bytes_impl(mp_obj_t self_in, bool big_endian, size_t len, byte *buf) {
     assert(MP_OBJ_IS_TYPE(self_in, &mp_type_int));
     mp_obj_int_t *self = self_in;

diff --git a/py/objint_mpz.c b/py/objint_mpz.c
@@ -107,6 +107,12 @@ char *mp_obj_int_formatted_impl(char **buf, size_t *buf_size, size_t *fmt_size,
     return str;
 }
 
+mp_obj_t mp_obj_int_from_bytes_impl(bool big_endian, size_t len, const byte *buf) {
+    mp_obj_int_t *o = mp_obj_int_new_mpz();
+    mpz_set_from_bytes(&o->mpz, big_endian, len, buf);
+    return MP_OBJ_FROM_PTR(o);
+}
+
 void mp_obj_int_to_bytes_impl(mp_obj_t self_in, bool big_endian, size_t len, byte *buf) {
     assert(MP_OBJ_IS_TYPE(self_in, &mp_type_int));
     mp_obj_int_t *self = MP_OBJ_TO_PTR(self_in);

diff --git a/tests/basics/int_bytes_long.py b/tests/basics/int_bytes_long.py
@@ -0,0 +1,7 @@
+b = bytes(range(20))
+
+il = int.from_bytes(b, "little")
+ib = int.from_bytes(b, "big")
+print(il)
+print(ib)
+print(il.to_bytes(20, "little"))
diff --git a/tests/basics/int_bytes_notimpl.py b/tests/basics/int_bytes_notimpl.py
@@ -2,8 +2,3 @@
     print((10).to_bytes(1, "big"))
 except Exception as e:
     print(type(e))
-
-try:
-    print(int.from_bytes(b"\0", "big"))
-except Exception as e:
-    print(type(e))
diff --git a/tests/basics/int_bytes_notimpl.py.exp b/tests/basics/int_bytes_notimpl.py.exp
@@ -1,2 +1 @@
 <class 'NotImplementedError'>
-<class 'NotImplementedError'>
diff --git a/tests/micropython/heapalloc_int_from_bytes.py b/tests/micropython/heapalloc_int_from_bytes.py
@@ -0,0 +1,8 @@
+# Test that int.from_bytes() for small number of bytes generates
+# small int.
+import micropython
+
+micropython.heap_lock()
+print(int.from_bytes(b"1", "little"))
+print(int.from_bytes(b"12", "little"))
+micropython.heap_unlock()
diff --git a/tests/micropython/heapalloc_int_from_bytes.py.exp b/tests/micropython/heapalloc_int_from_bytes.py.exp
@@ -0,0 +1,2 @@
+49
+12849
Original file line number	Diff line number	Diff line change
		@@ -1,2 +1 @@
		<class 'NotImplementedError'>
		<class 'NotImplementedError'>