From 226abedbf8364069e453291e655d6967098da47f Mon Sep 17 00:00:00 2001
From: Stefan Israelsson Tampe <stefan.itampe@gmail.com>
Date: Fri, 17 Aug 2018 16:02:55 +0200
Subject: from_bytes

---
 modules/language/python/bytes.scm          | 15 +++++++++++++
 modules/language/python/module/_python.scm |  2 +-
 modules/language/python/number.scm         | 34 +++++++++++++++++++++++++++++-
 3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/modules/language/python/bytes.scm b/modules/language/python/bytes.scm
index 494fd28..8cca953 100644
--- a/modules/language/python/bytes.scm
+++ b/modules/language/python/bytes.scm
@@ -1278,6 +1278,21 @@
     (slot-set! out 'd   1)
     out))
 
+(define-method (wrap-in (s <py-bytes>))
+  (let ((out (make <bytes-iter>)))
+    (slot-set! out 'bytes (slot-ref s 'bytes))
+    (slot-set! out 'i   0)
+    (slot-set! out 'd   1)
+    out))
+
+(define-method (wrap-in (s <py-bytearray>))
+  (let ((out (make <bytes-iter>)))
+    (slot-set! out 'vec (slot-ref s 'vec))
+    (slot-set! out 'n   (slot-ref s 'n))
+    (slot-set! out 'i   0)
+    (slot-set! out 'd   1)
+    out))
+
 (define-method (py-reversed (s <py-bytes>))
   (let ((out (make <bytes-iter>)))
     (slot-set! out 'bytes (slot-ref s 'bytes))
diff --git a/modules/language/python/module/_python.scm b/modules/language/python/module/_python.scm
index 46f840e..11d6710 100644
--- a/modules/language/python/module/_python.scm
+++ b/modules/language/python/module/_python.scm
@@ -39,7 +39,7 @@
                              SyntaxError bool compile
                              len dir next dict None property range
                              tuple bytes bytearray eval locals globals
-                             exec type object open __import__
+                             exec type object open __import__ frozenset
 			     Warning BytesWarning DeprecationWarning
                              )
   
diff --git a/modules/language/python/number.scm b/modules/language/python/number.scm
index b51cd6b..e25c612 100644
--- a/modules/language/python/number.scm
+++ b/modules/language/python/number.scm
@@ -4,7 +4,10 @@
   #:use-module (language python hash)
   #:use-module (language python list)
   #:use-module (language python try)
+  #:use-module (language python for)
+  #:use-module (language python def)
   #:use-module (language python exceptions)
+  #:use-module (language python bytes)
   #:use-module (language python persist)
   #:export (py-int py-float py-complex
                    py-/ py-logand py-logior py-logxor py-abs py-trunc
@@ -307,6 +310,35 @@
   (apply write (slot-ref o 'x) l))
 
 (define-python-class int (<py> <py-int>)
+  (define from_bytes
+    (class-method
+     (lam (self bytes byteorder (= signed #f))
+	  (for ((x : bytes)) ((l '()))
+	       (cons
+		(let ((i (if (and (number? x) (integer? x))
+			     x
+			     (list-ref (bv-scm x) 0))))
+		  (if (not (and (number? i) (integer? i)
+				(>= i 0) (<= i 356)))
+		      (raise (ValueError "wrong bytevector in from_bytes"))
+		      i))
+		l)
+	       #:final
+	       (begin
+		 (if (equal? byteorder "big")
+		     (set! l (reverse l)))
+		 (let lp ((s 0) (i 0) (l l))
+		   (if (pair? l)
+		       (let ((x (car l)))
+			 (if (null? (cdr l))
+			     (if (and signed (not (= 0 (logand x #x80))))
+				 (set! x (logand x #x7f))
+				 (set! signed #f)))
+			 (lp (logior s (ash x i)) (+ i 8) (cdr l)))
+		       (if signed
+			   (let ((mask (ash 1 (- i 1))))
+			     (- s mask))
+			   s))))))))
   (define __new__
     (letrec ((__new__
               (case-lambda
@@ -440,7 +472,7 @@
                          __rpow__ __rrshift__ __rshift__ __rsub__ __rtruediv__
                          __rxor__ __setattr__ __sizeof__ __str__ __sub__
                          __subclasshook__ __truediv__ __trunc__ __xor__
-                         bit_length conjugate denominator imag numerator
+                         bit_length conjugate denominator imag numerator from_bytes
                          real)))))
     (pylist-sort! l)
     l))
-- 
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