py: Fix bug in mpz_and function.

dpgeorge · dpgeorge · commit 561e42590307 · 2014-05-12T23:27:29.000+01:00
Addresses issue adafruit#610.
diff --git a/py/mpz.c b/py/mpz.c
@@ -213,8 +213,8 @@ STATIC uint mpn_and(mpz_dig_t *idig, const mpz_dig_t *jdig, uint jlen, const mpz
         *idig = *jdig & *kdig;
     }
 
-    for (; jlen > 0; --jlen, ++idig) {
-        *idig = 0;
+    // remove trailing zeros
+    for (; idig > oidig && *idig == 0; --idig) {
     }
 
     return idig - oidig;
diff --git a/tests/basics/int-big-and.py b/tests/basics/int-big-and.py
@@ -0,0 +1,8 @@
+print(0 & (1 << 80))
+print(0 & (1 << 80) == 0)
+print(bool(0 & (1 << 80)))
+
+#a = 0xfffffffffffffffffffffffffffff
+#print(a & (1 << 80))
+#print((a & (1 << 80)) >> 80)
+#print((a & (1 << 80)) >> 80 == 1)

Original file line number	Diff line number	Diff line change
`@@ -213,8 +213,8 @@ STATIC uint mpn_and(mpz_dig_t idig, const mpz_dig_t jdig, uint jlen, const mpz`
`213`	`213`	`idig = jdig & *kdig;`
`214`	`214`	`}`
`215`	`215`
`216`		`- for (; jlen > 0; --jlen, ++idig) {`
`217`		`- *idig = 0;`
	`216`	`+ // remove trailing zeros`
	`217`	`+ for (; idig > oidig && *idig == 0; --idig) {`
`218`	`218`	`}`
`219`	`219`
`220`	`220`	`return idig - oidig;`