commit 3e7415e846f2f75ed29e27e1211205ea6243e0c7
parent e64e20ac8136b6cf53601127fc5c69310d644eeb
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Fri, 4 May 2018 17:01:18 -0300
reorganization of '#if's for sellecting a type for 'Rand64' +
comments
Diffstat:
| M | lmathlib.c | | | 87 | +++++++++++++++++++++++++++++++++++++++++++++++++++---------------------------- |
| M | ltests.h | | | 6 | +++++- |
2 files changed, 61 insertions(+), 32 deletions(-)
diff --git a/lmathlib.c b/lmathlib.c
@@ -1,5 +1,5 @@
/*
-** $Id: lmathlib.c,v 1.130 2018/04/06 15:41:29 roberto Exp roberto $
+** $Id: lmathlib.c,v 1.131 2018/04/06 17:52:42 roberto Exp roberto $
** Standard mathematical library
** See Copyright Notice in lua.h
*/
@@ -257,27 +257,45 @@ static int math_type (lua_State *L) {
#endif
-#if (!defined(LUA_USE_C89) && defined(LLONG_MAX) && !defined(LUA_DEBUG)) \
- || defined(Rand64) /* { */
-
/*
-** Assume long long.
+** LUA_RAND32 forces the use of 32-bit integers in the implementation
+** of the PRN generator (mainly for testing).
*/
+#if !defined(LUA_RAND32) && !defined(Rand64)
+
+/* try to find an integer type with at least 64 bits */
+
+#if (LONG_MAX >> 31 >> 31) >= 1
+
+/* 'long' has at least 64 bits */
+#define Rand64 unsigned long
+
+#elif !defined(LUA_USE_C89) && defined(LLONG_MAX)
+
+/* there is a 'long long' type (which must have at least 64 bits) */
+#define Rand64 unsigned long long
+
+#elif (LUA_MAXINTEGER >> 31 >> 31) >= 1
+
+/* 'lua_Integer' has at least 64 bits */
+#define Rand64 LUA_UNSIGNED
+
+#endif
-#if !defined(Rand64)
-/* a 64-bit value */
-typedef unsigned long long Rand64;
#endif
+#if defined(Rand64) /* { */
+
/*
+** Standard implementation, using 64-bit integers.
** If 'Rand64' has more than 64 bits, the extra bits do not interfere
-** with the 64 initial bits, except in a right shift. Otherwise, we just
-** have to make sure we never use them.
+** with the 64 initial bits, except in a right shift. Moreover, the
+** final result has to discard the extra bits.
*/
/* avoid using extra bits when needed */
-#define trim64(x) ((x) & 0xffffffffffffffffU)
+#define trim64(x) ((x) & 0xffffffffffffffffu)
/* rotate left 'x' by 'n' bits */
@@ -315,24 +333,23 @@ static lua_Number I2d (Rand64 x) {
/* convert a 'Rand64' to a 'lua_Unsigned' */
#define I2UInt(x) ((lua_Unsigned)trim64(x))
-/* convert a 'lua_Unsigned' to an 'Rand64' */
+/* convert a 'lua_Unsigned' to a 'Rand64' */
#define Int2I(x) ((Rand64)(x))
-#else /* no long long }{ */
-
-/*
-** Use two 32-bit integers to represent a 64-bit quantity.
-*/
+#else /* no 'Rand64' }{ */
-#if LUAI_BITSINT >= 32
+/* get an integer with at least 32 bits */
+#if (INT_MAX >> 30) >= 1
typedef unsigned int lu_int32;
#else
typedef unsigned long lu_int32;
#endif
-/* a 64-bit value */
+/*
+** Use two 32-bit integers to represent a 64-bit quantity.
+*/
typedef struct Rand64 {
lu_int32 h; /* higher half */
lu_int32 l; /* lower half */
@@ -342,17 +359,18 @@ typedef struct Rand64 {
/*
** If 'lu_int32' has more than 32 bits, the extra bits do not interfere
** with the 32 initial bits, except in a right shift and comparisons.
-** Otherwise, we just have to make sure we never use them.
+** Moreover, the final result has to discard the extra bits.
*/
/* avoid using extra bits when needed */
-#define trim32(x) ((x) & 0xffffffffU)
+#define trim32(x) ((x) & 0xffffffffu)
/*
** basic operations on 'Rand64' values
*/
+/* build a new Rand64 value */
static Rand64 packI (lu_int32 h, lu_int32 l) {
Rand64 result;
result.h = h;
@@ -360,16 +378,19 @@ static Rand64 packI (lu_int32 h, lu_int32 l) {
return result;
}
+/* return i << n */
static Rand64 Ishl (Rand64 i, int n) {
lua_assert(n > 0 && n < 32);
return packI((i.h << n) | (trim32(i.l) >> (32 - n)), i.l << n);
}
+/* i1 ^= i2 */
static void Ixor (Rand64 *i1, Rand64 i2) {
i1->h ^= i2.h;
i1->l ^= i2.l;
}
+/* return i1 + i2 */
static Rand64 Iadd (Rand64 i1, Rand64 i2) {
Rand64 result = packI(i1.h + i2.h, i1.l + i2.l);
if (trim32(result.l) < trim32(i1.l)) /* carry? */
@@ -377,14 +398,17 @@ static Rand64 Iadd (Rand64 i1, Rand64 i2) {
return result;
}
+/* return i * 5 */
static Rand64 times5 (Rand64 i) {
return Iadd(Ishl(i, 2), i); /* i * 5 == (i << 2) + i */
}
+/* return i * 9 */
static Rand64 times9 (Rand64 i) {
return Iadd(Ishl(i, 3), i); /* i * 9 == (i << 3) + i */
}
+/* return 'i' rotated left 'n' bits */
static Rand64 rotl (Rand64 i, int n) {
lua_assert(n > 0 && n < 32);
return packI((i.h << n) | (trim32(i.l) >> (32 - n)),
@@ -416,7 +440,7 @@ static Rand64 nextrand (Rand64 *state) {
/*
-** Converts an 'Rand64' into a float.
+** Converts a 'Rand64' into a float.
*/
/* an unsigned 1 with proper type */
@@ -452,11 +476,12 @@ static lua_Number I2d (Rand64 x) {
}
+/* convert a 'Rand64' to a 'lua_Unsigned' */
static lua_Unsigned I2UInt (Rand64 x) {
- return ((lua_Unsigned)x.h << 31 << 1) | (lua_Unsigned)trim32(x.l);
+ return ((lua_Unsigned)trim32(x.h) << 31 << 1) | (lua_Unsigned)trim32(x.l);
}
-
+/* convert a 'lua_Unsigned' to a 'Rand64' */
static Rand64 Int2I (lua_Unsigned n) {
return packI((lu_int32)(n >> 31 >> 1), (lu_int32)n);
}
@@ -479,7 +504,7 @@ typedef struct {
** division). To get a uniform projection into [0, n], we first compute
** 'lim', the smallest Mersenne number not smaller than 'n'. We then
** project 'ran' into the interval [0, lim]. If the result is inside
-** [0, n], we are done. Otherwise, we try with another 'ran' until we
+** [0, n], we are done. Otherwise, we try with another 'ran', until we
** have a result inside the interval.
*/
static lua_Unsigned project (lua_Unsigned ran, lua_Unsigned n,
@@ -492,15 +517,15 @@ static lua_Unsigned project (lua_Unsigned ran, lua_Unsigned n,
lim |= (lim >> 4);
lim |= (lim >> 8);
lim |= (lim >> 16);
-#if (LUA_MAXINTEGER >> 30 >> 2) > 0
+#if (LUA_MAXINTEGER >> 30 >> 1) > 0
lim |= (lim >> 32); /* integer type has more than 32 bits */
#endif
}
- lua_assert((lim & (lim + 1)) == 0 /* 'lim + 1' is a power of 2 */
- && lim >= n /* not smaller than 'n' */
- && (lim == 0 || (lim >> 1) < n)); /* it is the smallest one */
- while ((ran &= lim) > n)
- ran = I2UInt(nextrand(state->s));
+ lua_assert((lim & (lim + 1)) == 0 /* 'lim + 1' is a power of 2, */
+ && lim >= n /* not smaller than 'n', */
+ && (lim == 0 || (lim >> 1) < n)); /* and it is the smallest one */
+ while ((ran &= lim) > n) /* project 'ran' into [0..lim] */
+ ran = I2UInt(nextrand(state->s)); /* not inside [0..n]? try again */
return ran;
}
diff --git a/ltests.h b/ltests.h
@@ -1,5 +1,5 @@
/*
-** $Id: ltests.h,v 2.57 2018/04/11 16:49:36 roberto Exp roberto $
+** $Id: ltests.h,v 2.58 2018/04/19 15:42:41 roberto Exp roberto $
** Internal Header for Debugging of the Lua Implementation
** See Copyright Notice in lua.h
*/
@@ -49,6 +49,10 @@
#define LUA_USE_JUMPTABLE 0
+/* use 32-bit integers in random generator */
+#define LUA_RAND32
+
+
/* memory-allocator control variables */
typedef struct Memcontrol {
unsigned long numblocks;
