commit c8121ce34b39c6fd31899f4da91e26063c8af54f
parent 7360f8d0fd91344deb583ff76b8250a1883dcd4c
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Mon, 12 Feb 2024 15:15:44 -0300
Revising code for Varint encoding in dumps
- Usign lua_Unsigned to count strings.
- Varint uses a type large enough both for size_t and lua_Unsigned.
- Most-Significant Bit 0 means last byte, to conform to common usage.
- (unrelated) Change in macro 'getaddr' so that multiplication is
by constants.
Diffstat:
3 files changed, 45 insertions(+), 29 deletions(-)
diff --git a/ldump.c b/ldump.c
@@ -30,7 +30,7 @@ typedef struct {
int strip;
int status;
Table *h; /* table to track saved strings */
- lua_Integer nstr; /* counter to number saved strings */
+ lua_Unsigned nstr; /* counter to number saved strings */
} DumpState;
@@ -83,26 +83,27 @@ static void dumpByte (DumpState *D, int y) {
/*
-** 'dumpSize' buffer size: each byte can store up to 7 bits. (The "+6"
-** rounds up the division.)
+** size for 'dumpVarint' buffer: each byte can store up to 7 bits.
+** (The "+6" rounds up the division.)
*/
-#define DIBS ((sizeof(size_t) * CHAR_BIT + 6) / 7)
+#define DIBS ((sizeof(varint_t) * CHAR_BIT + 6) / 7)
-static void dumpSize (DumpState *D, size_t x) {
+/*
+** Dumps an unsigned integer using the MSB Varint encoding
+*/
+static void dumpVarint (DumpState *D, varint_t x) {
lu_byte buff[DIBS];
- int n = 0;
- do {
- buff[DIBS - (++n)] = x & 0x7f; /* fill buffer in reverse order */
- x >>= 7;
- } while (x != 0);
- buff[DIBS - 1] |= 0x80; /* mark last byte */
+ int n = 1;
+ buff[DIBS - 1] = x & 0x7f; /* fill least-significant byte */
+ while ((x >>= 7) != 0) /* fill other bytes in reverse order */
+ buff[DIBS - (++n)] = (x & 0x7f) | 0x80;
dumpVector(D, buff + DIBS - n, n);
}
static void dumpInt (DumpState *D, int x) {
lua_assert(x >= 0);
- dumpSize(D, x);
+ dumpVarint(D, x);
}
@@ -125,22 +126,22 @@ static void dumpInteger (DumpState *D, lua_Integer x) {
*/
static void dumpString (DumpState *D, TString *ts) {
if (ts == NULL)
- dumpSize(D, 0);
+ dumpVarint(D, 0);
else {
TValue idx;
if (luaH_getstr(D->h, ts, &idx) == HOK) { /* string already saved? */
- dumpSize(D, 1); /* reuse a saved string */
- dumpInt(D, ivalue(&idx)); /* index of saved string */
+ dumpVarint(D, 1); /* reuse a saved string */
+ dumpVarint(D, l_castS2U(ivalue(&idx))); /* index of saved string */
}
else { /* must write and save the string */
TValue key, value; /* to save the string in the hash */
size_t size;
const char *s = getlstr(ts, size);
- dumpSize(D, size + 2);
+ dumpVarint(D, size + 2);
dumpVector(D, s, size + 1); /* include ending '\0' */
D->nstr++; /* one more saved string */
setsvalue(D->L, &key, ts); /* the string is the key */
- setivalue(&value, D->nstr); /* its index is the value */
+ setivalue(&value, l_castU2S(D->nstr)); /* its index is the value */
luaH_set(D->L, D->h, &key, &value); /* h[ts] = nstr */
/* integer value does not need barrier */
}
diff --git a/lundump.c b/lundump.c
@@ -37,7 +37,7 @@ typedef struct {
const char *name;
Table *h; /* list for string reuse */
size_t offset; /* current position relative to beginning of dump */
- lua_Integer nstr; /* number of strings in the list */
+ lua_Unsigned nstr; /* number of strings in the list */
lu_byte fixed; /* dump is fixed in memory */
} LoadState;
@@ -71,10 +71,9 @@ static void loadAlign (LoadState *S, int align) {
}
-#define getaddr(S,n,t) cast(t *, getaddr_(S,n,sizeof(t)))
+#define getaddr(S,n,t) cast(t *, getaddr_(S,(n) * sizeof(t)))
-static const void *getaddr_ (LoadState *S, int n, size_t sz) {
- size_t size = n * sz;
+static const void *getaddr_ (LoadState *S, size_t size) {
const void *block = luaZ_getaddr(S->Z, size);
S->offset += size;
if (block == NULL)
@@ -95,8 +94,8 @@ static lu_byte loadByte (LoadState *S) {
}
-static size_t loadUnsigned (LoadState *S, size_t limit) {
- size_t x = 0;
+static varint_t loadVarint (LoadState *S, varint_t limit) {
+ varint_t x = 0;
int b;
limit >>= 7;
do {
@@ -104,18 +103,18 @@ static size_t loadUnsigned (LoadState *S, size_t limit) {
if (x >= limit)
error(S, "integer overflow");
x = (x << 7) | (b & 0x7f);
- } while ((b & 0x80) == 0);
+ } while ((b & 0x80) != 0);
return x;
}
static size_t loadSize (LoadState *S) {
- return loadUnsigned(S, MAX_SIZET);
+ return cast_sizet(loadVarint(S, MAX_SIZET));
}
static int loadInt (LoadState *S) {
- return cast_int(loadUnsigned(S, INT_MAX));
+ return cast_int(loadVarint(S, INT_MAX));
}
@@ -149,9 +148,10 @@ static void loadString (LoadState *S, Proto *p, TString **sl) {
return;
}
else if (size == 1) { /* previously saved string? */
- int idx = loadInt(S); /* get its index */
+ /* get its index */
+ lua_Unsigned idx = cast(lua_Unsigned, loadVarint(S, LUA_MAXUNSIGNED));
TValue stv;
- luaH_getint(S->h, idx, &stv);
+ luaH_getint(S->h, l_castU2S(idx), &stv); /* get its value */
*sl = ts = tsvalue(&stv);
luaC_objbarrier(L, p, ts);
return; /* do not save it again */
@@ -175,7 +175,7 @@ static void loadString (LoadState *S, Proto *p, TString **sl) {
/* add string to list of saved strings */
S->nstr++;
setsvalue(L, &sv, ts);
- luaH_setint(L, S->h, S->nstr, &sv);
+ luaH_setint(L, S->h, l_castU2S(S->nstr), &sv);
luaC_objbarrierback(L, obj2gco(S->h), ts);
}
diff --git a/lundump.h b/lundump.h
@@ -7,6 +7,8 @@
#ifndef lundump_h
#define lundump_h
+#include <limits.h>
+
#include "llimits.h"
#include "lobject.h"
#include "lzio.h"
@@ -25,6 +27,19 @@
#define LUAC_FORMAT 0 /* this is the official format */
+
+/*
+** Type to handle MSB Varint encoding: Try to get the largest unsigned
+** integer available. (It was enough to be the largest between size_t and
+** lua_Integer, but the C89 preprocessor knows nothing about size_t.)
+*/
+#if !defined(LUA_USE_C89) && defined(LLONG_MAX)
+typedef unsigned long long varint_t;
+#else
+typedef unsigned long varint_t;
+#endif
+
+
/* load one chunk; from lundump.c */
LUAI_FUNC LClosure* luaU_undump (lua_State* L, ZIO* Z, const char* name,
int fixed);
