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added comments to several functions

This commit is contained in:
Roberto Ierusalimschy 2014-05-12 16:13:32 -03:00
parent 626124d2d8
commit 12bd01c567
1 changed files with 93 additions and 55 deletions
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148
lvm.c
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@ -1,5 +1,5 @@
/* /*
** $Id: lvm.c,v 2.205 2014/05/01 18:18:06 roberto Exp roberto $ ** $Id: lvm.c,v 2.206 2014/05/09 14:20:52 roberto Exp roberto $
** Lua virtual machine ** Lua virtual machine
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -56,7 +56,8 @@ static int tofloat (const TValue *obj, lua_Number *n) {
/* /*
** Try to convert a value to a float ** Try to convert a value to a float. Check 'isinteger' first, because
** in general the float case is already handled by the macro 'tonumber'.
*/ */
int luaV_tonumber_ (const TValue *obj, lua_Number *n) { int luaV_tonumber_ (const TValue *obj, lua_Number *n) {
TValue v; TValue v;
@ -69,7 +70,7 @@ int luaV_tonumber_ (const TValue *obj, lua_Number *n) {
*n = fltvalue(obj); *n = fltvalue(obj);
return 1; return 1;
} }
else if (ttisstring(obj) && else if (ttisstring(obj) && /* string convertible to number? */
luaO_str2num(svalue(obj), &v) == tsvalue(obj)->len + 1) { luaO_str2num(svalue(obj), &v) == tsvalue(obj)->len + 1) {
obj = &v; obj = &v;
goto again; /* convert result from 'luaO_str2num' to a float */ goto again; /* convert result from 'luaO_str2num' to a float */
@ -178,8 +179,12 @@ static int forlimit (const TValue *obj, lua_Integer *p, lua_Integer step,
} }
/*
** Main function for table access (invoking metamethods if needed).
** Compute 'val = t[key]'
*/
void luaV_gettable (lua_State *L, const TValue *t, TValue *key, StkId val) { void luaV_gettable (lua_State *L, const TValue *t, TValue *key, StkId val) {
int loop; int loop; /* counter to avoid infinite loops */
for (loop = 0; loop < MAXTAGLOOP; loop++) { for (loop = 0; loop < MAXTAGLOOP; loop++) {
const TValue *tm; const TValue *tm;
if (ttistable(t)) { /* `t' is a table? */ if (ttistable(t)) { /* `t' is a table? */
@ -187,32 +192,36 @@ void luaV_gettable (lua_State *L, const TValue *t, TValue *key, StkId val) {
const TValue *res = luaH_get(h, key); /* do a primitive get */ const TValue *res = luaH_get(h, key); /* do a primitive get */
if (!ttisnil(res) || /* result is not nil? */ if (!ttisnil(res) || /* result is not nil? */
(tm = fasttm(L, h->metatable, TM_INDEX)) == NULL) { /* or no TM? */ (tm = fasttm(L, h->metatable, TM_INDEX)) == NULL) { /* or no TM? */
setobj2s(L, val, res); setobj2s(L, val, res); /* result is the raw get */
return; return;
} }
/* else will try the tag method */ /* else will try metamethod */
} }
else if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_INDEX))) else if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_INDEX)))
luaG_typeerror(L, t, "index"); luaG_typeerror(L, t, "index"); /* no metamethod */
if (ttisfunction(tm)) { if (ttisfunction(tm)) { /* metamethod is a function */
luaT_callTM(L, tm, t, key, val, 1); luaT_callTM(L, tm, t, key, val, 1);
return; return;
} }
t = tm; /* else repeat with 'tm' */ t = tm; /* else repeat access over 'tm' */
} }
luaG_runerror(L, "gettable chain too long; possible loop"); luaG_runerror(L, "gettable chain too long; possible loop");
} }
/*
** Main function for table assignment (invoking metamethods if needed).
** Compute 't[key] = val'
*/
void luaV_settable (lua_State *L, const TValue *t, TValue *key, StkId val) { void luaV_settable (lua_State *L, const TValue *t, TValue *key, StkId val) {
int loop; int loop; /* counter to avoid infinite loops */
for (loop = 0; loop < MAXTAGLOOP; loop++) { for (loop = 0; loop < MAXTAGLOOP; loop++) {
const TValue *tm; const TValue *tm;
if (ttistable(t)) { /* `t' is a table? */ if (ttistable(t)) { /* `t' is a table? */
Table *h = hvalue(t); Table *h = hvalue(t);
TValue *oldval = cast(TValue *, luaH_get(h, key)); TValue *oldval = cast(TValue *, luaH_get(h, key));
/* if previous value is not nil, there must be a previous entry /* if previous value is not nil, there must be a previous entry
in the table; moreover, a metamethod has no relevance */ in the table; a metamethod has no relevance */
if (!ttisnil(oldval) || if (!ttisnil(oldval) ||
/* previous value is nil; must check the metamethod */ /* previous value is nil; must check the metamethod */
((tm = fasttm(L, h->metatable, TM_NEWINDEX)) == NULL && ((tm = fasttm(L, h->metatable, TM_NEWINDEX)) == NULL &&
@ -232,32 +241,40 @@ void luaV_settable (lua_State *L, const TValue *t, TValue *key, StkId val) {
else /* not a table; check metamethod */ else /* not a table; check metamethod */
if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_NEWINDEX))) if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_NEWINDEX)))
luaG_typeerror(L, t, "index"); luaG_typeerror(L, t, "index");
/* there is a metamethod */ /* try the metamethod */
if (ttisfunction(tm)) { if (ttisfunction(tm)) {
luaT_callTM(L, tm, t, key, val, 0); luaT_callTM(L, tm, t, key, val, 0);
return; return;
} }
t = tm; /* else repeat with 'tm' */ t = tm; /* else repeat assginment over 'tm' */
} }
luaG_runerror(L, "settable chain too long; possible loop"); luaG_runerror(L, "settable chain too long; possible loop");
} }
/*
** Compare two strings 'ls' x 'rs', returning an integer smaller-equal-
** -larger than zero if 'ls' is smaller-equal-larger than 'rs'.
** The code is a little tricky because it allows '\0' in the strings
** and it uses 'strcoll' (to respect locales) for each segments
** of the strings.
*/
static int l_strcmp (const TString *ls, const TString *rs) { static int l_strcmp (const TString *ls, const TString *rs) {
const char *l = getstr(ls); const char *l = getstr(ls);
size_t ll = ls->tsv.len; size_t ll = ls->tsv.len;
const char *r = getstr(rs); const char *r = getstr(rs);
size_t lr = rs->tsv.len; size_t lr = rs->tsv.len;
for (;;) { for (;;) { /* for each segment */
int temp = strcoll(l, r); int temp = strcoll(l, r);
if (temp != 0) return temp; if (temp != 0) /* not equal? */
else { /* strings are equal up to a `\0' */ return temp; /* done */
else { /* strings are equal up to a '\0' */
size_t len = strlen(l); /* index of first `\0' in both strings */ size_t len = strlen(l); /* index of first `\0' in both strings */
if (len == lr) /* r is finished? */ if (len == lr) /* 'rs' is finished? */
return (len == ll) ? 0 : 1; return (len == ll) ? 0 : 1; /* check 'ls' */
else if (len == ll) /* l is finished? */ else if (len == ll) /* 'ls' is finished? */
return -1; /* l is smaller than r (because r is not finished) */ return -1; /* 'ls' is smaller than 'rs' ('rs' is not finished) */
/* both strings longer than `len'; go on comparing (after the `\0') */ /* both strings longer than `len'; go on comparing after the '\0' */
len++; len++;
l += len; ll -= len; r += len; lr -= len; l += len; ll -= len; r += len; lr -= len;
} }
@ -265,29 +282,35 @@ static int l_strcmp (const TString *ls, const TString *rs) {
} }
/*
** Main operation less than; return 'l < r'.
*/
int luaV_lessthan (lua_State *L, const TValue *l, const TValue *r) { int luaV_lessthan (lua_State *L, const TValue *l, const TValue *r) {
int res; int res;
lua_Number nl, nr; lua_Number nl, nr;
if (ttisinteger(l) && ttisinteger(r)) if (ttisinteger(l) && ttisinteger(r)) /* both operands are integers? */
return (ivalue(l) < ivalue(r)); return (ivalue(l) < ivalue(r));
else if (tofloat(l, &nl) && tofloat(r, &nr)) else if (tofloat(l, &nl) && tofloat(r, &nr)) /* both are numbers? */
return luai_numlt(nl, nr); return luai_numlt(nl, nr);
else if (ttisstring(l) && ttisstring(r)) else if (ttisstring(l) && ttisstring(r)) /* both are strings? */
return l_strcmp(rawtsvalue(l), rawtsvalue(r)) < 0; return l_strcmp(rawtsvalue(l), rawtsvalue(r)) < 0;
else if ((res = luaT_callorderTM(L, l, r, TM_LT)) < 0) else if ((res = luaT_callorderTM(L, l, r, TM_LT)) < 0) /* no metamethod? */
luaG_ordererror(L, l, r); luaG_ordererror(L, l, r); /* error */
return res; return res;
} }
/*
** Main operation less than or equal to; return 'l <= r'.
*/
int luaV_lessequal (lua_State *L, const TValue *l, const TValue *r) { int luaV_lessequal (lua_State *L, const TValue *l, const TValue *r) {
int res; int res;
lua_Number nl, nr; lua_Number nl, nr;
if (ttisinteger(l) && ttisinteger(r)) if (ttisinteger(l) && ttisinteger(r)) /* both operands are integers? */
return (ivalue(l) <= ivalue(r)); return (ivalue(l) <= ivalue(r));
else if (tofloat(l, &nl) && tofloat(r, &nr)) else if (tofloat(l, &nl) && tofloat(r, &nr)) /* both are numbers? */
return luai_numle(nl, nr); return luai_numle(nl, nr);
else if (ttisstring(l) && ttisstring(r)) else if (ttisstring(l) && ttisstring(r)) /* both are strings? */
return l_strcmp(rawtsvalue(l), rawtsvalue(r)) <= 0; return l_strcmp(rawtsvalue(l), rawtsvalue(r)) <= 0;
else if ((res = luaT_callorderTM(L, l, r, TM_LE)) >= 0) /* first try `le' */ else if ((res = luaT_callorderTM(L, l, r, TM_LE)) >= 0) /* first try `le' */
return res; return res;
@ -298,15 +321,16 @@ int luaV_lessequal (lua_State *L, const TValue *l, const TValue *r) {
/* /*
** equality of Lua values. L == NULL means raw equality (no metamethods) ** Main operation for equality of Lua values; return 't1 == t2'.
** L == NULL means raw equality (no metamethods)
*/ */
int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2) { int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2) {
const TValue *tm; const TValue *tm;
if (ttype(t1) != ttype(t2)) { if (ttype(t1) != ttype(t2)) { /* not the same variant? */
if (ttnov(t1) != ttnov(t2) || ttnov(t1) != LUA_TNUMBER) if (ttnov(t1) != ttnov(t2) || ttnov(t1) != LUA_TNUMBER)
return 0; /* only numbers can be equal with different variants */ return 0; /* only numbers can be equal with different variants */
else { /* two numbers with different variants */ else { /* two numbers with different variants */
lua_Number n1, n2; lua_Number n1, n2; /* compare them as floats */
lua_assert(ttisnumber(t1) && ttisnumber(t2)); lua_assert(ttisnumber(t1) && ttisnumber(t2));
cast_void(tofloat(t1, &n1)); cast_void(tofloat(t2, &n2)); cast_void(tofloat(t1, &n1)); cast_void(tofloat(t2, &n2));
return luai_numeq(n1, n2); return luai_numeq(n1, n2);
@ -343,8 +367,13 @@ int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2) {
} }
/* macro used by 'luaV_concat' to ensure that element at 'o' is a string */
#define tostring(L,o) (ttisstring(o) || (luaV_tostring(L, o))) #define tostring(L,o) (ttisstring(o) || (luaV_tostring(L, o)))
/*
** Main operation for concatenation: concat 'total' values in the stack,
** from 'L->top - total' up to 'L->top - 1'.
*/
void luaV_concat (lua_State *L, int total) { void luaV_concat (lua_State *L, int total) {
lua_assert(total >= 2); lua_assert(total >= 2);
do { do {
@ -372,12 +401,12 @@ void luaV_concat (lua_State *L, int total) {
buffer = luaZ_openspace(L, &G(L)->buff, tl); buffer = luaZ_openspace(L, &G(L)->buff, tl);
tl = 0; tl = 0;
n = i; n = i;
do { /* concat all strings */ do { /* copy all strings to buffer */
size_t l = tsvalue(top-i)->len; size_t l = tsvalue(top-i)->len;
memcpy(buffer+tl, svalue(top-i), l * sizeof(char)); memcpy(buffer+tl, svalue(top-i), l * sizeof(char));
tl += l; tl += l;
} while (--i > 0); } while (--i > 0);
setsvalue2s(L, top-n, luaS_newlstr(L, buffer, tl)); setsvalue2s(L, top-n, luaS_newlstr(L, buffer, tl)); /* create result */
} }
total -= n-1; /* got 'n' strings to create 1 new */ total -= n-1; /* got 'n' strings to create 1 new */
L->top -= n-1; /* popped 'n' strings and pushed one */ L->top -= n-1; /* popped 'n' strings and pushed one */
@ -385,6 +414,9 @@ void luaV_concat (lua_State *L, int total) {
} }
/*
** Main operation 'ra' = #rb'.
*/
void luaV_objlen (lua_State *L, StkId ra, const TValue *rb) { void luaV_objlen (lua_State *L, StkId ra, const TValue *rb) {
const TValue *tm; const TValue *tm;
switch (ttnov(rb)) { switch (ttnov(rb)) {
@ -410,15 +442,18 @@ void luaV_objlen (lua_State *L, StkId ra, const TValue *rb) {
} }
lua_Integer luaV_div (lua_State *L, lua_Integer x, lua_Integer y) { /*
if (l_castS2U(y) + 1u <= 1u) { /* special cases: -1 or 0 */ ** Integer division; return 'm // n'.
if (y == 0) */
lua_Integer luaV_div (lua_State *L, lua_Integer m, lua_Integer n) {
if (l_castS2U(n) + 1u <= 1u) { /* special cases: -1 or 0 */
if (n == 0)
luaG_runerror(L, "attempt to divide by zero"); luaG_runerror(L, "attempt to divide by zero");
return intop(-, 0, x); /* y==-1; avoid overflow with 0x80000...//-1 */ return intop(-, 0, m); /* n==-1; avoid overflow with 0x80000...//-1 */
} }
else { else {
lua_Integer d = x / y; /* perform division */ lua_Integer d = m / n; /* perform division */
if ((x ^ y) >= 0 || x % y == 0) /* same signal or no rest? */ if ((m ^ n) >= 0 || m % n == 0) /* same signal or no rest? */
return d; return d;
else else
return d - 1; /* correct 'div' for negative case */ return d - 1; /* correct 'div' for negative case */
@ -426,33 +461,36 @@ lua_Integer luaV_div (lua_State *L, lua_Integer x, lua_Integer y) {
} }
lua_Integer luaV_mod (lua_State *L, lua_Integer x, lua_Integer y) { /*
if (l_castS2U(y) + 1u <= 1u) { /* special cases: -1 or 0 */ ** Integer modulus; return 'm % n'.
if (y == 0) */
lua_Integer luaV_mod (lua_State *L, lua_Integer m, lua_Integer n) {
if (l_castS2U(n) + 1u <= 1u) { /* special cases: -1 or 0 */
if (n == 0)
luaG_runerror(L, "attempt to perform 'n%%0'"); luaG_runerror(L, "attempt to perform 'n%%0'");
return 0; /* y==-1; avoid overflow with 0x80000...%-1 */ return 0; /* m % -1 == 0; avoid overflow with 0x80000...%-1 */
} }
else { else {
lua_Integer r = x % y; lua_Integer r = m % n;
if (r == 0 || (x ^ y) >= 0) if (r == 0 || (m ^ n) >= 0)
return r; return r;
else else
return r + y; /* correct 'mod' for negative case */ return r + n; /* correct 'mod' for negative case */
} }
} }
lua_Integer luaV_pow (lua_Integer x, lua_Integer y) { lua_Integer luaV_pow (lua_Integer m, lua_Integer n) {
lua_assert(y >= 0); lua_assert(n >= 0);
if (y == 0) if (n == 0)
return 1; /* x^0 == 1 */ return 1; /* m^0 == 1 */
else { else {
lua_Integer r = 1; lua_Integer r = 1;
for (; y > 1; y >>= 1) { for (; n > 1; n >>= 1) {
if (y & 1) r = intop(*, r, x); if (n & 1) r = intop(*, r, m);
x = intop(*, x, x); m = intop(*, m, m);
} }
r = intop(*, r, x); r = intop(*, r, m);
return r; return r;
} }
} }