//
// Next_Path_Throws: C
//
// Evaluate next part of a path.
//
REBOOL Next_Path_Throws(REBPVS *pvs)
{
REBPEF dispatcher;
REBVAL temp;
VAL_INIT_WRITABLE_DEBUG(&temp);
// Path must have dispatcher, else return:
dispatcher = Path_Dispatch[VAL_TYPE_0(pvs->value)];
if (!dispatcher) return FALSE; // unwind, then check for errors
pvs->item++;
//Debug_Fmt("Next_Path: %r/%r", pvs->path-1, pvs->path);
// object/:field case:
if (IS_GET_WORD(pvs->item)) {
pvs->selector = GET_MUTABLE_VAR_MAY_FAIL(pvs->item);
if (IS_UNSET(pvs->selector))
fail (Error(RE_NO_VALUE, pvs->item));
}
// object/(expr) case:
else if (IS_GROUP(pvs->item)) {
if (DO_VAL_ARRAY_AT_THROWS(&temp, pvs->item)) {
*pvs->value = temp;
return TRUE;
}
pvs->selector = &temp;
}
else // object/word and object/value case:
pvs->selector = pvs->item;
switch (dispatcher(pvs)) {
case PE_OK:
break;
case PE_SET_IF_END:
if (pvs->opt_setval && IS_END(pvs->item + 1)) {
*pvs->value = *pvs->opt_setval;
pvs->opt_setval = NULL;
}
break;
case PE_NONE:
SET_NONE(pvs->store);
case PE_USE_STORE:
pvs->value = pvs->store;
break;
default:
assert(FALSE);
}
if (NOT_END(pvs->item + 1)) return Next_Path_Throws(pvs);
return FALSE;
}
//
// Do_Path_Throws: C
//
// Evaluate an ANY_PATH! REBVAL, starting from the index position of that
// path value and continuing to the end.
//
// The evaluator may throw because GROUP! is evaluated, e.g. `foo/(throw 1020)`
//
// If label_sym is passed in as being non-null, then the caller is implying
// readiness to process a path which may be a function with refinements.
// These refinements will be left in order on the data stack in the case
// that `out` comes back as IS_FUNCTION().
//
// If `opt_setval` is given, the path operation will be done as a "SET-PATH!"
// if the path evaluation did not throw or error. HOWEVER the set value
// is NOT put into `out`. This provides more flexibility on performance in
// the evaluator, which may already have the `val` where it wants it, and
// so the extra assignment would just be overhead.
//
// !!! Path evaluation is one of the parts of R3-Alpha that has not been
// vetted very heavily by Ren-C, and needs a review and overhaul.
//
REBOOL Do_Path_Throws(
REBVAL *out,
REBSYM *label_sym,
const REBVAL *path,
REBVAL *opt_setval
) {
REBPVS pvs;
REBDSP dsp_orig = DSP;
assert(ANY_PATH(path));
// !!! There is a bug in the dispatch such that if you are running a
// set path, it does not always assign the output, because it "thinks you
// aren't going to look at it". This presumably originated from before
// parens were allowed in paths, and neglects cases like:
//
// foo/(throw 1020): value
//
// We always have to check to see if a throw occurred. Until this is
// streamlined, we have to at minimum set it to something that is *not*
// thrown so that we aren't testing uninitialized memory. A safe trash
// will do, which is unset in release builds.
//
if (opt_setval)
SET_TRASH_SAFE(out);
// None of the values passed in can live on the data stack, because
// they might be relocated during the path evaluation process.
//
assert(!IN_DATA_STACK(out));
assert(!IN_DATA_STACK(path));
assert(!opt_setval || !IN_DATA_STACK(opt_setval));
// Not currently robust for reusing passed in path or value as the output
assert(out != path && out != opt_setval);
assert(!opt_setval || !THROWN(opt_setval));
// Initialize REBPVS -- see notes in %sys-do.h
//
pvs.opt_setval = opt_setval;
pvs.store = out;
pvs.orig = path;
pvs.item = VAL_ARRAY_AT(pvs.orig); // may not be starting at head of PATH!
// Seed the path evaluation process by looking up the first item (to
// get a datatype to dispatch on for the later path items)
//
if (IS_WORD(pvs.item)) {
pvs.value = GET_MUTABLE_VAR_MAY_FAIL(pvs.item);
if (IS_UNSET(pvs.value))
fail (Error(RE_NO_VALUE, pvs.item));
}
else {
// !!! Ideally there would be some way to protect pvs.value during
// successive path dispatches to make sure it does not get written.
// This is semi-dangerously giving pvs.value a reference into the
// input path, which should not be modified!
pvs.value = VAL_ARRAY_AT(pvs.orig);
}
// Start evaluation of path:
if (IS_END(pvs.item + 1)) {
// If it was a single element path, return the value rather than
// try to dispatch it (would cause a crash at time of writing)
//
// !!! Is this the desired behavior, or should it be an error?
}
else if (Path_Dispatch[VAL_TYPE_0(pvs.value)]) {
REBOOL threw = Next_Path_Throws(&pvs);
// !!! See comments about why the initialization of out is necessary.
// Without it this assertion can change on some things:
//
// t: now
// t/time: 10:20:03
//
// (It thinks pvs.value has its THROWN bit set when it completed
// successfully. It was a PE_USE_STORE case where pvs.value was reset to
// pvs.store, and pvs.store has its thrown bit set. Valgrind does not
// catch any uninitialized variables.)
//
// There are other cases that do trip valgrind when omitting the
// initialization, though not as clearly reproducible.
//
assert(threw == THROWN(pvs.value));
if (threw) return TRUE;
// Check for errors:
if (NOT_END(pvs.item + 1) && !IS_FUNCTION(pvs.value)) {
// Only function refinements should get by this line:
fail (Error(RE_INVALID_PATH, pvs.orig, pvs.item));
}
}
else if (!IS_FUNCTION(pvs.value))
fail (Error(RE_BAD_PATH_TYPE, pvs.orig, Type_Of(pvs.value)));
if (opt_setval) {
// If SET then we don't return anything
assert(IS_END(pvs.item) + 1);
return FALSE;
}
// If storage was not used, then copy final value back to it:
if (pvs.value != pvs.store) *pvs.store = *pvs.value;
assert(!THROWN(out));
// Return 0 if not function or is :path/word...
if (!IS_FUNCTION(pvs.value)) {
assert(IS_END(pvs.item) + 1);
return FALSE;
}
if (label_sym) {
REBVAL refinement;
VAL_INIT_WRITABLE_DEBUG(&refinement);
// When a function is hit, path processing stops as soon as the
// processed sub-path resolves to a function. The path is still sitting
// on the position of the last component of that sub-path. Usually,
// this last component in the sub-path is a word naming the function.
//
if (IS_WORD(pvs.item)) {
*label_sym = VAL_WORD_SYM(pvs.item);
}
else {
// In rarer cases, the final component (completing the sub-path to
// the function to call) is not a word. Such as when you use a path
// to pick by index out of a block of functions:
//
// functions: reduce [:add :subtract]
// functions/1 10 20
//
// Or when you have an immediate function value in a path with a
// refinement. Tricky to make, but possible:
//
// do reduce [
// to-path reduce [:append 'only] [a] [b]
// ]
//
// !!! When a function was not invoked through looking up a word
// (or a word in a path) to use as a label, there were once three
// different alternate labels used. One was SYM__APPLY_, another
// was ROOT_NONAME, and another was to be the type of the function
// being executed. None are fantastic, we do the type for now.
*label_sym = SYM_FROM_KIND(VAL_TYPE(pvs.value));
}
// Move on to the refinements (if any)
++pvs.item;
// !!! Currently, the mainline path evaluation "punts" on refinements.
// When it finds a function, it stops the path evaluation and leaves
// the position pvs.path before the list of refinements.
//
// A more elegant solution would be able to process and notice (for
// instance) that `:APPEND/ONLY` should yield a function value that
// has been specialized with a refinement. Path chaining should thus
// be able to effectively do this and give the refined function object
// back to the evaluator or other client.
//
// If a label_sym is passed in, we recognize that a function dispatch
// is going to be happening. We do not want to pay to generate the
// new series that would be needed to make a temporary function that
// will be invoked and immediately GC'd So we gather the refinements
// on the data stack.
//
// This code simulates that path-processing-to-data-stack, but it
// should really be something in dispatch iself. In any case, we put
// refinements on the data stack...and caller knows refinements are
// from dsp_orig to DSP (thanks to accounting, all other operations
// should balance!)
for (; NOT_END(pvs.item); ++pvs.item) { // "the refinements"
if (IS_NONE(pvs.item)) continue;
if (IS_GROUP(pvs.item)) {
// Note it is not legal to use the data stack directly as the
// output location for a DO (might be resized)
if (DO_VAL_ARRAY_AT_THROWS(&refinement, pvs.item)) {
*out = refinement;
DS_DROP_TO(dsp_orig);
return TRUE;
}
if (IS_NONE(&refinement)) continue;
DS_PUSH(&refinement);
}
else if (IS_GET_WORD(pvs.item)) {
DS_PUSH_TRASH;
*DS_TOP = *GET_OPT_VAR_MAY_FAIL(pvs.item);
if (IS_NONE(DS_TOP)) {
DS_DROP;
continue;
}
}
else DS_PUSH(pvs.item);
// Whatever we were trying to use as a refinement should now be
// on the top of the data stack, and only words are legal ATM
//
if (!IS_WORD(DS_TOP))
fail (Error(RE_BAD_REFINE, DS_TOP));
// Go ahead and canonize the word symbol so we don't have to
// do it each time in order to get a case-insenstive compare
//
INIT_WORD_SYM(DS_TOP, SYMBOL_TO_CANON(VAL_WORD_SYM(DS_TOP)));
}
// To make things easier for processing, reverse the refinements on
// the data stack (we needed to evaluate them in forward order).
// This way we can just pop them as we go, and know if they weren't
// all consumed if it doesn't get back to `dsp_orig` by the end.
if (dsp_orig != DSP) {
REBVAL *bottom = DS_AT(dsp_orig + 1);
REBVAL *top = DS_TOP;
while (top > bottom) {
refinement = *bottom;
*bottom = *top;
*top = refinement;
top--;
bottom++;
}
}
}
else {
// !!! Historically this just ignores a result indicating this is a
// function with refinements, e.g. ':append/only'. However that
// ignoring seems unwise. It should presumably create a modified
// function in that case which acts as if it has the refinement.
//
// If the caller did not pass in a label pointer we assume they are
// likely not ready to process any refinements.
//
if (NOT_END(pvs.item + 1))
fail (Error(RE_TOO_LONG)); // !!! Better error or add feature
}
return FALSE;
}
//
// Next_Path_Throws: C
//
// Evaluate next part of a path.
//
REBOOL Next_Path_Throws(REBPVS *pvs)
{
REBPEF dispatcher;
// Path must have dispatcher, else return:
dispatcher = Path_Dispatch[VAL_TYPE(pvs->value)];
if (!dispatcher) return FALSE; // unwind, then check for errors
pvs->item++;
//Debug_Fmt("Next_Path: %r/%r", pvs->path-1, pvs->path);
// Determine the "selector". See notes on pvs->selector_temp for why
// a local variable can't be used for the temporary space.
//
if (IS_GET_WORD(pvs->item)) { // e.g. object/:field
pvs->selector
= GET_MUTABLE_VAR_MAY_FAIL(pvs->item, pvs->item_specifier);
if (IS_VOID(pvs->selector))
fail (Error_No_Value_Core(pvs->item, pvs->item_specifier));
SET_TRASH_IF_DEBUG(&pvs->selector_temp);
}
// object/(expr) case:
else if (IS_GROUP(pvs->item)) {
if (Do_At_Throws(
&pvs->selector_temp,
VAL_ARRAY(pvs->item),
VAL_INDEX(pvs->item),
IS_RELATIVE(pvs->item)
? pvs->item_specifier // if relative, use parent specifier...
: VAL_SPECIFIER(const_KNOWN(pvs->item)) // ...else use child's
)) {
*pvs->store = pvs->selector_temp;
return TRUE;
}
pvs->selector = &pvs->selector_temp;
}
else {
// object/word and object/value case:
//
COPY_VALUE(&pvs->selector_temp, pvs->item, pvs->item_specifier);
pvs->selector = &pvs->selector_temp;
}
switch (dispatcher(pvs)) {
case PE_OK:
break;
case PE_SET_IF_END:
if (pvs->opt_setval && IS_END(pvs->item + 1)) {
*pvs->value = *pvs->opt_setval;
pvs->opt_setval = NULL;
}
break;
case PE_NONE:
SET_BLANK(pvs->store);
case PE_USE_STORE:
pvs->value = pvs->store;
pvs->value_specifier = SPECIFIED;
break;
default:
assert(FALSE);
}
if (NOT_END(pvs->item + 1)) return Next_Path_Throws(pvs);
return FALSE;
}