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Code Issues 1 Releases Wiki Activity

Add error special form in Peg to allow construction of grammar errors

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for more useful grammars that could eventually be used in a compiler.
This commit is contained in:
Calvin Rose
2019-01-15 16:04:47 -05:00
parent 4eeadd7463
commit d0fc29338c
2 changed files with 32 additions and 16 deletions
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45
src/core/peg.c
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@@ -47,12 +47,12 @@ typedef enum {
RULE_POSITION, /* [] */
RULE_ARGUMENT, /* [argument-index] */
RULE_REPINDEX, /* [capture-index] */
RULE_BACKINDEX, /* [capture-index] */
RULE_CONSTANT, /* [constant] */
RULE_SUBSTITUTE, /* [rule] */
RULE_GROUP, /* [rule] */
RULE_REPLACE, /* [rule, constant] */
RULE_MATCHTIME, /* [rule, constant] */
RULE_ERROR, /* [rule] */
} Opcode;
/* Hold captured patterns and match state */
@@ -269,19 +269,12 @@ tail:
case RULE_REPINDEX:
{
int32_t index = ((int32_t *)rule)[1];
if (index >= s->captures->count) return NULL;
if (index < 0) index += s->captures->count;
if (index >= s->captures->count || index < 0) return NULL;
Janet capture = s->captures->data[index];
pushcap(s, capture, text, text);
return text;
}
case RULE_BACKINDEX:
{
int32_t index = ((int32_t *)rule)[1];
if (index >= s->captures->count) return NULL;
Janet capture = s->captures->data[s->captures->count - 1 - index];
pushcap(s, capture, text, text);
return text;
}
case RULE_CONSTANT:
{
pushcap(s, s->constants[rule[1]], text, text);
@@ -418,6 +411,27 @@ tail:
return result;
}
case RULE_ERROR:
{
int oldmode = s->mode;
s->mode = PEG_MODE_NORMAL;
int32_t old_cap = s->captures->count;
down1(s);
const uint8_t *result = peg_rule(s, s->bytecode + rule[1], text);
up1(s);
s->mode = oldmode;
if (!result) return NULL;
if (s->captures->count > old_cap) {
/* Throw last capture */
janet_panicv(s->captures->data[s->captures->count - 1]);
} else {
/* Throw generic error */
int32_t start = (int32_t)(text - s->text_start);
int32_t end = (int32_t)(result - s->text_start);
janet_panicf("match error in range (%d:%d)", start, end);
}
return NULL;
}
}
}
@@ -664,6 +678,9 @@ static void spec_substitute(Builder *b, int32_t argc, const Janet *argv) {
static void spec_group(Builder *b, int32_t argc, const Janet *argv) {
spec_onerule(b, argc, argv, RULE_GROUP);
}
static void spec_error(Builder *b, int32_t argc, const Janet *argv) {
spec_onerule(b, argc, argv, RULE_ERROR);
}
static void spec_between(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 3);
@@ -685,11 +702,7 @@ static void spec_reference(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 1);
Reserve r = reserve(b, 2);
int32_t index = peg_getinteger(b, argv[0]);
if (index < 0) {
emit_1(r, RULE_REPINDEX, -index - 1);
} else {
emit_1(r, RULE_BACKINDEX, index);
}
emit_1(r, RULE_REPINDEX, index);
}
static void spec_argument(Builder *b, int32_t argc, const Janet *argv) {
@@ -770,6 +783,7 @@ typedef struct {
Special special;
} SpecialPair;
/* Keep in lexical order (vim :sort works well) */
static const SpecialPair specials[] = {
{"!", spec_not},
{"$", spec_position},
@@ -790,6 +804,7 @@ static const SpecialPair specials[] = {
{"choice", spec_choice},
{"cmt", spec_matchtime},
{"constant", spec_constant},
{"error", spec_error},
{"group", spec_group},
{"if", spec_if},
{"if-not", spec_ifnot},