1
0
mirror of https://github.com/janet-lang/janet synced 2024-12-25 07:50:27 +00:00

Add some preliminary capturing ability to PEGs.

This commit is contained in:
Calvin Rose 2019-01-11 21:09:49 -05:00
parent 40845b5c1b
commit 1efca2ebe7

View File

@ -43,6 +43,7 @@ typedef struct {
const uint8_t *text_start;
const uint8_t *text_end;
JanetTable *grammar;
JanetArray *captures;
int flags;
} State;
@ -56,6 +57,10 @@ typedef struct {
Matcher matcher;
} MatcherPair;
/*
* Primitive Pattern Types
*/
/* Match a character range */
int32_t match_range(State *s, int32_t argc, const Janet *argv, const uint8_t *text) {
if (s->text_end <= text)
@ -82,6 +87,10 @@ int32_t match_set(State *s, int32_t argc, const Janet *argv, const uint8_t *text
return -1;
}
/*
* Combining Pattern Types
*/
/* Match the first of argv[0], argv[1], argv[2], ... */
int32_t match_choice(State *s, int32_t argc, const Janet *argv, const uint8_t *text) {
for (int32_t i = 0; i < argc; i++) {
@ -173,11 +182,57 @@ int32_t match_between(State *s, int32_t argc, const Janet *argv, const uint8_t *
return captured >= lo ? total_length : -1;
}
/* Capture a value */
int32_t match_capture(State *s, int32_t argc, const Janet *argv, const uint8_t *text) {
janet_fixarity(argc, 1);
int32_t result = match(s, argv[0], text);
if (result < 0) return -1;
janet_array_push(s->captures, janet_stringv(text, result));
return result;
}
/* Capture position */
int32_t match_position(State *s, int32_t argc, const Janet *argv, const uint8_t *text) {
janet_fixarity(argc, 0);
(void) argv;
janet_array_push(s->captures, janet_wrap_number(text - s->text_start));
return 0;
}
/* Capture group */
int32_t match_group(State *s, int32_t argc, const Janet *argv, const uint8_t *text) {
janet_fixarity(argc, 1);
int32_t old_count = s->captures->count;
int32_t result = match(s, argv[0], text);
if (result < 0) return -1;
/* Collect sub-captures into an array by popping new values off of the capture stack,
* and then putting them in a new array. Then, push hte new array back onto the capture stack. */
int32_t num_sub_captures = s->captures->count - old_count;
JanetArray *sub_captures = janet_array(num_sub_captures);
memcpy(sub_captures->data, s->captures->data + old_count, sizeof(Janet) * num_sub_captures);
sub_captures->count = num_sub_captures;
s->captures->count = old_count;
janet_array_push(s->captures, janet_wrap_array(sub_captures));
return result;
}
/* Capture a constant */
int32_t match_capture_constant(State *s, int32_t argc, const Janet *argv, const uint8_t *text) {
(void) text;
janet_fixarity(argc, 1);
janet_array_push(s->captures, argv[0]);
return 0;
}
/* Lookup for special forms */
static const MatcherPair specials[] = {
{"*", match_sequence},
{"+", match_choice},
{"-", match_minus},
{"<-", match_capture},
{"<-c", match_capture_constant},
{"<-p", match_position},
{"<-g", match_group},
{">", match_lookahead},
{"at-least", match_atleast},
{"at-most", match_atmost},
@ -228,8 +283,11 @@ static int32_t match(State *s, Janet peg, const uint8_t *text) {
if (!mp) janet_panicf("unknown special form %v", peg);
if (s->depth-- == 0)
janet_panic("recursed too deeply");
int32_t old_capture_count = s->captures->count;
int32_t result = mp->matcher(s, len - 1, items + 1, text);
s->depth++;
if (result < 0)
s->captures->count = old_capture_count;
return result;
}
case JANET_KEYWORD:
@ -261,8 +319,9 @@ static Janet cfun_match(int32_t argc, Janet *argv) {
s.text_end = bytes.bytes + bytes.len;
s.depth = JANET_RECURSION_GUARD;
s.grammar = NULL;
s.captures = janet_array(10);
int32_t result = match(&s, argv[0], bytes.bytes);
return janet_wrap_boolean(result >= 0);
return result >= 0 ? janet_wrap_array(s.captures) : janet_wrap_nil();
}
static const JanetReg cfuns[] = {