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Code Issues 1 Releases Wiki Activity

Add backmatch operator to pegs.

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(backmatch [tag?]) is similar to a back reference in regular expressions
(NOT to backwards capture in a peg). It only matches a pattern if
it exactly matches the text of the last capture. It does not consume
or push any captures to the capture stack.
This commit is contained in:
Calvin Rose 2019-08-24 18:57:01 -04:00
parent 78b5c94cb0
commit 711fe64a51
2 changed files with 53 additions and 2 deletions
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33
src/core/peg.c
View File

@ -59,6 +59,7 @@ typedef enum {
RULE_MATCHTIME, /* [rule, constant, tag] */
RULE_ERROR, /* [rule] */
RULE_DROP, /* [rule] */
RULE_BACKMATCH, /* [tag] */
} Opcode;
/* Hold captured patterns and match state */
@ -417,6 +418,24 @@ tail:
}
return NULL;
}
case RULE_BACKMATCH: {
uint32_t search = rule[1];
for (int32_t i = s->tags->count - 1; i >= 0; i--) {
if (s->tags->data[i] == search) {
Janet capture = s->captures->data[i];
if (!janet_checktype(capture, JANET_STRING))
return NULL;
const uint8_t *bytes = janet_unwrap_string(capture);
int32_t len = janet_string_length(bytes);
if (text + len > s->text_end)
return NULL;
return memcmp(text, bytes, len) ? NULL : text + len;
}
}
return NULL;
}
}
}
@ -754,12 +773,20 @@ static void spec_reference(Builder *b, int32_t argc, const Janet *argv) {
emit_2(r, RULE_GETTAG, search, tag);
}
static void spec_position(Builder *b, int32_t argc, const Janet *argv) {
static void spec_tag1(Builder *b, int32_t argc, const Janet *argv, uint32_t op) {
peg_arity(b, argc, 0, 1);
Reserve r = reserve(b, 2);
uint32_t tag = (argc) ? emit_tag(b, argv[0]) : 0;
(void) argv;
emit_1(r, RULE_POSITION, tag);
emit_1(r, op, tag);
}
static void spec_position(Builder *b, int32_t argc, const Janet *argv) {
spec_tag1(b, argc, argv, RULE_POSITION);
}
static void spec_backmatch(Builder *b, int32_t argc, const Janet *argv) {
spec_tag1(b, argc, argv, RULE_BACKMATCH);
}
static void spec_argument(Builder *b, int32_t argc, const Janet *argv) {
@ -824,6 +851,7 @@ static const SpecialPair peg_specials[] = {
{"argument", spec_argument},
{"at-least", spec_atleast},
{"at-most", spec_atmost},
{"backmatch", spec_backmatch},
{"backref", spec_reference},
{"between", spec_between},
{"capture", spec_capture},
@ -1029,6 +1057,7 @@ static void peg_unmarshal(void *p, JanetMarshalContext *ctx) {
case RULE_NOTNCHAR:
case RULE_RANGE:
case RULE_POSITION:
case RULE_BACKMATCH:
/* [1 word] */
i += 2;
break;

22
test/suite3.janet
View File

@ -356,6 +356,28 @@
(check-match janet-longstring "``` `` ```" true)
(check-match janet-longstring "`` ```" false)
# Backmatch
(def backmatcher-1 '(* (capture (any "x") :1) "y" (backmatch :1) -1))
(check-match backmatcher-1 "y" true)
(check-match backmatcher-1 "xyx" true)
(check-match backmatcher-1 "xxxxxxxyxxxxxxx" true)
(check-match backmatcher-1 "xyxx" false)
(check-match backmatcher-1 "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxy" false)
(check-match backmatcher-1 (string (string/repeat "x" 10000) "y") false)
(check-match backmatcher-1 (string (string/repeat "x" 10000) "y" (string/repeat "x" 10000)) true)
(def backmatcher-2 '(* '(any "x") "y" (backmatch) -1))
(check-match backmatcher-2 "y" true)
(check-match backmatcher-2 "xyx" true)
(check-match backmatcher-2 "xxxxxxxyxxxxxxx" true)
(check-match backmatcher-2 "xyxx" false)
(check-match backmatcher-2 "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxy" false)
(check-match backmatcher-2 (string (string/repeat "x" 10000) "y") false)
(check-match backmatcher-2 (string (string/repeat "x" 10000) "y" (string/repeat "x" 10000)) true)
# Optional
(check-match '(* (opt "hi") -1) "" true)