54 lines
1.4 KiB
C
54 lines
1.4 KiB
C
#include "parser_internal.h"
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typedef struct {
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const HParser *p1;
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const HParser *p2;
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} HTwoParsers;
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static HParseResult* parse_xor(void *env, HParseState *state) {
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HTwoParsers *parsers = (HTwoParsers*)env;
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// cache the initial state of the input stream
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HInputStream start_state = state->input_stream;
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HParseResult *r1 = h_do_parse(parsers->p1, state);
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HInputStream after_p1_state = state->input_stream;
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// reset input stream, parse again
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state->input_stream = start_state;
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HParseResult *r2 = h_do_parse(parsers->p2, state);
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if (NULL == r1) {
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if (NULL != r2) {
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return r2;
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} else {
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return NULL;
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}
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} else {
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if (NULL == r2) {
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state->input_stream = after_p1_state;
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return r1;
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} else {
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return NULL;
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}
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}
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}
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static HCFChoice* desugar_xor(HAllocator *mm__, void *env) {
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assert_message(0, "'h_xor' is not context-free, can't be desugared");
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return NULL;
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}
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static const HParserVtable xor_vt = {
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.parse = parse_xor,
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.isValidRegular = h_false,
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.isValidCF = h_false,
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.desugar = desugar_xor,
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};
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const HParser* h_xor(const HParser* p1, const HParser* p2) {
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return h_xor__m(&system_allocator, p1, p2);
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}
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const HParser* h_xor__m(HAllocator* mm__, const HParser* p1, const HParser* p2) {
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HTwoParsers *env = h_new(HTwoParsers, 1);
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env->p1 = p1;
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env->p2 = p2;
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return h_new_parser(mm__, &xor_vt, env);
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}
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