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difference and xor combinators done.

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This commit is contained in:
Meredith L. Patterson 2012-05-03 02:31:22 +01:00
parent 3016fd2460
commit 709884faf5
3 changed files with 89 additions and 5 deletions
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76
src/hammer.c
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@ -292,7 +292,7 @@ static parse_result_t* parse_butnot(void *env, parse_state_t *state) {
// cache the initial state of the input stream
input_stream_t start_state = state->input_stream;
parse_result_t *r1 = do_parse(parsers->p1, state);
// if r1 is null, bail out early
// if p1 failed, bail out early
if (NULL == r1) {
return NULL;
}
@ -302,7 +302,7 @@ static parse_result_t* parse_butnot(void *env, parse_state_t *state) {
parse_result_t *r2 = do_parse(parsers->p2, state);
// TODO(mlp): I'm pretty sure the input stream state should be the post-p1 state in all cases
state->input_stream = after_p1_state;
// if r2 is null, restore post-p1 state and bail out early
// if p2 failed, restore post-p1 state and bail out early
if (NULL == r2) {
return r1;
}
@ -324,8 +324,76 @@ const parser_t* butnot(const parser_t* p1, const parser_t* p2) {
return ret;
}
const parser_t* difference(const parser_t* p1, const parser_t* p2) { return NULL; }
const parser_t* xor(const parser_t* p1, const parser_t* p2) { return NULL; }
static parse_result_t* parse_difference(void *env, parse_state_t *state) {
two_parsers_t *parsers = (two_parsers_t*)env;
// cache the initial state of the input stream
input_stream_t start_state = state->input_stream;
parse_result_t *r1 = do_parse(parsers->p1, state);
// if p1 failed, bail out early
if (NULL == r1) {
return NULL;
}
// cache the state after parse #1, since we might have to back up to it
input_stream_t after_p1_state = state->input_stream;
state->input_stream = start_state;
parse_result_t *r2 = do_parse(parsers->p2, state);
// TODO(mlp): I'm pretty sure the input stream state should be the post-p1 state in all cases
state->input_stream = after_p1_state;
// if p2 failed, restore post-p1 state and bail out early
if (NULL == r2) {
return r1;
}
size_t r1len = token_length(r1);
size_t r2len = token_length(r2);
// if both match but p1's text is shorter than p2's, fail
if (r1len < r2len) {
return NULL;
} else {
return r1;
}
}
const parser_t* difference(const parser_t* p1, const parser_t* p2) {
two_parsers_t *env = g_new(two_parsers_t, 1);
env->p1 = p1; env->p2 = p2;
parser_t *ret = g_new(parser_t, 1);
ret->fn = parse_difference; ret->env = (void*)env;
return ret;
}
static parse_result_t* parse_xor(void *env, parse_state_t *state) {
two_parsers_t *parsers = (two_parsers_t*)env;
// cache the initial state of the input stream
input_stream_t start_state = state->input_stream;
parse_result_t *r1 = do_parse(parsers->p1, state);
input_stream_t after_p1_state = state->input_stream;
// reset input stream, parse again
state->input_stream = start_state;
parse_result_t *r2 = do_parse(parsers->p2, state);
if (NULL == r1) {
if (NULL != r2) {
return r2;
} else {
return NULL;
}
} else {
if (NULL == r2) {
state->input_stream = after_p1_state;
return r1;
} else {
return NULL;
}
}
}
const parser_t* xor(const parser_t* p1, const parser_t* p2) {
two_parsers_t *env = g_new(two_parsers_t, 1);
env->p1 = p1; env->p2 = p2;
parser_t *ret = g_new(parser_t, 1);
ret->fn = parse_xor; ret->env = (void*)env;
return ret;
}
const parser_t* repeat0(const parser_t* p) { return NULL; }
const parser_t* repeat1(const parser_t* p) { return NULL; }
const parser_t* repeat_n(const parser_t* p, const size_t n) { return NULL; }