424 lines
17 KiB
C++
424 lines
17 KiB
C++
#include "grammar-parser.h"
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#include <cstdint>
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#include <cwchar>
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#include <string>
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#include <utility>
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#include <stdexcept>
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#include <exception>
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namespace grammar_parser {
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// NOTE: assumes valid utf8 (but checks for overrun)
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// copied from whisper.cpp
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std::pair<uint32_t, const char *> decode_utf8(const char * src) {
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static const int lookup[] = { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 4 };
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uint8_t first_byte = static_cast<uint8_t>(*src);
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uint8_t highbits = first_byte >> 4;
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int len = lookup[highbits];
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uint8_t mask = (1 << (8 - len)) - 1;
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uint32_t value = first_byte & mask;
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const char * end = src + len; // may overrun!
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const char * pos = src + 1;
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for ( ; pos < end && *pos; pos++) {
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value = (value << 6) + (static_cast<uint8_t>(*pos) & 0x3F);
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}
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return std::make_pair(value, pos);
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}
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uint32_t get_symbol_id(parse_state & state, const char * src, size_t len) {
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uint32_t next_id = static_cast<uint32_t>(state.symbol_ids.size());
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auto result = state.symbol_ids.insert(std::make_pair(std::string(src, len), next_id));
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return result.first->second;
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}
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uint32_t generate_symbol_id(parse_state & state, const std::string & base_name) {
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uint32_t next_id = static_cast<uint32_t>(state.symbol_ids.size());
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state.symbol_ids[base_name + '_' + std::to_string(next_id)] = next_id;
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return next_id;
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}
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void add_rule(
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parse_state & state,
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uint32_t rule_id,
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const std::vector<whisper_grammar_element> & rule) {
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if (state.rules.size() <= rule_id) {
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state.rules.resize(rule_id + 1);
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}
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state.rules[rule_id] = rule;
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}
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bool is_word_char(char c) {
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return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || c == '-' || ('0' <= c && c <= '9');
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}
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std::pair<uint32_t, const char *> parse_hex(const char * src, int size) {
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const char * pos = src;
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const char * end = src + size;
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uint32_t value = 0;
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for ( ; pos < end && *pos; pos++) {
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value <<= 4;
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char c = *pos;
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if ('a' <= c && c <= 'f') {
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value += c - 'a' + 10;
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} else if ('A' <= c && c <= 'F') {
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value += c - 'A' + 10;
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} else if ('0' <= c && c <= '9') {
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value += c - '0';
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} else {
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break;
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}
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}
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if (pos != end) {
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throw std::runtime_error("expecting " + std::to_string(size) + " hex chars at " + src);
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}
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return std::make_pair(value, pos);
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}
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const char * parse_space(const char * src, bool newline_ok) {
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const char * pos = src;
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while (*pos == ' ' || *pos == '\t' || *pos == '#' ||
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(newline_ok && (*pos == '\r' || *pos == '\n'))) {
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if (*pos == '#') {
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while (*pos && *pos != '\r' && *pos != '\n') {
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pos++;
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}
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} else {
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pos++;
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}
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}
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return pos;
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}
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const char * parse_name(const char * src) {
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const char * pos = src;
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while (is_word_char(*pos)) {
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pos++;
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}
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if (pos == src) {
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throw std::runtime_error(std::string("expecting name at ") + src);
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}
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return pos;
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}
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std::pair<uint32_t, const char *> parse_char(const char * src) {
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if (*src == '\\') {
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switch (src[1]) {
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case 'x': return parse_hex(src + 2, 2);
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case 'u': return parse_hex(src + 2, 4);
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case 'U': return parse_hex(src + 2, 8);
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case 't': return std::make_pair('\t', src + 2);
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case 'r': return std::make_pair('\r', src + 2);
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case 'n': return std::make_pair('\n', src + 2);
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case '\\':
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case '"':
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case '[':
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case ']':
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return std::make_pair(src[1], src + 2);
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default:
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throw std::runtime_error(std::string("unknown escape at ") + src);
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}
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} else if (*src) {
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return decode_utf8(src);
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}
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throw std::runtime_error("unexpected end of input");
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}
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const char * parse_alternates(
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parse_state & state,
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const char * src,
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const std::string & rule_name,
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uint32_t rule_id,
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bool is_nested);
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const char * parse_sequence(
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parse_state & state,
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const char * src,
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const std::string & rule_name,
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std::vector<whisper_grammar_element> & out_elements,
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bool is_nested) {
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size_t last_sym_start = out_elements.size();
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const char * pos = src;
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while (*pos) {
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if (*pos == '"') { // literal string
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pos++;
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last_sym_start = out_elements.size();
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while (*pos != '"') {
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auto char_pair = parse_char(pos);
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pos = char_pair.second;
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out_elements.push_back({WHISPER_GRETYPE_CHAR, char_pair.first});
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}
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pos = parse_space(pos + 1, is_nested);
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} else if (*pos == '[') { // char range(s)
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pos++;
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enum whisper_gretype start_type = WHISPER_GRETYPE_CHAR;
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if (*pos == '^') {
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pos++;
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start_type = WHISPER_GRETYPE_CHAR_NOT;
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}
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last_sym_start = out_elements.size();
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while (*pos != ']') {
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auto char_pair = parse_char(pos);
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pos = char_pair.second;
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enum whisper_gretype type = last_sym_start < out_elements.size()
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? WHISPER_GRETYPE_CHAR_ALT
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: start_type;
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out_elements.push_back({type, char_pair.first});
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if (pos[0] == '-' && pos[1] != ']') {
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auto endchar_pair = parse_char(pos + 1);
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pos = endchar_pair.second;
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out_elements.push_back({WHISPER_GRETYPE_CHAR_RNG_UPPER, endchar_pair.first});
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}
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}
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pos = parse_space(pos + 1, is_nested);
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} else if (is_word_char(*pos)) { // rule reference
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const char * name_end = parse_name(pos);
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uint32_t ref_rule_id = get_symbol_id(state, pos, name_end - pos);
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pos = parse_space(name_end, is_nested);
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last_sym_start = out_elements.size();
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out_elements.push_back({WHISPER_GRETYPE_RULE_REF, ref_rule_id});
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} else if (*pos == '(') { // grouping
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// parse nested alternates into synthesized rule
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pos = parse_space(pos + 1, true);
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uint32_t sub_rule_id = generate_symbol_id(state, rule_name);
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pos = parse_alternates(state, pos, rule_name, sub_rule_id, true);
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last_sym_start = out_elements.size();
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// output reference to synthesized rule
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out_elements.push_back({WHISPER_GRETYPE_RULE_REF, sub_rule_id});
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if (*pos != ')') {
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throw std::runtime_error(std::string("expecting ')' at ") + pos);
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}
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pos = parse_space(pos + 1, is_nested);
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} else if (*pos == '*' || *pos == '+' || *pos == '?') { // repetition operator
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if (last_sym_start == out_elements.size()) {
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throw std::runtime_error(std::string("expecting preceeding item to */+/? at ") + pos);
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}
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// apply transformation to previous symbol (last_sym_start to end) according to
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// rewrite rules:
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// S* --> S' ::= S S' |
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// S+ --> S' ::= S S' | S
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// S? --> S' ::= S |
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uint32_t sub_rule_id = generate_symbol_id(state, rule_name);
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std::vector<whisper_grammar_element> sub_rule;
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// add preceding symbol to generated rule
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sub_rule.insert(
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sub_rule.end(), out_elements.begin() + last_sym_start, out_elements.end());
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if (*pos == '*' || *pos == '+') {
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// cause generated rule to recurse
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sub_rule.push_back({WHISPER_GRETYPE_RULE_REF, sub_rule_id});
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}
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// mark start of alternate def
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sub_rule.push_back({WHISPER_GRETYPE_ALT, 0});
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if (*pos == '+') {
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// add preceding symbol as alternate only for '+' (otherwise empty)
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sub_rule.insert(
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sub_rule.end(), out_elements.begin() + last_sym_start, out_elements.end());
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}
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sub_rule.push_back({WHISPER_GRETYPE_END, 0});
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add_rule(state, sub_rule_id, sub_rule);
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// in original rule, replace previous symbol with reference to generated rule
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out_elements.resize(last_sym_start);
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out_elements.push_back({WHISPER_GRETYPE_RULE_REF, sub_rule_id});
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pos = parse_space(pos + 1, is_nested);
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} else {
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break;
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}
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}
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return pos;
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}
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const char * parse_alternates(
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parse_state & state,
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const char * src,
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const std::string & rule_name,
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uint32_t rule_id,
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bool is_nested) {
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std::vector<whisper_grammar_element> rule;
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const char * pos = parse_sequence(state, src, rule_name, rule, is_nested);
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while (*pos == '|') {
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rule.push_back({WHISPER_GRETYPE_ALT, 0});
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pos = parse_space(pos + 1, true);
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pos = parse_sequence(state, pos, rule_name, rule, is_nested);
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}
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rule.push_back({WHISPER_GRETYPE_END, 0});
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add_rule(state, rule_id, rule);
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return pos;
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}
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const char * parse_rule(parse_state & state, const char * src) {
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const char * name_end = parse_name(src);
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const char * pos = parse_space(name_end, false);
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size_t name_len = name_end - src;
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uint32_t rule_id = get_symbol_id(state, src, name_len);
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const std::string name(src, name_len);
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if (!(pos[0] == ':' && pos[1] == ':' && pos[2] == '=')) {
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throw std::runtime_error(std::string("expecting ::= at ") + pos);
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}
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pos = parse_space(pos + 3, true);
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pos = parse_alternates(state, pos, name, rule_id, false);
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if (*pos == '\r') {
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pos += pos[1] == '\n' ? 2 : 1;
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} else if (*pos == '\n') {
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pos++;
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} else if (*pos) {
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throw std::runtime_error(std::string("expecting newline or end at ") + pos);
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}
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return parse_space(pos, true);
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}
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parse_state parse(const char * src) {
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try {
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parse_state state;
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const char * pos = parse_space(src, true);
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while (*pos) {
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pos = parse_rule(state, pos);
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}
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return state;
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} catch (const std::exception & err) {
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fprintf(stderr, "%s: error parsing grammar: %s\n", __func__, err.what());
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return parse_state();
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}
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}
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void print_grammar_char(FILE * file, uint32_t c) {
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if (0x20 <= c && c <= 0x7f) {
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fprintf(file, "%c", static_cast<char>(c));
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} else {
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// cop out of encoding UTF-8
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fprintf(file, "<U+%04X>", c);
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}
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}
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bool is_char_element(whisper_grammar_element elem) {
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switch (elem.type) {
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case WHISPER_GRETYPE_CHAR: return true;
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case WHISPER_GRETYPE_CHAR_NOT: return true;
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case WHISPER_GRETYPE_CHAR_ALT: return true;
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case WHISPER_GRETYPE_CHAR_RNG_UPPER: return true;
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default: return false;
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}
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}
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void print_rule_binary(FILE * file, const std::vector<whisper_grammar_element> & rule) {
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for (auto elem : rule) {
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switch (elem.type) {
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case WHISPER_GRETYPE_END: fprintf(file, "END"); break;
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case WHISPER_GRETYPE_ALT: fprintf(file, "ALT"); break;
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case WHISPER_GRETYPE_RULE_REF: fprintf(file, "RULE_REF"); break;
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case WHISPER_GRETYPE_CHAR: fprintf(file, "CHAR"); break;
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case WHISPER_GRETYPE_CHAR_NOT: fprintf(file, "CHAR_NOT"); break;
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case WHISPER_GRETYPE_CHAR_RNG_UPPER: fprintf(file, "CHAR_RNG_UPPER"); break;
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case WHISPER_GRETYPE_CHAR_ALT: fprintf(file, "CHAR_ALT"); break;
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}
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switch (elem.type) {
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case WHISPER_GRETYPE_END:
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case WHISPER_GRETYPE_ALT:
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case WHISPER_GRETYPE_RULE_REF:
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fprintf(file, "(%u) ", elem.value);
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break;
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case WHISPER_GRETYPE_CHAR:
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case WHISPER_GRETYPE_CHAR_NOT:
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case WHISPER_GRETYPE_CHAR_RNG_UPPER:
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case WHISPER_GRETYPE_CHAR_ALT:
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fprintf(file, "(\"");
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print_grammar_char(file, elem.value);
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fprintf(file, "\") ");
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break;
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}
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}
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fprintf(file, "\n");
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}
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void print_rule(
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FILE * file,
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uint32_t rule_id,
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const std::vector<whisper_grammar_element> & rule,
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const std::map<uint32_t, std::string> & symbol_id_names) {
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if (rule.empty() || rule.back().type != WHISPER_GRETYPE_END) {
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throw std::runtime_error(
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"malformed rule, does not end with WHISPER_GRETYPE_END: " + std::to_string(rule_id));
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}
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fprintf(file, "%s ::= ", symbol_id_names.at(rule_id).c_str());
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for (size_t i = 0, end = rule.size() - 1; i < end; i++) {
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whisper_grammar_element elem = rule[i];
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switch (elem.type) {
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case WHISPER_GRETYPE_END:
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throw std::runtime_error(
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"unexpected end of rule: " + std::to_string(rule_id) + "," +
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std::to_string(i));
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case WHISPER_GRETYPE_ALT:
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fprintf(file, "| ");
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break;
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case WHISPER_GRETYPE_RULE_REF:
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fprintf(file, "%s ", symbol_id_names.at(elem.value).c_str());
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break;
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case WHISPER_GRETYPE_CHAR:
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fprintf(file, "[");
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print_grammar_char(file, elem.value);
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break;
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case WHISPER_GRETYPE_CHAR_NOT:
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fprintf(file, "[^");
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print_grammar_char(file, elem.value);
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break;
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case WHISPER_GRETYPE_CHAR_RNG_UPPER:
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if (i == 0 || !is_char_element(rule[i - 1])) {
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throw std::runtime_error(
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"WHISPER_GRETYPE_CHAR_RNG_UPPER without preceding char: " +
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std::to_string(rule_id) + "," + std::to_string(i));
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}
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fprintf(file, "-");
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print_grammar_char(file, elem.value);
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break;
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case WHISPER_GRETYPE_CHAR_ALT:
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if (i == 0 || !is_char_element(rule[i - 1])) {
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throw std::runtime_error(
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"WHISPER_GRETYPE_CHAR_ALT without preceding char: " +
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std::to_string(rule_id) + "," + std::to_string(i));
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}
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print_grammar_char(file, elem.value);
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break;
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}
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if (is_char_element(elem)) {
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switch (rule[i + 1].type) {
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case WHISPER_GRETYPE_CHAR_ALT:
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case WHISPER_GRETYPE_CHAR_RNG_UPPER:
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break;
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default:
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fprintf(file, "] ");
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}
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}
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}
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fprintf(file, "\n");
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}
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void print_grammar(FILE * file, const parse_state & state) {
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try {
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std::map<uint32_t, std::string> symbol_id_names;
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for (auto kv : state.symbol_ids) {
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symbol_id_names[kv.second] = kv.first;
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}
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for (size_t i = 0, end = state.rules.size(); i < end; i++) {
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// fprintf(file, "%zu: ", i);
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// print_rule_binary(file, state.rules[i]);
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print_rule(file, uint32_t(i), state.rules[i], symbol_id_names);
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// fprintf(file, "\n");
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}
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} catch (const std::exception & err) {
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fprintf(stderr, "\n%s: error printing grammar: %s\n", __func__, err.what());
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}
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}
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std::vector<const whisper_grammar_element *> parse_state::c_rules() const{
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std::vector<const whisper_grammar_element *> ret;
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for (const auto & rule : rules) {
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ret.push_back(rule.data());
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}
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return ret;
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}
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}
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