tree-sitter/src/runtime/lexer.c

#include <stdio.h>
#include "runtime/lexer.h"
#include "runtime/tree.h"
#include "runtime/length.h"
#include "runtime/utf16.h"
#include "utf8proc.h"

#define LOG(...)                                                              \
  if (self->logger.log) {                                                     \
    snprintf(self->debug_buffer, TS_DEBUG_BUFFER_SIZE, __VA_ARGS__);          \
    self->logger.log(self->logger.payload, TSLogTypeLex, self->debug_buffer); \
  }

#define LOG_LOOKAHEAD()                                            \
  LOG((0 < self->data.lookahead && self->data.lookahead < 256) \
        ? "lookahead char:'%c'"                                    \
        : "lookahead char:%d",                                     \
      self->data.lookahead);

static const char empty_chunk[2] = { 0, 0 };

static void ts_lexer__get_chunk(Lexer *self) {
  TSInput input = self->input;
  if (!self->chunk ||
      self->current_position.bytes != self->chunk_start + self->chunk_size)
    input.seek(input.payload, self->current_position.chars,
               self->current_position.bytes);

  self->chunk_start = self->current_position.bytes;
  self->chunk = input.read(input.payload, &self->chunk_size);
  if (!self->chunk_size)
    self->chunk = empty_chunk;
}

static void ts_lexer__get_lookahead(Lexer *self) {
  uint32_t position_in_chunk = self->current_position.bytes - self->chunk_start;
  const uint8_t *chunk = (const uint8_t *)self->chunk + position_in_chunk;
  uint32_t size = self->chunk_size - position_in_chunk + 1;

  if (self->input.encoding == TSInputEncodingUTF8)
    self->lookahead_size =
      utf8proc_iterate(chunk, size, &self->data.lookahead);
  else
    self->lookahead_size = utf16_iterate(chunk, size, &self->data.lookahead);

  LOG_LOOKAHEAD();
}

static void ts_lexer__advance(void *payload, TSStateId state, bool skip) {
  Lexer *self = (Lexer *)payload;
  if (self->chunk == empty_chunk)
    return;

  if (self->lookahead_size) {
    self->current_position.bytes += self->lookahead_size;
    self->current_position.chars++;
    if (self->data.lookahead == '\n') {
      self->current_position.extent.row++;
      self->current_position.extent.column = 0;
    } else {
      self->current_position.extent.column++;
    }
  }

  if (skip) {
    LOG("skip_separator state:%d", state);
    self->token_start_position = self->current_position;
  } else {
    LOG("advance state:%d", state);
  }

  if (self->current_position.bytes >= self->chunk_start + self->chunk_size)
    ts_lexer__get_chunk(self);

  ts_lexer__get_lookahead(self);
}

/*
 *  The lexer's advance method is stored as a struct field so that generated
 *  parsers can call it without needing to be linked against this library.
 */

void ts_lexer_init(Lexer *self) {
  *self = (Lexer){
    .data =
      {
        .advance = ts_lexer__advance, .lookahead = 0, .result_symbol = 0,
      },
    .chunk = NULL,
    .chunk_start = 0,
    .logger = {},
  };
  ts_lexer_reset(self, length_zero());
}

static inline void ts_lexer__reset(Lexer *self, Length position) {
  self->token_start_position = position;
  self->current_position = position;

  if (self->chunk && (position.bytes < self->chunk_start ||
                      position.bytes >= self->chunk_start + self->chunk_size)) {
    self->chunk = 0;
    self->chunk_start = 0;
    self->chunk_size = 0;
  }

  self->lookahead_size = 0;
  self->data.lookahead = 0;
}

void ts_lexer_set_input(Lexer *self, TSInput input) {
  self->input = input;
  ts_lexer__reset(self, length_zero());
}

void ts_lexer_reset(Lexer *self, Length position) {
  if (!length_eq(position, self->current_position))
    ts_lexer__reset(self, position);
  return;
}

void ts_lexer_start(Lexer *self, TSStateId lex_state) {
  LOG("start_lex state:%d, pos:%u", lex_state, self->current_position.chars);

  self->token_start_position = self->current_position;
  self->data.result_symbol = 0;

  if (!self->chunk)
    ts_lexer__get_chunk(self);
  if (!self->lookahead_size)
    ts_lexer__get_lookahead(self);
}