1 files changed, 391 insertions, 0 deletions

diff --git a/src/tree_sitter/lexer.c b/src/tree_sitter/lexer.c
new file mode 100644
index 0000000000..3f8a4c0ae8
--- /dev/null
+++ b/src/tree_sitter/lexer.c
@@ -0,0 +1,391 @@
+#include <stdio.h>
+#include "./lexer.h"
+#include "./subtree.h"
+#include "./length.h"
+#include "./unicode.h"
+
+#define LOG(message, character)              \
+  if (self->logger.log) {                    \
+    snprintf(                                \
+      self->debug_buffer,                    \
+      TREE_SITTER_SERIALIZATION_BUFFER_SIZE, \
+      32 <= character && character < 127 ?   \
+        message " character:'%c'" :          \
+        message " character:%d",             \
+      character                              \
+    );                                       \
+    self->logger.log(                        \
+      self->logger.payload,                  \
+      TSLogTypeLex,                          \
+      self->debug_buffer                     \
+    );                                       \
+  }
+
+static const int32_t BYTE_ORDER_MARK = 0xFEFF;
+
+static const TSRange DEFAULT_RANGE = {
+  .start_point = {
+    .row = 0,
+    .column = 0,
+  },
+  .end_point = {
+    .row = UINT32_MAX,
+    .column = UINT32_MAX,
+  },
+  .start_byte = 0,
+  .end_byte = UINT32_MAX
+};
+
+// Check if the lexer has reached EOF. This state is stored
+// by setting the lexer's `current_included_range_index` such that
+// it has consumed all of its available ranges.
+static bool ts_lexer__eof(const TSLexer *_self) {
+  Lexer *self = (Lexer *)_self;
+  return self->current_included_range_index == self->included_range_count;
+}
+
+// Clear the currently stored chunk of source code, because the lexer's
+// position has changed.
+static void ts_lexer__clear_chunk(Lexer *self) {
+  self->chunk = NULL;
+  self->chunk_size = 0;
+  self->chunk_start = 0;
+}
+
+// Call the lexer's input callback to obtain a new chunk of source code
+// for the current position.
+static void ts_lexer__get_chunk(Lexer *self) {
+  self->chunk_start = self->current_position.bytes;
+  self->chunk = self->input.read(
+    self->input.payload,
+    self->current_position.bytes,
+    self->current_position.extent,
+    &self->chunk_size
+  );
+  if (!self->chunk_size) {
+    self->current_included_range_index = self->included_range_count;
+    self->chunk = NULL;
+  }
+}
+
+// Decode the next unicode character in the current chunk of source code.
+// This assumes that the lexer has already retrieved a chunk of source
+// code that spans the current position.
+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;
+
+  if (size == 0) {
+    self->lookahead_size = 1;
+    self->data.lookahead = '\0';
+    return;
+  }
+
+  UnicodeDecodeFunction decode = self->input.encoding == TSInputEncodingUTF8
+    ? ts_decode_utf8
+    : ts_decode_utf16;
+
+  self->lookahead_size = decode(chunk, size, &self->data.lookahead);
+
+  // If this chunk ended in the middle of a multi-byte character,
+  // try again with a fresh chunk.
+  if (self->data.lookahead == TS_DECODE_ERROR && size < 4) {
+    ts_lexer__get_chunk(self);
+    chunk = (const uint8_t *)self->chunk;
+    size = self->chunk_size;
+    self->lookahead_size = decode(chunk, size, &self->data.lookahead);
+  }
+
+  if (self->data.lookahead == TS_DECODE_ERROR) {
+    self->lookahead_size = 1;
+  }
+}
+
+// Advance to the next character in the source code, retrieving a new
+// chunk of source code if needed.
+static void ts_lexer__advance(TSLexer *_self, bool skip) {
+  Lexer *self = (Lexer *)_self;
+  if (!self->chunk) return;
+
+  if (skip) {
+    LOG("skip", self->data.lookahead);
+  } else {
+    LOG("consume", self->data.lookahead);
+  }
+
+  if (self->lookahead_size) {
+    self->current_position.bytes += self->lookahead_size;
+    if (self->data.lookahead == '\n') {
+      self->current_position.extent.row++;
+      self->current_position.extent.column = 0;
+    } else {
+      self->current_position.extent.column += self->lookahead_size;
+    }
+  }
+
+  const TSRange *current_range = NULL;
+  if (self->current_included_range_index < self->included_range_count) {
+    current_range = &self->included_ranges[self->current_included_range_index];
+    if (self->current_position.bytes == current_range->end_byte) {
+      self->current_included_range_index++;
+      if (self->current_included_range_index < self->included_range_count) {
+        current_range++;
+        self->current_position = (Length) {
+          current_range->start_byte,
+          current_range->start_point,
+        };
+      } else {
+        current_range = NULL;
+      }
+    }
+  }
+
+  if (skip) self->token_start_position = self->current_position;
+
+  if (current_range) {
+    if (self->current_position.bytes >= self->chunk_start + self->chunk_size) {
+      ts_lexer__get_chunk(self);
+    }
+    ts_lexer__get_lookahead(self);
+  } else {
+    ts_lexer__clear_chunk(self);
+    self->data.lookahead = '\0';
+    self->lookahead_size = 1;
+  }
+}
+
+// Mark that a token match has completed. This can be called multiple
+// times if a longer match is found later.
+static void ts_lexer__mark_end(TSLexer *_self) {
+  Lexer *self = (Lexer *)_self;
+  if (!ts_lexer__eof(&self->data)) {
+    // If the lexer is right at the beginning of included range,
+    // then the token should be considered to end at the *end* of the
+    // previous included range, rather than here.
+    TSRange *current_included_range = &self->included_ranges[
+      self->current_included_range_index
+    ];
+    if (
+      self->current_included_range_index > 0 &&
+      self->current_position.bytes == current_included_range->start_byte
+    ) {
+      TSRange *previous_included_range = current_included_range - 1;
+      self->token_end_position = (Length) {
+        previous_included_range->end_byte,
+        previous_included_range->end_point,
+      };
+      return;
+    }
+  }
+  self->token_end_position = self->current_position;
+}
+
+static uint32_t ts_lexer__get_column(TSLexer *_self) {
+  Lexer *self = (Lexer *)_self;
+  uint32_t goal_byte = self->current_position.bytes;
+
+  self->current_position.bytes -= self->current_position.extent.column;
+  self->current_position.extent.column = 0;
+
+  if (self->current_position.bytes < self->chunk_start) {
+    ts_lexer__get_chunk(self);
+  }
+
+  uint32_t result = 0;
+  while (self->current_position.bytes < goal_byte) {
+    ts_lexer__advance(&self->data, false);
+    result++;
+  }
+
+  return result;
+}
+
+// Is the lexer at a boundary between two disjoint included ranges of
+// source code? This is exposed as an API because some languages' external
+// scanners need to perform custom actions at these bounaries.
+static bool ts_lexer__is_at_included_range_start(const TSLexer *_self) {
+  const Lexer *self = (const Lexer *)_self;
+  if (self->current_included_range_index < self->included_range_count) {
+    TSRange *current_range = &self->included_ranges[self->current_included_range_index];
+    return self->current_position.bytes == current_range->start_byte;
+  } else {
+    return false;
+  }
+}
+
+void ts_lexer_init(Lexer *self) {
+  *self = (Lexer) {
+    .data = {
+      // The lexer's methods are stored as struct fields so that generated
+      // parsers can call them without needing to be linked against this
+      // library.
+      .advance = ts_lexer__advance,
+      .mark_end = ts_lexer__mark_end,
+      .get_column = ts_lexer__get_column,
+      .is_at_included_range_start = ts_lexer__is_at_included_range_start,
+      .eof = ts_lexer__eof,
+      .lookahead = 0,
+      .result_symbol = 0,
+    },
+    .chunk = NULL,
+    .chunk_size = 0,
+    .chunk_start = 0,
+    .current_position = {0, {0, 0}},
+    .logger = {
+      .payload = NULL,
+      .log = NULL
+    },
+    .included_ranges = NULL,
+    .included_range_count = 0,
+    .current_included_range_index = 0,
+  };
+  ts_lexer_set_included_ranges(self, NULL, 0);
+}
+
+void ts_lexer_delete(Lexer *self) {
+  ts_free(self->included_ranges);
+}
+
+static void ts_lexer_goto(Lexer *self, Length position) {
+  self->current_position = position;
+  bool found_included_range = false;
+
+  // Move to the first valid position at or after the given position.
+  for (unsigned i = 0; i < self->included_range_count; i++) {
+    TSRange *included_range = &self->included_ranges[i];
+    if (included_range->end_byte > position.bytes) {
+      if (included_range->start_byte > position.bytes) {
+        self->current_position = (Length) {
+          .bytes = included_range->start_byte,
+          .extent = included_range->start_point,
+        };
+      }
+
+      self->current_included_range_index = i;
+      found_included_range = true;
+      break;
+    }
+  }
+
+  if (found_included_range) {
+    // If the current position is outside of the current chunk of text,
+    // then clear out the current chunk of text.
+    if (self->chunk && (
+      position.bytes < self->chunk_start ||
+      position.bytes >= self->chunk_start + self->chunk_size
+    )) {
+      ts_lexer__clear_chunk(self);
+    }
+
+    self->lookahead_size = 0;
+    self->data.lookahead = '\0';
+  }
+
+  // If the given position is beyond any of included ranges, move to the EOF
+  // state - past the end of the included ranges.
+  else {
+    self->current_included_range_index = self->included_range_count;
+    TSRange *last_included_range = &self->included_ranges[self->included_range_count - 1];
+    self->current_position = (Length) {
+      .bytes = last_included_range->end_byte,
+      .extent = last_included_range->end_point,
+    };
+    ts_lexer__clear_chunk(self);
+    self->lookahead_size = 1;
+    self->data.lookahead = '\0';
+  }
+}
+
+void ts_lexer_set_input(Lexer *self, TSInput input) {
+  self->input = input;
+  ts_lexer__clear_chunk(self);
+  ts_lexer_goto(self, self->current_position);
+}
+
+// Move the lexer to the given position. This doesn't do any work
+// if the parser is already at the given position.
+void ts_lexer_reset(Lexer *self, Length position) {
+  if (position.bytes != self->current_position.bytes) {
+    ts_lexer_goto(self, position);
+  }
+}
+
+void ts_lexer_start(Lexer *self) {
+  self->token_start_position = self->current_position;
+  self->token_end_position = LENGTH_UNDEFINED;
+  self->data.result_symbol = 0;
+  if (!ts_lexer__eof(&self->data)) {
+    if (!self->chunk_size) ts_lexer__get_chunk(self);
+    if (!self->lookahead_size) ts_lexer__get_lookahead(self);
+    if (
+      self->current_position.bytes == 0 &&
+      self->data.lookahead == BYTE_ORDER_MARK
+    ) ts_lexer__advance(&self->data, true);
+  }
+}
+
+void ts_lexer_finish(Lexer *self, uint32_t *lookahead_end_byte) {
+  if (length_is_undefined(self->token_end_position)) {
+    ts_lexer__mark_end(&self->data);
+  }
+
+  uint32_t current_lookahead_end_byte = self->current_position.bytes + 1;
+
+  // In order to determine that a byte sequence is invalid UTF8 or UTF16,
+  // the character decoding algorithm may have looked at the following byte.
+  // Therefore, the next byte *after* the current (invalid) character
+  // affects the interpretation of the current character.
+  if (self->data.lookahead == TS_DECODE_ERROR) {
+    current_lookahead_end_byte++;
+  }
+
+  if (current_lookahead_end_byte > *lookahead_end_byte) {
+    *lookahead_end_byte = current_lookahead_end_byte;
+  }
+}
+
+void ts_lexer_advance_to_end(Lexer *self) {
+  while (self->chunk) {
+    ts_lexer__advance(&self->data, false);
+  }
+}
+
+void ts_lexer_mark_end(Lexer *self) {
+  ts_lexer__mark_end(&self->data);
+}
+
+bool ts_lexer_set_included_ranges(
+  Lexer *self,
+  const TSRange *ranges,
+  uint32_t count
+) {
+  if (count == 0 || !ranges) {
+    ranges = &DEFAULT_RANGE;
+    count = 1;
+  } else {
+    uint32_t previous_byte = 0;
+    for (unsigned i = 0; i < count; i++) {
+      const TSRange *range = &ranges[i];
+      if (
+        range->start_byte < previous_byte ||
+        range->end_byte < range->start_byte
+      ) return false;
+      previous_byte = range->end_byte;
+    }
+  }
+
+  size_t size = count * sizeof(TSRange);
+  self->included_ranges = ts_realloc(self->included_ranges, size);
+  memcpy(self->included_ranges, ranges, size);
+  self->included_range_count = count;
+  ts_lexer_goto(self, self->current_position);
+  return true;
+}
+
+TSRange *ts_lexer_included_ranges(const Lexer *self, uint32_t *count) {
+  *count = self->included_range_count;
+  return self->included_ranges;
+}
+
+#undef LOG