Cleanup Lexer (#466)

* Add class LexerSource: it encapsulates reading data from a source,
  either buffer or file.
* Add class LexerSourceLineFinder: it uses a LexerSource to read a line
  from the source for displaying in errors. It lazily caches line
  numbers -> file offsets, so no work is done unless an error occurs.
* Make WastLexer a class instead of a struct.

1 files changed, 131 insertions, 0 deletions

diff --git a/src/lexer-source.cc b/src/lexer-source.cc
new file mode 100644
index 00000000..13ca713e
--- /dev/null
+++ b/src/lexer-source.cc
@@ -0,0 +1,131 @@
+/*
+ * Copyright 2017 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "lexer-source.h"
+
+#include <algorithm>
+
+#define CHECK_RESULT(expr)  \
+  do {                      \
+    if (WABT_FAILED(expr))  \
+      return Result::Error; \
+  } while (0)
+
+namespace wabt {
+
+LexerSourceFile::LexerSourceFile(const std::string& filename)
+  : filename_(filename) {
+  file_ = fopen(filename.c_str(), "rb");
+}
+
+LexerSourceFile::~LexerSourceFile() {
+  if (file_)
+    fclose(file_);
+}
+
+std::unique_ptr<LexerSource> LexerSourceFile::Clone() {
+  std::unique_ptr<LexerSourceFile> result(new LexerSourceFile(filename_));
+
+  Offset offset = 0;
+  if (WABT_FAILED(Tell(&offset)) || WABT_FAILED(result->Seek(offset)))
+    result.reset();
+
+  return std::move(result);
+}
+
+Result LexerSourceFile::Tell(Offset* out_offset) {
+  if (!file_)
+    return Result::Error;
+
+  long offset = ftell(file_);
+  if (offset < 0)
+    return Result::Error;
+
+  *out_offset = offset;
+  return Result::Ok;
+}
+
+size_t LexerSourceFile::Fill(void* dest, size_t size)  {
+  if (!file_)
+    return 0;
+  return fread(dest, 1, size, file_);
+}
+
+Result LexerSourceFile::ReadRange(OffsetRange range,
+                                  std::vector<char>* out_data) {
+  Offset old_offset = 0;
+  CHECK_RESULT(Tell(&old_offset));
+  CHECK_RESULT(Seek(range.start));
+
+  std::vector<char> result(range.size());
+  if (range.size() > 0) {
+    size_t read_size = Fill(result.data(), range.size());
+    if (read_size < range.size())
+      result.resize(read_size);
+  }
+
+  CHECK_RESULT(Seek(old_offset));
+
+  *out_data = std::move(result);
+  return Result::Ok;
+}
+
+Result LexerSourceFile::Seek(Offset offset) {
+  if (!file_)
+    return Result::Error;
+
+  int result = fseek(file_, offset, SEEK_SET);
+  return result < 0 ? Result::Error : Result::Ok;
+}
+
+LexerSourceBuffer::LexerSourceBuffer(const void* data, Offset size)
+    : data_(data), size_(size), read_offset_(0) {}
+
+std::unique_ptr<LexerSource> LexerSourceBuffer::Clone() {
+  LexerSourceBuffer* result = new LexerSourceBuffer(data_, size_);
+  result->read_offset_ = read_offset_;
+  return std::unique_ptr<LexerSource>(result);
+}
+
+Result LexerSourceBuffer::Tell(Offset* out_offset) {
+  *out_offset = read_offset_;
+  return Result::Ok;
+}
+
+size_t LexerSourceBuffer::Fill(void* dest, Offset size) {
+  Offset read_size = std::min(size, size_ - read_offset_);
+  if (read_size > 0) {
+    const void* src = static_cast<const char*>(data_) + read_offset_;
+    memcpy(dest, src, read_size);
+    read_offset_ += read_size;
+  }
+  return read_size;
+}
+
+Result LexerSourceBuffer::ReadRange(OffsetRange range,
+                                    std::vector<char>* out_data) {
+  OffsetRange clamped = range;
+  clamped.start = std::min(clamped.start, size_);
+  clamped.end = std::min(clamped.end, size_);
+  if (clamped.size()) {
+    std::vector<char> result(clamped.size());
+    const void* src = static_cast<const char*>(data_) + clamped.start;
+    memcpy(result.data(), src, clamped.size());
+  }
+  return Result::Ok;
+}
+
+}  // namespace wabt