1 files changed, 212 insertions, 0 deletions
diff --git a/src/wasm/source-map.cpp b/src/wasm/source-map.cpp
new file mode 100644
index 000000000..7ad26e898
--- /dev/null
+++ b/src/wasm/source-map.cpp
@@ -0,0 +1,212 @@
+/*
+ * Copyright 2024 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 "source-map.h"
+#include "support/colors.h"
+
+namespace wasm {
+
+std::vector<char> defaultEmptySourceMap;
+
+void MapParseException::dump(std::ostream& o) const {
+  Colors::magenta(o);
+  o << "[";
+  Colors::red(o);
+  o << "map parse exception: ";
+  Colors::green(o);
+  o << text;
+  Colors::magenta(o);
+  o << "]";
+  Colors::normal(o);
+}
+
+void SourceMapReader::readHeader(Module& wasm) {
+  assert(pos == 0);
+  if (buffer.empty()) {
+    return;
+  }
+
+  auto skipWhitespace = [&]() {
+    while (pos < buffer.size() && (buffer[pos] == ' ' || buffer[pos] == '\n')) {
+      ++pos;
+    }
+  };
+
+  auto findField = [&](const char* name) {
+    bool matching = false;
+    size_t len = strlen(name);
+    size_t index = 0;
+    while (1) {
+      char ch = get();
+      if (ch == '\"') {
+        if (matching) {
+          if (index == len) {
+            // We matched a terminating quote.
+            break;
+          }
+          matching = false;
+        } else {
+          // Beginning of a new potential match.
+          matching = true;
+          index = 0;
+        }
+      } else if (matching && name[index] == ch) {
+        ++index;
+      } else if (matching) {
+        matching = false;
+      }
+    }
+    skipWhitespace();
+    expect(':');
+    skipWhitespace();
+    return true;
+  };
+
+  auto readString = [&](std::string& str) {
+    std::vector<char> vec;
+    skipWhitespace();
+    expect('\"');
+    while (1) {
+      if (maybeGet('\"')) {
+        break;
+      }
+      vec.push_back(get());
+    }
+    skipWhitespace();
+    str = std::string(vec.begin(), vec.end());
+  };
+
+  if (!findField("sources")) {
+    throw MapParseException("cannot find the 'sources' field in map");
+  }
+
+  skipWhitespace();
+  expect('[');
+  if (!maybeGet(']')) {
+    do {
+      std::string file;
+      readString(file);
+      wasm.debugInfoFileNames.push_back(file);
+    } while (maybeGet(','));
+    expect(']');
+  }
+
+  if (findField("names")) {
+    skipWhitespace();
+    expect('[');
+    if (!maybeGet(']')) {
+      do {
+        std::string symbol;
+        readString(symbol);
+        wasm.debugInfoSymbolNames.push_back(symbol);
+      } while (maybeGet(','));
+      expect(']');
+    }
+  }
+
+  if (!findField("mappings")) {
+    throw MapParseException("cannot find the 'mappings' field in map");
+  }
+
+  expect('\"');
+  if (maybeGet('\"')) {
+    // There are no mappings.
+    location = 0;
+    return;
+  }
+
+  // Read the location of the first debug location.
+  location = readBase64VLQ();
+}
+
+std::optional<Function::DebugLocation>
+SourceMapReader::readDebugLocationAt(size_t currLocation) {
+  if (pos >= buffer.size()) {
+    return std::nullopt;
+  }
+
+  while (location && location <= currLocation) {
+    do {
+      char next = peek();
+      if (next == ',' || next == '\"') {
+        // This is a 1-length entry, so the next location has no debug info.
+        hasInfo = false;
+        break;
+      }
+
+      hasInfo = true;
+      file += readBase64VLQ();
+      line += readBase64VLQ();
+      col += readBase64VLQ();
+
+      next = peek();
+      if (next == ',' || next == '\"') {
+        hasSymbol = false;
+        break;
+      }
+
+      hasSymbol = true;
+      symbol += readBase64VLQ();
+
+    } while (false);
+
+    // Check whether there is another record to read the position for.
+    char next = get();
+    if (next == '\"') {
+      // End of records.
+      location = 0;
+      break;
+    }
+    if (next != ',') {
+      throw MapParseException("Expected delimiter");
+    }
+
+    // Set up for the next record.
+    location += readBase64VLQ();
+  }
+
+  if (!hasInfo) {
+    return std::nullopt;
+  }
+
+  auto sym = hasSymbol ? symbol : std::optional<uint32_t>{};
+  return Function::DebugLocation{file, line, col, sym};
+}
+
+int32_t SourceMapReader::readBase64VLQ() {
+  uint32_t value = 0;
+  uint32_t shift = 0;
+  while (1) {
+    auto ch = get();
+    if ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch < 'g')) {
+      // last number digit
+      uint32_t digit = ch < 'a' ? ch - 'A' : ch - 'a' + 26;
+      value |= digit << shift;
+      break;
+    }
+    if (!(ch >= 'g' && ch <= 'z') && !(ch >= '0' && ch <= '9') && ch != '+' &&
+        ch != '/') {
+      throw MapParseException("invalid VLQ digit");
+    }
+    uint32_t digit =
+      ch > '9' ? ch - 'g' : (ch >= '0' ? ch - '0' + 20 : (ch == '+' ? 30 : 31));
+    value |= digit << shift;
+    shift += 5;
+  }
+  return value & 1 ? -int32_t(value >> 1) : int32_t(value >> 1);
+}
+
+} // namespace wasm