Bug 1377007 - Implementation of the Token Reader dedicated to testing;r=arai,jorendorff
authorDavid Teller <dteller@mozilla.com>
Wed, 13 Sep 2017 15:30:19 +0200
changeset 448372 70ae74a3a1b764a1fa2d22296edb56f181526995
parent 448371 f1eeaf08ba77457d639f82f4be1230c88da1d19d
child 448373 bdbaccfb070ed6d0ab9099eb7ea52f5cf7abc88b
push id8527
push userCallek@gmail.com
push dateThu, 11 Jan 2018 21:05:50 +0000
treeherdermozilla-beta@95342d212a7a [default view] [failures only]
perfherder[talos] [build metrics] [platform microbench] (compared to previous push)
reviewersarai, jorendorff
bugs1377007
milestone59.0a1
first release with
nightly linux32
nightly linux64
nightly mac
nightly win32
nightly win64
last release without
nightly linux32
nightly linux64
nightly mac
nightly win32
nightly win64
Bug 1377007 - Implementation of the Token Reader dedicated to testing;r=arai,jorendorff This patch ports to SpiderMonkey the tokenizer currently implemented in the external binjs-ref tool. While this tokenizer will clearly not be the tokenizer eventually shipped to end-users (whether in Firefox or in binjs-ref), the plan is to keep it both in binjs-ref and in SpiderMonkey (Nightly only) as a tool for helping test the higher layers of Binjs. MozReview-Commit-ID: 1i6XnVIf8p5
js/src/frontend/BinTokenReaderTester.cpp
js/src/frontend/BinTokenReaderTester.h
js/src/jsapi-tests/binast/tokenizer/tester/test-empty-list.binjs
js/src/jsapi-tests/binast/tokenizer/tester/test-empty-untagged-tuple.binjs
js/src/jsapi-tests/binast/tokenizer/tester/test-nested-lists.binjs
js/src/jsapi-tests/binast/tokenizer/tester/test-simple-string.binjs
js/src/jsapi-tests/binast/tokenizer/tester/test-simple-tagged-tuple.binjs
js/src/jsapi-tests/binast/tokenizer/tester/test-string-with-escapes.binjs
js/src/jsapi-tests/binast/tokenizer/tester/test-trivial-list.binjs
js/src/jsapi-tests/binast/tokenizer/tester/test-trivial-untagged-tuple.binjs
js/src/jsapi-tests/moz.build
js/src/jsapi-tests/testBinASTReader.cpp
js/src/jsapi-tests/testBinTokenReaderTester.cpp
js/src/moz.build
new file mode 100644
--- /dev/null
+++ b/js/src/frontend/BinTokenReaderTester.cpp
@@ -0,0 +1,529 @@
+#include "frontend/BinTokenReaderTester.h"
+
+#include "mozilla/EndianUtils.h"
+#include "gc/Zone.h"
+
+namespace js {
+namespace frontend {
+
+using BinFields = BinTokenReaderTester::BinFields;
+using AutoList = BinTokenReaderTester::AutoList;
+using AutoTaggedTuple = BinTokenReaderTester::AutoTaggedTuple;
+using AutoTuple = BinTokenReaderTester::AutoTuple;
+
+BinTokenReaderTester::BinTokenReaderTester(JSContext* cx, const uint8_t* start, const size_t length)
+    : cx_(cx)
+    , start_(start)
+    , current_(start)
+    , stop_(start + length)
+    , latestKnownGoodPos_(0)
+{ }
+
+BinTokenReaderTester::BinTokenReaderTester(JSContext* cx, const Vector<uint8_t>& chars)
+    : cx_(cx)
+    , start_(chars.begin())
+    , current_(chars.begin())
+    , stop_(chars.end())
+    , latestKnownGoodPos_(0)
+{ }
+
+bool
+BinTokenReaderTester::raiseError(const char* description)
+{
+    MOZ_ASSERT(!cx_->isExceptionPending());
+    TokenPos pos;
+    latestTokenPos(pos);
+    JS_ReportErrorASCII(cx_, "BinAST parsing error: %s at offsets %u => %u",
+                        description, pos.begin, pos.end);
+    return false;
+}
+
+bool
+BinTokenReaderTester::readBuf(uint8_t* bytes, uint32_t len)
+{
+    MOZ_ASSERT(!cx_->isExceptionPending());
+    MOZ_ASSERT(len > 0);
+
+    if (stop_ < current_ + len)
+        return raiseError("Buffer exceeds length");
+
+    for (uint32_t i = 0; i < len; ++i)
+        *bytes++ = *current_++;
+
+    return true;
+}
+
+bool
+BinTokenReaderTester::readByte(uint8_t* byte)
+{
+    return readBuf(byte, 1);
+}
+
+
+// Nullable booleans:
+//
+// 0 => false
+// 1 => true
+// 2 => null
+bool
+BinTokenReaderTester::readMaybeBool(Maybe<bool>& result)
+{
+    updateLatestKnownGood();
+    uint8_t byte;
+    if (!readByte(&byte))
+        return false;
+
+    switch (byte) {
+      case 0:
+        result = Some(false);
+        break;
+      case 1:
+        result = Some(true);
+        break;
+      case 2:
+        result = Nothing();
+        break;
+      default:
+        return raiseError("Invalid boolean value");
+    }
+    return true;
+}
+
+bool
+BinTokenReaderTester::readBool(bool& out)
+{
+    Maybe<bool> result;
+
+    if (!readMaybeBool(result))
+        return false;
+
+    if (result.isNothing())
+        return raiseError("Empty boolean value");
+
+    out = *result;
+    return true;
+}
+
+// Nullable doubles (little-endian)
+//
+// 0x7FF0000000000001 (signaling NaN) => null
+// anything other 64 bit sequence => IEEE-764 64-bit floating point number
+bool
+BinTokenReaderTester::readMaybeDouble(Maybe<double>& result)
+{
+    updateLatestKnownGood();
+
+    uint8_t bytes[8];
+    MOZ_ASSERT(sizeof(bytes) == sizeof(double));
+    if (!readBuf(reinterpret_cast<uint8_t*>(bytes), ArrayLength(bytes)))
+        return false;
+
+    // Decode little-endian.
+    const uint64_t asInt = LittleEndian::readUint64(bytes);
+
+    if (asInt == 0x7FF0000000000001) {
+        result = Nothing();
+    } else {
+        // Canonicalize NaN, just to make sure another form of signalling NaN
+        // doesn't slip past us.
+        const double asDouble = CanonicalizeNaN(BitwiseCast<double>(asInt));
+        result = Some(asDouble);
+    }
+
+    return true;
+}
+
+bool
+BinTokenReaderTester::readDouble(double& out)
+{
+    Maybe<double> result;
+
+    if (!readMaybeDouble(result))
+        return false;
+
+    if (result.isNothing())
+        return raiseError("Empty double value");
+
+    out = *result;
+    return true;
+}
+
+// Internal uint32_t
+//
+// Encoded as 4 bytes, little-endian.
+bool
+BinTokenReaderTester::readInternalUint32(uint32_t* result)
+{
+    uint8_t bytes[4];
+    MOZ_ASSERT(sizeof(bytes) == sizeof(uint32_t));
+    if (!readBuf(bytes, 4))
+        return false;
+
+    // Decode little-endian.
+    *result = LittleEndian::readUint32(bytes);
+
+    return true;
+}
+
+
+
+// Nullable strings:
+// - "<string>" (not counted in byte length)
+// - byte length (not counted in byte length)
+// - bytes (UTF-8)
+// - "</string>" (not counted in byte length)
+//
+// The special sequence of bytes `[255, 0]` (which is an invalid UTF-8 sequence)
+// is reserved to `null`.
+bool
+BinTokenReaderTester::readMaybeChars(Maybe<Chars>& out)
+{
+    updateLatestKnownGood();
+
+    if (!readConst("<string>"))
+        return false;
+
+    // 1. Read byteLength
+    uint32_t byteLen;
+    if (!readInternalUint32(&byteLen))
+        return false;
+
+    // 2. Reject if we can't read
+    if (current_ + byteLen < current_) // Check for overflows
+        return raiseError("Arithmetics overflow: string is too long");
+
+    if (current_ + byteLen > stop_)
+        return raiseError("Not enough bytes to read chars");
+
+    // 3. Check null string (no allocation)
+    if (byteLen == 2 && *current_ == 255 && *(current_ + 1) == 0) {
+        // Special case: null string.
+        out = Nothing();
+        current_ += byteLen;
+        return true;
+    }
+
+    // 4. Other strings (bytes are copied)
+    out.emplace(cx_);
+    if (!out->resize(byteLen)) {
+        ReportOutOfMemory(cx_);
+        return false;
+    }
+    PodCopy(out->begin(), current_, byteLen);
+    current_ += byteLen;
+
+    if (!readConst("</string>"))
+        return false;
+
+    return true;
+}
+
+bool
+BinTokenReaderTester::readChars(Chars& out)
+{
+    Maybe<Chars> result;
+
+    if (!readMaybeChars(result))
+        return false;
+
+    if (result.isNothing())
+        return raiseError("Empty string");
+
+    out = Move(*result);
+    return true;
+}
+
+template <size_t N>
+bool
+BinTokenReaderTester::matchConst(const char (&value)[N])
+{
+    MOZ_ASSERT(N > 0);
+    MOZ_ASSERT(value[N - 1] == 0);
+    MOZ_ASSERT(!cx_->isExceptionPending());
+
+    if (current_ + N - 1 > stop_)
+        return false;
+
+    // Perform lookup, without side-effects.
+    if (!std::equal(current_, current_ + N - 1 /*implicit NUL*/, value))
+        return false;
+
+    // Looks like we have a match. Now perform side-effects
+    current_ += N - 1;
+    updateLatestKnownGood();
+    return true;
+}
+
+
+// Untagged tuple:
+// - "<tuple>";
+// - contents (specified by the higher-level grammar);
+// - "</tuple>"
+bool
+BinTokenReaderTester::enterUntaggedTuple(AutoTuple& guard)
+{
+    if (!readConst("<tuple>"))
+        return false;
+
+    guard.init();
+    return true;
+}
+
+template <size_t N>
+bool
+BinTokenReaderTester::readConst(const char (&value)[N])
+{
+    updateLatestKnownGood();
+    if (!matchConst(value))
+        return raiseError("Could not find expected literal");
+
+    return true;
+}
+
+// Tagged tuples:
+// - "<tuple>"
+// - "<head>"
+// - non-null string `name`, followed by \0 (see `readString()`);
+// - uint32_t number of fields;
+// - array of `number of fields` non-null strings followed each by \0 (see `readString()`);
+// - "</head>"
+// - content (specified by the higher-level grammar);
+// - "</tuple>"
+bool
+BinTokenReaderTester::enterTaggedTuple(BinKind& tag, BinFields& fields, AutoTaggedTuple& guard)
+{
+    // Header
+    if (!readConst("<tuple>"))
+        return false;
+
+    if (!readConst("<head>"))
+        return false;
+
+    // This would probably be much faster with a HashTable, but we don't
+    // really care about the speed of BinTokenReaderTester.
+    do {
+
+#define FIND_MATCH(CONSTRUCTOR, NAME) \
+        if (matchConst(#NAME "\0")) { \
+            tag = BinKind::CONSTRUCTOR; \
+            break; \
+        } // else
+
+        FOR_EACH_BIN_KIND(FIND_MATCH)
+#undef FIND_MATCH
+
+        // else
+        return raiseError("Invalid tag");
+    } while(false);
+
+    // Now fields.
+    uint32_t fieldNum;
+    if (!readInternalUint32(&fieldNum))
+        return false;
+
+    fields.clear();
+    if (!fields.reserve(fieldNum))
+        return raiseError("Out of memory");
+
+    for (uint32_t i = 0; i < fieldNum; ++i) {
+        // This would probably be much faster with a HashTable, but we don't
+        // really care about the speed of BinTokenReaderTester.
+        BinField field;
+        do {
+
+#define FIND_MATCH(CONSTRUCTOR, NAME) \
+            if (matchConst(#NAME "\0")) { \
+                field = BinField::CONSTRUCTOR; \
+                break; \
+            } // else
+
+            FOR_EACH_BIN_FIELD(FIND_MATCH)
+#undef FIND_MATCH
+
+            // else
+            return raiseError("Invalid field");
+        } while (false);
+
+        // Make sure that we do not have duplicate fields.
+        // Search is linear, but again, we don't really care
+        // in this implementation.
+        for (uint32_t j = 0; j < i; ++j) {
+            if (fields[j] == field) {
+                return raiseError("Duplicate field");
+            }
+        }
+
+        fields.infallibleAppend(field); // Already checked.
+    }
+
+    // End of header
+
+    if (!readConst("</head>"))
+        return false;
+
+    // Enter the body.
+    guard.init();
+    return true;
+}
+
+// List:
+//
+// - "<list>" (not counted in byte length);
+// - uint32_t byte length (not counted in byte length);
+// - uint32_t number of items;
+// - contents (specified by higher-level grammar);
+// - "</list>" (not counted in byte length)
+//
+// The total byte length of `number of items` + `contents` must be `byte length`.
+bool
+BinTokenReaderTester::enterList(uint32_t& items, AutoList& guard)
+{
+    if (!readConst("<list>"))
+        return false;
+
+    uint32_t byteLen;
+    if (!readInternalUint32(&byteLen))
+        return false;
+
+    const uint8_t* stop = current_ + byteLen;
+
+    if (stop < current_) // Check for overflows
+        return raiseError("Arithmetics overflow: list is too long");
+
+    if (stop > this->stop_)
+        return raiseError("Incorrect list length");
+
+    guard.init(stop);
+
+    if (!readInternalUint32(&items))
+        return false;
+
+    return true;
+}
+
+void
+BinTokenReaderTester::updateLatestKnownGood()
+{
+    MOZ_ASSERT(current_ >= start_);
+    const size_t update = current_ - start_;
+    MOZ_ASSERT(update >= latestKnownGoodPos_);
+    latestKnownGoodPos_ = update;
+}
+
+size_t
+BinTokenReaderTester::offset() const
+{
+    return latestKnownGoodPos_;
+}
+
+void
+BinTokenReaderTester::latestTokenPos(TokenPos& pos)
+{
+    pos.begin = latestKnownGoodPos_;
+    pos.end = current_ - start_;
+    MOZ_ASSERT(pos.end >= pos.begin);
+}
+
+void
+BinTokenReaderTester::AutoBase::init()
+{
+    initialized_ = true;
+}
+
+BinTokenReaderTester::AutoBase::AutoBase(BinTokenReaderTester& reader)
+    : reader_(reader)
+{ }
+
+BinTokenReaderTester::AutoBase::~AutoBase()
+{
+    // By now, the `AutoBase` must have been deinitialized by calling `done()`.
+    // The only case in which we can accept not calling `done()` is if we have
+    // bailed out because of an error.
+    MOZ_ASSERT_IF(initialized_, reader_.cx_->isExceptionPending());
+}
+
+bool
+BinTokenReaderTester::AutoBase::checkPosition(const uint8_t* expectedEnd)
+{
+    if (reader_.current_ != expectedEnd)
+        return reader_.raiseError("Caller did not consume the expected set of bytes");
+
+    return true;
+}
+
+BinTokenReaderTester::AutoList::AutoList(BinTokenReaderTester& reader)
+    : AutoBase(reader)
+{ }
+
+void
+BinTokenReaderTester::AutoList::init(const uint8_t* expectedEnd)
+{
+    AutoBase::init();
+    this->expectedEnd_ = expectedEnd;
+}
+
+bool
+BinTokenReaderTester::AutoList::done()
+{
+    MOZ_ASSERT(initialized_);
+    initialized_ = false;
+    if (reader_.cx_->isExceptionPending()) {
+        // Already errored, no need to check further.
+        return false;
+    }
+
+    // Check that we have consumed the exact number of bytes.
+    if (!checkPosition(expectedEnd_))
+        return false;
+
+    // Check suffix.
+    if (!reader_.readConst("</list>"))
+        return false;
+
+    return true;
+}
+
+BinTokenReaderTester::AutoTaggedTuple::AutoTaggedTuple(BinTokenReaderTester& reader)
+    : AutoBase(reader)
+{ }
+
+bool
+BinTokenReaderTester::AutoTaggedTuple::done()
+{
+    MOZ_ASSERT(initialized_);
+    initialized_ = false;
+    if (reader_.cx_->isExceptionPending()) {
+        // Already errored, no need to check further.
+        return false;
+    }
+
+    // Check suffix.
+    if (!reader_.readConst("</tuple>"))
+        return false;
+
+    return true;
+}
+
+BinTokenReaderTester::AutoTuple::AutoTuple(BinTokenReaderTester& reader)
+    : AutoBase(reader)
+{ }
+
+bool
+BinTokenReaderTester::AutoTuple::done()
+{
+    MOZ_ASSERT(initialized_);
+    initialized_ = false;
+    if (reader_.cx_->isExceptionPending()) {
+        // Already errored, no need to check further.
+        return false;
+    }
+
+    // Check suffix.
+    if (!reader_.readConst("</tuple>"))
+        return false;
+
+    return true;
+}
+
+} // namespace frontend
+} // namespace js
new file mode 100644
--- /dev/null
+++ b/js/src/frontend/BinTokenReaderTester.h
@@ -0,0 +1,356 @@
+#ifndef frontend_BinTokenReaderTester_h
+#define frontend_BinTokenReaderTester_h
+
+#include "mozilla/Maybe.h"
+
+#include "frontend/BinToken.h"
+#include "frontend/TokenStream.h"
+
+#include "js/TypeDecls.h"
+
+#if !defined(NIGHTLY_BUILD)
+#error "BinTokenReaderTester.* is designed to help test implementations of successive versions of JS BinaryAST. It is available only on Nightly."
+#endif // !defined(NIGHTLY_BUILD)
+
+namespace js {
+namespace frontend {
+
+using namespace mozilla;
+using namespace JS;
+
+/**
+ * A token reader for a simple, alternative serialization format for BinAST.
+ *
+ * This serialization format, which is also supported by the reference
+ * implementation of the BinAST compression suite, is designed to be
+ * mostly human-readable and easy to check for all sorts of deserialization
+ * errors. While this format is NOT designed to be shipped to end-users, it
+ * is nevertheless a very useful tool for implementing and testing parsers.
+ *
+ * Both the format and the implementation are ridiculously inefficient:
+ *
+ * - the underlying format tags almost all its data with e.g. `<tuple>`, `</tuple>`
+ *   to aid with detecting offset errors or format error;
+ * - the underlying format copies list of fields into every single node, instead
+ *   of keeping them once in the header;
+ * - every kind/field extraction requires memory allocation and plenty of string
+ *   comparisons;
+ * - ...
+ *
+ * This token reader is designed to be API-compatible with the standard, shipped,
+ * token reader. For these reasons:
+ *
+ * - it does not support any form of look ahead, push back;
+ * - it does not support any form of error recovery.
+ */
+class MOZ_STACK_CLASS BinTokenReaderTester
+{
+  public:
+    // A list of fields, in the order in which they appear in the stream.
+    using BinFields = Vector<BinField, 8>;
+
+    // A bunch of characters. At this stage, there is no guarantee on whether
+    // they are valid UTF-8. Future versions may replace this by slice into
+    // the buffer.
+    using Chars     = Vector<uint8_t, 32>;
+
+    class AutoList;
+    class AutoTuple;
+    class AutoTaggedTuple;
+
+  public:
+    /**
+     * Construct a token reader.
+     *
+     * Does NOT copy the buffer.
+     */
+    BinTokenReaderTester(JSContext* cx, const uint8_t* start, const size_t length);
+
+    /**
+     * Construct a token reader.
+     *
+     * Does NOT copy the buffer.
+     */
+    BinTokenReaderTester(JSContext* cx, const Vector<uint8_t>& chars);
+
+    // --- Primitive values.
+    //
+    // Note that the underlying format allows for a `null` value for primitive
+    // values.
+    //
+    // Reading will return an error either in case of I/O error or in case of
+    // a format problem. Reading if an exception in pending is an error and
+    // will cause assertion failures. Do NOT attempt to read once an exception
+    // has been cleared: the token reader does NOT support recovery, by design.
+
+    /**
+     * Read a single `true | false | null` value.
+     *
+     * @param out Set to `Nothing` if the data specifies that the value is `null`.
+     * Otherwise, `Some(true)` or `Some(false)`.
+     *
+     * @return false If a boolean could not be read. In this case, an error
+     * has been raised.
+     */
+    MOZ_MUST_USE bool readMaybeBool(Maybe<bool>& out);
+    MOZ_MUST_USE bool readBool(bool& out);
+
+    /**
+     * Read a single `number | null` value.
+     *
+     * @param out Set to `Nothing` if the data specifies that the value is `null`.
+     * Otherwise, `Some(x)`, where `x` is a valid `double` (i.e. either a non-NaN
+     * or a canonical NaN).
+     *
+     * @return false If a double could not be read. In this case, an error
+     * has been raised.
+     */
+    MOZ_MUST_USE bool readMaybeDouble(Maybe<double>& out);
+    MOZ_MUST_USE bool readDouble(double& out);
+
+    /**
+     * Read a single `string | null` value.
+     *
+     * @param out Set to `Nothing` if the data specifies that the value is `null`.
+     * Otherwise, `Some(x)`, where `x` is a `string`.
+     *
+     * WARNING: At this stage, the `string` encoding has NOT been validated.
+     *
+     * @return false If a string could not be read. In this case, an error
+     * has been raised.
+     */
+    MOZ_MUST_USE bool readMaybeChars(Maybe<Chars>& out);
+    MOZ_MUST_USE bool readChars(Chars& out);
+
+    // --- Composite values.
+    //
+    // The underlying format does NOT allows for a `null` composite value.
+    //
+    // Reading will return an error either in case of I/O error or in case of
+    // a format problem. Reading from a poisoned tokenizer is an error and
+    // will cause assertion failures.
+
+    /**
+     * Start reading a list.
+     *
+     * @param length (OUT) The number of elements in the list.
+     * @param guard (OUT) A guard, ensuring that we read the list correctly.
+     *
+     * The `guard` is dedicated to ensuring that reading the list has consumed
+     * exactly all the bytes from that list. The `guard` MUST therefore be
+     * destroyed at the point where the caller has reached the end of the list.
+     * If the caller has consumed too few/too many bytes, this will be reported
+     * in the call go `guard.done()`.
+     *
+     * @return out If the header of the list is invalid.
+     */
+    MOZ_MUST_USE bool enterList(uint32_t& length, AutoList& guard);
+
+    /**
+     * Start reading a tagged tuple.
+     *
+     * @param tag (OUT) The tag of the tuple.
+     * @param fields (OUT) The ORDERED list of fields encoded in this tuple.
+     * @param guard (OUT) A guard, ensuring that we read the tagged tuple correctly.
+     *
+     * The `guard` is dedicated to ensuring that reading the list has consumed
+     * exactly all the bytes from that tuple. The `guard` MUST therefore be
+     * destroyed at the point where the caller has reached the end of the tuple.
+     * If the caller has consumed too few/too many bytes, this will be reported
+     * in the call go `guard.done()`.
+     *
+     * @return out If the header of the tuple is invalid.
+     */
+    MOZ_MUST_USE bool enterTaggedTuple(BinKind& tag, BinTokenReaderTester::BinFields& fields, AutoTaggedTuple& guard);
+
+    /**
+     * Start reading an untagged tuple.
+     *
+     * @param guard (OUT) A guard, ensuring that we read the tuple correctly.
+     *
+     * The `guard` is dedicated to ensuring that reading the list has consumed
+     * exactly all the bytes from that tuple. The `guard` MUST therefore be
+     * destroyed at the point where the caller has reached the end of the tuple.
+     * If the caller has consumed too few/too many bytes, this will be reported
+     * in the call go `guard.done()`.
+     *
+     * @return out If the header of the tuple is invalid.
+     */
+    MOZ_MUST_USE bool enterUntaggedTuple(AutoTuple& guard);
+
+    /**
+     * Return the position of the latest token.
+     */
+    void latestTokenPos(TokenPos& out);
+    size_t offset() const;
+
+    /**
+     * Raise an error.
+     *
+     * Once `raiseError` has been called, the tokenizer is poisoned.
+     */
+    MOZ_MUST_USE bool raiseError(const char* description);
+
+     /**
+      * Poison this tokenizer.
+      */
+    void poison();
+
+  private:
+    /**
+     * Read a single byte.
+     */
+    MOZ_MUST_USE bool readByte(uint8_t* byte);
+
+    /**
+     * Read several bytes.
+     *
+     * If there is not enough data, or if the tokenizer has previously been
+     * poisoned, return `false` and report an exception.
+     */
+    MOZ_MUST_USE bool readBuf(uint8_t* bytes, uint32_t len);
+
+    /**
+     * Read a single uint32_t.
+     */
+    MOZ_MUST_USE bool readInternalUint32(uint32_t*);
+
+    /**
+     * Read a sequence of chars, ensuring that they match an expected
+     * sequence of chars.
+     *
+     * @param value The sequence of chars to expect, NUL-terminated. The NUL
+     * is not expected in the stream.
+     */
+     template <size_t N>
+     MOZ_MUST_USE bool readConst(const char (&value)[N]);
+
+     /**
+     * Read a sequence of chars, consuming the bytes only if they match an expected
+     * sequence of chars.
+     *
+     * @param value The sequence of chars to expect, NUL-terminated. The NUL
+     * is not expected in the stream.
+     * @return true if `value` (minus NUL) represents the next few chars in the
+     * internal buffer, false otherwise. If `true`, the chars are consumed,
+     * otherwise there is no side-effect.
+     */
+    template <size_t N>
+    MOZ_MUST_USE bool matchConst(const char (&value)[N]);
+
+    /**
+     * Update the "latest known good" position, which is used during error
+     * reporting.
+     */
+    void updateLatestKnownGood();
+
+  private:
+    JSContext* cx_;
+
+    // `true` if we have encountered an error. Errors are non recoverable.
+    // Attempting to read from a poisoned tokenizer will cause assertion errors.
+    bool poisoned_;
+
+    // The first byte of the buffer. Not owned.
+    const uint8_t* start_;
+
+    // The current position.
+    const uint8_t* current_;
+
+    // The last+1 byte of the buffer.
+    const uint8_t* stop_;
+
+
+    // Latest known good position. Used for error reporting.
+    size_t latestKnownGoodPos_;
+
+    BinTokenReaderTester(const BinTokenReaderTester&) = delete;
+    BinTokenReaderTester(BinTokenReaderTester&&) = delete;
+    BinTokenReaderTester& operator=(BinTokenReaderTester&) = delete;
+
+  public:
+    // The following classes are used whenever we encounter a tuple/tagged tuple/list
+    // to make sure that:
+    //
+    // - if the construct "knows" its byte length, we have exactly consumed all
+    //   the bytes (otherwise, this means that the file is corrupted, perhaps on
+    //   purpose, so we need to reject the stream);
+    // - if the construct has a footer, once we are done reading it, we have
+    //   reached the footer (this is to aid with debugging).
+    //
+    // In either case, the caller MUST call method `done()` of the guard once
+    // it is done reading the tuple/tagged tuple/list, to report any pending error.
+
+    // Base class used by other Auto* classes.
+    class MOZ_STACK_CLASS AutoBase
+    {
+      protected:
+        explicit AutoBase(BinTokenReaderTester& reader);
+        ~AutoBase();
+
+        // Raise an error if we are not in the expected position.
+        MOZ_MUST_USE bool checkPosition(const uint8_t* expectedPosition);
+
+        friend BinTokenReaderTester;
+        void init();
+
+        // Set to `true` if `init()` has been called. Reset to `false` once
+        // all conditions have been checked.
+        bool initialized_;
+        BinTokenReaderTester& reader_;
+    };
+
+    // Guard class used to ensure that `enterList` is used properly.
+    class MOZ_STACK_CLASS AutoList : public AutoBase
+    {
+      public:
+        explicit AutoList(BinTokenReaderTester& reader);
+
+        // Check that we have properly read to the end of the list.
+        MOZ_MUST_USE bool done();
+      protected:
+        friend BinTokenReaderTester;
+        void init(const uint8_t* expectedEnd);
+      private:
+        const uint8_t* expectedEnd_;
+    };
+
+    // Guard class used to ensure that `enterTaggedTuple` is used properly.
+    class MOZ_STACK_CLASS AutoTaggedTuple : public AutoBase
+    {
+      public:
+        explicit AutoTaggedTuple(BinTokenReaderTester& reader);
+
+        // Check that we have properly read to the end of the tuple.
+        MOZ_MUST_USE bool done();
+    };
+
+    // Guard class used to ensure that `readTuple` is used properly.
+    class MOZ_STACK_CLASS AutoTuple : public AutoBase
+    {
+      public:
+        explicit AutoTuple(BinTokenReaderTester& reader);
+
+        // Check that we have properly read to the end of the tuple.
+        MOZ_MUST_USE bool done();
+    };
+
+    // Compare a `Chars` and a string literal (ONLY a string literal).
+    template <size_t N>
+    static bool equals(const Chars& left, const char (&right)[N]) {
+        MOZ_ASSERT(N > 0);
+        MOZ_ASSERT(right[N - 1] == 0);
+        if (left.length() + 1 /* implicit NUL */ != N)
+            return false;
+
+        if (!std::equal(left.begin(), left.end(), right))
+          return false;
+
+        return true;
+    }
+};
+
+} // namespace frontend
+} // namespace js
+
+#endif // frontend_BinTokenReaderTester_h
new file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..da01d11ad0fa16a02f162d329fb3cd7ba3977eb1
GIT binary patch
literal 21
Uc$~Az$t*6hV_|>*8+|Yr05Ts0pa1{>
new file mode 100644
--- /dev/null
+++ b/js/src/jsapi-tests/binast/tokenizer/tester/test-empty-untagged-tuple.binjs
@@ -0,0 +1,1 @@
+<tuple></tuple>
\ No newline at end of file
new file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..d20681c3cc1dd283dee8568cfaa854af41335d5f
GIT binary patch
literal 90
zc$~Az$t*6h^JHLPU<6_tFwX?YVgm7sONuh{((Ram?6mxR8+|ArSv)DR2qCTy)()ir
D@ZuQQ
new file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..4dd9869685ebb23c52fa3f61a299fb94df82428b
GIT binary patch
literal 34
fc$~8-E-A{)OSj`?U|=ZD%q_@CRe*@t=tE@y!tV>9
new file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..395fdb4476b5632e0445b8e17aa76c3f91c31a57
GIT binary patch
literal 81
zc$~8-DJ{rJwX?}cO-!*1NGvHyEy`nHVqjp%OkpTX%qdM}u+az0*%X%)W#*;ZF$3k&
X^7C!<q5OQI<^!h`IUQ{DAtnI;9z+@$
new file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..b895cf16b7e053f6e50dff48f37d62b6f9d30126
GIT binary patch
literal 44
pc$~8-E-A{)OScneU|@hS70NS9G89salM@S4ixn6c8Eo{SY5+ZI4gmlF
new file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..b92d59df5ea358770349b9bd2cb1f0b1c14eb9d8
GIT binary patch
literal 69
vc$~Az$t*6hGhtw0U;<*B;*z4wymUKeAUiET-$ozGM;1>?EJBFugS7(yf`AkA
new file mode 100644
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..7100fae76b620b7ecce0e6b7304c10ecaccd0823
GIT binary patch
literal 63
qc$~8-DJ{rJwX-QMDay=Cw_|2tU`Wf)x6z04k;Rh|ixA@a5PblXG8CBr
--- a/js/src/jsapi-tests/moz.build
+++ b/js/src/jsapi-tests/moz.build
@@ -132,16 +132,26 @@ if CONFIG['ENABLE_ION']:
         'testJitRValueAlloc.cpp',
     ]
 
 if CONFIG['ENABLE_STREAMS']:
     UNIFIED_SOURCES += [
         'testReadableStream.cpp',
     ]
 
+if CONFIG['JS_BUILD_BINAST'] and CONFIG['JS_STANDALONE']:
+    # Standalone builds leave the source directory untouched,
+    # which lets us run tests with the data files intact.
+    # Otherwise, in the current state of the build system,
+    # we can't have data files in js/src tests.
+    UNIFIED_SOURCES += [
+        'testBinTokenReaderTester.cpp'
+    ]
+
+
 DEFINES['EXPORT_JS_API'] = True
 
 LOCAL_INCLUDES += [
     '!..',
     '..',
 ]
 
 if CONFIG['ENABLE_INTL_API'] and CONFIG['MOZ_ICU_DATA_ARCHIVE']:
new file mode 100644
--- /dev/null
+++ b/js/src/jsapi-tests/testBinASTReader.cpp
@@ -0,0 +1,197 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+
+#include "mozilla/Vector.h"
+
+#if defined(XP_UNIX)
+
+#include <dirent.h>
+#include <sys/stat.h>
+
+#elif defined(XP_WIN)
+
+#include <windows.h>
+
+#endif
+
+#include "frontend/BinSource.h"
+#include "frontend/FullParseHandler.h"
+#include "frontend/ParseContext.h"
+#include "frontend/Parser.h"
+
+#include "jsapi-tests/tests.h"
+
+using UsedNameTracker = js::frontend::UsedNameTracker;
+
+extern void readFull(const char* path, Vector<uint8_t>& buf);
+
+void readFull(JSContext* cx, const char* path, Vector<char16_t>& buf) {
+    buf.shrinkTo(0);
+
+    Vector<uint8_t> intermediate(cx);
+    readFull(path, intermediate);
+
+    if (!buf.appendAll(intermediate))
+        MOZ_CRASH();
+}
+
+BEGIN_TEST(testBinASTReaderECMAScript2)
+{
+    const char BIN_SUFFIX[] = ".binjs";
+    const char TXT_SUFFIX[] = ".js";
+
+    CompileOptions options(cx);
+    options.setIntroductionType("unit test parse")
+           .setFileAndLine("<string>", 1);
+
+#if defined(XP_UNIX)
+
+    const char PATH[] = "jsapi-tests/binast/parser/tester/";
+
+    // Read the list of files in the directory.
+    DIR* dir = opendir(PATH);
+    if (!dir)
+        MOZ_CRASH();
+
+
+    while (auto entry = readdir(dir)) {
+        // Find files whose name ends with ".binjs".
+        const char* d_name = entry->d_name;
+
+#elif defined(XP_WIN)
+
+    const char PATH[] = "jsapi-tests\\binast\\parser\\tester\\*.binjs";
+
+    WIN32_FIND_DATA FindFileData;
+    HANDLE hFind = FindFirstFile(PATH, &FindFileData);
+    for (bool found = (hFind != INVALID_HANDLE_VALUE);
+            found;
+            found = FindNextFile(hFind, &FindFileData)
+    {
+        const char* d_name = FindFileData.cFileName;
+
+#endif // defined(XP_UNIX) || defined(XP_WIN)
+
+        const size_t namlen = strlen(d_name);
+        if (namlen < sizeof(BIN_SUFFIX))
+            continue;
+        if (strncmp(d_name + namlen - (sizeof(BIN_SUFFIX) - 1), BIN_SUFFIX, sizeof(BIN_SUFFIX)) != 0)
+            continue;
+
+        // Find text file.
+        UniqueChars txtPath(static_cast<char*>(js_malloc(namlen + sizeof(PATH) + 1)));
+        strncpy(txtPath.get(), PATH, sizeof(PATH));
+        strncpy(txtPath.get() + sizeof(PATH) - 1, d_name, namlen);
+        strncpy(txtPath.get() + sizeof(PATH) + namlen - sizeof(BIN_SUFFIX), TXT_SUFFIX, sizeof(TXT_SUFFIX));
+        txtPath[sizeof(PATH) + namlen - sizeof(BIN_SUFFIX) + sizeof(TXT_SUFFIX) - 1] = 0;
+        fprintf(stderr, "Testing %s\n", txtPath.get());
+
+        // Read text file.
+        Vector<char16_t> txtSource(cx);
+        readFull(cx, txtPath.get(), txtSource);
+
+        // Parse text file.
+        UsedNameTracker txtUsedNames(cx);
+        if (!txtUsedNames.init())
+            MOZ_CRASH();
+        js::frontend::Parser<js::frontend::FullParseHandler, char16_t> parser(cx, cx->tempLifoAlloc(), options, txtSource.begin(), txtSource.length(),
+                                                  /* foldConstants = */ false, txtUsedNames, nullptr,
+                                                  nullptr);
+        if (!parser.checkOptions())
+            MOZ_CRASH();
+
+        auto txtParsed = parser.parse(); // Will be deallocated once `parser` goes out of scope.
+        RootedValue txtExn(cx);
+        if (!txtParsed) {
+            // Save exception for more detailed error message, if necessary.
+            if (!js::GetAndClearException(cx, &txtExn))
+                MOZ_CRASH();
+        }
+
+        // Read binary file.
+        UniqueChars binPath(static_cast<char*>(js_malloc(namlen + sizeof(PATH) + 1)));
+        strncpy(binPath.get(), PATH, sizeof(PATH));
+        strncpy(binPath.get() + sizeof(PATH) - 1, d_name, namlen);
+        binPath[namlen + sizeof(PATH) - 1] = 0;
+
+        Vector<uint8_t> binSource(cx);
+        readFull(binPath.get(), binSource);
+
+        // Parse binary file.
+        js::frontend::UsedNameTracker binUsedNames(cx);
+        if (!binUsedNames.init())
+            MOZ_CRASH();
+
+        js::frontend::BinASTParser reader(cx, cx->tempLifoAlloc(), binUsedNames, options);
+
+        auto binParsed = reader.parse(binSource); // Will be deallocated once `reader` goes out of scope.
+        RootedValue binExn(cx);
+        if (binParsed.isErr()) {
+            // Save exception for more detailed error message, if necessary.
+            if (!js::GetAndClearException(cx, &binExn))
+                MOZ_CRASH();
+        }
+
+        // The binary parser should accept the file iff the text parser has.
+        if (binParsed.isOk() && !txtParsed) {
+            fprintf(stderr, "Text file parsing failed: ");
+
+            js::ErrorReport report(cx);
+            if (!report.init(cx, txtExn, js::ErrorReport::WithSideEffects))
+                MOZ_CRASH();
+
+            PrintError(cx, stderr, report.toStringResult(), report.report(), /* reportWarnings */ true);
+            MOZ_CRASH("Binary parser accepted a file that text parser rejected");
+        }
+
+        if (binParsed.isErr() && txtParsed) {
+            fprintf(stderr, "Binary file parsing failed: ");
+
+            js::ErrorReport report(cx);
+            if (!report.init(cx, binExn, js::ErrorReport::WithSideEffects))
+                MOZ_CRASH();
+
+            PrintError(cx, stderr, report.toStringResult(), report.report(), /* reportWarnings */ true);
+            MOZ_CRASH("Binary parser rejected a file that text parser accepted");
+        }
+
+        if (binParsed.isErr()) {
+            fprintf(stderr, "Binary parser and text parser agree that %s is invalid\n", txtPath.get());
+            continue;
+        }
+
+#if defined(DEBUG) // Dumping an AST is only defined in DEBUG builds
+        // Compare ASTs.
+        Sprinter binPrinter(cx);
+        if (!binPrinter.init())
+            MOZ_CRASH();
+        DumpParseTree(binParsed.unwrap(), binPrinter);
+
+        Sprinter txtPrinter(cx);
+        if (!txtPrinter.init())
+            MOZ_CRASH();
+        DumpParseTree(txtParsed, txtPrinter);
+
+        if (strcmp(binPrinter.string(), txtPrinter.string()) != 0) {
+            fprintf(stderr, "Got distinct ASTs when parsing %s:\n\tBINARY\n%s\n\n\tTEXT\n%s\n", txtPath.get(), binPrinter.string(), txtPrinter.string());            
+            MOZ_CRASH();
+        }
+        fprintf(stderr, "Got the same AST when parsing %s\n", txtPath.get());
+
+#endif // defined(DEBUG)
+    }
+
+#if defined(XP_WIN)
+    if (!FindClose(hFind))
+        MOZ_CRASH("Could not close Find");
+#endif // defined(XP_WIN)
+
+    return true;
+}
+END_TEST(testBinASTReaderECMAScript2)
+
new file mode 100644
--- /dev/null
+++ b/js/src/jsapi-tests/testBinTokenReaderTester.cpp
@@ -0,0 +1,321 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <string.h>
+#include <sys/stat.h>
+
+#if defined (XP_WIN)
+#include <windows.h>
+#elif defined(XP_UNIX)
+#include <fcntl.h>
+#include <unistd.h>
+#endif // defined (XP_WIN) || defined (XP_UNIX)
+
+#include "frontend/BinTokenReaderTester.h"
+#include "gc/Zone.h"
+
+#include "js/Vector.h"
+
+#include "jsapi-tests/tests.h"
+
+using Tokenizer = js::frontend::BinTokenReaderTester;
+using Chars = Tokenizer::Chars;
+
+// Hack: These tests need access to resources, which are present in the source dir
+// but not copied by our build system. To simplify things, we chdir to the source
+// dir at the start of each test and return to the previous directory afterwards.
+
+#if defined(XP_UNIX)
+
+#include <sys/param.h>
+
+static int gJsDirectory(0);
+void enterJsDirectory() {
+// Save current directory.
+    MOZ_ASSERT(gJsDirectory == 0);
+    gJsDirectory = open(".", O_RDONLY);
+    MOZ_ASSERT(gJsDirectory != 0, "Could not open directory '.'");
+// Go to the directory provided by the test harness, if any.
+    const char* destination = getenv("CPP_UNIT_TESTS_DIR_JS_SRC");
+    if (destination) {
+        if (chdir(destination) == -1)
+            MOZ_CRASH_UNSAFE_PRINTF("Could not chdir to %s", destination);
+    }
+}
+
+void exitJsDirectory() {
+    MOZ_ASSERT(gJsDirectory);
+    if (fchdir(gJsDirectory) == -1)
+        MOZ_CRASH("Could not return to original directory");
+    if (close(gJsDirectory) != 0)
+        MOZ_CRASH("Could not close js directory");
+    gJsDirectory = 0;
+}
+
+#else
+
+char gJsDirectory[MAX_PATH] = { 0 };
+
+void enterJsDirectory() {
+    // Save current directory.
+    MOZ_ASSERT(strlen(gJsDirectory) == 0);
+    auto result = GetCurrentDirectory(MAX_PATH, gJsDirectory);
+    if (result <= 0)
+        MOZ_CRASH("Could not get current directory");
+    if (result > MAX_PATH)
+        MOZ_CRASH_UNSAFE_PRINTF("Could not get current directory: needed %ld bytes, got %ld\n", result, MAX_PATH);
+
+    // Find destination directory, if any.
+    char destination[MAX_PATH];
+    if (!GetEnvironmentVariable("CPP_UNIT_TESTS_DIR_JS_SRC", destination, MAX_PATH)) {
+        if (GetLastError() != ERROR_ENVVAR_NOT_FOUND)
+            MOZ_CRASH("Could not get CPP_UNIT_TESTS_DIR_JS_SRC");
+        else
+            return;
+    }
+
+    // Go to the directory.
+    if (SetCurrentDirectory(destination) != 0)
+        MOZ_CRASH_UNSAFE_PRINTF("Could not chdir to %s", destination);
+}
+
+void exitJsDirectory() {
+    MOZ_ASSERT(strlen(gJsDirectory) > 0);
+    if (SetCurrentDirectory(gJsDirectory) != 0)
+        MOZ_CRASH("Could not return to original directory");
+    gJsDirectory[0] = 0;
+}
+
+#endif // defined(XP_UNIX) || defined(XP_WIN)
+
+void readFull(const char* path, js::Vector<uint8_t>& buf) {
+    enterJsDirectory();
+    buf.shrinkTo(0);
+    FILE* in = fopen(path, "r");
+    if (!in)
+        MOZ_CRASH_UNSAFE_PRINTF("Could not open %s: %s", path, strerror(errno));
+
+    struct stat info;
+    if (stat(path, &info) < 0)
+        MOZ_CRASH_UNSAFE_PRINTF("Could not get stat on %s", path);
+
+    if (!buf.growBy(info.st_size))
+        MOZ_CRASH("OOM");
+
+    int result = fread(buf.begin(), 1, info.st_size, in);
+    if (fclose(in) != 0)
+        MOZ_CRASH("Could not close input file");
+    if (result != info.st_size)
+        MOZ_CRASH("Read error");
+    exitJsDirectory();
+}
+
+
+// Reading a simple string.
+BEGIN_TEST(testBinTokenReaderTesterSimpleString)
+{
+    js::Vector<uint8_t> contents(cx);
+    readFull("jsapi-tests/binast/tokenizer/tester/test-simple-string.binjs", contents);
+    Tokenizer tokenizer(cx, contents);
+
+    Maybe<Chars> found;
+    CHECK(tokenizer.readMaybeChars(found));
+
+    CHECK(Tokenizer::equals(*found, "simple string")); // FIXME: Find a way to make CHECK_EQUAL use `Tokenizer::equals`.
+
+    return true;
+}
+END_TEST(testBinTokenReaderTesterSimpleString)
+
+// Reading a string with embedded 0.
+BEGIN_TEST(testBinTokenReaderTesterStringWithEscapes)
+{
+    js::Vector<uint8_t> contents(cx);
+    readFull("jsapi-tests/binast/tokenizer/tester/test-string-with-escapes.binjs", contents);
+    Tokenizer tokenizer(cx, contents);
+
+    Maybe<Chars> found;
+    CHECK(tokenizer.readMaybeChars(found));
+
+    CHECK(Tokenizer::equals(*found, "string with escapes \0\1\0")); // FIXME: Find a way to make CHECK_EQUAL use `Tokenizer::equals`.
+
+    return true;
+}
+END_TEST(testBinTokenReaderTesterStringWithEscapes)
+
+// Reading an empty untagged tuple
+BEGIN_TEST(testBinTokenReaderTesterEmptyUntaggedTuple)
+{
+    js::Vector<uint8_t> contents(cx);
+    readFull("jsapi-tests/binast/tokenizer/tester/test-empty-untagged-tuple.binjs", contents);
+    Tokenizer tokenizer(cx, contents);
+
+    {
+        Tokenizer::AutoTuple guard(tokenizer);
+        CHECK(tokenizer.enterUntaggedTuple(guard));
+        CHECK(guard.done());
+    }
+
+    return true;
+}
+END_TEST(testBinTokenReaderTesterEmptyUntaggedTuple)
+
+// Reading a untagged tuple with two strings
+BEGIN_TEST(testBinTokenReaderTesterTwoStringsInTuple)
+{
+    js::Vector<uint8_t> contents(cx);
+    readFull("jsapi-tests/binast/tokenizer/tester/test-trivial-untagged-tuple.binjs", contents);
+    Tokenizer tokenizer(cx, contents);
+
+    {
+        Tokenizer::AutoTuple guard(tokenizer);
+        CHECK(tokenizer.enterUntaggedTuple(guard));
+
+        Maybe<Chars> found_0;
+        CHECK(tokenizer.readMaybeChars(found_0));
+        CHECK(Tokenizer::equals(*found_0, "foo")); // FIXME: Find a way to make CHECK_EQUAL use `Tokenizer::equals`.
+
+        Maybe<Chars> found_1;
+        CHECK(tokenizer.readMaybeChars(found_1));
+        CHECK(Tokenizer::equals(*found_1, "bar")); // FIXME: Find a way to make CHECK_EQUAL use `Tokenizer::equals`.
+
+        CHECK(guard.done());
+    }
+
+    return true;
+}
+END_TEST(testBinTokenReaderTesterTwoStringsInTuple)
+
+// Reading a tagged tuple `Pattern { id: "foo", value: 3.1415}`
+BEGIN_TEST(testBinTokenReaderTesterSimpleTaggedTuple)
+{
+    js::Vector<uint8_t> contents(cx);
+    readFull("jsapi-tests/binast/tokenizer/tester/test-simple-tagged-tuple.binjs", contents);
+    Tokenizer tokenizer(cx, contents);
+
+    {
+        js::frontend::BinKind tag;
+        Tokenizer::BinFields fields(cx);
+        Tokenizer::AutoTaggedTuple guard(tokenizer);
+        CHECK(tokenizer.enterTaggedTuple(tag, fields, guard));
+
+        CHECK(tag == js::frontend::BinKind::Pattern);
+
+        Maybe<Chars> found_id;
+        const double EXPECTED_value = 3.1415;
+        Maybe<double> found_value;
+
+        // Order of fields is not deterministic in the encoder (we could make
+        // it deterministic for the test, though, since we already know the binary).
+        if (fields[0] == js::frontend::BinField::Id) {
+            CHECK(fields[1] == js::frontend::BinField::Value);
+            CHECK(tokenizer.readMaybeChars(found_id));
+            CHECK(tokenizer.readMaybeDouble(found_value));
+        } else if (fields[0] == js::frontend::BinField::Value) {
+            CHECK(fields[1] == js::frontend::BinField::Id);
+            CHECK(tokenizer.readMaybeDouble(found_value));
+            CHECK(tokenizer.readMaybeChars(found_id));
+        } else {
+            CHECK(false);
+        }
+
+        CHECK(EXPECTED_value == *found_value); // Apparently, CHECK_EQUAL doesn't work on `double`.
+        CHECK(Tokenizer::equals(*found_id, "foo"));
+        CHECK(guard.done());
+    }
+
+    return true;
+}
+END_TEST(testBinTokenReaderTesterSimpleTaggedTuple)
+
+
+// Reading an empty list
+BEGIN_TEST(testBinTokenReaderTesterEmptyList)
+{
+    js::Vector<uint8_t> contents(cx);
+    readFull("jsapi-tests/binast/tokenizer/tester/test-empty-list.binjs", contents);
+    Tokenizer tokenizer(cx, contents);
+
+    {
+        uint32_t length;
+        Tokenizer::AutoList guard(tokenizer);
+        CHECK(tokenizer.enterList(length, guard));
+
+        CHECK(length == 0);
+        CHECK(guard.done());
+    }
+
+    return true;
+}
+END_TEST(testBinTokenReaderTesterEmptyList)
+
+// Reading `["foo", "bar"]`
+BEGIN_TEST(testBinTokenReaderTesterSimpleList)
+{
+    js::Vector<uint8_t> contents(cx);
+    readFull("jsapi-tests/binast/tokenizer/tester/test-trivial-list.binjs", contents);
+    Tokenizer tokenizer(cx, contents);
+
+    {
+        uint32_t length;
+        Tokenizer::AutoList guard(tokenizer);
+        CHECK(tokenizer.enterList(length, guard));
+
+        CHECK(length == 2);
+
+        Maybe<Chars> found_0;
+        CHECK(tokenizer.readMaybeChars(found_0));
+        CHECK(Tokenizer::equals(*found_0, "foo"));
+
+        Maybe<Chars> found_1;
+        CHECK(tokenizer.readMaybeChars(found_1));
+        CHECK(Tokenizer::equals(*found_1, "bar"));
+
+        CHECK(guard.done());
+    }
+
+    return true;
+}
+END_TEST(testBinTokenReaderTesterSimpleList)
+
+
+// Reading `[["foo", "bar"]]`
+BEGIN_TEST(testBinTokenReaderTesterNestedList)
+{
+    js::Vector<uint8_t> contents(cx);
+    readFull("jsapi-tests/binast/tokenizer/tester/test-nested-lists.binjs", contents);
+    Tokenizer tokenizer(cx, contents);
+
+    {
+        uint32_t outerLength;
+        Tokenizer::AutoList outerGuard(tokenizer);
+        CHECK(tokenizer.enterList(outerLength, outerGuard));
+        CHECK(outerLength == 1);
+
+        {
+            uint32_t innerLength;
+            Tokenizer::AutoList innerGuard(tokenizer);
+            CHECK(tokenizer.enterList(innerLength, innerGuard));
+            CHECK(innerLength == 2);
+
+            Maybe<Chars> found_0;
+            CHECK(tokenizer.readMaybeChars(found_0));
+            CHECK(Tokenizer::equals(*found_0, "foo"));
+
+            Maybe<Chars> found_1;
+            CHECK(tokenizer.readMaybeChars(found_1));
+            CHECK(Tokenizer::equals(*found_1, "bar"));
+
+            CHECK(innerGuard.done());
+        }
+
+        CHECK(outerGuard.done());
+    }
+
+    return true;
+}
+END_TEST(testBinTokenReaderTesterNestedList)
--- a/js/src/moz.build
+++ b/js/src/moz.build
@@ -639,16 +639,20 @@ FINAL_LIBRARY = 'js'
 
 if CONFIG['NIGHTLY_BUILD']:
     DEFINES['ENABLE_BINARYDATA'] = True
     DEFINES['ENABLE_SIMD'] = True
     DEFINES['ENABLE_WASM_THREAD_OPS'] = True
 
 if CONFIG['JS_BUILD_BINAST']:
     # Using SOURCES as UNIFIED_SOURCES causes mysterious bugs on 32-bit platforms.
+    # These parts of BinAST are designed only to test evolutions of the
+    # specification.
+    SOURCES += ['frontend/BinTokenReaderTester.cpp']
+    # These parts of BinAST should eventually move to release.
     SOURCES += ['frontend/BinToken.cpp']
 
 # Wasm code should use WASM_HUGE_MEMORY instead of JS_CODEGEN_X64
 # so that it is easy to use the huge-mapping optimization for other
 # 64-bit platforms in the future.
 
 if CONFIG['JS_CODEGEN_X64']:
     DEFINES['WASM_HUGE_MEMORY'] = True