Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1588 insertions, 0 deletions

diff --git a/gfx/ots/tests/cff_charstring_test.cc b/gfx/ots/tests/cff_charstring_test.cc
new file mode 100644
index 0000000000..18e077e8f0
--- /dev/null
+++ b/gfx/ots/tests/cff_charstring_test.cc
@@ -0,0 +1,1588 @@
+// Copyright (c) 2010-2017 The OTS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cff_charstring.h"
+
+#include <gtest/gtest.h>
+
+#include <climits>
+#include <vector>
+
+#include "cff.h"
+
+// Returns a biased number for callsubr and callgsubr operators.
+#define GET_SUBR_NUMBER(n) ((n) - 107)
+#define ARRAYSIZE(a) (sizeof(a) / sizeof(a[0]))
+
+namespace {
+
+// A constant which is used in AddSubr function below.
+const int kOpPrefix = INT_MAX;
+
+// Encodes an operator |op| to 1 or more bytes and pushes them to |out_bytes|.
+// Returns true if the conversion succeeds.
+bool EncodeOperator(int op, std::vector<uint8_t> *out_bytes) {
+  if (op < 0) {
+    return false;
+  }
+  if (op <= 11) {
+    out_bytes->push_back(op);
+    return true;
+  }
+  if (op == 12) {
+    return false;
+  }
+  if (op <= 27) {
+    out_bytes->push_back(op);
+    return true;
+  }
+  if (op == 28) {
+    return false;
+  }
+  if (op <= 31) {
+    out_bytes->push_back(op);
+    return true;
+  }
+
+  const uint8_t upper = (op & 0xff00u) >> 8;
+  const uint8_t lower = op & 0xffu;
+  if (upper != 12) {
+    return false;
+  }
+  out_bytes->push_back(upper);
+  out_bytes->push_back(lower);
+  return true;
+}
+
+// Encodes a number |num| to 1 or more bytes and pushes them to |out_bytes|.
+// Returns true if the conversion succeeds. The function does not support 16.16
+// Fixed number.
+bool EncodeNumber(int num, std::vector<uint8_t> *out_bytes) {
+  if (num >= -107 && num <= 107) {
+    out_bytes->push_back(num + 139);
+    return true;
+  }
+  if (num >= 108 && num <= 1131) {
+    const uint8_t v = ((num - 108) / 256) + 247;
+    const uint8_t w = (num - 108) % 256;
+    out_bytes->push_back(v);
+    out_bytes->push_back(w);
+    return true;
+  }
+  if (num <= -108 && num >= -1131) {
+    const uint8_t v = (-(num + 108) / 256) + 251;
+    const uint8_t w = -(num + 108) % 256;
+    out_bytes->push_back(v);
+    out_bytes->push_back(w);
+    return true;
+  }
+  if (num <= 32768 && num >= -32767) {
+    const uint8_t v = (num % 0xff00u) >> 8;
+    const uint8_t w = num % 0xffu;
+    out_bytes->push_back(28);
+    out_bytes->push_back(v);
+    out_bytes->push_back(w);
+    return true;
+  }
+  return false;
+}
+
+// Adds a subroutine |subr| to |out_buffer| and |out_subr|. The contents of the
+// subroutine is copied to |out_buffer|, and then the position of the subroutine
+// in |out_buffer| is written to |out_subr|. Returns true on success.
+bool AddSubr(const int *subr, size_t subr_len,
+             std::vector<uint8_t>* out_buffer, ots::CFFIndex *out_subr) {
+  size_t pre_offset = out_buffer->size();
+  for (size_t i = 0; i < subr_len; ++i) {
+    if (subr[i] != kOpPrefix) {
+      if (!EncodeNumber(subr[i], out_buffer)) {
+        return false;
+      }
+    } else {
+      if (i + 1 == subr_len) {
+        return false;
+      }
+      ++i;
+      if (!EncodeOperator(subr[i], out_buffer)) {
+        return false;
+      }
+    }
+  }
+
+  ++(out_subr->count);
+  out_subr->off_size = 1;
+  if (out_subr->offsets.empty()) {
+    out_subr->offsets.push_back(pre_offset);
+  }
+  out_subr->offsets.push_back(out_buffer->size());
+  return true;
+}
+
+// Validates |char_string| and returns true if it's valid.
+bool Validate(const int *char_string, size_t char_string_len,
+              const int *global_subrs, size_t global_subrs_len,
+              const int *local_subrs, size_t local_subrs_len) {
+  std::vector<uint8_t> buffer;
+  ots::CFFIndex* char_strings_index = new ots::CFFIndex;
+  ots::CFFIndex global_subrs_index;
+  ots::CFFIndex* local_subrs_index = new ots::CFFIndex;
+
+  if (char_string) {
+    if (!AddSubr(char_string, char_string_len,
+                 &buffer, char_strings_index)) {
+      return false;
+    }
+  }
+  if (global_subrs) {
+    if (!AddSubr(global_subrs, global_subrs_len,
+                 &buffer, &global_subrs_index)) {
+      return false;
+    }
+  }
+  if (local_subrs) {
+    if (!AddSubr(local_subrs, local_subrs_len,
+                 &buffer, local_subrs_index)) {
+      return false;
+    }
+  }
+
+  ots::Buffer ots_buffer(&buffer[0], buffer.size());
+
+  ots::FontFile* file = new ots::FontFile();
+  file->context = new ots::OTSContext();
+  ots::Font* font = new ots::Font(file);
+  ots::OpenTypeCFF* cff = new ots::OpenTypeCFF(font, OTS_TAG_CFF);
+  cff->charstrings_index = char_strings_index;
+  cff->local_subrs = local_subrs_index;
+  bool ret = ots::ValidateCFFCharStrings(*cff,
+                                         global_subrs_index,
+                                         &ots_buffer);
+  delete file->context;
+  delete file;
+  delete font;
+  delete cff;
+
+  return ret;
+}
+
+// Validates |char_string| and returns true if it's valid.
+bool ValidateCharStrings(const int *char_string, size_t char_string_len) {
+  return Validate(char_string, char_string_len, NULL, 0, NULL, 0);
+}
+
+}  // namespace
+
+TEST(ValidateTest, TestRMoveTo) {
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kRMoveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1,  // width
+      1, 2, kOpPrefix, ots::kRMoveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kRMoveTo,
+      1, 2, 3, kOpPrefix, ots::kRMoveTo,  // invalid number of args
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestHMoveTo) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kHMoveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1,  // width
+      1, kOpPrefix, ots::kHMoveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kHMoveTo,
+      1, 2, kOpPrefix, ots::kHMoveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestVMoveTo) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1,  // width
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, kOpPrefix, ots::kVMoveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestRLineTo) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, kOpPrefix, ots::kRLineTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, kOpPrefix, ots::kRLineTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, kOpPrefix, ots::kRLineTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kRLineTo,  // can't be the first op.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestHLineTo) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, kOpPrefix, ots::kHLineTo,
+      1, 2, kOpPrefix, ots::kHLineTo,
+      1, 2, 3, kOpPrefix, ots::kHLineTo,
+      1, 2, 3, 4, kOpPrefix, ots::kHLineTo,
+      1, 2, 3, 4, 5, kOpPrefix, ots::kHLineTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kHLineTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kHLineTo,  // can't be the first op.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestVLineTo) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, kOpPrefix, ots::kVLineTo,
+      1, 2, kOpPrefix, ots::kVLineTo,
+      1, 2, 3, kOpPrefix, ots::kVLineTo,
+      1, 2, 3, 4, kOpPrefix, ots::kVLineTo,
+      1, 2, 3, 4, 5, kOpPrefix, ots::kVLineTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kVLineTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVLineTo,  // can't be the first op.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestRRCurveTo) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, kOpPrefix, ots::kRRCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, kOpPrefix, ots::kRRCurveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kRRCurveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, 5, 6, kOpPrefix, ots::kRRCurveTo,  // can't be the first op.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestHHCurveTo) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, kOpPrefix, ots::kHHCurveTo,
+      1, 2, 3, 4, 5, kOpPrefix, ots::kHHCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, kOpPrefix, ots::kHHCurveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, kOpPrefix, ots::kHHCurveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, kOpPrefix, ots::kHHCurveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, 5, kOpPrefix, ots::kHHCurveTo,  // can't be the first op.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestHVCurveTo) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      // The first form.
+      1, 2, 3, 4, kOpPrefix, ots::kHVCurveTo,
+      1, 2, 3, 4, 5, kOpPrefix, ots::kHVCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, kOpPrefix, ots::kHVCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
+      kOpPrefix, ots::kHVCurveTo,
+      // The second form.
+      1, 2, 3, 4, 5, 6, 7, 8, kOpPrefix, ots::kHVCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, kOpPrefix, ots::kHVCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
+      kOpPrefix, ots::kHVCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
+      22, 23, 24, 25, kOpPrefix, ots::kHVCurveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, kOpPrefix, ots::kHVCurveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, kOpPrefix, ots::kHVCurveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, kOpPrefix, ots::kHVCurveTo,  // can't be the first op.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestRCurveLine) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, kOpPrefix, ots::kRCurveLine,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
+      kOpPrefix, ots::kRCurveLine,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, kOpPrefix, ots::kRCurveLine,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      // can't be the first op.
+      1, 2, 3, 4, 5, 6, 7, 8, kOpPrefix, ots::kRCurveLine,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestRLineCurve) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, kOpPrefix, ots::kRLineCurve,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, kOpPrefix, ots::kRLineCurve,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, kOpPrefix, ots::kRLineCurve,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      // can't be the first op.
+      1, 2, 3, 4, 5, 6, 7, 8, kOpPrefix, ots::kRLineCurve,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestVHCurveTo) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      // The first form.
+      1, 2, 3, 4, kOpPrefix, ots::kVHCurveTo,
+      1, 2, 3, 4, 5, kOpPrefix, ots::kVHCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, kOpPrefix, ots::kVHCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
+      kOpPrefix, ots::kVHCurveTo,
+      // The second form.
+      1, 2, 3, 4, 5, 6, 7, 8, kOpPrefix, ots::kVHCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, kOpPrefix, ots::kVHCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
+      kOpPrefix, ots::kVHCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,
+      22, 23, 24, 25, kOpPrefix, ots::kVHCurveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, kOpPrefix, ots::kVHCurveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, kOpPrefix, ots::kVHCurveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, kOpPrefix, ots::kVHCurveTo,  // can't be the first op.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestVVCurveTo) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, kOpPrefix, ots::kVVCurveTo,
+      1, 2, 3, 4, 5, kOpPrefix, ots::kVVCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, kOpPrefix, ots::kVVCurveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, kOpPrefix, ots::kVVCurveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kVVCurveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, kOpPrefix, ots::kVVCurveTo,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, kOpPrefix, ots::kVVCurveTo,  // can't be the first op.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestFlex) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, kOpPrefix, ots::kFlex,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kFlex,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, kOpPrefix, ots::kFlex,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, kOpPrefix, ots::kFlex,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestHFlex) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, kOpPrefix, ots::kHFlex,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kHFlex,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, kOpPrefix, ots::kHFlex,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, 5, 6, 7, kOpPrefix, ots::kHFlex,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestHFlex1) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, kOpPrefix, ots::kHFlex1,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kHFlex1,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, kOpPrefix, ots::kHFlex1,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, 5, 6, 7, 8, 9, kOpPrefix, ots::kHFlex1,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestFlex1) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, kOpPrefix, ots::kFlex1,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kFlex1,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, kOpPrefix, ots::kFlex1,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, kOpPrefix, ots::kFlex1,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestEndChar) {
+  {
+    const int char_string[] = {
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallSubr,
+    };
+    const int local_subrs[] = {
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(Validate(char_string, ARRAYSIZE(char_string),
+                         NULL, 0,
+                         local_subrs, ARRAYSIZE(local_subrs)));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallGSubr,
+    };
+    const int global_subrs[] = {
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(Validate(char_string, ARRAYSIZE(char_string),
+                         global_subrs, ARRAYSIZE(global_subrs),
+                         NULL, 0));
+  }
+}
+
+TEST(ValidateTest, TestHStem) {
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      0,  // width
+      1, 2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      0, 1, 2, kOpPrefix, ots::kHStem,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, kOpPrefix, ots::kHStem,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestVStem) {
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kVStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, kOpPrefix, ots::kVStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      0,  // width
+      1, 2, kOpPrefix, ots::kVStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      0, 1, 2, kOpPrefix, ots::kVStem,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, kOpPrefix, ots::kVStem,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestHStemHm) {
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kHStemHm,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, kOpPrefix, ots::kHStemHm,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      0,  // width
+      1, 2, kOpPrefix, ots::kHStemHm,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      0, 1, 2, kOpPrefix, ots::kHStemHm,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, kOpPrefix, ots::kHStemHm,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestVStemHm) {
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kVStemHm,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, kOpPrefix, ots::kVStemHm,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      0,  // width
+      1, 2, kOpPrefix, ots::kVStemHm,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      0, 1, 2, kOpPrefix, ots::kVStemHm,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kVMoveTo,
+      1, 2, 3, 4, 5, kOpPrefix, ots::kVStemHm,  // invalid
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestHintMask) {
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kHintMask, 0x00,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kHStem,
+      3, 4, 5, 6, kOpPrefix, ots::kHintMask, 0x00,  // vstem
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      kOpPrefix, ots::kHintMask, 0x00,  // no stems to mask
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kHStem,
+      3, 4, 5, kOpPrefix, ots::kHintMask, 0x00,  // invalid vstem
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestCntrMask) {
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kCntrMask, 0x00,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kHStem,
+      3, 4, 5, 6, kOpPrefix, ots::kCntrMask, 0x00,  // vstem
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      kOpPrefix, ots::kCntrMask, 0x00,  // no stems to mask
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, kOpPrefix, ots::kHStem,
+      3, 4, 5, kOpPrefix, ots::kCntrMask, 0x00,  // invalid vstem
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestAbs) {
+  {
+    const int char_string[] = {
+      -1, kOpPrefix, ots::kAbs,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      kOpPrefix, ots::kAbs,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestAdd) {
+  {
+    const int char_string[] = {
+      0, 1, kOpPrefix, ots::kAdd,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kAdd,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestSub) {
+  {
+    const int char_string[] = {
+      2, 1, kOpPrefix, ots::kSub,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kSub,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestDiv) {
+  // TODO(yusukes): Test div-by-zero.
+  {
+    const int char_string[] = {
+      2, 1, kOpPrefix, ots::kDiv,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kDiv,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestNeg) {
+  {
+    const int char_string[] = {
+      -1, kOpPrefix, ots::kNeg,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      kOpPrefix, ots::kNeg,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestRandom) {
+  {
+    const int char_string[] = {
+      kOpPrefix, ots::kRandom,  // OTS rejects the operator.
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestMul) {
+  {
+    const int char_string[] = {
+      2, 1, kOpPrefix, ots::kMul,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kMul,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestSqrt) {
+  // TODO(yusukes): Test negative numbers.
+  {
+    const int char_string[] = {
+      4, kOpPrefix, ots::kSqrt,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      kOpPrefix, ots::kSqrt,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestDrop) {
+  {
+    const int char_string[] = {
+      1, 1, kOpPrefix, ots::kAdd,
+      kOpPrefix, ots::kDrop,
+      1, 2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      kOpPrefix, ots::kDrop,  // invalid
+      1, 2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestExch) {
+  {
+    const int char_string[] = {
+      1, 1, kOpPrefix, ots::kAdd,
+      kOpPrefix, ots::kDup,
+      kOpPrefix, ots::kExch,
+      kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 1, kOpPrefix, ots::kAdd,
+      kOpPrefix, ots::kExch,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestIndex) {
+  {
+    const int char_string[] = {
+      1, 2, 3, -1, kOpPrefix, ots::kIndex,  // OTS rejects the operator.
+      kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestRoll) {
+  {
+    const int char_string[] = {
+      1, 2, 2, 1, kOpPrefix, ots::kRoll,  // OTS rejects the operator.
+      kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestDup) {
+  {
+    const int char_string[] = {
+      1, 1, kOpPrefix, ots::kAdd,
+      kOpPrefix, ots::kDup,
+      kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      kOpPrefix, ots::kDup,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestPut) {
+  {
+    const int char_string[] = {
+      1, 10, kOpPrefix, ots::kPut,  // OTS rejects the operator.
+      1, 2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestGet) {
+  {
+    const int char_string[] = {
+      1, 10, kOpPrefix, ots::kGet,  // OTS rejects the operator.
+      1, 2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestAnd) {
+  {
+    const int char_string[] = {
+      2, 1, kOpPrefix, ots::kAnd,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kAnd,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestOr) {
+  {
+    const int char_string[] = {
+      2, 1, kOpPrefix, ots::kOr,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kOr,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestNot) {
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kNot,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      kOpPrefix, ots::kNot,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestEq) {
+  {
+    const int char_string[] = {
+      2, 1, kOpPrefix, ots::kEq,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, kOpPrefix, ots::kEq,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestIfElse) {
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, kOpPrefix, ots::kIfElse,
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, kOpPrefix, ots::kIfElse,  // invalid
+      2, kOpPrefix, ots::kHStem,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestCallSubr) {
+  // Call valid subr.
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallSubr,
+    };
+    const int local_subrs[] = {
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(Validate(char_string, ARRAYSIZE(char_string),
+                         NULL, 0,
+                         local_subrs, ARRAYSIZE(local_subrs)));
+  }
+  // Call undefined subr.
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(-1), kOpPrefix, ots::kCallSubr,
+    };
+    const int local_subrs[] = {
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(Validate(char_string, ARRAYSIZE(char_string),
+                          NULL, 0,
+                          local_subrs, ARRAYSIZE(local_subrs)));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(1), kOpPrefix, ots::kCallSubr,
+    };
+    const int local_subrs[] = {
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(Validate(char_string, ARRAYSIZE(char_string),
+                          NULL, 0,
+                          local_subrs, ARRAYSIZE(local_subrs)));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(-1), kOpPrefix, ots::kCallSubr,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallSubr,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(1), kOpPrefix, ots::kCallSubr,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestCallGSubr) {
+  // Call valid subr.
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallGSubr,
+    };
+    const int global_subrs[] = {
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(Validate(char_string, ARRAYSIZE(char_string),
+                         global_subrs, ARRAYSIZE(global_subrs),
+                         NULL, 0));
+  }
+  // Call undefined subr.
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(-1), kOpPrefix, ots::kCallGSubr,
+    };
+    const int global_subrs[] = {
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(Validate(char_string, ARRAYSIZE(char_string),
+                          global_subrs, ARRAYSIZE(global_subrs),
+                          NULL, 0));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(1), kOpPrefix, ots::kCallGSubr,
+    };
+    const int global_subrs[] = {
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(Validate(char_string, ARRAYSIZE(char_string),
+                          global_subrs, ARRAYSIZE(global_subrs),
+                          NULL, 0));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(-1), kOpPrefix, ots::kCallGSubr,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallGSubr,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(1), kOpPrefix, ots::kCallGSubr,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestCallGSubrWithComputedValues) {
+  {
+    // OTS does not allow to call(g)subr with a subroutine number which is
+    // not a immediate value for safety.
+    const int char_string[] = {
+      0, 0, kOpPrefix, ots::kAdd,
+      kOpPrefix, ots::kCallGSubr,
+    };
+    const int global_subrs[] = {
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(Validate(char_string, ARRAYSIZE(char_string),
+                          global_subrs, ARRAYSIZE(global_subrs),
+                          NULL, 0));
+  }
+}
+
+TEST(ValidateTest, TestInfiniteLoop) {
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallSubr,
+    };
+    const int local_subrs[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallSubr,
+    };
+    EXPECT_FALSE(Validate(char_string, ARRAYSIZE(char_string),
+                          NULL, 0,
+                          local_subrs, ARRAYSIZE(local_subrs)));
+  }
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallGSubr,
+    };
+    const int global_subrs[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallGSubr,
+    };
+    EXPECT_FALSE(Validate(char_string, ARRAYSIZE(char_string),
+                          global_subrs, ARRAYSIZE(global_subrs),
+                          NULL, 0));
+  }
+  // mutual recursion which doesn't stop.
+  {
+    const int char_string[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallSubr,
+    };
+    const int global_subrs[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallSubr,
+    };
+    const int local_subrs[] = {
+      GET_SUBR_NUMBER(0), kOpPrefix, ots::kCallGSubr,
+    };
+    EXPECT_FALSE(Validate(char_string, ARRAYSIZE(char_string),
+                          global_subrs, ARRAYSIZE(global_subrs),
+                          local_subrs, ARRAYSIZE(local_subrs)));
+  }
+}
+
+TEST(ValidateTest, TestStackOverflow) {
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+      1, 2, 3, 4, 5, 6, 7, 8,
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_TRUE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
+      1, 2, 3, 4, 5, 6, 7, 8, 9,  // overflow
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestDeprecatedOperators) {
+  {
+    const int char_string[] = {
+      kOpPrefix, 16,  // 'blend'.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      kOpPrefix, (12 << 8) + 8,  // 'store'.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      kOpPrefix, (12 << 8) + 13,  // 'load'.
+      kOpPrefix, ots::kEndChar,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}
+
+TEST(ValidateTest, TestUnterminatedCharString) {
+  // No endchar operator.
+  {
+    const int char_string[] = {
+      123,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      123, 456,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+  {
+    const int char_string[] = {
+      123, 456, kOpPrefix, ots::kReturn,
+    };
+    EXPECT_FALSE(ValidateCharStrings(char_string, ARRAYSIZE(char_string)));
+  }
+}