gecko-dev/dom/canvas/WebGLValidateStrings.cpp

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 "WebGLValidateStrings.h"

#include "WebGLContext.h"

namespace mozilla {

bool TruncateComments(const nsAString& src, nsAString* const out) {
  const size_t dstByteCount = src.Length() * sizeof(src[0]);
  const UniqueBuffer dst(malloc(dstByteCount));
  if (!dst) return false;

  auto srcItr = src.BeginReading();
  const auto srcEnd = src.EndReading();
  const auto dstBegin = (decltype(src[0])*)dst.get();
  auto dstItr = dstBegin;

  const auto fnEmitUntil = [&](const decltype(srcItr)& nextSrcItr) {
    while (srcItr != nextSrcItr) {
      *dstItr = *srcItr;
      ++srcItr;
      ++dstItr;
    }
  };

  const auto fnFindSoonestOf = [&](const nsString* needles, size_t needleCount,
                                   size_t* const out_foundId) {
    auto foundItr = srcItr;
    while (foundItr != srcEnd) {
      const auto haystack = Substring(foundItr, srcEnd);
      for (size_t i = 0; i < needleCount; i++) {
        if (StringBeginsWith(haystack, needles[i])) {
          *out_foundId = i;
          return foundItr;
        }
      }
      ++foundItr;
    }
    *out_foundId = needleCount;
    return foundItr;
  };

  ////

  const nsString commentBeginnings[] = {NS_LITERAL_STRING("//"),
                                        NS_LITERAL_STRING("/*"),
                                        nsString()};  // Final empty string for
                                                      // "found nothing".
  const nsString lineCommentEndings[] = {NS_LITERAL_STRING("\\\n"),
                                         NS_LITERAL_STRING("\n"), nsString()};
  const nsString blockCommentEndings[] = {NS_LITERAL_STRING("\n"),
                                          NS_LITERAL_STRING("*/"), nsString()};

  while (srcItr != srcEnd) {
    size_t foundId;
    fnEmitUntil(fnFindSoonestOf(commentBeginnings, 2, &foundId));
    fnEmitUntil(srcItr +
                commentBeginnings[foundId].Length());  // Final empty string
                                                       // allows us to skip
                                                       // forward here
                                                       // unconditionally.
    switch (foundId) {
      case 0:  // line comment
        while (true) {
          size_t endId;
          srcItr = fnFindSoonestOf(lineCommentEndings, 2, &endId);
          fnEmitUntil(srcItr + lineCommentEndings[endId].Length());
          if (endId == 0) continue;
          break;
        }
        break;

      case 1:  // block comment
        while (true) {
          size_t endId;
          srcItr = fnFindSoonestOf(blockCommentEndings, 2, &endId);
          fnEmitUntil(srcItr + blockCommentEndings[endId].Length());
          if (endId == 0) continue;
          break;
        }
        break;

      default:  // not found
        break;
    }
  }

  MOZ_ASSERT((dstBegin + 1) - dstBegin == 1);
  const uint32_t dstCharLen = dstItr - dstBegin;
  if (!out->Assign(dstBegin, dstCharLen, mozilla::fallible)) return false;

  return true;
}

////////////////////////////////////////////////////////////////////////////////

static bool IsValidGLSLChar(char16_t c) {
  if (('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') ||
      ('0' <= c && c <= '9')) {
    return true;
  }

  switch (c) {
    case ' ':
    case '\t':
    case '\v':
    case '\f':
    case '\r':
    case '\n':
    case '_':
    case '.':
    case '+':
    case '-':
    case '/':
    case '*':
    case '%':
    case '<':
    case '>':
    case '[':
    case ']':
    case '(':
    case ')':
    case '{':
    case '}':
    case '^':
    case '|':
    case '&':
    case '~':
    case '=':
    case '!':
    case ':':
    case ';':
    case ',':
    case '?':
      return true;

    default:
      return false;
  }
}

static bool IsValidGLSLPreprocChar(char16_t c) {
  if (IsValidGLSLChar(c)) return true;

  switch (c) {
    case '\\':
    case '#':
      return true;

    default:
      return false;
  }
}

////

bool ValidateGLSLPreprocString(WebGLContext* webgl, const nsAString& string) {
  for (size_t i = 0; i < string.Length(); ++i) {
    const auto& cur = string[i];

    if (!IsValidGLSLPreprocChar(cur)) {
      webgl->ErrorInvalidValue("String contains the illegal character 0x%x.",
                               cur);
      return false;
    }

    if (cur == '\\' && !webgl->IsWebGL2()) {
      // Todo: Backslash is technically still invalid in WebGLSL 1 under even
      // under WebGL 2.
      webgl->ErrorInvalidValue("Backslash is not valid in WebGL 1.");
      return false;
    }
  }

  return true;
}

bool ValidateGLSLVariableName(const nsAString& name, WebGLContext* webgl) {
  if (name.IsEmpty()) return false;

  const uint32_t maxSize = webgl->IsWebGL2() ? 1024 : 256;
  if (name.Length() > maxSize) {
    webgl->ErrorInvalidValue(
        "Identifier is %u characters long, exceeds the"
        " maximum allowed length of %u characters.",
        name.Length(), maxSize);
    return false;
  }

  for (size_t i = 0; i < name.Length(); ++i) {
    const auto& cur = name[i];
    if (!IsValidGLSLChar(cur)) {
      webgl->ErrorInvalidValue("String contains the illegal character 0x%x'.",
                               cur);
      return false;
    }
  }

  nsString prefix1 = NS_LITERAL_STRING("webgl_");
  nsString prefix2 = NS_LITERAL_STRING("_webgl_");

  if (Substring(name, 0, prefix1.Length()).Equals(prefix1) ||
      Substring(name, 0, prefix2.Length()).Equals(prefix2)) {
    webgl->ErrorInvalidOperation("String contains a reserved GLSL prefix.");
    return false;
  }

  return true;
}

}  // namespace mozilla